heidelberg cylinder

Hey does anybody known how to stop a HB cylinder from slipping off impression? at the moment I have to roll up some card to form a tube and then wedge it against the handle.

 

Open the door and you can see what's happening, sounds like the cam needs adjusting or broken spring?

Or the emergency lever by the delivery may need adjusting also, try jiggling it a bit.

 

Is this a "K" cylinder or an "S" cylinder? Does it come off impression suddenly or gradually? Does it keep feeding sheets or does it stop feeding sheets, then trip off?

 

not sure if it's a k or s (how do i tell). The impression handle slips back a little bit with each impression about an inch all up and the paper continues to feed.
cheers

 

K-Line press are 25" (64 cm) or smaller, and have a sloping feeder table. S-Line press are 28" (74 cm) and larger, and have a horizontal feeder table. The difference is important as they are completely different presses, and one difference is how each goes on, and stays on impression.

 

WGS it's a S cylinder

 

Here's the most common reason. I suspect you (someone) oiled the press recently (Gasp!). The method Heidelberg uses to go on impression is by sliding a wedge across a machined flat in the side frame. The wedge moves when you pull the handle to "impression". It is held in impression one, by the weight of the cylinder, and two, friction. If the wedge has too much lubrication or the lube is too viscous, as the cylinder rotates and comes in contact with the form, the weight of the cylinder is unloaded on the wedge slightly, allowing it to move. A number of impressions causes it to move across the wedge till you get an inadequate impression, though it generally never comes off completely.

The fix is to locate the oil holes on each side of the press that leads to the wedge. The one on the operator side is easy, you can see it going to the wedge. The gear side is a little harder, as it doesn't go straight down to the wedge, but it should be easy enough to find. Flush these out several times with some press wash. Repeat the next day. It should go back to normal in a day or two. Heidelberg painted these yellow, indicating that they should be lubed weekly, and they used a larger copper tube for the purpose, leading press operators to think it needed a lot of oil. It does not. A couple of drops every month or so is all.