Laser not completing jobs correctly

[Jack Cope]

Hello again all,

My large Chinese laser has been giving me a headache this week as all the jobs that go through it come out miss aligned. The laser will start a job correctly but will start putting cuts out of place as the job progresses leading to the whole job to be incorrect.

I have been using this vector drawing of a motorcycle as a test example as its fairly complex with a lot of direction changes and as you can see the drawing is not completed correctly. The bottom one was done at a very low speed to see if that would stop the error however it still persisted.
WhatsApp Image 2018-05-25 at 17.38.04.jpeg

One thing I have noticed is that the same parts of files seem to fail, however they don't fail consistently (ie sometimes those parts will be fine and others will fail). Thinking it was a file error I've spent some time fixing lines and so on so I don't think this is an error with the files. I've also tried running the files through RDworks and Lightburn to see if it was a software issue.

I suspect it could be;

- damage to the belts/gears/drive wheels, I haven't taken them off but I've not noticed any teeth missing or slackness

- damage to the steppers, not something I'd know how to diagnose!

- something wrong with the voltage inputs, again not something I'd know much about

Any advice would be most appreciated, this machine being down is quite frustrating and the seller, as always, is not much help!

[Kev Williams]

engraving moving at or about the same place but not all the time, sounds exactly like one of the X stepper motor wires, that loop up and around in the 'drag chain', is broken or nearly so at some point- I've had this happen on two different machines and the results are the same-- Listen to the machine as it engraves, if it sounds 'grind-y' or otherwise sounds like it's laboring when the misfires happen, high probability of a bad wire:

My Chinese Triumph:
chain3.jpgbrokenwire.jpg

-and my 'western' Gravograph LS900..
9wire2.jpg9wire3.jpg

[Jack Cope]

Thanks for the reply Kev. Went through the entire machine looking for breaks, fixed a few that were found, and still had the issue. As a last resort I wired the old controller back in (we upgraded it to a Ruida controller) and the problem went away. I've asked for a replacement, presumably sometimes these things are just defective!

[Kev Williams]

Troubleshooting is 9/10 of the battle, glad you nailed the problem!