Laser suddenly shifts engraving field several inches

[matt zabel]

Hello, I'm having an issue with my Universal M-360 60watt laser. Midway through raster engraving, the laser head will suddenly jump several inches to the left, often bumping into the rail, before continuing to engrave in this new location. This results in a ruined image (not cool!), since the top half is 3-4 inches offset from the bottom half! Sometimes it happens towards the end of the engraving and sometimes right at the beginning. It started when I was engraving a whole sheet of business cards in wood veneer. I thought I had fixed the issue by engraving the sheet one row at a time, but now it's happening with most files, regardless of the size.It seems unpredictable and has happened with different files on different days over the last 4 days.
I would really appreciate ANY help or suggestions you might have.

Thanks in advance!

-matt.

[Dan Hintz]

Is this the old model that used memory sticks on the motherboard? If so, take them out and clean the contacts with an eraser. If that doesn't work, try replacing the sticks with new ones.

[John Volkmar]

Matt, this problem almost always has to do with the X axis components ( bearings, Idler, drive gear and/or, belt, or even the stepper motor ). I would turn the power off and move the head all the way left and right. It should be smooth with no binding in any place. After that check I would check your belt tension, ( should be 150 grams at a 1/2" deflection ) and then probably replace the belt and X drive gear if still slipping. If you have a local rep they could come in and tune the machine up in under an hour.

[matt zabel]

Dan and John - thank you both for the quick replies. I really appreciate it.

Is this the old model that used memory sticks on the motherboard? If so, take them out and clean the contacts with an eraser. If that doesn't work, try replacing the sticks with new ones.

Dan - Not that I know of...I'm not sure where the motherboard is, but I don't know of any memory sticks used with the system. I print directly to the engraver from my PC via a usb-parallel port cable.

this problem almost always has to do with the X axis components ( bearings, Idler, drive gear and/or, belt, or even the stepper motor ). I would turn the power off and move the head all the way left and right. It should be smooth with no binding in any place.

John - It is definitely not smoothly sliding left to right. It will slide a couple inches, but then stops and won't budge until I apply more pressure, then it jumps several inches at a time - not smoothly sliding at all. I did try tightening the belt, but I don't have a tensioning scale, so I only tightened a half turn or so. If anything, this made the problem slightly worse. I'm suspecting it is the x-drive motor or gear, as you suggested, but am not sure I have the skills to get into those areas! I just emailed the local ULS rep, assuming they will be able to set up a service call or refer me to someone else who can, but appreciate any other help you guy (or others) might suggest.

[John Volkmar]

So you need to take the x axis apart and check each component to see what has worn out. I would guess that either the stepper motor is gone or the Drive gear itself has slipped down on the shaft of the stepper motor and is contacting the Y bearing plate causing the binding that you are feeling. It won't work very well until you replace the compnent(s).

[Scott Shepherd]

I've also seen the drive pulley not be on their in alignment, so as it's spinning, the belt rides against the flange on the pulley, then it gets to a point where it's really riding up the flange and it "pops" back into the track.

As for belt tension, I think it was shown to me that if you take a pencil and pull the belt towards you, and drop the pencil down between the belt and the X-Axis cross beam, the tension is right when the pencil won't fall out on it's own. Sounds odd, but it works pretty well.