Designjet T770 Sheet feed sensor

[theengel]

I went to work on a designjet T770, which wouldn't drop the "unload paper from sheet feeder" message. I ran the sheet sensor calibration, and it failed. I ran it again, and it passed. The machine worked fine.

Two weeks later, the machine will print a few inches of something, stop, cut the page, then unload the roll (a few inches of the print are still on the roll--it cuts it right in the middle of the print), and go to the ready to load paper state.

I'm thinking the sheet sensor is intermittently showing paper present, and needs to be replaced. Any other ideas?

[Kiran Otter]

Re: Designjet T770 Sheet feed sensor

Sounds like you're on the right track. I'm just curious; if you disconnect the sensor, does it work correctly? Or does it constantly think there is cut-sheet paper loaded?

If they never use cut-sheet paper, this might be a solution.

Kiran

[theengel]

Re: Designjet T770 Sheet feed sensor

LOL... I didn't think of that. That would have been a good test. They don't use the sheet feed, but they're so desperate for the machine to work, I'm rushing the part and going in on a Saturday to fix it. Man, I should have thought of that--that way I'd have been sure.

[theengel]

Re: Designjet T770 Sheet feed sensor

So if I unplug the sheet sensor, I'm unable to load the roll, because the machine detects paper present there. I loaded paper, and then unplugged the sheet sensor, and I get the same thing I started with--it prints a few inches, cuts the paper, and then unloads the roll, saying "job canceled, out of paper".

I swapped paper out sensor with one from another machine. No difference.

I ran the carriage assembly diagnostics (as instructed in the manual when you replace the paper out sensor.) When the screen says "moving carriage", it goes all the way to the right, all the way to the left (activating the cutter blade), and then a few inches over the paper, before it stops with this message:

Plotter 004.jpg

I was finally able to get an entire carriage diagnostics to work after a few tries. Then I ran one or two print jobs with no problems. On the third job, it started doing it again, printing a few inches and stopping.

I can't imagine what's causing this.

I also cleaned all the connectors leading into the E-module. The e-module diagnostics passed.

[D Hook]

Re: Designjet T770 Sheet feed sensor

I know this is an old, old post but was wondering if you found the solution. Be interested to know if you have time.

Thanks!

[Kiran Otter]

Re: Designjet T770 Sheet feed sensor

I don't know why I didn't follow up on this one. My initial guess would be something to do with the rewinder. If the printer senses too much tension when advancing the media it will stop printing because it thinks it has reached the end of the roll. There's a calibration for this as well.

Another possible cause of this is if the rollers inside the roll cover, are coming in contact with the blue end on the spindle. This happens if you're using a non-standard paper width like 30", or 15". You should remove the roller that is coming in contact with the blue spindle end. I ran into this recently, though the user had been using the odd paper widths for years, so I'm not sure how common this is.

Also if the black end of the spindle is damaged by the user dropping the roll onto it, it can interfere with the housing where the spindle goes, but you should also have chronic alignment issues, I would suspect.

Anyway, hopefully theengel will let us know what the solution was.

Kiran

[blackcat4866]

Re: Designjet T770 Sheet feed sensor

I don't know why I didn't follow up on this one. My initial guess would be something to do with the rewinder. If the printer senses too much tension when advancing the media it will stop printing because it thinks it has reached the end of the roll. There's a calibration for this as well...

Kiran

I was thinking about this as well. I had gone back to a T2530, maybe the third time. I had misunderstood the calibration procedure and called a colleague at another branch of the company. I've used this many times since then. I remove all paper, power OFF/ON, and wait until the machine asks for paper. The machine has done a base rewinder calibration. I load paper and it works. It might be worth trying.

If there really is paper (or a paper scrap) in the sheet feeder, you may have to do some disassembly at the rear to investigate. =^..^=