It seems I read this somewhere but can’t be sure. The statement was that the Heidelberg Windmill 13/18 had a closed pressure 70 ton psi, and the 10/15 of 40 tons psi. Can anyone confirm this?
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As per Heidelberg sales material:
13x18 is 60 tons. 10x15 is 40 tons.
Thanks, I was close. It was so long ago when I read it, thought it might have been my imagination.
RREEBB- you should be aware that the 40 and 60 ton pressure is TOTAL pressure, not pressure per square inch. There is a huge difference between the two.
A 10 x 15 @ 40 tons total pressure will press at 533 psi across the entire platen, and proportionally higher with less area of coverage. With 50% coverage, it will press with 1066 psi. However, if you are only printing 1 square inch of area, it will indeed press it with 40 tons. (It’s just simple math.)
I did a whole study of press pressures a few years ago. The results are posted here at Briar Press somewhere. One of the odd things I discovered is that humble Kelsey Press can produce relatively high pressures IF the print area is small.
Press overload is something diecutters are always concerned about. It takes about 200lbs pressure per inch of steel rule to cut. Not sure about printing especially with deep impression. If gutters between cuts are narrow you run the risk of a bed of nails effect. Often it is better to do two passes with half the die load and a less expensive die. I would think the letterpress print experts have been dealing with this for 100’s of years.
Whenever doing a kisscut or diecut or scoring job, I make double sure the impression is backed way out and work it in gradually. That precaution has saved me a lot of damage and frustration. The minute adjustment of the impression lever really helps, but is more of a challenge on the 13/18 press. RREEBB
when i die or kiss cut i tape a piece of paper behind the die on the chase to insure a long die life and due to the age of my press try not to adjust anything i dont have too.
If your press is level all most makeready should be under the plate but sometimes a bit of scotch tape on the plate will do. Behind the die is another quick fix.