I am operating a MO 25.5 2/c and have run across an adjustment on the infeed drum. It is not referred to in our manuals and although I think I know its purpose I am not sure how and when to use it. Its a dial in the center of the drum and is numbered. I have cleaned it up and set it to zero. Any input or info would be helpful, Thanks.
Leave it at zero if at all possible. This is a sheet compensator. this is used to help with fit at the tail. If your not having fit issues at the tail leave it alone. If you are this sometimes will bring the fit in a bit. Always put this dial back to zero when its not needed. What this is doing is actually bending the ranger drum a bit. This in time will end up breaking the pad bar. Also if you dont put this back to zero it puts alot of unneeded load on the compensator wearing it out prematurely.
@exheidmech... Can you explain a bit more, does this sheet compensator stretches the sheet in lateral direction? How does it help in register at tail edge?
When the ranger drum closes on the sheet there is no deflection of the gripper bar regardless of the selection on the compensator. As the ranger drum rotates toward the impression cylinder the gripper bar on the ranger drum is bent very slightly causing a destortion onto the sheet. Its this distortion that allows you as the printer to make the print wider or narrower via the sheet compensator. The effect onto the sheet has alot to do with paper weight and condition of the compensator itself. Hopefully this helps
Thanx exheidmech. 1 more question, What is the proper position and method for adjusting the ranger drum grippers?
I'll jump in here, Asif. First, for ease of access to adjusting screws (depending on vintage of press, older machines require a modified Phillips type screwdriver shank, newer machines a 3mm Allen) I remove some of the curved guides. Mark their position for easier replacement. Wire brush grippers and pad rail. Be sure rail is set to "paper". With feeder engaged (or barrier disabled by whatever means) insert tissue strips into grippers at the point the pad rail is exactly 90 degrees to register plate. I use a 3 inch precision machinist's square. At this point, be sure all grippers are opened by means of adjusting set screws. Adjust all grippers to uniform medium drag on strips. Obviously, you should be sure urethanes are not ridged, replace if needed.