Hello everyone

[Stefan Denecke]

Hi everyone!

I'm Stefan from Münster in Germany.
About a year ago I've bought myself a chinese laser cutter. I chose a blue and grey "omtech 50W" machine from eBay along with a S&A CW5000 water chiller.

I've had some experience using a laser from my workplace - I'm a teacher at a Design School - and always dreamt of owning such a marvelous piece of equipment myself. After finding out, that they became quite affordable I got one. Also I watched a ton of YT videos regarding buying one of these china machines. Naturally I thought that I was quite prepared for owning, operating and servicing the little dragon.

I bought lightburn and never touched RDworks.

Since I can't use the machine in my own home it is located in my father's small workshop. I have to drive a little to use it. Because of that during this year I used it quite sparingly and spend more time tinkering with it. I equipped the machine with an analog ammeter, retrofitted an air assist, tried and failed to install a lightburn camera (never got a stable, repeatable angle to the working area or LB refused to show the camera picture) and was in general quite happy - until recently when the whoes began and I ran in a technical brick wall.

Seems I wasn't prepared at all.
The controller says that I have less than 8 hours of laser "on time" but suddenly I can't cut 3 mm material of any kind any more. I aligned the mirrors in every achsis to my best ability, exchanged the default (mo?) mirrors to quite expensive copper gold plated ones, bought a new 2" CVD-Znse Lens (US II-VI) (replacing the original 2" lens expecting it to be somewhat better ...). I Upgrades the air pump to a Hailea ACO318. To no avail. If anything everytime I got back to the workshop the machines performance got even worse. As If it was degrading by not using it ...

In addition the last time I did some testing my machine can't produce round circles any longer. I get random wobble or misaligned start and stop position resulting in unclosed circles. Sometimes it is more pronounced but the circle never appears quite round. I retightened the belts, checked for any obvious play in the laser head or gantry and railings but everything seems rock solid. I read about grub screws but I checked my stepper motors and the toothed pulleys (?) appear to be press fitted - at least I didn't see any screw holes. Granted I did not take the belts appart and for the y-achsis I would have to take the tube out and disassemble the back it seems.

So, long story short I'm quite frustrated and a little disheartened and came here after bingeing a lot of Russ's videos, seeking help with fellow laser owners.

Cheers

[Pete Cyr]

Welcome Stefan - sorry for your troubles.
1. Back up your Vendor setting if have not already. (Did you change any values in the vendor setting since purchase)
2. "my machine can't produce round circles any longer. I get random wobble or misaligned start and stop position resulting in unclosed circles."
check to be sure your lens is snugly secured. There should be a silicone washer on one or both sides of the lens locking ring. You don't want to tighten and crack the lens - just snug enough the lens doesn't move. This is the most probable issue with your circles but has little or nothing to do with the depth of cut.
3. A number of issue affect longevity. Typically, they are rated for 10,000hrs. I would suspect the tube is the issue since the power supply is still working and it will not perform as it did when purchased.

[Stefan Denecke]

Yea, the backup idea came a little late. I made two changes prior to making a backup of my machine settings: set a limit to the power output of tube 1 (formerly 60 % now back at 99 %) and enabling the air assist. As far as I can tell no other setting where changed at least not intentionally. I didn't touch steps, size, speeds etc. I wish I had made a backup earlier.

I'll check the lens holder next time I'm in my workshop, thanks for the advice. Propably had taken apart the machine before looking there *fingers crossed".

I made a mode burn for the laser tube and got some interesting results. I'll attach a picture. You can notice a significant change in the beam after each mirror. I doubt it actually is a mirror issue though. I switched the gold coated one to my old mo mirrors and the result is pretty much the same.

One strange thing that confuses me as well: I habe a ZYE 60W power supply with an integrated ammeter - I also installed an analog ammeter. But the devices show different values - the analog one tends to be about 2 mA higher. I already tried a second analog one with similar results. I really don't know which value to trust and trusting the wrong one could potentially overdrive the tube. Normally there shouldn't be any change of amps in the circut am I right?

[Pete Cyr]

"Normally there shouldn't be any change of amps in the circut am I right?"

Yes - but different devices are apt to give different values because of calibration or circuit impedance.
I would use the most conservative value to limit amps.