Problem- losing steps at random times

[Rouckie1]

Hello,

I don't have much experience with stepper motors and am having some difficulties with my z-axis. It's a 1452 OzInch stepper motor that is on the knee of a 2500 Lbs bridgeport style machine. Everything works fine, accelaration goes without problems, I can get high speed. The problem is, once in a while the motor halts. This does happen at speeds less then half of the top speed and while the knee is beyond the acceleration stage. So obviously, the motor is powerfull enough, but why does this happen? resonance?

example: the knee has allready travelled 3 inches up or down at a steady speed with a light cut, everything goes smoothly, and once of a sudden the motor stops, accompanied with the noise of a stepper that lost steps. (mach 3 keeps on counting).

thanks,

Roel

[James Newton]

Mechanical binding? Overheat?

[rouckie]

I might have found the reason. But, it brings another problem.

While moving the x-axis, I noticed a short stop (the computer stopped giving pulses to the stepper during let's say half a second), and continued to the desired position. While this did work out for that move on the x-axis, it might be the reason for the z-axis to halt, because the acceleration from zero to the feedrate after the stop is to fast for that axis.

Is this something that happens on a regular basis? what can be done to solve this problem?

ps: Thanks for the reply James.

[James Newton]

What software? If you are running in windows (and I think *nix as well) you may be encountering a case of the OS becoming occupied with some background task and not allowing the CNC software to run in real time.

That's one reason why I use TurboCNC in DOS, no multitasking = no hiccups. It also allows me to use an old 'throw away' PC and not risk my nice iron on the high power interface.

I'm honestly amazed I don't hear of more problems with that sort of thing happening on Windows hosted programs.

[rouckie]

I'm running Mach3. I allready thought about this being the problem. Maybe Emc2 is a better choice for this reason?

I was also thinking about the usbcnc solution, any thoughts about this one?
Eding CNC - PC based CNC control

[James Newton]

If the OS is what is causing the CNC program to hiccup, then changing to EMC2 or EDNG isn't going to make any difference. You might try asking on the Mach 3 or other related forums for advice on how to stop the hiccups from happening.... Or go get an old freebie Win98 machine, boot up in the command prompt, and run TurboCNC.

[vger]

James, EMC2 runs under real time linux. I've been using TurboCNC but am going to switch to EMC2. Better editor, visual motion display, DRO follows while in motion, and other advantages.

If the OS is causing the interuption, then all the axis would stop at the same time.

rouckie, You mentioned there was a noise in the Z when it stopped. That really sounds like something may be binding up. Can you check with a hand wheel?

Steve

[Dorsal]

I think it's either electrical noise or port interruptions.
Do the stops coincide with the blower from your room heater switching on? The new "motion sensing" light switch? What's new in the room?
Have you run the "drivertest.exe" file, found in the root directory of Mach?

[James Newton]

vger, in his 12-09-2010, 12:32 PM post, Rouckie1 said the X axis stopped and he could see it on the screen. So it isn't just the Z and it /is/ the software.

It's good to hear that EMC2 runs under linux, but then you have to install Linux right? I've tried that in the past, and it did NOT go well... for me anyway. I guess there are people who can make that work, but I'll stick to good old TurboCNC for now. I can edit on my good machine and have all the fancy displays and simulations I want there... the old box carries out the orders just fine.

[rouckie]

the noise is just after the stop I think. the stepper stops and then has to go full speed without the acceleration curve... this it can't do, so the motor stands still.

[vger]

rouckie,

Are you by chance trying to run the machine from a laptop? There are known issues with laptops doing this sort of thing because they are busy checking battery charge status and other things.

Is there a certain feed rate at which the Z stops like this? If so, you might try adjusting the acceleration rate down a bit and the max speed up a bit and try looking for a particular speed that this happens. If it happens even when running very slow, then it is most likely something binding up a bit. What kind of linear actuator does this machine have? Ballscrews?

James,

When you download the ISO for EMC2 (and burn it to a CD of course) it has Linux and EMC2 on the disk. It will allow you to run it to try it without actually installing it on your drive if you want. If you do want to install it, it is a pretty well fully automatic install.

Steve