Vertical banding

[Peter Martins]

I posted earlier in the year about vertical banding on l26500.

It's clear reading the replies and other posts that there is a lot of people struggling with this and whatever the cause it.

We did not have time or resources at the time to look into it further and the customer upgraded to 570.

Messing with settings seems to be the only solution and hp have a video suggesting what can be done in this regard.

Now I'm faced with the issue again, on a 28500 printer.

This time the printer as working great until the pulley bearing failed.

Since then it's produced very little good work, with patchy vertical banding on blocks of various colours in the same place.

And it seems to be a problem on a lot of models. One moment they are ok, next it's got problem, which does not go away.

I think i can rule out
Printheads - they are perfect
Belt condition
Carriage wiper bushes and dirty rails/ poor lubrication..
Encoder strip
Trailing cable - it's in great condition.

I'm also not going to mess with settings as it seems to be just tinkering.

So what else could it be??

Thank you for reading this.

Bristol inkjet ltd

 

[balstestrat]

How about you post few pictures of the issue.
Picture is worth a thousand words...

 

[Peter Martins]

here are some

 

[balstestrat]

Didn't quite work... No pictures.

 

[Peter Martins]

Great news. It's sorted.
After hours of testing about 20 things and 12 hours on the machine I finally got it printing WITHOUT vertical bands.

Luckily the customer let me in on a Sunday and I had time to explore and test all the possible causes, without distraction and stress

 

[balstestrat]

That's great and all but what was the problem and solution???

 

[Peter Martins]

I sorted it by reversing the trailing cable.

There must be minor damage the cables after it has done 10,000,000 or whatever passes. Just a small variation in conductivity will create a minor change in the print quality, this is long long before it breaks down completely.

Only only on large panels did it show.

The cable looked fine but was not. The machine had done 42,000 m2 and this must have been replaced a few time before

Its a simple and cheap solution.

Remanufactured trailing cables are available for 1st call for service in Birmingham, UK. And also are listed on ebay

 

[balstestrat]

Yeah... I was guessing so. Trailing cable really being the only reason for "blocks of various colours in the same place".

 

[Peter Martins]

I thought it was sorted.

it was not.

This is what I think happened
Belt Bearing failed leading to
Extra strain on motor causing damage.
Belt replaced but now vertical banding
But it was random pattern. So it made sense to think the trailing cable had been disturbed while replacing the belt.

Reversing tc seemed to work for a bit. Or did it?

But when used the motor degraded further.
So I assumed the tc reversal did not work.

Replaced the tc with a new one.
But banding was worse.

This time however there was a sort of repeat at 6cm, which is exactly the circumferance of the spindle, (this showed up much better on the phone camera)

Finally replaced the motor and it cured the problem and seemed to run more smoothly, and with less noise.