Heidelberg 15 x 20 cylinder impression problem

I am having some issues with a Heidelberg cylinder press not staying on impression during printing of normal coverage …..and even light coverage work. When I start up and feed paper then put the handle all the way to the right, the cylinder will invariably bounce up upon meeting the form and the handle will jump to the left by a small distance in response. “This can’t be normal” I thought, so I pulled the cover off of the op side to see what was what. I studied everything for about an hour and disassembled it further and discovered that the cylinder is lowered and impression activated via a simple rack and pinion system with 2 large screws (1 op side, 1 drive side). The screw thread is pretty aggressive in order to raise/lower the cylinder in the range of maybe 10mm with less than 100 degrees rotation of the pinion so it seems natural that it would spin under pressure and transfer the energy to the handle. I studied further. I saw only a well oiled, beautifully machined press with no apparent broken or missing parts. If at least I had the weight of the massive cylinder working in my favor, that might be of some help but apparently it’s held at near zero gravity by large springs underneath to keep the switching action easy for the operator. I need help. What’s going on here?


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It’s been many decades since I ran this press. I do remember when pulling the lever to the right, it has to be at a precise time. Otherwise it gets thrown back. Maybe you’re engaging too soon. ? I’m sure someone will have an answer for you. Good luck.


When activated either manually or by full delivery (or mis-delivery) the throw off mechanism is working properly and not interfering with normal operation.


I should also add that the specified packing thickness is being used (for the type of paper selected) and the photopolymer + base is .918”

Is the imp/feed lever moving the way to the “stop” ? this is a bar inside with an adjustment bolt acting as the actual “stop” for the lever. (Many of these get broken off by “enthusiastic operators”, leaving behind a round stud in the side frame). If it is going to the stop, is the lever indicator on the cover going well into the “black section”, positioning it on full impression. if this is also the case, I have seen many Cyl that, one has to “Hold” the lever there for 3-5 sheets. Then it should stay. If this also does not work, look for the “missed sheet” tooth kicking the imp lever off. An in depth inspection of the vacuum system may be in order. There is also a mechanism in the delivery (op side of press) that senses a “full table” or “jam”, there. it is a very subtle linkage, but does a lot. This needs to be made working well or the imp/feed lever will kick off.
If it is just “nudging at bit” off with each sheet, look for worn parts in the linkage. There is prob more than one issue there.

Hi EricM,

Thanks for the reply. The handle goes to the end of the black region but not past. Nothing is tripping the throw-off mechanism either. It just seems that when the cylinder meets any work, it simply bounces up ….apparently taking the path of least resistance …..with nothing holding it firmly in place; at least nothing that I can see. This press is at a new job and although I have run these presses in the past, I don’t recall having this problem. I literally need to hold the handle in position during the run.

If this press has been set up as a die-cutter, I would pull the form and then run the cylinder under impression and see if the problem shows up there. Then, stop the press under impression with the cylinder halfway down the bed and check if the cylinder bearers are in contact with the bed bearers.

There is a particular rebuilder that I’ve seen some work of that the bed bearers (or something else) were not in contact with the cylinder bearers—the press is a die-killer for sure.