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Really need help
« on: August 12, 2009, 03:57:58 PM »
I see the Smooth Stepper discussion area is not taking new posts.

I have been working with Mach3 for about three months now and am convinced that this application is working well for most of you, but I continue to have problems with instability (losing steps) and am curious if anybody thinks adding a Smooth Stepper card might help me.

Right now I have a PC running Windows XP dedicated to this project.  I have run the System Test and it reports the system tests OK, and the "spikes" are nice & short... I have also uninstalled all programs from that PC except for Mach3 a G-Code editor, a file comparison utility, and a Parallel port monitor (none of which which are running when Mach3 is running) I have the graphic toolpath display turned off.

My PC inputs data from LPT1 to a Probotix PBX-RF RF Isolated CNC Breakout Board (and a Probotix relay board for spindle on/off) and tailstock (extend/retract).  The oputput ot the RF isolator is wired into a Slo-Syn SS2000-DP4 drive and two Slo-Syn KML092F07 Stepper motors.  I'm using Mach3 Turn. Everything works, except that the stepper motors (particularly the Z-Axis) fail to return exactly to their starting points, as My g-code calls for at the end of a run.

I have shielded cable from the output of the Probotix card, but the card itself is not installed inside a grounded metal enclosure. The output of the drive connects to the stepper motors using shielded cable. The shield is tied to earth ground. There is a splice at each stepper motor, and from there the wiring is exposed. The shield is tied to earth ground. The exposed leads are about 3" long at each motor. The Z-Axis motor is particularly unstable; it misses the home position most of the time and the error ranges from (say) three or four pulses to maybe 25 pulses. Once in a "blue moon", Z will return to zero. X is the other way. X might miss 1 or two steps "once in a blue moon" but returns exactly to zero, most of the time.

I have tried numerous settings of maximum speed settings in Motor Tuning; I have tried numerous settings of Accel/Decel to no avail.  I have tried using the Sherline 1/2 step mode, which helps occasionally. I have turned Sherline off and tried pulse widths as high as 14. (I read that 15 or higher can cause the system to lock up). A max speed of 300 mm/min would be nice to obtain.

I wrote a simple G-code program that exercises the saddle in the Z-Axis back & forth at full speed (G0) for 50mm four times... then the X-Axis in/out 50mm four times at full speed (G0) four times.  This profile NEVER MISSES! The problem seems to show up when curring curves and both motors are running simultaneously at varying rates...

There has to be an answer to this problem.
Is there anything wrong with my choice of the Probotix RF isolator?
Would getting a Smooth-stepper card help?  If so, does the Smooth Stepper provide the necessary isolation? Should I then install a simple breakout board on the Probotix's place?
I'm going to go to the shop tomorrow and run through the procedures in your report to optimixe Windows... Maybe that will help.

Any suggestions or answers would be greatly appreciated.
I like the idea of the Smooth Stepper using the USB port and that it's parallel pouts are probably more stable than the PCs LPT1 port.
It even suggests that we might be able to use a laptop at the lathe... Another plus for us...

My sincere thanks for any advice you might be able to share...
« Last Edit: August 12, 2009, 04:00:11 PM by TunerTom »

Offline Hood

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Re: Really need help
« Reply #1 on: August 12, 2009, 04:17:12 PM »
Where in the world are you, just with you saying mm.
Hood
Re: Really need help
« Reply #2 on: August 12, 2009, 04:35:58 PM »
I'm in Massillon, Ohio, USA

Are you near Loch Ness?

Offline Hood

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Re: Really need help
« Reply #3 on: August 12, 2009, 04:48:11 PM »
Ah ok, just if you were in the UK I could have loaned you a SS to see if it sorted you out.
Nope probably 150 plus miles away from Nessie, then again to you USA guys thats probably close ;D

Hood
Re: Really need help
« Reply #4 on: August 12, 2009, 04:52:10 PM »
Hood,

I will gladly buy the SS if someone thinks it will help.
If there is some glaring error in my present setup, I hope somebody will tell me...


Tom
« Last Edit: August 13, 2009, 04:55:33 AM by TunerTom »

Offline Hood

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Re: Really need help
« Reply #5 on: August 12, 2009, 05:03:32 PM »
Cant say whether it would help or not as dont know where the issue lies :( If it was a bad pulse then yes it would, if its a problem outwith the computer then likely it wouldnt.
Hood
Re: Really need help
« Reply #6 on: August 12, 2009, 05:10:14 PM »
Thanks...
Re: Really need help
« Reply #7 on: August 12, 2009, 05:14:21 PM »
OK, but we have a fairly new laptop running Windows Vista.
Is it worth trying an SS on that machine?

Offline Hood

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Re: Really need help
« Reply #8 on: August 12, 2009, 05:18:50 PM »
Not a Vista fan myself and never used it for Mach but I think quite a few people do.
Do you have a scope? If you do check the pulse that is going to the drives.
Hood
Re: Really need help
« Reply #9 on: August 12, 2009, 05:43:49 PM »
I don't like Vista either

I have the following scope on order...  $55.00
Hope it will be adequate.

http://www.seeedstudio.com/depot/digital-storage-oscilloscope-with-panels-p-167.html

« Last Edit: August 13, 2009, 04:56:28 AM by TunerTom »