[drmbx33]

Hi folks,

I have no clue what is going on but I did some successful cuts with the machine at the beginning (begginers' luck?). I use linuxcnc and parallel port and I started to have errors in my cuts. I realized the problem was not skipped steps but x-axis motor to stop working for a few seconds every now and then.

After checking all sort of details with the computer and configuration (elongating step pulses and other different ideas I picked up here) I was not able to stop that behavior, so I thought it might be a thermal problem: maybe x-axis driver was overheating and entering on some form of thermal shutdown. I opened the box and changed the switches to the minimum current. it did not mattered!

I closed EMC2 program and I realized the x-axis motors that were holding position did stop holding position every now and then (I could notice a subtle noise every time energy stopped flowing through motor windings and when it was back). So that suggested me software was not to be blamed here.

Later, I powered off my computer and the problem of the motor stopping holding position was repeated every now and then (each minute or so for a few seconds). What the heck?

So I removed the parallel port cable from the computer and the problem disappeared: x-axis motor will hold position forever now.

Using a second computer (a different model) did not cause any trouble and the CNC machine worked happily and trouble-free then.

Of course I am going to keep the machine with this second computer but I am at a loss at what could have caused the above mentioned issue. (All devices are powered from the same power socket and ground connection).

Any ideas?

Thanks a lot!

[aarggh]

Sounds like maybe a signal conditioning or earthing/noise issue. Did you check in the BIOS the parallel port was set correctly?

Ideally you need to check BIOS settings are right, and then look at the signals coming out to check they are the right levels, and if they have noise on them. Visually checking earth/ground connections would be an idea.

cheers, Ian

[drmbx33]

Thanks a lot Ian for your input. From the back of my mind I reckon I adjusted BIOS for "improving" configuration at a certain point. I won't be surprised it was that single action that changed the machine from working flawlessly to start having this weird behavior. Should I select EPP, SPP or ECP on the BIOS?

[aarggh]

From memory ECP is what you want, but also turn off any power saving settings in the BIOS, this link also has some good information:

LinuxCNC Documentation Wiki: TroubleShooting

cheers, Ian