Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Jim_V on September 20, 2011, 02:29:15 AM

Title: Computer Problems-Jittery steppers
Post by: Jim_V on September 20, 2011, 02:29:15 AM

Here's the problem-I just built a cnc plasma table, and got all the electronics hooked up.  The motors move, but they run rough as hell.  To narrow things down, I borrowed another computer, installed mach3 with the same settings, and the problems disappeared.  The computer that runs rough is a Dell GX620 I got refurbished on Ebay.  Everything on the computer seems fine, except when it comes to the motors. I even tried installing a parallel port card I had, and it didn't make any difference.  Anybody seen anything like this?  Or should I start looking for another computer?

Title: Re: Computer Problems-Jittery steppers
Post by: jimthefish on September 20, 2011, 02:42:09 AM

Hi, I had a problem like yours and used the diagnostic page to chek the computers speed and balance. Mach videos tells you how to check this and gives advice on what is a good computer speed and balance. Replaced computer unfortunatley. Hope this helps. Jimthefish

Title: Re: Computer Problems-Jittery steppers
Post by: Hood on September 20, 2011, 02:56:24 AM

Try the optimisation steps detailed on the downloads page of the main site.
Hood

Title: Re: Computer Problems-Jittery steppers
Post by: Jim_V on September 20, 2011, 04:04:22 AM

I did all the optimization steps, unfortunately it had no effect.   

Title: Re: Computer Problems-Jittery steppers
Post by: Hood on September 20, 2011, 04:51:08 AM

What have you got the Pulse width on Motor tuning page set to?
I know some Dellls can be problematic with Mach.
Hood

Title: Re: Computer Problems-Jittery steppers
Post by: RICH on September 20, 2011, 06:41:38 AM

Quote

Anybody seen anything like this?

I have a Dell GX520, has on-board graphics card,  and its a fine pc except for running Mach via the PP ( worked with the SS).
I tried everything I could think of and was a no go. The problem is ringing on the pulse signal. You can't get rid of it. You need to look at the pulse using an o'scope. On mine there were two pulses present and lagging in time for every pulse sent. Sounded like someone was hitting the steppers with a mallet. Also have a Dell laptop ...no good. Tried a few other Dell's and same problem.

FWIW,
RICH

Title: Re: Computer Problems-Jittery steppers
Post by: rrc1962 on September 20, 2011, 12:21:41 PM

The older Dells work great (Full tower GX260).  The full size desktops and small form factor desktops are almost always a no-go.  I've had mixed results with the newer towers.  It works out OK because the old GX260's work like a charm and you can just about get them for nothing. 

Title: Re: Computer Problems-Jittery steppers
Post by: Jim_V on September 21, 2011, 11:49:54 PM

Just picked up a gx270 from a local repair guy.  Plugged everything in, all problems fixed, motors all run smooth now.  Thanks everyone for helping me figure this out.