[apriorius]

I bought this 80w Chinese laser back in 2008 I think and it's been a real workhorse! Recently however it's been acting funny. Sometimes it cuts as normal, but other times the dimensions are off. Circles will be out of round and certain straight segments will suddenly have a slight angle to them. Also the engrave feature seems to have real problems; sometimes going off track for a line or two and other times the laser will simply not fire for a couple lines. Finally, when it gets all wacky the cut will be very rough instead of the normal smooth cut.

The laser is 80w and uses LaserCut 5.0 and the MPC6515 control card. I usually work in Corel draw, export a .dxf file and import it to LaserCut.

Attachment 183174

In this picture you can see one of the issues. The hole with the red arrow does not close correctly, while the hole with the green arrow does. The simple part is being cut multiple times using the Array Output function in Lasercut. So theoretically these parts should be identical.

Attachment 183176

Whenever this issue occurs the edge starts getting very rough. The red arrow is the bad edge, the green is the normal edge I get.

Very odd stuff, and I can't figure out where the problem is coming from. I can cut the exact same file and sometimes it works great while others it's nothing but trouble. Nothing has changed in terms of the ground, power supply, anything. Does anyone have an idea?

[Exsecratio]

Yup the steppers are losing steps, that would explain the parts not being cut properly and the finish on the edge.

It may be the motors or it may be the actual step driver cards, hard to say without knowing the electrical signals being sent from the cards.

Sorry it's not better news

best wishes

Dave

[apriorius]

Well poop.

I just tried again on thinner material with a file that it cut just fine the other day. Results:

Attachment 183180

Would the steppers losing steps also affect laser power? Because when this happens it frequently fails to cut through all the way dispite being on the same power/speed setting.

I also tried engraving again and had the same problem - the laser will fail to fire on a line or two from time to time, and the alignment seems way out of whack.

[Exsecratio]

Yup, it doesn't actually affect power per-se, what it's doing is jumping so when the laser fires it's not cutting a continuous line. That's what causes the crap finish.

PWM in basic terms (Thanks to the Tweakmeister for explaining it to me) can be considered to be Length of Pulse in a given time period. PRF (RF machines) basically means number of pulses in a given time period.

If the steppers are losing steps the length of pulse will no longer sync with the distance travelled, ergo there will be times when the head moves but the laser is not powered. Once steps are lost things can go all out of wack as each move is relative to the last position. (Incremental mode rather than absolute for the CNC minded).

What you end up with is a stitching effect with the final position not meeting up with the start point.

The reason it doesn't cut through is the laser isn't "burning" a continuous line anymore.

best wishes

Dave

ps: you could rule out a drawing problem but if it has always worked before that's unlikely unless you have changed something.

[apriorius]

Ah ok, that's super helpful Dave. I may fiddle with the wiring a bit but honestly I'm thinking maybe it's time to just replace the stepper and controllers. I've gotten five good years out of them so I can't complain. This is a G. Weike machine so maybe they'll offer some support.

Thanks very much for your help!

[fixtureman1]

Steppers normally don't go bad like that. It could be a bad wire or something binding the stepper or a belt that needs adjusting Also static can cause steppers from missing and jumping so check your ground wire.

[EXLASer]

Hello ,
From the port of that un-closed circle , you need to check is there any gap on X axis .In my opionion , it is probabley got a gap between the ratio part on X axis .The ratio was consist of big gear ,small gear ,and they are fixed on a steel column inside . Check as following : While powering on , with your hand pull the laser head with some strength but not too much. If you can feel a little jump ,that means the big gear or the smaller gear was loosed from the column . Anyhow ,it is 5 years ,may be need to fasten again ,with all parts like belt ,wiring need to check again . Belts should not be too tension and especially checking any disconnect wiring on PSU and controller ,as it is firing time or not ,it maybe the poor contact. We don't exclude the possibility of a bad controller . And by the way ,check Y axis gap exist at the same time .
Optics should be confirmed good as well .

Best regards,
Mary Lee
XYZ Machinery

[Rolf_K]

Sorry, posting inadvertently duplicated.

Well poop.

I just tried again on thinner material with a file that it cut just fine the other day. Results:

Attachment 183180

Would the steppers losing steps also affect laser power? Because when this happens it frequently fails to cut through all the way dispite being on the same power/speed setting.

I also tried engraving again and had the same problem - the laser will fail to fire on a line or two from time to time, and the alignment seems way out of whack.

[Rolf_K]

Before I bought my 50 want Chinese laser I had budgeted for an American-made controller (ANGI from Solustan) and other expenses.
Luckily the laser and XY motion worked but I was unable to install the software and get the controller to read any kind of files whether from computer or a thumb drive.
To make a long story short there were a host of electrical and mechanical problems, I will just list a few: Rusty slides, loose and missing nuts and bolts, no lock-washers, high-voltage arcing in the connector, wires spliced by twisting together but not soldered, no ground connection on 115 V AC input receptacle, no safety interlocks, water and air pump 220 V and conspicuously missing any kind of manufacturers identification tag.
Just a side note, the machine was bought on eBay for about $2500 delivered.
Junked the controller and wired in the Agni, corrected most of the problems listed above, got most everything working a couple of days ago, then my hard drive crapped out and I have not been able to fully test everything.
There are several lessons in the story, one is that you can have several problems at one time and this makes it extremely difficult to troubleshoot.

Well poop.

I just tried again on thinner material with a file that it cut just fine the other day. Results:

Attachment 183180

Would the steppers losing steps also affect laser power? Because when this happens it frequently fails to cut through all the way dispite being on the same power/speed setting.

I also tried engraving again and had the same problem - the laser will fail to fire on a line or two from time to time, and the alignment seems way out of whack.