In previous articles, I discussed “Bottom Line” profits and losses and how everyone needs to be held accountable to ensure profits are held to their maximum. I also discussed personnel, training, and the importance of establishing procedures.

We all know that money is lost in the printing process, in part due to issues I discussed earlier. Unfortunately, a majority of our profits are lost during the period from when the job actually starts to when the job is completed. The quality of tools we use (cylinders, ink/ink filtration, and doctor blades) are directly related to whether or not we have a positive/negative profit margin, and if we, as printers, decide to purchase these tools based on cost alone, we can only expect to get what we pay for.

All three “Key Elements” (cylinders, Ink filtration and doctor blades) are equally important; however, I need to discuss them in this specific order because cylinders and ink filtration directly impact the success or failure of doctor blades. These three elements will be covered only as they relate to printers who are using solventbased ink—the reason being that 95 percent of gravure printers in North America are solvent-based.

CYLINDERS

Maintaining consistent quality of gravure cylinders affects your “Bottom Line,” and RZ (chrome roughness) and HV (chrome hardness), the process elements of your cylinders, are most likely inconsistent from one cylinder to the next. And, what does this cause? Process variation!

Cylinder quality is inconsistent for two primary reasons:

• 1 – The cylinder manufacturer does not have its process under control.
• 2 – You are not specific enough in requesting element parameters.

Printers continue to allow cylinders to be delivered to their pressrooms with huge variations in both RZ and HV, but this is not only the engraver’s responsibility. It’s also the responsibility of the printer! These variations will create the need for the operator to investigate and determine what the causes of printing issues are during the run. They will cause printing defects, downtime, questionable product quality, and waste. If the operator cannot “cure” the issue completely while running the material, then from the point the issue started to the end of the roll may be complete waste.

RZ – CHROME ROUGHNESS

The RZ (chrome roughness) is necessary to:

• 1 – Lubricate – Lubricates the doctor blade to reduce the contact area temperature to ensure the doctor blade wears into smaller fragments instead of melting, which forms burrs, which we all know causes drag outs.
• 2 – Sharpen – Keeps the contact area of the doctor blade clean (reduce defects) and sharp (cleaner print).

One of the biggest misconceptions in rotogravure is what the actual RZ roughness of the cylinder is and what it should be. Some customers will tell you that they have a spec of .20μm or .30μm. If they are testing with a Profilometer, this may be the case; however, the Profilometer does not distinguish between a polish that is cylindrical (figure 1) and one that is diagonally polished (figure 2). The illustration below shows that both types of polish direction could have the same RZ value.

The finish chrome RZ value that I found works the best for most applications is .40 μm for printing film and .60 μm for paper. The difference is the surface tension of the two substrates. The RZ can be verified with a profilometer as pictured below.

Get involved with your engraver and work together to set up specifications that work best for your application. Have a banded cylinder done with several different polishes to determine what works best for you. Once your specifications are set, hold everyone accountable for maintaining these specifications.

Note: I have visited several engravers and have found their process to be very impressive. These engravers do want what’s best for their customers. Sometimes, surprisingly, it’s the printer who doesn’t ask for or expect the best.

To recap what we have discussed so far:

• 1 – Change is necessary and good.
• 2 – Bottom line profits must be maximized to remain competitive.
• 3 – The importance of establishing policies/procedures and training all employees accordingly.
• 4 – Everyone must be held accountable (managers, employees and vendors).
• 5 –  Cylinder quality is a key element that must be controlled to reduce process variation.

All of the Key Elements must be held to a tight standard to eliminate process variation. Do not accept a range for tolerances. Pick a value and expect that value. This will reduce process variation.

If you need help with assessments or training for the best doctor blade solution, contact one of our experts for a consultative evaluation. Our team will be able to help you with solutions.

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Cylinders RZ/HV