A printer recently sent us four-color samples on 70# C2S litho text which were cracking horribly when folded. They couldn’t get rid of the problem with their own scoring devices and wondered if the EZ-Fit or Fast Fit Tri-Creaser would take care of the problem.
We like to say that 70# text is in the ‘experimental’ category, with regard to creasing using Technifold products. Why? In short, a good creasing job is the result of de-laminating the sheet internally such that it can be folded without cracking on the outside and with a nice bead on the inside. (Read more about that topic here.) The thinner the sheet, the harder it is to do this. Generally when the thickness of the sheet falls below .005” it will be much harder to crease, hence our ‘experimental’ label.
Despite the 'experimental' nature of thin paper stock, we always urge everyone to test the Tri-Creaser on even the lightest of stocks. The success rate with text stocks, especially digital, in the 50-100# range has been significant. In this particular case, because it was a thin offset litho stock, I wanted to take a look at it first so as not to send the customer’s folding machine operators on a wild goose chase.
I decided to run the job in question with 2 identical Technifold creasing tools on one of our scoring machines and then fold it on our Baum 714XLT. After a brief setup, one score line was perfect but the other was slitting the sheet. Even though I can do this stuff in my sleep, I triple-checked my setup to see if I was missing something obvious. I wasn’t. (One tool however, had been stored in a different spot in the warehouse before being intalled on the scoring machine.)
Then I remembered a suggestion sent in by a customer who faced a similar problem last winter. He discovered that an unusually cold weekend actually affected the performance of the creasing rib and a few seconds of pre-heating with a heat gun solved his problem. I removed the rib, put it on top of a warm baseboard heater for 3 or 4 minutes and re-installed it on the Tri-Creaser. Bingo, the slitting disappeared and the job ran perfectly.
It makes sense, especially when you are running a stock + scoring tool combination that is at the outside edges of the performance envelope. The closer you are to the edge of this envelope, the smaller the change needed to go from acceptable to non-acceptable. In this case a cold weekend in our office led to a tiny change in the hardness of the rubber along with a slight decrease in the moisture level of the paper, thus producing a cut sheet rather than a nice crease or score.
During these cold weather months it’s good to be a little more aware of temperature changes and if possible, keep them to a minimum. Temperature affects the properties of all matter and in most cases this won’t have an impact on the performance of your bindery equipment. Sometimes it does.
So if you see unexpected changes in the performance of your creasing tools, or you find yourself struggling with light stocks, consider a little pre-heat for those creasing ribs. And be sure to check out this list of previous cold weather articles here. Tis the season!