View Full Version : ULS PS25 intermittent issue with Y-axis

Justin Jiroutek
02-03-2012, 12:30 AM

I have a ULS PS25 laser engraving system with an intermittent issue. The problem that I am seeing is that sometimes the Y-axis does not want to home, and sometimes stalls during a raster job. If the gantry is placed in the middle of the table at the time of homing the Y-axis does not want to home at all. When the Y-axis does not home, the back 2 red led indicators are not lit (total of 4 red leds, back 2 not lit) on my gold colored power supply. With power off, manually moving the gantry back and forth through the range of the table feels smooth without any binding. I am able to home the machine succesfully if I position the gantry (Y-axis) near the home position before the system initates the homing sequence.

After the system does home, I am able to cut parts without too much of an issue. I've had the Y-axis quit working, or stall once in the middle of cutting a part. I was able to shutdown, re-home with Y near the home position first, and run several jobs succesfully afterwards. The last time I've run the machine I had an issue with homing, but once it was homed I was able to run without any issues. I ran 6 different cutting jobs without a glitch over a period of about 6 hours. The gantry was moving over the whole area of the table during this time. Also, I was cutiing 3/16" acrylic and my speed is set fairly low around .6 inside the ULS Windows driver.

The issue is worse when trying to raster as the Y-axis likes to stall more frequently in the middle of a job. Meanwhile the X-axis continues to run, along with the laser. Needless to say I don't walk too far from it when it's running. Sometimes I can raster with no problems, but I am at the point where I don't really trust the machine to be able complete a raster job successfully. When the Y-axis stalls, both of the back 2 led indicators are not lit on the gold colored power supply. The fan on the unit is working.

Anyone have any inputs as to where my issue might be? I'm positive that it is my power suppy malfunctioning, but I was looking for reassurance...


Mike Null
02-03-2012, 6:22 AM
Have you checked your belts for slippage and are the set screws on the bearings that control the Y axis movement secure?

Sorry I can't recall the nomenclature for these items --it has been a long time since I had a ULS.

Justin Jiroutek
02-03-2012, 7:22 AM
Mechanically the machine appears to be sound. I see where your going with checking the bearings, however the 2 led indicators on my power supply drop out when the issue occurs. I would think that if something was slipping it wouldn't necessarily disable the output on the power supply. However I suppose if one side of the gantry is not in sync with the other that it could cause a problem. I do not suspect that this is happening, but I will definately verify it. Would this type of mechanical fault disable the output to the motor? I'm not sure, but I don't believe it would since there is no feedback from the motor.


Dan Hintz
02-03-2012, 7:23 AM
Sounds like the power supply might be dieing, or there's a short in the motor windings/cable causing the PS to clamp down.

Mike Null
02-03-2012, 8:38 AM

What I am suggesting would affect the engraving alignment but not the electronics.

Mike Mackenzie
02-03-2012, 12:50 PM

Reseat the U-Step board in the gold box. You have to remove the mother board and top plate from the gold box. Leave the Mother board attached to the plate. Get an air hose and blow out the gold box and reaseat the board you see in there. Before putting the MOB back on check to see if the cooling fan on the gold box is running correctly.

If the problem still exists then you have a Y axis driver that is starting to fail.

Sorry you have a PS the MOB does not have to be removed only the top cover on the gold box.

Justin Jiroutek
02-03-2012, 10:46 PM
Thank you all for your help. As I stated before I had a hard time homing the machine the last time I did some cutting. This morning I did some more troubleshooting in efforts to provide more information the with regards to the problem. This time when I tried homing the machine I didn't have any issues at all. I move the gantry to several places on the table and it homed with no issues. I couldn't get it to fail. It is quite sporadic, sometimes I don't have problem, sometimes I do.

I will follow Mike Mackenzie's advice, run the machine some more when I get some time and will report back. Also, does anyone know if there are end of travel sensors for the Y-axis, or any other sensor that might disable the output? I wish I had an electrical schematic for the machine...

Thanks again,

Mike Mackenzie
02-04-2012, 6:23 PM

If it is not homing correctly then I suspect the Limit switch they are optical switches and are very close to the exhaust plenum.

I uploaded a pdf diagram of the motion system that shows where the limit switches are try to clean them with a q-tip and some lens cleaner. They go bad so I would not be surprised if you have to replace them.

Justin Jiroutek
02-08-2012, 8:44 PM

I did re-seat the U-step board, but the issue did not go away. Sometimes when I turn on the machine the back 2 LED's aren't lit, and the Y-axis will not home.

Also I noticed that when I turn on power to the machine, sometimes the fans that cool the laser don't turn on. You can see them try to turn, or flinch when the switch is pressed. If I do a power cycle to the machine sometimes they will turn on, sometimes they won't. If the laser cooling fans are running and I can home the machine, it will run. However, at any given time the back 2 LED indicators on the gold box will drop out and my Y-Axis will not run until I power cycle. I no longer believe the issue is a function of the gantry position due to the sporadic nature of the issue.

I feel more confident that I have an issue with my power supply. I will have to try and track down a replacement.


Paul Grothouse
02-09-2012, 9:29 PM
I had the same problem with my Universal ILS. I chased it for weeks. It ended up being a bad cable. I am not sure how your machine is configured, but mine has a small board on the laser head that is controlled by a thin ribbon cable. This board controls a lot of the functions of the homing etc, I always assumed it just did the autofocus. This cable does not take abuse well, mine got bent one time. After we replaced the cable the problems went away.

Universal tech support is very good, I recommend you access them.