How many samples do I need? (with lots of assumptions)

by John Seymour, John the Math Guy

In an earlier post, I looked at the question “How many samples of a production run do I need to assure that 68% are within tolerance?” I concluded with “at least 300, and preferably 1,200. In the first pass I made only one assumption – that the sampling of parts to test was done at random. I answered the question with no information about the metric or about the process.

For my answer, I reduced the question down to a simple one. Suppose that a green M&M is put into a bucket/barrel/swimming pool whenever a good part is produced, and that a red M&M is put in whenever a bad part is produced. For the testing of this production run, M&Ms are pulled out at random, and noted as being either good or bad. After tallying the color of each M&M, they are replaced into the bucket/barrel/swimming pool.

Christmas m and ms

Note the assumptions. I assume that the production run is sampled at run with replacement. And that’s about it.

Statistics of color difference values

Today I answer the question with a whole lot of additional assumptions. Today I assume that the metric being measured and graded is the color difference value, in units of ΔE. And I make some assumptions about the statistical nature of color differences.

I assembled real-world data to create an archetypal cumulative probability density function (CPDF) of color difference data from a collection of 262 color difference data sets each with 300 to 1,600 data points. In total, my result is a distillation of  317,667 color differences from 201 different print devices, including web offset, coldset, flexo, and ink jet printers. So, a lot of data was reduced to a set of 101 percentile points shown in the image below. Note that this curve has been normalized to have a median value of 1.0 ΔE, on the assumption that all the curves have the same shape, but differ in scale.

Archetypal CPDF of deltaE

Archetypal cumulative probability density function for color difference data (ΔEab)

For my analysis, it is assumed that all color difference data has this same shape. Note that if one has a data set of color difference data, it can be transformed to relate to this archetype by dividing all the color difference values by the median of the data set. In my analysis of the 262 data sets, this may not of been an excellent assumption, but then again, it was not a bad assumption.

The archetypal curve is based on data from printing test targets each with of hundreds of CMYK values, and not from production runs of 10,000 copies of a single CMYK patch. For this analysis, I make the assumption that run-time color differences behave kinda the same. I’ve seen data from a couple three press runs. I dunno, might not be such a good assumption.

Let’s see… are there any other assumptions that I am making today? Oh yeah… I have based the archetypal CPDF on color difference data based on the original 1976 ΔE formula and not the 2000. Today, I don’t know how much of a difference this makes. Some day, I might know.

Monte Carlo simulation of press runs

I did some Monte Carlo simulations with all the aforementioned assumptions. I was asking a variation on the question asked in the previous blog. Instead of asking what the how many samples were needed to make a reliable pass/fail call, I asked how many samples were needed to get a reliable estimate of the 68th percentile. Subtle difference, but that’s the nature of statistics.

As in the previous blog, I will start with the example of the printer who pulls only three samples and from these three, determines the 68th percentile. I’m not sure just how you get a 68th percentile from only three samples, but somehow when I use the PERCENTILE function in Excel or the Quantile function in Mathematica, they give me a number. I assume that the number means something reasonable.

Now for a couple more assumptions. I will assume that the tolerance threshold is 4 ΔE (in other words, 68% must be less than 4 ΔE), and that the printer is doing a pretty decent job of holding this – 68% of the samples are below 3.5 ΔE. One would hope that the printer gets the thumbs up on the job almost all the time, right?

Gosh, that would be nice, but my Monte Carlo simulation says that this just ain’t gonna happen. I ran the test 10,000 times. Each time, I drew three random samples from the archetypal CPDF shown above. From those, I calculated a 68th percentile. The histogram below shows the distribution of the 68th percentiles determined this way. Nearly 55% of the press runs were declared out of tolerance.

68th is 3 point 5, three samples

Distribution of estimates for the 68th percentile, determined from 3 random samples

There is something just a tad confusing here. The assumption was that the press runs had a 68th percentile of 3.5 ΔE. Wouldn’t you expect that at least 50% of the runs were in tolerance? Yes, I think you might, but note two things: First, the distribution above is not symmetrical. Second, as I said before, determining the 68th percentile of a set of three data points is a bit of a slippery animal.

When this printer saw how many were failing, he asked for my advice. I pointed him to my previous blog, and he said “1200?!?!?  Are you kidding me!?!?  I can’t even afford to measure 300 samples!” He ignored me, and never paid me my $10,000 consulting fee, but I heard through the grapevine that he did start pulling 30 samples. That’s why I get paid the big bucks. So people can ignore my advice.

68th is 3 point 5, 30 samples

Distribution of estimates for the 68th percentile, determined from 30 random samples

The image above shows what happened when he started measuring the color error on 30 samples per press run. Much better. Now only about 13% of the press runs are erroneously labelled “bad product”. What happened after that depended on how sharp the teeth were in the contract between the printer and print buyer. Maybe the print buyer just shrugged it off when one out of every 8 print runs were declared out of tolerance? Maybe there’s a lawsuit pending? I don’t know. That particular printer never called me up with a status report.

What if the printer had heeded my advice and started pulling 300 samples to determine the 68th percentile? The results from one last Monte Carlo experiment are shown below. Here the printer pulled all 300 samples that I asked for. At the end of 10,000 press runs, the printer had only three examples where a good press run was called “bad”.

68th is 3 point 5, 300 samples

Distribution of estimates for the 68th percentile, determined from 300 random samples

Print buyer’s perspective

The previous examples were from the printer’s perspective, where the printer responds with self-righteous indignation when sadistical control process has the gall to say that a good run is bad. We now turn this around and look at the print buyer’s perspective.

Let’s say that a printer is doing work that is not up to snuff… I dunno… let’s say that the 68th percentile is at 4.5 ΔE. If the print buyer is a forgiving sort, then maybe this is OK by him. But then again, maybe his wife might tell him to stop being such a door mat?  (I am married to a woman who tells her spouse that all the time, especially when it comes to clients not paying.) We can’t simulate what this print buyer’s wife will tell him, but we can simulate how often statistical process control will erroneously tell him that a 4.5 ΔE run was good.

The results are similar, as I guess we would expect. If your vision of “statistical process control” means three samples, then 21.1% of the bad jobs will be given the rubber stamp of approval. The printer may like that, but I don’t think the print buyer’s spouse will stand for it.

If you up the sampling to 10 samples, quite paradoxically, the rate of mis-attribution goes up to 35.7%. That darn skewed distribution.

Pulling thirty samples doesn’t help a great deal either. With 30 samples, the erroneous use of the “approved” stamp goes down only to 15.7%. If the count is increased to 100, then about 4.7% of the bad runs are called “good”. But when 300 samples are pulled, the number drops way down to 0.06%.

Conclusions

I ran the simulation with a number of different sample sizes and a number of different underlying levels of “quality of production run”.  The results are below. The percentages are the probability of making a wrong decision. In the first three lines of the table (3.0 ΔE to 3.75 ΔE), this is the chance that a good job will be called bad. In the next three lines of the table, this is the chance that a bad job will be called good.

Actual 68th N = 3 N = 10 N = 30 N = 100 N = 300
3.0 ΔE 37.0% 4.0% 0.6% 0.0% 0.0%
3.5 ΔE 54.6% 18.1% 12.9% 1.5% 0.0%
3.75 ΔE 61.1% 29.0% 30.2% 13.2% 4.8%
4.25 ΔE 25.9% 47.5% 29.7% 20.9% 5.1%
4.5 ΔE 21.1% 35.7% 15.7% 4.7% 0.1%
5.0 ΔE 13.1% 19.6% 2.9% 0.0% 0.0%

 

Calculation of this table is a job for an applied math guy. Interpreting the table is a job for a statistician, which is at the edge of my competence. Deciding how to use this table is beyond my pay grade. It depends on how comfortable you are with the various outcomes. If, as a printer, you are confident that your process has a 68th percentile of 3.0 ΔE or less, then 30 samples should prove that point. And if your process slips a bit to the 3.5 ΔE level, and you are cool with having one out of eight of these jobs recalled, then don’t let no one talk you into more than 30 samples. If you don’t want those jobs recalled though…

If, as a print buyer, you really have no intention of cracking down on a printer until they hit the 5 ΔE mark, then you may be content with 30 samples. But if you want to have some teeth in the contract when a printer goes over 4.5 ΔE, then you need to demand at least 100 samples.

First addendum

You will note that my answer was a little different than the previous blog post where I made minimal assumptions. If I make all the assumptions that are in this analysis, then the number of samples required (to demonstrate that 68% of the colors are within a threshold color difference) is smaller than the previous blog might  have suggested. Note that If one has a data set of color difference data, it can be transformed to relate to this archetype by dividing all the color difference values by the median of the data set. Then again, that one word (“assume“, and its derivatives) in bold print has appears on this page 22 times…

Second addendum

In the first section, I mentioned “sampling with replacement”, which means that you might sample a given product twice. Kind of a waste of time, really. Especially for small production runs, where the likelihood of duplicated effort is larger. Taken to the extreme, my conclusion was clearly absurd. Do I really need to pull 300 samples for my run of 50 units?!!?!?!

Well, no. Clearly one would sample a production run without replacement. But, in my world, a production run of 10,000 units is on the small side, so I admit to the myopic vision. For the purposes of this discussion, if the production run is over 10,000, it doesn’t matter a whole lot whether a few of the 1,200 samples are measured twice.

About the Author

John Seymour holds the title principal engineer for QuadTech, where he has been doing research in printing, color theory, and imaging since 1992. John was instrumental in the development of QuadTech’s Color Control System and AccuCam. John currently holds seventeen patents and has authored thirty technical papers. He is an expert on the Committee for Graphic Arts Technologies Standards and ISO TC 130, and currently serves on the board of the Technical Association of the Graphic Arts. He writes a blog under the pen name “John the Math Guy”, which is described as “applied math and color science with a liberal sprinkling of goofy humor.”

Prior to working with QuadTech, John worked as a scientific programmer in medical imaging, satellite imagery, electron microscopy, and spectroscopy. He holds bachelor’s degrees in mathematics and in computer science from the University of Wisconsin-Madison.

John had a hobby job as a karaoke host, going under the name “John the Revelator”, and before that his hobby job was teaching remedial math at a local university. He likes to think that he is gifted at “edutainment.” John teaches a color science class for QuadTech and has traveled as far as South Africa, England, Germany, and Hong Kong on speaking engagements.

Visit John’s Blog, John, the Math Guy – Applied math and color science with a liberal sprinkling of goofy humor, at http://johnthemathguy.blogspot.com/

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How many samples do I need?

by John Seymour, John the Math Guy

Simple question:  If I am sampling a production run to verify tolerances, how many production pieces do I need to sample?

It’s an easily stated question, and also an important one. Millions of dollars may be at stake if a production run has to be scrapped or if the customer has to be reimbursed for a run that was out of tolerance (so-called “makegoods”). On the other side, the manufacturer may need to spend tens or hundreds of thousands of dollars on equipment to perform inspection.

For certain manufactured goods, 100% compliance is required. The cost of delivering a bad Mercedes, pharmaceutical, or lottery ticket is very high, so pretty much every finished good has to be inspected. But in most cases, the cost of a few bad goods is not that great. If a few cereal boxes burst because of a bad glue seal, or if a page in the Color Scientist Monthly is smeared, but how bad can that be?  It’s a calculated risk of product waste versus inspection cost.

Now if the foldout featuring the PlayColor of the Month is smeared, that’s another story.

Heineken

I volunteer to do 100% inspection of the taste of these products!

In the world I live in – printing – contracts often stipulate a percentage of product that must be within a given tolerance. This is reflected in the ISO standards. I have pointed out previously thatISO 12647-2 requires 68% of the color control patches within a run be within a specified tolerance. The thought is, if we get 68% of the samples within a “pretty good” tolerance, then 95% will be within a “kinda good” tolerance. All that bell curve kinda stuff.

A press run may have tens of thousands or even millions of impressions. Clearly you don’t need to sample all of the control patches in the press run in order to establish the 68%, but how many samples are needed to get a good guess?

Maybe three samples?

Keeping things simple, let’s assume that I pull three samples from the run, and measure those. There are four possible outcomes: all three might be in compliance, two of the three might be in compliance, only one may be in compliance, or none of the samples might be in compliance. I’m going to cheat just a tiny bit, and pretend that if two or more of the three pass, then I am in compliance. That’s 66.7% versus 68%. It’s an example. Ok?

I am also going to assume that random sampling is done, or more accurately, that the sampling is done in such a way that the variations in the samples are independent. Note that pulling three samples in a row almost certainly violates this. Sampling at the end of each batch, roll, or work shift probably also violates this. And at the very least, the samples must be staggered through the run.

Under those assumptions, we can start looking at the likelihood of different outcomes. The table below shows the eight possible outcomes, and the ultimate diagnosis of the production run.

Sample 1 Sample 2 Sample 3 Run diagnosis Probability
Not so good Not so good Not so good Fail (1-p)3
Not so good Not so good Good Fail p (1-p)2
Not so good Good Not so good Fail p (1-p)2
Not so good Good Good Pass p2 (1-p)
Good Not so good Not so good Fail p (1-p)2
Good Not so good Good Pass p2 (1-p)
Good Good Not so good Pass p2 (1-p)
Good Good Good Pass p3

 

Four of the possibilities show that the run was passed, and four show it failing, but this is not to say that there is a 50% chance of passing. The possible outcomes are not equally likely. It depends on the probability that any particular sample is good. If, for example, the production run were to be overwhelmingly in compliance (as one would hope), the probability that all four samples would come up good is very high.

The right-most column helps us quantify this. If the probability of pulling a good sample is p, then the probability of pulling three good samples is p3. From this, we can quantify the likelihood that we will get at least the requisite two good samples out of three to qualify the production run as good.

Probability of ok-ing the run based on three samples = p2 (1-p) + p2 (1-p) + p2 (1-p) + p3

Things start going bad

What could possibly go wrong?  We have proper random sampling, and we have a very official looking formula.

Actually, two different things could go wrong. First off, the production run might be perfectly good, but, by luck of the draw, two or three bad samples were drawn. I’m pretty sure the manufacturer wouldn’t like that.

The other thing that could go wrong is that the production run was actually out of tolerance (more than one-third of the pieces were bad), but this time Lady Tyche (the Goddess of Chance) favored the manufacturer. The buyer probably wouldn’t like that.

From the formula above, we can plot the outcomes as a function of the true percentage that were in tolerance. The plot conveniently shows the four possibilities: correctly rejected, incorrectly accepted, correctly accepted, and incorrectly accepted.

Accept and reject from three samples

Outcomes when 3 samples are used to test for conformance

Looking at the plot, we can see if 40% of the widgets in the whole run were in tolerance, then there is a 35.2% chance that the job will be given the thumbs up, and consequently a 64,8% chance of being given the thumbs down as it should. The manufacturers who are substandard will be happy that they still have a fighting chance if the right samples are pulled for testing. This of course is liable to be a bit disconcerting for the folks that buy these products.

But, the good manufacturers will bemoan the fact that even when they do a stellar job of getting 80% of the widgets widgetting properly, there is still a chance of more than 10% that the job will be kicked out.

Just in case you were wondering, the area of the red (representing incorrect decisions) is 22.84%. That seems like a pretty good way to quantify the efficacy of deciding about the run based on three samples.

How about 30 samples?

Three samples does sound a little skimpy — even for a lazy guy like me. How about 30? The Seymourgraph for 30 samples is shown below. It does look quite a bit better… not quite so much of the bad decision making, especially when it comes to wrongly accepting lousy jobs. Remember the manufacturer who got away with shipping lots that were only 40% in tolerance one in three times? If he is required to sample 30 products to test for compliance, all of a sudden his chance of getting away with this drops way down to 0.3%. Justice has been served!

Accept and reject from thirty samples

Outcomes when 30 samples are used to test for conformance

And at the other end, the stellar manufacturer who is producing 80% of the products in tolerance now has only a 2.6% chance of being unfairly accused of shoddy merchandise. That’s better, but if I were a stellar manufacturer, I would prefer not to get called out on the carpet once out of 40 jobs. I would look into doing more sampling so I could demonstrate my prowess.

The area of the red curve is now 6.95%, by the way. I’m not real sure what that means. It kinda means that the mistake rate is about 7%, but you gotta be careful. The mistake rate for a particular factory depends on the percentage that are produced to within a tolerance. This 7% mistake rate has to do with the mistake rate for pulling 30 samples over all possible factories.

I am having a hard time getting my head around that, but it still strikes me that this is a decent way to measure the efficacy of pulling 30 samples.

How about 300 samples?

So… thirty samples feels like a lot of samples, especially for a lazy guy like me. I guess if it was part of my job, I could deal with it. But as we saw in the last section, it’s probably not quite enough. Misdiagnosing the run 7% of the time sounds a bit harsh.

Let’s take it up a notch to 300 samples. The graph, shown below, looks pretty decent. The mis-attributions occur only between about 59% and 72%. One could make the case that, if the condition of the production facility is cutting it that close, then it might not be so bad for them to be called out on the carpet once in a while.

Accept and reject from three hundred samples

Outcomes when 300 samples are used to test for conformance

Remember looking at the area of the red part of the graph… the rate of mis-attributions?  The area was 22.84% when we took 3 samples. It went down to 6.95% with 30 samples. With 300 samples, the mis-attribution rate goes down to 2.17%.

The astute reader may have noticed that each factor of ten increase in the number of samples will decrease the mis-attribution error by a factor of three. In general, one would expect that the mis-attribution rate drops by square root of the number of samples. Multiplying the sampling rate by ten will decrease the mis-attribution rate by the square root of ten, which is about 3.16.

If our goal is to bring the mis-attribution rate down to 1%, we would need to pull about 1,200 samples. While 300 samples is beyond my attention span, 1,200 samples is way beyond my attention span. Someplace in there, the factory needs to consider investing in some automated inspection equipment.

The Squishy Answer

So, how many samples do we need?

That’s kind of a personal question… personal in that it requires a bit more knowledge. If the production plant is pretty darn lousy –let’s say only 20% of the product within tolerance — then you don’t need many samples to establish the foregone conclusion. Probably more than 3 samples, but the writing is on the wall before 30 samples have been tested. Similarly, if the plant is stellar, and produces product that is in tolerance 99% of the time, then you won’t need a whole lot of samples to statistically prove that at least 68% are within tolerance.

Then again, if you actually knew that the plant was producing 20% or 99% of the product in tolerance, then you wouldn’t need to do any sampling, anyway. The only reason we are doing sampling is because we don’t know.

The question gets a little squishy as you get close to the requested percentage. If your plant is consistently producing 68.1% of the product in tolerance, you would need to do a great deal of sampling to prove to a statistician that the plant was actually meeting the 68% in tolerance quota.

So… you kinda have to consider all possibilities. Go in without any expectations about the goodness of the production plant. Assume that the actual compliance rate could be anything.

The Moral of the Story

If I start with the assumption that the production run could produce anywhere between 0% and 100% of the product in tolerance, and that each of these is equally likely, then if I take around 1,200 samples, I have about a 99% chance of correctly determining if 68% of the run is in tolerance.

If you find yourself balking at that amount of hand checking, then it’s high time you looked into some automated testing.

About the Author

John Seymour holds the title principal engineer for QuadTech, where he has been doing research in printing, color theory, and imaging since 1992. John was instrumental in the development of QuadTech’s Color Control System and AccuCam. John currently holds seventeen patents and has authored thirty technical papers. He is an expert on the Committee for Graphic Arts Technologies Standards and ISO TC 130, and currently serves on the board of the Technical Association of the Graphic Arts. He writes a blog under the pen name “John the Math Guy”, which is described as “applied math and color science with a liberal sprinkling of goofy humor.”

Prior to working with QuadTech, John worked as a scientific programmer in medical imaging, satellite imagery, electron microscopy, and spectroscopy. He holds bachelor’s degrees in mathematics and in computer science from the University of Wisconsin-Madison.

John had a hobby job as a karaoke host, going under the name “John the Revelator”, and before that his hobby job was teaching remedial math at a local university. He likes to think that he is gifted at “edutainment.” John teaches a color science class for QuadTech and has traveled as far as South Africa, England, Germany, and Hong Kong on speaking engagements.

Visit John’s Blog, John, the Math Guy – Applied math and color science with a liberal sprinkling of goofy humor, at http://johnthemathguy.blogspot.com/

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Navigating the Way to Structural Packaging Innovation

ANTHEM-LOGO-600

By Tim James, Senior Director of Structural Packaging and Innovation, Anthem

In Greek mythology, Scylla is a six-headed sea monster that eats sailors who sail too close. Charybdis is a whirlpool capable of swallowing your ship whole. The only problem is, you have to sail right between Scylla and Charybdis to discover what’s beyond.

Getting to a new place with your packaging can be a lot like that. On one side, if your new package doesn’t retain the identity and appeal of the old one – plus meaningful advantages – unhappy consumers can bite you. On the other side, if manufacturers can’t or won’t retool to produce it, your new package could be sunk before it even reaches the shelf.

Some brands try to chart a safe course, avoiding any risk. They’re unlikely
to get any further than they’ve already come. Other brands brave the journey of structural innovation, only to be done in by entrenched consumers or manufacturers.

Heroic brands find a way through to the future.

MAKING FLEXIBILITY AN ADVANTAGE
The most notable innovation in packaging over the last ten years has
been the rise of flexible solutions across a wide variety of product categories. Flexible pouches can lower material requirements and reduce energy, printing, transportation, warehousing and other costs. They can shrink
the brand’s environmental footprint. And they can help brands go to
market faster.

But what happens to the brand equity you’ve built into a rigid bottle – that iconic shape, its familiar usability, the feeling that it belongs there, on the store shelf and in the shopper’s home?

The label alone should never be your brand’s sole differentiator. When a packaging innovation takes away a familiar shape for your brand, it has to give something back that engages your consumers even more than before – an instantly recognizable advantage that’s desirable and proprietary.

A classic example of this is baby food. When moms saw the familiar glass jar replaced by flexible pouches in the store, they immediately realized the advantages of a package that’s safer, easier to carry, less messy, and even more enjoyable for baby. For the purpose of feeding babies, the new flexible package was inherently more attractive to shoppers than the old glass jar.

But what about another product category, where the advantages of flexible packaging may not be so obvious? How do you bring a radical change to the shelf without getting bitten by shoppers who identify strongly with your old package?

BRINGING CONSUMERS INTO THE DESIGN PROCESS
Ideally, shoppers should recognize your brand in-store, immediately understand the functional benefits of your new package, try it, and never miss the old bottle when they realize how much better your new pouch fits their lives. To make sure that happens, you need to get actual consumers involved as early as possible in the product development process.

For example, we recently undertook a design exercise for bringing flexible packaging to hand soaps, shower gels and other personal care products. The goal was to design a stand-up pouch that would benefit a well-known brand by lowering material and production costs while enabling easier recyclability. However, it could only succeed by appealing to consumers.

We had to make the package easier to use while giving it a form that
is instantly recognizable both for its beauty and functional advantages – enabling it to become the next iconic expression of the brand’s values and equities.

We sketched many pouch concepts – a handle for hanging, a shower-stall suction cup, a headstand pouch that dispenses from the base, a “bag in
a bottle” concept with a rigid shell that accepts refill pouches, and many more. We also sketched many closures – snap-off, twist-off, pull-out, flip-up, and others. To evaluate these ideas, we turned to actual users as early as possible in the design process.

That meant assembling pouches, 3D-printing closures and other parts, and getting fully functional prototypes into the hands of consumer/testers. Within two or three weeks of the project kickoff, we already had real-world consumers evaluating our first five working prototypes.

FAILING FASTER AND BETTER
When you observe consumers using prototypes the same way they’d use the product at home, you can quickly see where you’re missing the mark, develop new prototypes, and test again. You can identify risks and chart a better course. Rinse and repeat until you have a flexible package people are excited about using, with no reservations.

For example, we developed a prototype that seemed very elegant, with a simple and beautiful twist-off closure. Expectations ran high, until a tester pointed out something that should have been obvious: “The cap is going to get dropped in the shower and go down the drain.”

Far from disappointed, the team went eagerly back to their sketches, CAD renderings and 3D printers to create an elegant, integrated closure that is easier to use. The whole point of this iterative design/prototype/test process is to fail quickly and fail as often as necessary – so you can keep moving on toward the one design everyone loves to use and wants to take home.

Consumers can also help you understand how to reveal brand meaning through packaging structure. For example, while testing the “bag-in-a-bottle” prototype with its
rigid holder, one woman remarked that she wouldn’t be particularly interested – but her husband would love something like that. He could just throw it in his bag and take it to the gym without worrying about it. Plus it had a masculine look and feel.

Through that tester’s observations, a design that had been created as a functional exercise revealed its true meaning in its inherent appeal for men.

GETTING MANUFACTURERS ONBOARD
Engaging consumers flawlessly is only half the challenge. You also need to bring manufacturers a package design they can actually produce – without inordinate capital expense or disruption to their current production lines.

Just as important as iterative prototyping and consumer testing, you should be auditing manufacturers. By speaking with OEMs and analyzing production facilities, your goal
is to learn all the details of the existing production setup, then determine what new investments and changes will be required to manufacture your proposed package.

Some projects may require the new package to be produced on existing manufacturing lines, with minimal modification. Such a limitation can be challenging, but it doesn’t mean you can’t innovate. Instead, it’s something you need to know up-front in order to avoid taking your design down impractical paths.

Whatever the project’s constraints, you need to continually validate each design iteration against what’s practical to manufacture.

SETTING SAIL
Don’t be afraid of your customers. They are not a six-headed monster. Let them help you. Don’t be afraid of your manufacturer. They’re not an unalterable whirlpool. Get in there and see if you can change the manufacturing flow just enough to make a difference for your brand.

Brand change always involves risk, but the bigger risk is not changing. To discover your structural packaging innovation, with confidence, get everyone on board and set sail.

Tim_James_2013About the Author:
Tim James is Senior Director of Structural Packaging and Innovation, at Anthem, a global creative agency that actively connects brands with consumers by amplifying desirability to drive brand performance. Tim has been working in the product and industrial design industry for the last 12 years in London, Oslo, and New York. He is an honors graduate in product design from Ravensbourne College of Design and Communication in Kent, England. http://www.anthemww.com

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Doctor Blade Installation: Correct Angle and Pressure are Needed for Consistent Performance

FlexoConcepts-logo

The anilox roll and doctor blades are designed to work together to deliver a precise amount of ink to the plate.  It is important to take time during a doctor blade installation in order to ensure print quality.  A doctor blade that’s installed correctly will have uniform, balanced contact with the anilox roll and remove ink consistently across its surface.  Blade positioning, orientation, angle and pressure will affect the delivery of a precise amount of ink to the plate, and proper installation will give the printer control over consistent, repeatable print quality.

Doctor Blade Installation

Positioning and Orientation

It is essential that the metering and containment blades be positioned correctly when they are installed.  Depending on the rotation of the anilox roll, the metering blade could be positioned on the top or the bottom of the chamber.  Keep in mind that the metering blade is always the last blade to contact the roll before the ink transfers to the plate.  The containment blade is installed in the opposite location.  If the two blades are installed in reverse, the metering blade will not achieve the appropriate point of contact with the roll and remove the correct amount of ink before transfer.  It is important to remember that the bevel tip should point away from the roll or towards the chamber to prevent streaking.

TruPoint_Orange_Contact_AngleAngle

The angle at which the blade comes into contact with the anilox roll is also crucial to proper doctor blade installation and optimum blade performance.  Ideally, the contact angle should be 30° tangent to the anilox roll

circumference.  In reverse angle and chamber blade applications, the doctor blade angle should be between 28° and 32°.  If the blade angle drops below 28°, a larger part of the blade’s edge will come into contact with the roll.  When this happens, the contact area is too big to meter effectively and the blade may allow ink to pass underneath or “hydroplane” at high speeds.  If the angle exceeds 32°, it will result in faster wear on the blade.

Pressure

When a doctor blade chamber is properly aligned, light pressure between the anilox roll and doctor blade is all that’s needed to produce a clean wiping action.  The recommended pressure is 25 to 30 lbs. or 1.7 to 2 bars.  Anything more than that will lead to a deterioration in print quality, wasted ink and substrate, and accelerated blade and anilox wear.

A good way to tell if you’re using the correct amount of doctor blade pressure is to look at the roll once it’s inked.  Before increasing pressure, the anilox roll will appear glossy.  This is a sign that too  much ink is remaining on the surface.  Pressure should be increased gradually until a satin finish appears on the surface of the roll.  A satin finish is a good indication that the correct amount of pressure has been achieved and the doctor blade is effectively shearing the excess ink from the roll.  If pressure is increased beyond this point, the doctor blade edge will bend and hydroplane.  The roll will again begin to look glossy because it is flooded with too much ink.

The doctor blade plays a key role in the performance of the anilox roll and the printer’s control over print quality.  Take the time to double-check blade positioning, orientation, pressure and angle during doctor blade installation to guarantee that the anilox roll delivers the precise volume of ink for which it was designed.

About Flexo Concepts

Headquartered in Plymouth, Massachusetts, Flexo Concepts manufactures TruPoint doctor blades, the TruPoint QuikWash™ System and wash-up blades, and MicroClean™ dry media anilox cleaning systems.  All products are designed to improve print quality and reduce operational costs for flexographic and offset printers.  Flexo Concepts maintains distribution locations in North America, South America, Europe, Asia, Africa and Australia.  For more information about the company and its products visit www.flexoconcepts.com.

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Filed under Corrugated, Doctor Blades, Narrow Web, Printing

The Yellow Brick Road to Continuous Improvement: “Lions and tigers and bears, oh my!”

sgk_logo_pms

by John Lawrence, Business Development Director, Europe at SGK and member of SGK’s Continuous Improvement Practice

Many will remember the rhythmical chanting of Dorothy Gale (played by Judy Garland) and her unusual counterparts in the in 1939 version of The Wizard of Oz. For those of you fortunate enough to have experienced the film, whether as a child or through your own children, Dorothy is swept away to the magical land of Oz by a tornado and embarks on a journey to find the Wizard who can help get her home.

This classic film has featured prominently in my household over the last few months as my 4-year-old stares in wonder at the challenges and barriers placed in Dorothy’s way as she follows the “yellow brick road.” It got me thinking about process and the supply chain within the graphics industry. Dorothy asks a fair question that applies to our industry, “Is there a place where there isn’t any trouble? Do you suppose there is such a place, Toto?”

In the graphics industry, we all strive to find this place over the rainbow and similarly we also fear the lions, tigers and bears on the journey. Of course, the goal is to reduce our chances of meeting such characters and obstacles, but the real question is what we can learn from the ones we do come across. In Dorothy’s case her encounter with the Cowardly Lion leads not only to friendship and an alliance to achieve her ultimate goal of going home, but also to an understanding that he too has an objective to fulfill.

The yellow brick road is a metaphor for a prescribed journey or process to a destination. Brick-by-brick Dorothy gets closer to her destination with the help of her friends. She follows a prescribed and well-travelled route with no intention of ever leaving it. But on the other hand, she doesn’t look close enough at the solution, which she and her friends already possess. Glinda (the Good Witch of the North) had already revealed that Dorothy’s Ruby Slippers were magical – just not revealing their specific power.

Continuous Improvement is about listening, learning and implementing new ways of working to improve brand performance. Ultimately it is about reflecting on a process that delivers incremental and transformational change. In The Wizard of Oz, a transformational change is achieved by two characters: the Wizard himself – not because he had any magical powers – but simply because he was able to identify how Dorothy, the Cowardly Lion, the Scarecrow and the Tin Man could take greater ownership of their challenges. The second transformational character was Glinda who had the solution all along, it was just that no one had asked her or, more importantly, no one had listened.

In the world of graphics supply chains it is often a belief that it is someone else’s responsibility to solve a perceived challenge or prevent it from occurring. But in reality all stakeholders within a supply chain should continually be seeking ways to improve their own performance.

As consultants we examine more strategic elements that include deciding how to increase the value of the delivery process output to the customer and how much flexibility is valuable in the process to meet changing needs. Our goal however can only be achieved through these stakeholders appreciating their critical role and ownership of the solution.

Granted that the film itself would have been very short if the characters had identified “value add” vs. “non-value add activity” too early on in the story, but they would have achieved their objectives far quicker and more effectively.

In the real world we must also determine the best avenues of support by stakeholders in the supply chain, technology, resource and agency partners. We understand that by developing the most efficient workflow a business will benefit from:

  • Increased customer loyalty and market share
  • Achieve growth in sales and earnings
  • Sustain competitive advantages
  • Improve stakeholder value
  • Reduce risk

In short, evaluation and implementation of better ways of working drives quality, delivery and a key element in the current environment: cost.

SGK’s Continuous Improvement practice recently worked with a global FMCG organisation that was faced with the common challenges of an outdated graphics design workflow, as well as global markets challenged by a lack of resources. They sought improvements to cost, service and agility of design execution across the graphics supply chain. This business recognised the need for change and has since evolved its model – by listening to employees – and implementing new ways of working that have delivered multi-million pound (£) savings, reduced risk of product recall, quality consistency in operations across large and small markets, increased delivery capacity, and importantly, wide ranging acknowledgment of the improvement and efficiencies in the working lives of key brand owner stakeholders. This organisation’s graphics “yellow brick road” was a far more pleasant journey through the collaborative approach to improvement and a sustainable approach to implementation.

Why evolving through Continuous Improvement is a must.
Inefficiency is common as organisations grow over time. As companies change additional layers of stakeholders can lead to decentralised and ambiguous accountability of process. What should be a relatively straightforward, streamlined workflow becomes bogged down in a complex and time-consuming web of competing agendas, obsolete policies, and siloed communications.

Just as in The Wizard of Oz, self-inflicted barriers within brand environments can make for a long road to your destination. However there are tools and practices that will improve the quality of your branded assets, allow you to go to market faster, at a lower cost and with more efficient use of resources that will help cut out non-value-added time and energy from your branded material supply chains.

At SGK, we don’t claim to wear ruby slippers, but we do recognise from experience that stakeholders within your business do. Given the opportunity to tap them together, change can happen and the results truly can be magical.

Learn more about how to achieve better marketing supply chain performance from SGK’s Continuous Improvement Practice.

John Lawrence Head ShotAbout the Author:
John Lawrence leads SGK’s Continuous Improvement Practice (CIP) in Europe, helping brands build strategies that deliver optimized graphic processes, technology and roles to accelerate brand performance. John has worked in both agency and brand positions over his career and is passionate about devising and delivering solutions for his clients to help develop and grow their brands. http://www.sgkinc.com

john.lawrence@sgkinc.com

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Filed under Branding, Printing

Field tests with print samples using XRGA and Techkon instruments

techkon-logo

by Allison Lakacha, Techkon

A previous blog post (“Consistent Color Measurement”) discussed instrument settings and procedures to ensure consistent color measurement throughout the supply chain. Once these are all in place, how well will instruments agree?All spectrophotometer manufacturers quote “repeatability” as one of their specs. This is the degree to which an instrument agrees with itself when making measurements of the same spot on the same sample, over a short period of time. Instrument repeatability is a small number, often less than 0.1 ΔE*ab. This number is misleading, since it is by far not the limiting factor. And it sets up an expectation that different instruments should agree this closely.There have been a number of studies by researchers where different instruments have been compared. John Seymour presented a paper at TAGA 2013 where he summarized the results of seven studies. Quoting from his paper:It’s difficult to distill these studies down to a single number, but it is fair to say that 1.0 ΔE*ab is a reasonable estimate for average disagreement, and that seeing disagreement greater than 2.0 ΔE*ab is not uncommon.

Our Own Tests With 4 Instrument Models

To see where things stand in field use, we measured a range of printed colors. Both spot and process colors were included. Each color was measured using four spectrophotometers:

  • Three X-Rite models – 939, SpectroEye, and eXact
  • One Techkon SpectroDens

All instruments were within the certification from their manufacturer. The three X-Rite instruments are all XRGA certified. The fourth instrument is a Techkon SpectroDens. In each case, the print was measured at approximately the same spot.

The goal was to try and answer the following questions:

  1. What is the typical variation we can expect when measuring printed colors with different instruments ?
  2. How does the Techkon SpectroDENS compare with X-Rite’s XRGA certified instruments ?

TABLE 1: Color values measured on 4 different instruments using M0 condition. Samples had little or no fluorescence.

colorvalues_table_final

FIGURE 1: Blue bars show inter-instrument agreement between Techkon SpectroDENS and three different X-Rite models. Orange bars show inter-instrument agreement between three different XRGA certified X-Rite models in field use.

interinstrument_final

We reduced the measurement data to color differences in ΔE00 between 6 different pairs of instruments. Three of these pairs were between Techkon SpectroDENS and X-Rite models. The other three pairs were between the X-Rite models themselves. In this exercise, average color differences in ΔE00 ranging from 0.24 to 0.55 were found when considering all 16 colors. The maximum color difference in ΔE00 for any color between any pair of instruments was 1.06. This represents what can be expected in commercial practice for certified and well-maintained instruments. The variation between instruments is within expected tolerance for printing of brand colors (color difference in ΔE00 of 2.0 to 3.0). It is worthwhile to note that the Techkon SpectroDENS agrees with the X-Rite units almost as well as the X-Rite instruments agree amongst themselves.

What about M1?
All previous measurements were under M0 mode, and on samples with little or no fluorescence. What about M1 measurements on fluorescent samples? Dave Wyble et al. measured fluorescent reference tiles with seven M1 instruments from three instrument manufacturers, including Techkon. These reference tiles were also measured by the Canadian national standards lab, NRC. The results showed a broader dispersion among the eight instruments in M1 mode for the most highly fluorescent samples than we would see in M0 measurement condition. This paper titled “”Investigation of the Implementation Aspects of the M1 Condition” was presented at 2015 TAGA by Wyble and Seymour and will be published soon. We hope to further explore the topic of inter-instrument agreement in the presence of fluorescence and UV light in a separate post.

What is XRGA?
When X-Rite joined with GretagMacbeth in 2006, they had to deal with a unique problem. They now needed to harmonize the measurements from instruments that had been designed and manufactured by different companies on different continents. The acronym “XRGA” was coined to brand this effort of reconciling measurements to a newly adopted common reference point. It is not a universal standard, but an internal reference point used by X-Rite to calibrate different instrument models in adherence to standards (ISO 13655, in particular). Other instruments developed according to ISO standards that are calibrated according to best practice manufacturing processes can be expected to agree with each other as well as XRGA instruments. More about XRGA here.

In Conclusion

  1. Inter-instrument agreement is important where production samples are compared to reference data set that was obtained from a different device. If the standard and sample can be measured on the same device, there is normally no need to be concerned about inter-instrument agreement.
  2. We found that print samples measured on different instrument models can typically be expected to vary by average ΔE00 of 0.5 for M0. With fluorescent samples, the M1 measurement condition shows somewhat larger variations according to a recent study by Wyble and Seymour.
  3. From our data collected using field instruments in normal pressroom use conditions, we observed that Techkon SpectroDENS agrees with the X-Rite units about as well as X-Rite instruments agree amongst themselves.

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Filed under Color Management, Printing

How to Modernize Your Packaging Graphics Management Process From Start To Finish

Paul_Haggett

By Bill Farrisee, VP, Managing Director, Latin America, Schawk

Executive Summary
As technology continues to change, opening up more possibilities, but becoming more specialized and complex at the same time, marketers and brand owners can no longer afford to maintain the status quo when it comes to protecting their brand equity.

But by continuing to subscribe to the myth that there’s ‘no cost’ for prepress, consumer products companies worldwide are jeopardizing the integrity of their brand’s assets. And this, in turn, compromises their packaging’s ability to communicate as powerfully as it can to consumers.

This paper uncovers the high consequences of the ‘no-cost’ myth and explains what marketers and brand owners can do now to protect their prepress and optimize their packaging graphics management process from start to finish.


 

There’s no denying it, the prospect of “no cost” or “free” services can be extremely enticing. But when it comes to protecting brand standards and the integrity of your products’ printed packaging, marketers and brand owners must fully consider how the “free prepress” myth could impact brand integrity and your bottom line.

By believing that there is no cost for prepress, consumer products companies worldwide are missing out on big opportunities. This commodity purchasing strategy, which was intended to save money is actually costing more in the long run. And it’s preventing marketers and brand owners from modernizing their packaging graphics management process.

The reality is prepress is never free. You will be paying for it no matter what a vendor tells you. In fact, if you’re a marketer or purchasing agent and you hear a vendor say, “There’s no cost for prepress work,” you should run away! A statement like this is untrue because the cost is simply bundled into the cost of printing. You’re getting a low cost on a poorly executed package. Just what you paid for.

With over 60 years of helping the world’s most loved brands prepare their products for store shelves, we’ve observed problematic assumptions about the cost of prepress, which lead to big problems for marketers and the brands they manage. You may be familiar with these issues, some of which include:

  • Package printing expertise is not seen as a requirement.
  • Marketers’ lack of control throughout the package printing process.
  • Lower standards create lower expectations.
  • Revisions are needed and standards are set by accident.
  • The best price may not deliver consistent quality.

These challenges, common to many large consumer products companies, present serious consequences to the company’s package printing and to the brand as a whole. Let’s examine some of the effects of subscribing to the “no cost” for prepress myth.

“Bundled fees” mean marketers pay more.
This might not be much of a problem if a package prints only once and only at one printer. But what if that package prints twice or three times or 10 times? Then the costs of prepress are being paid for as part of the packaging price each time that package prints. So when costs are included in the price of the packaging, this often means the marketer is not saving money at all. In fact, they’re paying many times over unnecessarily for prepress with potentially compromised quality each time because a benchmark standard was never properly established.

Different printers, different results.
Consider what happens when package printing is moved from one supplier to another. The original printer probably won’t be happy that they’ve lost business to a competitor. How likely is it that they will send their prepress work to another printer? If anything is sent, it’s most likely the original artwork that was sent from their client – not the actual artwork that was used to print the package. Remember: the “final artwork” was modified to fit the particular situation at the original printer. The new printer receives the artwork and starts the entire prepress process over again. Different printer, different press, different specifications, different results.

Who’s got the final artwork?
The design and artwork that marketing approved from the designers will eventually be passed to purchasing and on to printers and the printer’s prepress suppliers (either internal or external). Suddenly marketing needs their current artwork. Where is it? Who has it? It isn’t what the design firm produced because that was changed by Printer A. It isn’t Printer A’s prepress work because that was passed to Printer B when Printer A lost the business. And it isn’t at Printer B because they had to modify the design for their conditions, which are different form Printer A. The hard truth is that nobody has the final artwork that actually produced the packaging in the market! Or, just as bad, there are multiple versions of the artwork, depending on how many suppliers were involved. Either way, you’re back at square one.

As you can see, the “no-cost” myth actually has very high cost consequences. And these costs far outweigh the perceived benefits of saving some money in the short-term. In order to optimize your packaging graphics management process and take control of the quality of your branded materials, here are four things you must do:

  1. Maintain design integrity.
    Marketing departments already have budgets for the design work that is required for developing packaging graphics and images. It’s a natural extension of the design phase to assure that the design is executed all the way to the consumer the way it was intended to by the designers. It’s the details that are responsible for maintaining the integrity of the design so that the package communicates as powerfully as it can to consumers.
  1. Develop a realistic budget.
    In order for marketing to take over the complete management of the graphics reproduction for its packages, marketers must develop a budget that includes all the work that is necessary between the time the design firm is developing concepts to the time the job is printed. Once you acknowledge that prepress is never free, this becomes easier. Remember, prepress may be communicated to you as “no cost” and it may appear to be the lowest cost, but neither is true.
  1. Involve the right groups.
    A system that includes the CPG company or retailer, the designers and a packaging prepress company is the best solution. By bringing the three operations together, the quality of the brand image can be developed and maintained throughout the process. Each operation can have various responsibilities but the team approach has proven successful for many consumer products companies in the United States, Canada and Asia, as well as Latin America, where a few leading CPG companies have already adopted this process.
  1. Let the experts help.
    An experienced and specialized packaging prepress company brings unique value to the supply chain. The right packaging prepress company works with all the major packaging printing methods and packaging materials. It understands the print process limitations and can bring that information for the team during the design process so that the selected design can be reproduced effectively across a wide range of packaging styles and print methods.

WHAT’S THE ADVANTAGE?
The right packaging prepress company provides a color management system that works with the designers and the printers to assure that brand graphics are reproduced properly and consistently. In addition a print management process is developed to help qualify new printers and monitor the print reproduction of existing printers. The system provides feedback to all the partners in the process to assure continuous improvement. Some of the advantages include:

Centralized graphics elements deliver efficiency
A system like this centralizes the graphic elements in one location that can manage and distribute the packaging graphics to all the partners in the supply chain. This way a consumer products company has control and has the opportunity to repurpose their graphics for various marketing needs whether it’s packaging, point-of-purchase displays, sell sheets/brochures, or web pages.

Digital asset management delivers efficiency
Digital asset management (DAM) systems are available to help consumer products companies gain better control of their packaging graphics, speed the approval process, allow for more thorough and complete communication and allow internal and external supplier access to information globally, seven days per week, 24 hours a day.

Measureable results
All this leads to improved speed to market, which drives sales and reduces costs. A recent case study shows how a major consumers products company in the U.S. was able to reduce time to market from 16 weeks to four weeks, while reducing artwork rework by 50 percent and costs by 20 percent.

These are just some of the benefits of working directly with a packaging prepress supplier and paying the right price for the best prepress services available. As opposed to paying the wrong price by believing that there is “no cost” for prepress. Utilizing a color management system will keep you from spending more than you have to, from impeding your speed to market and jeopardizing brand equity with inconsistent reproduction.

Your brand deserves the very best. Learn more about how to overcome the complex logistics and outdated practices that are impeding brand integrity and keeping consumers from experiencing your products the way they should.

Or contact a member of our team with specific inquiries.

 About the Author:
Bill_FarriseeBill Farrisee, VP, Managing Director, Latin America, at Schawk, has 28+ years of experience in the packaging and pre-media services. As founder of Schawk Latin America, Bill has 17 years of experience managing businesses in LATAM. He received his Bachelor of Science in Packaging from Rochester Institute of Technology and MBA from James Madison University. bfarrisee@schawk.com

Schawk is a global brand deployment company that produces brand assets and protects brand equities. Schawk identifies and deploys scalable solutions to address a brand’s complex production and delivery needs through proven expertise in workflow, resourcing, color management and imaging. We bring our clients’ brands to market faster, with greater accuracy, consistency and efficiency across mediums, protecting the equities that make them more desirable and profitable. Schawk is part of SGK, which is a division of Matthews International Corporation. For more information visit: http://www.schawk.com

© 2015 Matthews International Corporation. All Rights Reserved. No part of this work may be reproduced in any form without written permission from the copyright holder. Schawk is a registered trademark of Matthews International Corporation. The Schawk logo is a trademark of Matthews International Corporation. All other trademarks are the property of their respective trademark owners.

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Filed under Branding, Prepress

Standardisation of Ink Transfer for Converting Corrugated Paper Board

 PamarcoLogo-300

by David Parr, Pamarco Global Graphics, Europe

The recent release by FEFCO of a new Standard for Converting equipment further emphasises the constant demand by the corrugated industry for consistent print quality, regardless of the press equipment being used. By categorising the key elements of the printing process, such as “Colour variation”, “Ink Consumption”, “Ink system cleanliness after wash-up”, printers, Press OEM and suppliers, can now all work to a common defined standard for converting corrugated paper. This will help to ensure their products are correctly specified and toleranced, in order to meet the specific targets of each of their clients.

To document this standard, the FEFCO team, collected and analysed considerable amounts of data, with a fundamental part of the printing section being to understand and quantify the process of Ink transfer through the printing system. In order do this, it is first important to define the term “Ink Transfer”. Within the corrugated converting system, “Ink Transfer” can be defined as “the weight of ink applied to the board, every print repeat”. In relative terms, it can be quantified by measuring how much ink is at the start of the process, specifically, the quantity of ink carried by the anilox roll, in relation to the quantity of ink at the end of the process, essentially, the amount of ink on the surface of the paper board. By defining and measuring the quantity of Ink as an Ink Film Thickness (IFT) in microns (um), it is possible to calculate the relative Ink transfer through the flexo printing process using the simple calculation:

Relative Ink Transfer in Flexo =

% IFT = IFT on Paper board x 100%
IFT on Anilox

FEFCO Standard calculation for Ink Transfer

Why is understanding Ink transfer important? Taking a look at the causes of common defects in flexo printing, will quickly answer this question, with the majority of defects such as Dot gain, dirty print, skip out, mottling, pin-holing, to name a few, being caused by having too much or too little ink, being transferred through the printing system. This leads to variations in print quality from press to press and from job to job. These are the major hurdles to achieving right-first-time graphics and consistent printed box quality. To eliminate these defects is a constant batttle for convertors, meaning that incorrect Ink transfer can frequently be the direct cause of delays with press set-up, increased downtime, product reject & waste and increased consumable costs. For high quality, cost conscious printers, Ink Transfer matters a lot!

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Study of Ink Transfer: In a recent project to study Ink Transfer in corrugated printing, one of several sponsored by Pamarco Global Graphics, industry specialist Wilbert Streefland, organised a series of tests on the Bobst Masterflex press, located at a DS Smith plant in Germany. By installation of 2 calibrated Pamarco Eflo anilox rolls into the chambered inking systems, the target was to measure Ink transfer through the converting process and to study the changes in Ink transfer in relation to the common variables of corrugated flexo printing. The key variables tested were 1) Press speed, 2) Paper Board type & quality, 3) Ink density, 4) Water addition to ink 5) Single colour & Wet-on-wet, 6) Full & half tone plates and 7) Anilox specification & cell profile.

Test variables: Range (Supplier)
Press speed: 3500 & 7000 Sheets per hr (Bobst Masterflex HD)
Paper board type
& quality:
Uncoated White top Kraft & Semi-Coated (Not specified)
Ink density: Low density & High density (Flint)
Water addition
to Ink:
0%, 10% & 20% water concentrations
Single colour
& Wet-on-wet:
Full tone magenta & cyan and half tone black plates (Flint)
Anilox specifications
& type:
Screens, 100, 160 & 320 l/cm, Ink Film thicknes 5 & 10 um,   EFlo, 75 degress extended cells (Pamarco), Hexagon, 60 degree (Bobst press rolls)

 

Weighing the ink loss after each print repeat: One of the unique feature of the trial, was the method used to measure ink transfer. By installation of a precision weigh scale under the ink bucket on each of the print units, and linking with a press sensor to trigger the ink weight measurement with every sheet that passes through the print station, it was possible to accurately measure the ink loss with every sheet of board printed. In a series of 7 different trials, using over 10,000 sheets of board, at print speeds of up to 7000 sheets per hour, the data collected and analysed exceeded 60,000 individual weight measurements.

By measuring the exact Ink film thickness of the anilox at the start of the process and by knowing how much ink was deposited on each sheet of board, it was possible to calculate the exact quantity of ink transferred through the process. Hence by monitoring the variations in relative ink transfer with every changing variable, it was possible to determine, which variables had the most significant effect on ink transfer.

pamarco15-06-02

One unexpected finding of the testing was that the ink loss on one print unit was significantly higher than on other units, to a point where ink transfer had exceeded normal print conditions. This led the team to identify a leaking ink pipe, which was causing ink to be deposited to waste at a rate of several kilograms per hour and a cost of many euros per day. Besides corrupting the data until the problem was fixed, the obvious conclusion of this chance discovery was to consider that the inclusion of an inexpensive weigh scale on each press ink station, could easily identify these types of faults and lead to substantial savings in ink costs on a daily basis. “Press manufacturers take note of potential upgrades!”

What are the key factors for good ink transfer in flexo: Several of the conclusions from the trial were expected, such as the addition of water can improve ink transfer, but is offset by a substantial reduction in print density. The trials certainly proved that the addition of uncontrolled quantities of water to the ink is definitely not recommended when trying to maintain controllable levels of colour density. Other results which indicated that wet-on-wet printing gave higher ink transfer than single colour printing were less predictable and would require further testing to quantify the impact on high graphic printing.

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EFlo anilox: Based on previous tests and industry experiences, it was no surprise to learn that the EFlo anilox had the highest ink transfer in all tests, with the extended cells, proving to give optimum ink transfer under all conditions. However one of the most significant and unexpected findings from the trials was that the relative ink transfer values in all tests, always stayed within the range of 12 to 35%, a surprising low value and certainly one which leads you to ask, what happens to the rest of the ink?

Press speed & Ink density: The tests demonstrated that when using high density inks, speed variations between 3500 & 7000 sheets per hour, had very little impact on ink transfer. However when using low density or water diluted inks, which is probably more normal conditions for many board convertors, higher press speed, gave reduced the ink transfer.

The substrate is critical: One of the fundamental conclusions of the trial and one which is no surprise to many experienced corrugated printers is that minimum amount if ink that needs to be transferred to the paper substrate is dictated BY THE SUBSTRATE! This means that selection of anilox specification to suit the type of paper board remains the critical decision for printers and press OEM. When printing on un-coated board, you should select an anilox which has sufficient Ink Film Thickness (often referred to as Cell Volume), to provide enough ink for good coverage and print density on that board. This project has shown that changing ink density and press speed will only take you so far; therefore matching anilox specification to paper board remains a fundamental decision for optimising print results.

In conclusion, it is believed that these trials are the most comprehensive study of ink transfer through the flexo converting process in a practical and commercial printing environment, but as with many ground breaking projects, in answering some questions, many new questions are also raised. Certainly it is thought provoking that 65-88% of ink remains within the inking system either in the doctor blade chamber & pipework , on the surface of anilox roll. Little wonder that maintaining the cleanliness of anilox remains a major task for printers when trying to produce consistent print results”.

Better understanding of how ink is moved through the whole press system, will lead to discovering how ink transfer can be further optimised, helping to improve converting performance and reducing costs. In the meantime, having the knowledge to specify anilox and inks that give optimum ink transfer and printing performance in relation to the paper board, and maintaining the inking system in a clean condition, remains an essential part of the corrugated converting process.

David Parr, a mechanical engineer, is Technical Sales Manager for Pamarco Global Graphics, Europe. He has worked in the flexo industry since 1986 and is a specialist in anilox technology.

Wilbert Streefland, formally the Technical Development Manager at SCA is owner of Technology Coaching BV and is a specialist consultant for organisations driving developments in printing throughout the world.

For full test results and more information about Ink Transfer, please contact David Parr, Pamarco Global Graphics at david.parr@pamarcoglobal.com or Wilbert Streefland, Technology Coaching, BV at wilbert.streefland@tcbvba.be .

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Filed under Corrugated, Ink, Plate Technology

New Polymer Doctor Blades are Safe Substitutes for Steel in Flexible Packaging Applications

FlexoConcepts-logo
by Flexo Concepts

 

Blade_Safety_Accident_Free_Days_215x275If you are using steel doctor blades, you are probably well aware of the risk of serious cuts from handling the blades. Pressroom injuries can be expensive in terms of morale and accident-related expenses. Today’s next generation polymer blades combine the best of traditional plastic and steel blades and provide safe substitutes for steel in flexible packaging applications.

As steel doctor blades wear, their tips become honed through contact with the anilox roll, leaving razor-sharp edges. Press operators need to be extremely careful and wear protective gloves when removing the worn blades from the press to avoid injuries.

Until recently, steel was the only material capable of producing the high quality print required in flexible packaging applications so printers had no choice but to accept these risks. While plastic blades were safer, they were not able to achieve a fine enough contact area with the high line screen rolls.

Today’s next generation polymer blades act as a hybrid between steel and plastic and offer a safe alternative to steel. The combination of an advanced polymer material and an innovative “MicroTip®” design allows these blades to perform in highly demanding applications where previously steel was the only option. Due to their material composition, the new polymer blades are safe to handle even when worn. Converting to these blades will reduce lost-time accidents and can save a printer a lot of money in terms of workman’s compensation insurance rates, medical bills, labor replacement expenses and press downtime.

When it comes to the pressroom, safety is everyone’s concern. Flexible packaging printers no longer have to accept the danger that comes with using steel blades to get the print quality their customers demand. To greatly reduce the risk of injury and associated costs, try substituting next generation polymer blades for steel.

About Flexo Concepts

Headquartered in Plymouth, Massachusetts, Flexo Concepts manufactures TruPoint doctor blades, the TruPoint QuikWash™ System and wash-up blades, and MicroClean™ dry media anilox cleaning systems.  All products are designed to improve print quality and reduce operational costs for flexographic and offset printers.  Flexo Concepts maintains distribution locations in North America, South America, Europe, Asia, Africa and Australia.  For more information about the company and its products visit www.flexoconcepts.com.

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Pressroom Color Management – Taking It to a New Level

By Salmon Creek Media & Marketing

PolyFirst Packaging is one of the largest producers of specialty plastic bags, pouches and plastic packaging in the country. In 1998, PolyFirst Packaging started with a mission to produce the highest quality plastic film and bags, on time and at a fair price. They stuck to their guns and are now produce a breadth of products that rivals anyone in the county. Running multiple facilities in Wisconsin and Illinois. They extrude their own films and convert a wide variety of plastic packaging running state of the art printing and laminating equipment.

In 2014, the company wanted to take a more objective approach to color matching and at the same time simplify the data that the press operators use, so they began to look for a tool to help their press operators make better decisions about color adjustments on press. (We wanted to take a more objective approach to color matching and yet simplify the data that the press operators use.)

Choosing a Software Product

Ryan Fischer, Printing and Prepress Team Lead at PolyFirst Packaging, first heard about SpotOn! Flexo in early 2014 while talking with a representative from All Printing Resources (APR). He observed a demonstration of the software at the FTA InfoFlex 2014 and then witnessed firsthand its application during a live press run in early September 2014 when APR’s Richard Black attended a press characterization at PolyFirst Packaging. Black had SpotOn! Flexo loaded onto his laptop, and after watching the press operators struggle to get color he opened his laptop and started taking some measurements.

“My initial reaction was mixed because of its simplicity,” Fischer explained. “I’m used to complicated color management tools that throw a lot of data at you, but after reading John (John the Math Guy) Seymour’s article titled ‘are my CIELAB knobs?’ I had a paradigm-shift. In terms of processes, it made sense to me that CIELAB-centric color-management software belonged in the ink LAB (no pun intended), and density-centric software belonged press side.”

Fischer and the pressroom manager, Mitch Wieczorek, discussed the software and decided to purchase SpotOn! Flexo for their press operators because of its simplicity as compared to conventional color management software.

“Once we saw this unique software in action, we knew it was what we wanted,” said Fischer. “It focuses on color density, which we stress as being the primary step for ink toning on press, and it has the ability to predict what affect pressroom adjustments will have.”

Working with the Software

APR sent the PolyFirst IT team a link for downloading that included a “Read Me” file with installation instructions. The installation went smoothly, and very quickly the pressroom team, with no training, was setting up jobs with the easy-to-follow instructions.

PolyFirst trialed the software for 30 days before purchasing it, and the feedback is that press operators would have been unhappy if it had been removed the software from their computers after the 30-day trial.

“We saw close to a 50 percent reduction in what I would call ‘ink-toning time’ during the 30-day trial,” stated Fischer, “mainly due to the usefulness of the software in preventing the press operator from making incorrect adjustments. In the past, we may have added a base color to change the hue or chroma of toned ink because of his perception. With the new software, those potentially unnecessary steps are removed if the software shows, for example, that the operator can achieve color by just adding extender.”

Today, five PolyFirst press operators and four from management/administration are using the SpotOn! Flexo software.

The Benefits Realized


In addition to gains mentioned previously, the new software provides PolyFirst with a well-organized database for a digital color library. Other software programs required searches of the full library, color-by-color. When a job is pulled up in SpotOn! Flexo, only the colors applicable to that job are shown without having to dig through an expansive full library.

Workflow Benefits
Communication between prepress and press is more clear and concise. In the past, prepress communicated a color on a spec sheet, and it was up to the press operator to find the color. Typically, the specification was in the form of a simple Pantone number, and the problem with that is that “Pantone colors” have a tendency to multiply when they become mixed inks. One customer’s approved color that may be designated with a specific Pantone number may not match another customer’s approved color in terms of L*a*b*, even though the Pantone numbers are identical.

Now, prepress assigns colors through SpotOn! Flexo. Prepress sets up a job in the software, and the press operator simply pulls up the job, and the specific color targets applicable for the job are right there. The software removes ambiguity and reduces the amount of time a press operator previously spent searching PolyFirst’s color libraries for the appropriate colors to apply to a job.

Quality Benefits

According to Fischer, “SpotOn! Flexo establishes standards and tolerance sets differently than other software programs I have worked with. Not only do jobs have specific color sets, but each color set can also have standards and tolerances applied. So, if a customer has required standards that may differ from our own standards, those standards can be applied to the job.”

“For example, if our standards are delta-E00<3.0 (D50/2), and our customer requires delta-E76<2.0 (D65/2), we can apply those standards to the colors in that customer’s job. Instead of communicating the customer’s requirements through a specification and relying on the press operator to change his settings where the potential for error exists, those settings can be automatically applied along with the color targets.

“I’ve worked with software programs that require those settings to be set manually. If there are multiple presses running and using a single workstation, the operator from press A may switch the setting specific to his job, not reset them when finished, and when the operator from press B takes his measurements, if he doesn’t notice the change it could result in an inaccurate measurement without operator B ever noticing. This is not a problem with SpotOn! Flexo because each color-set and each job can have independent settings.”

Customer Satisfaction Benefits

Quality benefits go hand-in-hand with customer satisfaction. Many customers today have sophisticated expectations in terms of color management. Those expectations may include color management software requirements, tolerance requirements, digital library requirements or a host of other things that SpotOn! Flexo accomplishes.

“It’s an exciting display piece to have press-side,” Fisher said. “We’ve had customers press-side for press checks who have been impressed with the use of the software while their jobs were being set up.”

polyfirst-logoAbout PolyFirst Packaging

PolyFirst has become the preferred choice for custom packaging and custom design printing. Their state-of-the-art printing presses print up to eight colors, both process and spot colors allowing for greater flexibility when designing a package. In addition to printed bags, they also print rollstock for vertical and horizontal form fill and seal (V/F/F/S) applications. 

PolyFirst offers one-stop shopping by working with existing art files or creating new art; they can work with practically any art file you provide. Their design team will work with you to create the ideal package for your product. Visit www.polyfirst.com for more information.

spoton-flexoAbout SpotOn! Flexo

SpotOn! Flexo is new, leading-edge technology that makes it possible to get optimum color reproduction and density information for any spot color, right at your fingertips. SpotOn! Flexo utilizes Predictive Analysis to determine the best ink density for optimum color reproduction. There are many timesaving and cost-cutting benefits of SpotOn! Flexo software. A major benefit is the reduced press “make-ready” time trying to obtain the correct color match to a spot or custom/brand color. Spot On! Flexo addresses the typical way density is identified and optimizes it. For more information about SpotOn! Flexo software, visit www.spotonflexo.com. 

scmm-talking-boxesAbout Salmon Creek Media & Marketing 

Salmon Creek Media & Marketing provides a wide range of services in support of social media and traditional marketing initiatives. From marketing and advertising materials to social media management, blast e-mails and e-newsletters to Web-site development , we provide a full array of products and services to position a company and its products in front of its customers. We work with customers to understand the process, identify their goals and objectives, and create a plan to achieve their marketing objectives. Visit www.salmoncreekmedia.com.

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