Yep that is quite possible, went to the machine today & all is fine, perhaps me showing them last time that it is impossible to happen has stopped them doing it?
We have had this problem on a couple machines and have found the following
1 Clean the centering sensor and the black plate below it( if the paint is worn use felt marker to blacken the plate)
2 Clean all rollers in the PFU and check the bushings in the white rollers
3 Level the PFU to the body of the copier, then put a level on the vertical frame below the front mounting pin. If its not level then grab the bottom frame and push or pull it level(YES IT WILL MOVE EVEN WITH THE FEET PLANTED AND ALL THE WEIGHT ON IT) We have shifted the centering by as much as 4 mm with very little effort by pulling this to level the vertical frame. Because the mount points are so high if the frame is not vertically level then what you find is that you can shift it but if you move the bottom one way then the top will go the opposite direction. These units need some way of attaching the bottom frames of the copier and the PFU so the customer cannot move them by just shutting the drawers(3000 sheets of paper is like hitting it with a sludge hammer).
4 The main problem is that the stock locations of the mounts are fixed with no way given to adjust the true center of the trays to the true center of the copier. The only centering is done with software adjusting the position of the image but this breaks down when you exceed the maximum range of the sensor and you get the 5mm shift. Even the good old DI620 had a screw to adjust the manual centering of the bottom paper tray. We have tried to shim the trays themselves but due to the drive couplings and electrical connectors, this will not work
5 We have , on one machine as a test, modified the mounts for the PFU by slotting the holes where they attach to the copier to allow for manual centering of the PFU to the body of the copier. The adjustment is done by turning off auto tray centering and setting the tray centering to 0 on both trays. Then adjust the body of the PFU to the body of the copier to give the best average centering of both tray 4 and 5. Then turn on the auto centering and adjust both trays for proper centering. This PFU also now has a third mount plate from the bottom frame of the copier to the bottom frame of the PFU( crude but effective) To date this has fixed an ongoing problem with this machine but it has only been a few weeks.
This is what our team up here has seen and what we have tried so far.
I wanted to run a month before posting my results. The machine has stopped jumping. The fix was in the PFU I replaced the black metal plate that the paper moves over. Alot of the paint had worn off and I believe that the sensor was picking up possibly stray light. That was the only component I replaced and we have run over 100,000 sheets through it. I am going to replace the black metal plate in the ADU also when I get some time.
The sudden 5mm shift is because the auto correction "gives up" when the paper is more than 5mm offset. So, if the LCT isn't aligned to the machine, and the guides aren't symetrical, and the paper is a little bit out of square or width, you can easily see the paper entering with too large an offset.
Maybe 99 pages are just 4mm offset and the auto correction cleans up, but the 100th page is 5mm off and the image seems to "jump"..
All you have to do to get the side guide to jump is have a tray nearly full of paper and shut it firmly. Happens regularly and definitely causes the 5mm jump.
Turn the centering sensors off as described above then run the tray centering adjustment test pattern to see if the guides are out of place.
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