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Skewed feed on 360

Morkel

New Member
This one is a wierd one, and it's definitely a machine fault, but I wanted to see if anyone else has experienced anything like it. It actually started as three seemingly unrelated problems that now seem to be very much related.

The first issue we had was that after the printer had been on for a while, say, half a day, there would be a noticeable lag in the responsiveness of the control panel. Most obviously, when you are selecting a media that you've just loaded, there is literally a 5 second lag after you confirm the media type before it allows you to open the window to slide the edge holders. As in, you press the buttin to confirm, and it takes 5 seconds for it to change the colour of the button, acknowledging that you've pressed it. Often you're not sure if you actually did press it, so you do it 3 or more times just to be safe, and it still just bums around for a while, thinking. If you restart the printer, the control panel goes back to being quick and responsive. Somewhat annoying, but alone, no big issue.

The second issue is that we'd had print alignment issues, like the passes are stepped slightly incorrect, the sort of thing you'd expect from a grubby encoder strip, or just the heads needing alignment. After cleaning the encoder strip and doing alignments, it's exactly the same. Restart the printer, and it is perfect. Which made me think that it was related to the above processing lag, in that there's a software glitch. It's happened multipe times, sometimes as bad a stepping a good 10mm sideways over 50mm of print length. This is a bit more worrying of course than just a slow menu.

The last one was a *****. We'd had the machine for 6 months (bought it new). Out of the blue, we had two medias that had always printer perfectly, all of a sudden getting head strikes on one side. We looked at every possible cause, like too much heat causing it to ripple, like the takeup reel not being loaded straight (alternating between loading it up before printing, then during printing, then not using the takeup at all), a thousand other things. One media was a textured SAV fabric-based wall graphic, so you could understand a bit of stretch, but the other was a film for pull-up banners - no stretch at all and we'd used maybe 10 rolls of it to that point with no issues. We couldn't find what was causing it. The strange thing was that it always got ripples on one side of the media. Not the same side every time, sometimes on the right, sometimes on the left, but once it started it would stay down that side. The strikes were occurring after the media had passed the edge holders, as it'd be there that the ripples in the media would hit the head as it passed over. In the end, with no cause found, we'd resorted to manually gaffer-taping the metal edge holders from our L28500 below the standard ones, meaning the media's edge was held down all the way to where the media disappeared behind the window in to the curing unit.

Just yesterday it all came together. Printing a poster that was only 1000 x 700mm, one of the workshop guys brought it back to me and said it's not straight, it doesn't fit the frame. We measured it, and sure enough one edge was 8mm shorter than the opposite edge. Thinking the guy had trimmed it wrong (I never make mistakes of course, it couldn't be the file...), I asked to see the scrap, and sure enough he'd cut it to the exact crop marks. And looking closer at the print, there was a definite alignment issue on one side. Here's the kicker though - the alignment issue wasn't on the scan axis, it was on the feed. One side of the media had fed 8mm more then the other, over just 700mm of print length.

Here are the pics:

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As you can see, scan axis is pretty good. But you can definitely see inconsistencies in the feed axis, especially with the blue on yellow, where the top of the pic has okay alignment but the bottom is way out. Restarted the printer, printed it again (same file from the rip, just dragged back up and hit print again), and it's perfect.

So this has me thinking that it's all related. For some reason, after the printer has been on for a while, it starts having brain farts and glitching. Maybe it has something to do with how it comes out of sleep mode??? How a software glitch could cause one side of the media to feed at a different rate to the other I don't know. I would have thought for sure that the rate that the rollers move the media would be locked. And it can't be a mechanical issue, like the media is somehow slipping, otherwise why would simply restarting the printer fix it?

Anyone else ever seen anything like this?
 

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dypinc

New Member
I haven't seen the alignment issue, but maybe I better keep a closer eye on it.

The menu issue, now that is familiar. Mine gets so bad at times that I have to reboot the printer. On a daily basis the menu lag is the most annoying thing about this printer.

Back to our color shifting. Now I am wondering if it might be related to the same thing as well. Next time I catch it off I am going to print a test print reboot and print the same test print again.
 

rjssigns

Active Member
I don't have a latex printer, but all should work about the same in regards to material feed. It's losing steps. With my Roland the rear Paper Interrupt sensor was working intermittently. Even though I could load material and print it would drift. It needs that sensor info to trigger something that allows the encoder to work properly.

With the sensor out of commission you could not do any type of calibrations, linear or otherwise. Since the HP's are so automated you may have no way of doing a sensor check. It also may not be alerting you to something being out of whack. My Roland doesn't.

Once I got the Paper Interrupt replaced it worked great until the encoder strip finally gave up. Both were cheap fixes.

If the HP runs the same as my Roland here's another tidbit. If you're losing steps towards the head park side(control panel) it's the encoder strip. This is only valid if all sensors/calibrations are on point.

Not sure how you'd check it with an HP though.
 

greysquirrel

New Member
So much here I may have to re-read to add...media striking one side
remove media, lift blue pinch lever arm, open glass...no gently flex the pinch wheels upward...these are plastic so be careful...use your thumb and focus on section that has a small mettle prong...do this across the entire length...you are no trying to bend...you are just flexing upward. These pinches ship too tight, even on aqueous printers...it may be biting irregular or stronger on one point causing the buckle of the media and head strikes.

screen delay..
they all seem to take a little bit to sense touch...just keep reminding yourself that it is not an iPad! Remember the HP tablet that took too long to come to market and by the time it did it was too underpowered? I do...I think that's where these screens are coming from...make sure your firmware is up to date as well...if the lag is still there...call for service while it's still under warranty. HP will replace it.
 

greysquirrel

New Member
Told you

the fabric media...
what is your temp? Every profile has temps at 230 degrees...way to hot imo
Adh vinyl 210-215, banner 215-220, photo paper 200-205, fabric 205-210...that's were I start .....if you have too much heat...it causes media to rise(heat rises) and media will go with it...vacuum will not help...edge guards may...

tracking issue
is omas enabled in profile? This can be turned on and off...is the camera clean? There is a calibration that can be done to correct...
 

greysquirrel

New Member
Lastly
print alignment issue
obviously, make sure linear encoder is clean...warm water and shammy from maintannce kit..
and if you haven't oils unit and filled oiler at install...most people do not...it's a good time to do this now that you are 6 months in...
power off printer from rear, open maintenance door and gently pull cartridge forward(this will free carriage) open glass
place 4-5 drops of oil on pad on left side of carriage at rail...on right side of carriage near the rail is the oiler...put oil in that hole...8-10 drops
then I will put a few lines of oil on main lower rail and a few on back upper rail...get in right side of cabinet and look at top...then manual override carriage left and right to work oil into pads

then
I have seen this a few times..heads are not seated tightly
remove each Printhead and reseat making sure they have a solid connection
power back up
perform head alignment and color calibration...see if that helps
 

Morkel

New Member
I appreciate all that feedback, but you must have missed the part where it only happens after the printer has been on for a while, the same as the lag. When you first turn the printer on, and for the first couple of hours, it is perfect. No lag, no skew, no head strikes.
 
I appreciate all that feedback, but you must have missed the part where it only happens after the printer has been on for a while, the same as the lag. When you first turn the printer on, and for the first couple of hours, it is perfect. No lag, no skew, no head strikes.

Regarding the skew issue: Are you using the take-up reel when this issue occurs or not?
 

AF

New Member
How wide is the media you are using? The heavy metal take up loop former can easily cause the distortion and skew you describe. Get the plastic adjustable loop formers to remedy.

You mention turning the printer on daily. Do you power it down at night or let it go into sleep mode? HP recommends leaving the machines on and letting them go into standby at night as it puts less stress on certain parts (mainly ink system).

The panel delay sounds like a thermal issue. The machine heats up after running for a while and a cold solder joint, bad crimp or faulty electronic component malfunctions after it expands due to being warmed up. Very difficult to locate these faults and the HP field techs are useless in this situation.
 

Morkel

New Member
The All Day Breakfast artwork looks familiar, everything else sounds incredibly frustrating!

Indeed :) Are you doing these too are you?

How wide is the media you are using? The heavy metal take up loop former can easily cause the distortion and skew you describe. Get the plastic adjustable loop formers to remedy.

You mention turning the printer on daily. Do you power it down at night or let it go into sleep mode? HP recommends leaving the machines on and letting them go into standby at night as it puts less stress on certain parts (mainly ink system).

The panel delay sounds like a thermal issue. The machine heats up after running for a while and a cold solder joint, bad crimp or faulty electronic component malfunctions after it expands due to being warmed up. Very difficult to locate these faults and the HP field techs are useless in this situation.

We turn the printer off at night because of this regular problem. If it is a heat related issue (which it could well be), I guess it wouldn't be a stretch to think that glitchy electronics could result in a mechanical malfunction of the feed rollers, since everything is electronically-controlled. Anyone know how they're made? I would have assumed that they're one piece, so that it always tracks at exactly the same rate on across the full width.

For argument's sake though restarting it would only temporarily fix the problem. The fans go nuts to cool it down on shutdown, but once it starts up and heats up again the issue would surely resurface after not much time at all. Further confusing the issue is that we're running HP's own 421 poster paper, and it only runs at 80 degrees C. We've had banner materials and SAV's running much hotter and for way longer without the issue, because I've printed it fresh after a restart.

As I mentioned earlier it shouldn't be because of the take-up. The issue occurs whether we're using it or not. That poster from the photos was so short that it didn't even touch the ground hanging out of the printer.

FTR, did another poster last night, 1600mm long. One edge measured 1589mm (crop mark to crop mark), the other 1566mm. So it's running short, with 23mm difference on one side to the other. I've left the printer off all night and am about to print it again with a cool fresh machine. Will see what happens.
 

Morkel

New Member
This time it came out 1591mm & 1593mm. So it's short, but only 2mm difference on each side. Printing short makes me think OMAS. I'm going to turn it off, see if it gets closer to the 1600mm (and see how much the quality is effected). And next time I'm getting the lag I'll do the same, print without OMAS, see if it's more consistent side-to-side.
 

AF

New Member
This time it came out 1591mm & 1593mm. So it's short, but only 2mm difference on each side. Printing short makes me think OMAS. I'm going to turn it off, see if it gets closer to the 1600mm (and see how much the quality is effected). And next time I'm getting the lag I'll do the same, print without OMAS, see if it's more consistent side-to-side.

Short runs on a latex machine will always have the most distortion, bowing and length discrepancies. This is because of how the end of the media changes shape during curing as compared to rest of the media. You should be able to enter length adjustments and bowing compensation in your rip for any particular media. But in order to get accurate measurements you need to print the test plot at least 5 or 10 feet from the end of the media and between 2 other jobs so the media is fully distorted at the test plot.
 

Morkel

New Member
Short runs on a latex machine will always have the most distortion, bowing and length discrepancies. This is because of how the end of the media changes shape during curing as compared to rest of the media. You should be able to enter length adjustments and bowing compensation in your rip for any particular media. But in order to get accurate measurements you need to print the test plot at least 5 or 10 feet from the end of the media and between 2 other jobs so the media is fully distorted at the test plot.

This is not the issue. What you're describing would be the media itself shrinking or distorting. That's not the issue - the ink is being dropped in the wrong position because the media is feeding unevenly and skewing.
 

AF

New Member
This is not the issue. What you're describing would be the media itself shrinking or distorting. That's not the issue - the ink is being dropped in the wrong position because the media is feeding unevenly and skewing.

If you used the metal loop former with that particular roll of media, the media will have developed uneven tension on the roll. The feed rollers are moving at the same speed but the tension across the roll is now uneven. If you then try to print a short job without the take-up, the tension is still in the media roll and thus still uneven across the feed rollers. The only solution is to unload the media, cut a few feet off the roll, and rewind the roll by hand. This will eliminate the distorted media from the roll and restore tension. It should load and print without the issue from that point forward.
 

kanini

New Member
About the lag; have you tried to do a file system check? HP manual says to do this every six months or so. Just a 0.05 that don't take long to try, though I doubt myself it will help, just throwing it out here...
 

Morkel

New Member
If you used the metal loop former with that particular roll of media, the media will have developed uneven tension on the roll. The feed rollers are moving at the same speed but the tension across the roll is now uneven. If you then try to print a short job without the take-up, the tension is still in the media roll and thus still uneven across the feed rollers. The only solution is to unload the media, cut a few feet off the roll, and rewind the roll by hand. This will eliminate the distorted media from the roll and restore tension. It should load and print without the issue from that point forward.

I see where you're coming from, but I don't think this is the issue. For one, this recent media has never been on the takeup reel. Secondly, after that first dodgy print, the media on the roll had a big crinkle from the uneven feed, so I trimmed off a good 1.5 to 2 metres of it before feeding it back in to the machine.

The nail in the coffin though is the media that first did this - it's a typical roll of grey-back pull-up film. We'd gone through probably 10 rolls of the stuff, sometimes on the takeup, sometimes not, and it had always printed flawlessly. Out of the blue it did the uneven feed. I'm absolutely positive that this is a software / electronic glitch, not a mechanical limitation.

About the lag; have you tried to do a file system check? HP manual says to do this every six months or so. Just a 0.05 that don't take long to try, though I doubt myself it will help, just throwing it out here...

I have not done this and I will do this first thing in the morning. Much appreciated! I have taken note of all the most recent occurrances, so even if there's nothing showing in the check, I'll at least have some date/time stamps for the HP tech to look at. Thankfully it's the state's top HP tech, not just the dude the reseller sends out. Appointment booked in for 9am on Friday.
 
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