Need Help HP370 Print Passes Not Aligned

[rdm01]

We're printing a large project, about 10 rolls of media through our 370. The following problem has occurred twice.

Printer runs fine for 3-4 rolls over 2 days, then all of the sudden the passes are misaligned and everything is blurry. Run test prints, they look fine. Try the file again, blurry. You can see that on a crop mark, where 5 passes should have landed on top of each other, they're about 1/8-1/16 inch apart.

Last time we had to switch printers and sort of just forgot about the issue. Now we're battling it again.

Thoughts?

 

[FrankW]

What media do you print? We had a similar issue with a customers printer, the media (a thin paper) slides between the lower rubber roller and the upper pinch rollers. could be that you need to clean the rubber rollers.

Maybe decreasing the input roller tension in the profile settings would help too.

 

[rdm01]

It is a Ritrama calendered vinyl. After this started I got an error related to the OMAS sensor, but all internet searches say this is relatively unimportant.

 

[FrankW]

The OMAS-Sensor is the Sensor in the platen who controls the feed amount (sometimes you see it through thin media, is a red light flashing below the media). This sensor could run into problems with very smooth media backs like PET, because it reads the structure of the back to do its job. And of course it could be defect.

Regularly if the feed wont work correctly, the maximum will be grainy prints and rough printed edges in feed direction.

If your problem results from a defective OMAS, you can switch it off in the media profile settings and do a manual feed adjustment through print quality menu (print the sample, check the best feed value and set it in media profile settings). But could be too that the OMAS-Error is a result of sliding media.

 

[rdm01]

I've cleaned the sensor, disabled the sensor - I don't think it's the problem.

I cleaned the pinch rollers and lowered/raised the back roll tension. I can't, for the life of me, figure out what's going on.

 

[Kreckohr]

try the printhead alignment . If the automatic printhead alignment does not work , or you even get an error, there could be a possibility that the line sensor is dirty and just needs a cleaning with a cotton swab.