Image distortion Bizhub c452

[comicscollective]

When we print the image distorts irregularly. We can print a grid outline on the same sheet of paper by reloading it, and every time the image prints differently. The first vertical line is always the same, but it twists from there. The horizontals are also better than the verticals, so it's not just a twist in the paper. The image is no longer square. And when we print duplex it is horribly off.


So far we have replaced the transfer and fusing units and run image stabilization and gradation. Does anyone know what else might cause this problem?

Thanks,
David

[Max]

post examples

[Albonline]

go through the image quality adjustments, in the service manual.

[D_L_P]

The horizontals are also better than the verticals, so it's not just a twist in the paper. The image is no longer square.


In the analog days we called that 'optical' skew. Skewed in one direction can only be a few things. I'm 99% sure it's your print head (laser) but it's also possible your mirror assembly is crooked.

To find out for sure, try scanning the image to a computer and printing on different printer, it should be fine. Printing test pattern from service mode such as the lead edge erase should be skewed.

If the scan is off it's you mirror assembly, if the print is off its your print head. There are adjustments in service mode for skew:

machine > skew adjustment or machine > scan area > centering

[comicscollective]

Here's a scan. This is a grid printed four times on a single sheet fed through the bypass tray, but it looks about the same from any of the regular trays as well. 29370

[comicscollective]

Forgive me if this is a stupid question. But I guess I'm wondering if the laser being bad would cause the image to be different with each printing. One time it will be in a certain spot and the next time the line will be 1/8 of an inch away from where it was. I thought a laser issue might cause it to print askew, but that it would print in the same wrong spot every time and not vary between each printing. Or am I just totally mistaken.

[splblazer91]

Your image wont open up but it sounds to me like you are describing a registration problem. Might try swapping that out. Does the paper ever jam? Try stopping the machine while the image is still on the xfer belt and see if it is distorted before or after it reaches the page.

[comicscollective]

The problem is over all trays including the bypass tray. But it never jams in any of them. I've stopped it while feeding through the bypass and it appears to be occurring before the fuser unit. The timing roller and second transfer roller both look good, but that doesn't guarantee anything.

Please try this link for an image.

http://s17.postimg.org/og8rtiw33/Image_18.jpg

[D_L_P]

Forgive me if this is a stupid question. But I guess I'm wondering if the laser being bad would cause the image to be different with each printing. One time it will be in a certain spot and the next time the line will be 1/8 of an inch away from where it was. I thought a laser issue might cause it to print askew, but that it would print in the same wrong spot every time and not vary between each printing. Or am I just totally mistaken.

Not a stupid question at all. The first time I saw it fix an issue like that I was scratching my head. It probably has something to do with the beam detect varying, which would cause the start position of each line to vary but not the line itself. One example (I'm pretty sure it was here on copytechnet.com) the sub scan was straight while the main scan actually zig-zagged back and forth down the entire page. Laser fix'd it. The one I remember running into would be fine on 81/2 x 11 but on legal or ledger about 3/4 down the page it would skew in one direction only, almost exactly like what you posted. Imagine the grid perfect for 3/4 of the page while the last 1/4 looked like your example. Directional skew can't come from paper feed. It's the scanner physically crooked or print head (laser) varying the start of each line.

[comicscollective]

Very interesting, thank you for sharing your knowledge and experience. So does this just mean the PH unit needs to be replaced, or is there an adjustment that would fix it? Since the problem occurs when printing, not just scanning, I assume the machine-scan area-centering adjustment wouldn't help. The machine-print head skew adjustment is only for adjusting color in relation to k, which again is not applicable. The only adjustment that would seem to come into play at all is the machine-print area-centering or lead edge adjustment. Is that a fair assessment?

[D_L_P]

Very interesting, thank you for sharing your knowledge and experience. So does this just mean the PH unit needs to be replaced, or is there an adjustment that would fix it? Since the problem occurs when printing, not just scanning, I assume the machine-scan area-centering adjustment wouldn't help. The machine-print head skew adjustment is only for adjusting color in relation to k, which again is not applicable. The only adjustment that would seem to come into play at all is the machine-print area-centering or lead edge adjustment. Is that a fair assessment?

The centering adjust would adjust both axis so it wouldn't eliminate it. The PH would need replaced.

Here's the thread about the directional skew:

http://www.copytechnet.com/forums/canon/75191-canon-ir3300-bent-copies-prints-xerox.html

Different copier but same concept. The canon tech said to repace the laser.

[blackcat4866]

Laser failures were much more common on Sharps of a few years ago. The sort of symptoms we'd see were:

1) zigzagged lines in the subscan direction (varying start of scan) like your sample
2) jitters in the subscan direction (varying mirror motor speed)
3) black lanes of varying width in the main scan direction (laser cuts out)
4) beam detect errors (when the mirror motor doesn't turn the laser beam is not detected, or laser failure)
5) light or blurry areas in the printed image consistently in the subscan direction or shadows around areas of heavy fill (dirty laser optics)
6) loud noise when the laser spins up (mirror motor imminent failure)
7) Image registration in the main scan direction varies radically, like consistently 3" off the side of the page, far beyond the adjustment range (laser controller board failure)

=^..^=

[comicscollective]

First, let me again thank everyone who has posted on here and given their time to help. I do appreciate it.


Second, I'm afraid that the problem persists after changing the ph unit (print head assembly, laser, or whatever else you want to call it). From one printing to the next, the lines shift. More so in the vertical than the horizontal, but they all start out about the same, and then distort more during the length of the paper.

So far I have replaced the transfer belt, fuser unit, and ph unit. I have done skew adjust, image stabilization, and gradation. Additionally, I reset the counters for the transfer belt and fuser (not that it matters).

The only three things I can think of that might be at all an issue are:

1. I do not have a plate spring holding the ph unit in place. It is the small clip in the center top of the ph unit in the photo attached to the frame by one screw. So there is nothing actually holding the print head down. It only sits in place by gravity. However, I was told that this clip is only the 451, and is not needed on the 452.
29439
2. Could this be a result of the IDC sensor being bad, or out of place?

3. Although it looks fine, and has life left on it according to the counter, could the k drum cause this issue? But even if the black drum was shifting during imaging, I don't think the other colors would follow suit even though they are adjusted according to black.

If anyone has any ideas, please share them. At this point there's a lot of new parts involved in this unit, and it would be a huge hit to have to walk away from it.

[MVPunisher]

How did you make it out here>?