A Recipe for Flexo Printing Success

As a young man growing up in southeastern Indiana, I had a favorite time of year: Christmas!

My grandmother would bake tins of homemade cookies for the kids and grandchildren. My siblings and I could not wait to get our hands on these cookies. There was never a bad cookie; we could count on the same cookie, or even better, year after year. Over the years, grandma made improvements through minor alterations of the recipe and measuring the success.

Unfortunately, since the passing of my grandmother, we no longer can have this sweet sensation due to the fact that the key holder is no longer with us. How can we duplicate the recipe without 1.) The key holder and 2.) A documented recipe?

Since the beginning of time, we have had instructions or a recipe to make or build just about anything. From building the Sears Tower to putting together a child’s toy, which I can testify is not an easy task, all are built using a recipe or documented instructions.

My grandmother’s cookie recipe is a lot like controlling our recipes in the pressroom, making adjustments where necessary and measuring the impact that those changes may or may not have. We are expected to produce the same product over and over. The only way to ensure this happens is to document and measure our process and its parameters to meet our customers' expectations.

If we fail to give our operators the recipe to reproduce an image, we cannot expect them to get the same result from print run to print run.

What should our recipe contain? How can we control our recipe? I hope to answer these questions below, however, there are many specialty converters that have proprietary technology and may have to add to the recipe to control these specialized variables. Each phase of the organization should carry its own recipe attached to the master order when received. I would like to focus on establishing a recipe for mounting, ink lab, press, and quality control.

Mounting
Expecting our operators to reproduce an image can only be as good as what is given to them. Having a recipe to follow in the mounting department is crucial in duplicating an image.

This is our first look at how our job will look and register with our plates, cylinders, gears, etc. Some items that should be contained in our mounting recipe are as follows:

  1. Plate or mold number—With many jobs using common plates and multiple SKUs, it is vital that we verify we are using the proper plates. If trim is available, I suggest putting this job number in the trim.
  2. Cylinder pitch, size and gear requirements are necessary, as well as your tolerance for TIR (total indicated runout). Typically 0.0005 in. for process and 0.001 in. for line work.
  3. The mounter must know the sequence of how the colors will print and the colors to be used to make the proof as realistic as possible.
  4. The repeat, number of lanes to be printed, and the width of substrate all are important information for the mounter. No one likes to cut off target marks and eyelines after they have printed on the drum during set up. It also would be a good idea to include what the cut width and repeat tolerances are to give the mounter an acceptable tolerance with which to work.
  5. Does the job require a sleeve? If so, what is the sleeve thickness and width?
  6. Does this particular job require any build-up tape? If so, what type of build up needs to be used, and what is the thickness of the tape to be used?
  7. What type of tape will be used, and what are the characteristics and thickness of the tape? High density, medium, low, etc.
  8. What type of plate material and thickness will be used?
  9. And, of course, the obvious would be a sample, previous proof, or in the case of a new job, the customers signed proof as a road map of what has previously been determined as acceptable.

Ink Lab
Due to the flexographic business being primarily a visual business and our eyes being stimulated by color, it is a necessity to have a recipe-built system for color control. Many goods are purchased on a daily basis entirely on the way they appeal to our eyes. Many companies have gained business on their ability to maintain strict color control.

Likewise, many companies have lost business by not controlling color within the tolerances set. Whether it be dispensed through an IMS (Ink Management System) or premixed at the ink vendor, it still is necessary to Q.C. ink prior to going press side. Verifying the color, strength, and ink type is correct will minimize downtime for color matching and possible quality rejects.

The ink is a necessary and vital component to your recipe control. Consider some of the following recommendations to be added to your recipe:

  • Ink system type—Many ink systems exist, such as fade resistant, heat resistant, lamination…I won’t begin to name them all. However you would not want an ink with a high nitrocellulose content to be run as a lamination ink. The two webs would never stick. Keep your ink systems separate, and document the proper system based on the characteristics of the product.
  • Ink formulations—How did we make the ink last time? Are we using the same ingredients? Did we accurately measure those ingredients?
  • Ink Drawdowns—Has the ink been drawndown using the same volume anilox we will use on the press? If you use a ceramic anilox with a doctor blade on the press, you better be using a proofer containing a ceramic roll and doctor blade, too. If you are printing on metallized film, you need to proof on metallized film.
  • Color Target—What is the color target for the ink prior to leaving the ink room? If your customer requires a Delta E cmc (Color Measurement Committee) of >2, I suggest the ink leaving the ink room to be less than Delta E cmc of >1.0-1.5.
  • Viscosity and pH (if applicable)—If the job ran previously at 30 on a #2 Zahn cup, I would suggest you bring the ink to the press at 35 on a #2 Zahn. This depends on your ink system; some inks break down quite a bit when agitation and pumping through a doctor blade occurs.

This is exactly the reason you have an ink recipe. The last run may have been brought out at 35 seconds and ran at 30 on the press. Therefore, the ink recipe would require the ink at 35 and the recipe for the press would be 30.

The Press
The press is the business end of what we do. All other processes prior to the press can have a negative or positive affect on the outcome of our run. In order for us to be successful, it is vital that we supply the press operator with the tools necessary to complete the job in an efficient and timely manner.

If the ink is off color or the plates were not proofed and verified, our press operator has zero chance to succeed on a given job. When the proper checks and balances have been made prior to going press side, we increase our ability to duplicate a given image by ten fold.

Let’s look at some crucial ingredients the pressman may need to be successful:

  • Decks—What decks will be used and what sequence has been proven the most successful in previous runs? Many printers have experienced drying issues and in some cases skipping a deck has helped them to improve quality and increase press speeds.
  • Assigning Color Decks—What color is to be printed in each deck? Does the operator verify that the ink system, color, and formulation number matches the previous run?
  • Viscosity/pH—These are crucial components of any recipe and have an impact on the overall quality and ability of a job to be a success. Keeping your ink in control and within the ink company’s specifications will always generate the best results for any given print run.
  • Speed—How fast a job runs impacts quality and profitability?
  • Tension—Depending on the press, tension should be documented at the unwind, PIV (Positively Infinitely Variable), and rewind areas. Each job uses different substrates, and it is important to know what tension will allow the web to float through the press without distorting its dimensions.
  • Temperature—In a wide web, central impression press you most likely have between-color dryers as well as an overhead tunnel. Both are very important, and the temperatures need to be documented on the recipe.
  • Anilox rolls—Since the anilox roll provides ink film thickness to the plate, it is absolutely necessary to know what line screen, volume, and geometry was used to create the image you are trying to duplicate. If a 360 line screen, 4.3 volume roll was used to create the original image, we will need to use the same volume roll to increase our odds at achieving the same color.

And there are many other obvious items such as, material, die number, chill temps, etc.

We have only scratched the surface of what needs to be contained in our recipe control systems. Should quality be contained in the recipe? Of course, every job has different quality requirements and our operators need to know what the requirements and tolerances are of the job they’re printing.

A recipe is a must have in the business today due to advancements in our graphic images and tighter-than-ever tolerances being required by our customers.

Some of you may be asking what I meant in the beginning paragraph regarding the key holder and not being able to duplicate my grandmother’s recipe. The point is this: If one operator prints the initial job and is not required to document settings and conditions, it would be virtually impossible for the next operator to duplicate the original, thus resulting in a variation in the image. Does this cost us money when this happens? Yes, if one operator is able to meet the quality requirements of the job at 600 fpm and another operator meets the same quality requirements at 500 fpm, haven’t we lost money?

The equation is simple: one operator documenting all conditions plus a second operator using that recipe plus other operators being able to access the same recipe equals the success of the organization and customers.

The key holder to the recipe should be everyone who works in the organization, all sharing information to insure quality and long-term profitability of the company. If a recipe control system doesn’t exist or is in doubt, gather your people, find out what information is needed by sales, customer service, quality, production, and most importantly, your customers. Document it, and track your successes through measurement of the quality and profitability of your organization.

I guarantee the success and profitability of your company will experience a trend line that gains in your favor.


Mike Huey is employed at Harper Corp. of America as the Midwest technical graphics advisor for The Harper Graphic Solutions team. He has been employed in the flexographic business for 14 years. Mike’s previous experience was working for a flexible packaging company in the Chicagoland area as operator, technical and management functions. Mike was certified by the National Council for Skills Standards as an expert flexographer in 2001. Contact Mike at mhuey@harperimage.com.



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