Archive for the ‘Printing’ Category

Calculating ink coverage based on weight

January 31, 2018

Ed asks,

“We are creating a program to quote customer requirements as quickly and accurately as possible but we are stuck with ink / printing issues.

Is there a conversion that may help us translate grams of ink to square centimeters / inches of printing?”

Your ink supplier should be able to tell you how many sq. in. or sq. cm. a pound or gram of ink will cover. This will change depending on the viscosity, substrate, anilox roll volume, ink manufacturer and ink type. So in your calculator (estimator) you may want to provide the option to select from a pre-programmed list of inks, or allow the estimator to enter a pounds per inch or grams per centimeter variable.

Then of course you’ll need to know the sq inches of coverage for each color. You could simply calculate the area of the sheet and then assign a light, medium, or heavy coverage variable to simplify the calculation of inches of coverage.

UPDATE: Roger Poteet, Poteet Printing Systems, has reached out to share their experience and knowledge with us through the Poteet Ink Estimator complied and provided by Poteet Printing. I also want to thank Andrew at Compass Packaging for sharing his knowledge and experience with the Poteet Estimator in the comment below.

– Ralph

Printing on Hot Corrugated

March 3, 2015

Jason asks,

Could you explain why it’s not recommended to print on hot corrugate fresh from the corrugator?
I know this isn’t common practice, but there are times when it is necessary when a rush order comes in.

Once corrugated sheets come off the corrugator they should be allowed a bit of time to cure. This will allow the sheet time to stabilize and adjust to the relative humidity of the environment, etc. Slight size changes can take place during this time. If you go straight from the corrugator to the converting process, it is possible that you could end up with a finished product that doesn’t meet the customer’s specification.

Basically ink dries by absorption and evaporation. The chemical characteristics of the ink, mainly pH levels, and temperature, greatly influence drying as well. When you induce significant temperature change to the equation, such as hot board, you change the entire drying process. This will most likely result in ink drying before it has time to absorb into the fibres of the sheet, or it may cause the ink to dry on the plate. Both situations can result in poor coverage/print quality and excessive build up on the plates.

Hot sheets can also cause “baking” of the printing plates which will significantly reduce the plates’ ability to properly transfer ink as well as the overall life of the printing plates.

A hot sheet could also possibly experience more crush as it goes through the converting process than a cured sheet would, and therefore result in a degradation of product quality. A sheet that isn’t properly cured may also be more likely to create rolled scores.

Converting equipment can also be affected by hot sheets. The functional characteristics of urethane components such as feed belts or wheels, transfer belts, pull collars, and in some cases even cutting die rubber can be decreased by hot sheets. The coefficient of friction of feed belts and wheels can be reduced causing registration and skew issues. Die cutting rubber can be overheated causing reduced ejection rates and rubber life.

There are probably other issues that we’ve overlooked here, but I hope this gives you some idea of why running hot corrugated is not a good practice.

— Ralph

Does Flexo Printing Affect Gamma Ray Sterilization

February 10, 2014

Steve asks:

Well, I’ve got an interesting one for you.
We have a major customer who is a global leader in medical device manufacturing. We have a 55” long x 4 x 1 catheter package we do for them. 100% flexo printed. Their question is… “Do we have any documentation, or data on whether flexo print on corrugated affects the characteristics and performance of Gamma Ray sterilization?” We are quite comfortable with data we have on ETO (ethylene oxide) but Gamma is sketchy territory.

Would you or perhaps Clemson have any input for us? The engineers are looking to provide a rationale in their proposal for FDA etc.

I can honestly say that is a question I’ve never been asked before! For insight to this question I reached out to our friends at BCM Inks for some input. Ted Vernardakis, Ph.D., R&D Director/QA Manager for BCM Inks offers this explanation.

“Gamma rays are the most energetic, most powerful and most penetrating radiation of the electromagnetic spectrum. They are more powerful and penetrating than X-rays. They travel through just about everything except lead. Therefore they pass through corrugated board and flexo printing unobstructed, like a hot knife cutting through butter. Corrugated board and/or flexo ink has no effect on Gamma Ray sterilization, whatsoever.”

Hope this helps.


Disposing of Ink Buckets and Cutting Dies

March 7, 2013

Chase asks:

Our plant uses a lot of ink and are constantly obsoleting cutting dies. Both of these process leave us with a waste stream that I cannot find a buyer for. The ink is in standard 5 gallon buckets and we have switched to all plastic handles to make it easier to recycle and take a step of removing metal handles form the process so the whole bucket can be recycled, but i cannot find anyone who wants to fool with the recycling of these buckets even thought the ink residue is water soluble and non-toxic.

We wash these out, but are not in the business of cleaning ink buckets we are a corrugated converter, so there is still some ink that is not washed off. On the other hand is our cutting die situation. Do you know of a good way to recycle or otherwise use these dies without just tossing them out? It is costing us quite a bit of money for extra dumpsters to handle the buckets and dies.

In the January/February 2013 issue of Paperboard Packaging Magazine’s Products & Services section (page 22) there was mention of a Die Recycling Program developed by Triangle Dies & Supplies. They may also have an option for your ink buckets.

You may want to contact them.