Designjet 500 Colors Misaligned

[theengel]

I've got a designjet 500 where the colors print offset from each other. New printheads, new belt, swapped encoder strip from a working machine. I'm attaching an image of the printhead alignment pattern (the alignment errored out). It looks like every time the carriage does one of the quick passes, that magenta bar moves a little bit. Also, you can see in the middle of the black pattern, how the blocks get squished together at one spot.

I'm thinking either the motor, the Electronics Module or the carriage itself, but I'm not sure where to start.

Oh--paper advance calibration passed just fine.

dj500.jpg

[kuby]

Re: Designjet 500 Colors Misaligned

I am thinking if it is like the other models, there are two bushing that go with the carriage assy that pertain to the carriage bar. If you put them back in wrong that will cause some play when the carriage goes back and forth causing misalignment. Also make sure that the carriage bar is free from dried ink and well oiled for free movement.

Something to check, had this happen on one just about a week ago.

[Kiran Otter]

Re: Designjet 500 Colors Misaligned

The print head alignment is not a diagnostic image, other than you can see if a head is failing or totally dead. The image you provided looks normal to me. If the alignment fails, you may have a bad line sensor, a bad carriage, or the media being used is too reflective. Make sure you do the alignment on bond media, not glossy or anything exotic.

For image diagnostics, run the troubleshooting in the Ink menu instead and follow the service manual. Again, the alignment needs to be performed successfully first.

Do you have an example of the end user's print that is showing a defect?

When you replaced the belt, did you use a genuine HP belt or one from China?

Kuby is correct; those bushings can be inserted upside down, however they should never be removed in the first place. Also make sure the rear carriage bushing hasn't been damaged or is missing.

Kiran

Clipboard01.pngRear carriage bushing.jpg

[_SuabE_]

Re: Designjet 500 Colors Misaligned

Is the carriage assembly running smoothly during initialization, no tilting movement during home position? Is this problem comes out after carriage belt replacement? if it is check the carriage belt alignment, probably misaligned..

[theengel]

Re: Designjet 500 Colors Misaligned

Thanks everyone.

You're right Kiran, there's no reason to take those bushings out. But low and behold, someone had done just that. When I brought in a new carriage unit and compared the two, the bushings were in backwards (and one was broke). I should have clued in on that while I was taking it apart the first time and noticed all the misplaced screws.

[Kiran Otter]

Re: Designjet 500 Colors Misaligned

Here's a print head alignment from a working printer. Note the missing nozzles in the black. I took out the head and it was caked with ink. I scrubbed it with a paper towel and Simple Green and it came clean, works perfect now. (I can't recommend doing this because it will sometimes make it worse, but they had a spare black head, so I figured worse case I'd just replace it.)

ScanImage001.jpg

So was the problem the bushings? I always know when someone who doesn't know what they're doing has been into one of these printers. They don't know how to remove the carriage so start taking things out that should never be touched.

Kiran

[theengel]

Re: Designjet 500 Colors Misaligned

It's a little frustrating, because there's no way that printer worked right ever since it was taken apart. So the first conversation should have begun something like:

"Hi, we took this carriage out and now the machine's colors won't line up."

But then again, I really should have caught it. I knew the screws were all in the wrong places, and I should have found a picture to compare it to before messing with anything else. It's not easy to remember how those bushings are placed. In fact, after replacing 15+ belts per year on these, this is the first time I've ever actually taken a bushing out and held it in my hand.

[Lance15]

Re: Designjet 500 Colors Misaligned

Never removed those bushings either. Wouldn't know what they look like when they are in correctly.

Does anyone have pictures of right and wrong?

As theengel said, after many belt replacements under my belt (ha, ha) as well, I've never seen those bushings out of the carriage.

[theengel]

Re: Designjet 500 Colors Misaligned

I ordered new bushings and stuff for it. I'll take a picture and post the wrong and right ways to install.

[Kiran Otter]

Re: Designjet 500 Colors Misaligned

500 carriage bushings.jpg

I only ran into this issue once, after a customer tried to replace the belt themselves and of course had no business trying to do so. They didn't even put the screws and washers back that hold these bushings in, so I discovered them partly sticking out which lead me to also discover they were inserted incorrectly.

There are other threads about this issue out there.

https://superuser.com/questions/756854/hp-designjet-500-printhead-allignment-issue

I even posted about the correct and incorrect position of these bushings previously here.

http://www.copytechnet.com/forums/hp/98972-hp-designjet-500-juddering-2.html#post471257

Kiran