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Mach III and Gecko 201s Problem - HELP !
« on: September 28, 2006, 11:06:51 AM »
I have a CNC Router set up that has what I believe to be resonance problems. I Emailed
GeckoDrive support and they told me that my problem was "Constant Contouring"
within Mach II was set up incorrectly. I don't seem to find a reference to constant

Let me start with a description of the problem and the tests I have run.

To begin with, this was a running machine. I had just recently built a system using
controllers from SB Microstep. Two of these controllers have failed completely and
I have replaced them with Gecko 201's My system runs on 35 volts with 1.8 degree
bipolar motors rated at 4 amps/1.8 volts max. The computer is running Mach III on a
Windows 2k OS. If you are wondering why I did not simply go back to SB-Microstep, it is
because they no longer answer any type of inquiries either sales or support.

OK - On to the problem

Straight lines plot and cut perfect, even if both axis are active at the same time ( ie.
an angular plot). Circles are having a problem and I have seen this before elsewhere.
If I disconnect all but the X Axis output, the resulting plot is a straight line along the X
with an acceleration and deceleration due to the circle being plotted. At two points,
approximately 25 and 75 % points, the motor chatters/backsteps and or fails to step for
a brief period. If you alter this process and do everything as above on the Y Axis, the
same results occur.

The jogging and straight line plotting work perfectly. I might even comment that the
Gecko 201's are exceptionally smooth and quiet during jog. I have tried every kind
of acceleration and velocity selection I can think of to try.

Can anyone point me to Geckos "Constant Contouring" comment or otherwise shed
some light on this. I suspect this to be a resonance problem since it seemes to appear
at a given plot speed but how can I damp this out ?

Moonlight Media

Offline Chip

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Re: Mach III and Gecko 201s Problem - HELP !
« Reply #1 on: September 28, 2006, 06:05:13 PM »
Hi, Moonlight Media

I would think there referring to Constant Velocity, CV mode in Mach, it blends corners, to keep the cutting speed constint.

Try setting to Exact Stop Mode, in Config, General Logic Config, Motion Mode, to Exact Stop. for cutting sharp corners Mill Work.

Hope this Helps, Chip
Re: Mach III and Gecko 201s Problem - HELP !
« Reply #2 on: September 28, 2006, 09:19:18 PM »
Do you have backlash turned on?
Fixing problems one post at a time ;)

Re: Mach III and Gecko 201s Problem - HELP !
« Reply #3 on: September 28, 2006, 11:09:40 PM »
I will check out both backlash and constant velocity settings tommorrow. Thank you
both for the response.