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Mach 3 resets zero when running
« on: October 20, 2013, 11:02:25 PM »
I am running Mach 3 as the controller for my home grown 3d printer. It works fairly well with a couple glitches.

I am running X,Y and Z (NEMA 23 Steppers) and an A axis (NEMA 17). There is no rotary encoder, or other feed back - strictly step counts.

I have a breakout board (active)  and 3.5 amp controller cards.  

I originally had the steppers configured for high torque, low speed operation and was using an old dell XP  box (circa 2002). I don't remember the clock speed, but it was less than 1.5 gig. 512k RAM. I was running Mach3 at 25k pulse.

With that configuration I would occasionally have a mishap where the machine would lose counts and essentially re zero making the print offset by 1/4 inch or so. The problem was only occasional and I lived with it.

I wanted to print faster so I reworded the stepper motors for speed.  In motor tuning I could easily triple the hight torque speed even with my old computer  in high torque the motors ran at about 600 mm per. High speed wiring  took the speed up to 2k mm per. However when I ran a program the motors would lock up and scream.  So I slowed the motors to about 1500 per but the zero would reset all of the time. Where before the rewrire I could use the computer while the program was running , after rewire in would only run as the controller.  That was ok but the offset shift continued with regularity.

So I bought anther computer which helped but did not solve the problem  the new ( tome) computer is  3.2 gig, dual core etc. I can run programs at 2400 mm per but occasionally the zero will shift. This happens 1 time over three or four prints. ( 1 time per two hours of printing)

I have tried different setting (25 k up to 100k) with no appreciable change.

Has anyone experienced this problem and found a fix?  Sorry about the length of this post but I wanted to get a complete description of the problem right off.

Sometimes when it happens I can hear a change in the motors, other time I hear nothing. I can force the offset by running another program while Mach is still running.

Thanks, pete

Offline Hood

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Re: Mach 3 resets zero when running
« Reply #1 on: October 21, 2013, 03:24:29 AM »
When you are talking about Offset I presume what you you are really seeing is that you are missing steps, ie Mach still thinks it is in the correct position but the acyual axies are not there?
It could be a number of things such as motor tuning too high for your setup.
Motors not powerful enough or axis binding.
Bad pulse stream.
Have you tried setting to Sherline mode?
Is the active state of your pulse pin the correct way for your drives?

Hood
Re: Mach 3 resets zero when running
« Reply #2 on: October 21, 2013, 07:05:37 PM »
The offset that I describe is as you've suggested. Another way to say it is that I zero the x and y run the program. It jumps at some point.  When I run the next print, without changing the zero it, the next print starts 1/4 inch away.

I don't know what the surliness settings will do but I'll give it a shot  tonight.

Thanks for the help...

Offline Hood

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Re: Mach 3 resets zero when running
« Reply #3 on: October 22, 2013, 03:12:32 AM »
Sherline mode will widen the pulse to 40 uS which some stepper drives require.
Hood