Doubling on Gear Side Guide

[quinton77]

Hello everyone,

Hello all. As the thread title states, I have been experiencing some trouble with the gear side guide when running on that guide.

The machine is a 2002 LS, in pretty good shape. We can run all day long on the operator guide and have no issues, no fan out, no fit problems, nothing, runs very well print quality wise. The issue is running on the gear side guide. The side guides are the bearing and spring kind. I have the buckle plates set, lightest spring that will pull the sheets. Smoother bar is set properly, nothing dragging the sheet.

The problem occurs when we are backing up a job and have to run on the gear guide. The operator side of the sheets fans out, and doubles worse the further back on the sheet it goes. I have changed side guides with the same feeder set up, no doubling or fan out when pulling to the operator guide, doubles when pulling to the gear.

It shows up more with thinner paper of course, we run mostly 80# text, and it still shows up on 100# text. I have cleaned and set the swing arm grippers, there is nothing weird going on there. So I presume at the moment.

All the cam followers are greased and rolling with no issues, the A transfer grippers are set at 3, as well as the transfer cylinders. Nothing is binding the sheet as it registers.


I have not set the A transfer grippers, as I never had to set them before.

My question to you guys is this, what is the proper procedure for setting the A transfer grippers, and have any of you experienced this problem at one time or another? If so what was the issue causing the problem, and how did you fix it?

 

[alibryan]

It's not the A cylinder grippers. If it was, you would see distortion regardless of which side guide is being used.

 

[turbotom1052]

It's not the A cylinder grippers. If it was, you would see distortion regardless of which side guide is being used.

Don't believe this is true in all cases. Typically most jobs start out running on the near sideguide, and then finish up on the far guide. Ive seen instances where the original guide may cause a distortion in the sheet on the first pass that goes un noticed until you begin to back the job up. Sometimes this distortion can come from gripper issues too. Often this distortion winds up being magnified towards the tail of the sheet. A slight case of poor side guiding, or a slight pulling out of the sheet from the grippers can cause a doubling effect on the first pass that's not a glaring issue until you try to back the job up. In this case, as mentioned by the OP, the problem will multiply, as the job is backed up and be more evident the further towards the tail corners of the sheet you go. If this is happening you will usually see evidence of this in the color bars, provided that the bars are imaged towards the tail of the sheet. This problem is made more prevalent when you consider the joys of modern technology. Modern day, closed loop inking systems have gotten many new guys to the biznez too reliant on them systems. Ive seen many cases of guys who just pull a sheet, and throw it up on the scanner thinking that the press technology will do all the work. Ive even seen seasoned veterans become lazy and FORGET all they've learned about pressmanship. This a perfect example of why too much dependance on technology has created an industry of button pushers.
To the original poster.... Play close attention to your slur bars as you print the first side of the sheet, particularly in the tail corners of the sheet. You need to pull a series of at least 4 to 5 consecutive sheets and look at each of them in the corners. If you notice the slur bars showing even the slightest sign of a double on the first pass, then you can be pretty sure that upon backup you will encounter what you've described. You can further prove this out by running a lift of the freshly printed sheets through the press same side up, to see how it registers to itself. Pay close attention to any small black type near the tail corners for signs of doubling. By doing what I suggest you will learn BEFORE the entire job is printed if there is a problem and save yourself the time and paper of a re print. If you can narrow it down to a side guide problem, then you might try starting out with the far guide and finishing up on the near guide. Of course successful trouble shooting of this issue has me assuming that your running a decent quality sheet of paper. If your printing on job lot stock then its all a crapshoot!!!

 

[Bloke]

If you have a conventional bearing pull side lay then can I suggest the problem is with off lay timing. Easily check this by feeling the pull bearing as the press is being inched. With no paper on the feed board, it should begin to contact at 290 degrees and lift at 340 degrees. This allows 10 degrees for the sheet to settle in the front lays before the swing grippers close and advance the sheet into the press. Double check by comparing your near lay timing positions.