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Author Topic: Mach3 motor rapid tuning  (Read 2658 times)

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Mach3 motor rapid tuning
« on: September 08, 2014, 12:06:10 PM »
So we have been using mach3 with HSM works for quite a while and have noticed that when we use the adaptive clearing feature, our y axis is loosing steps (only that axis). We have come to the conclusion that maybe the rapid isn't set right or the acceleration isn't. you can follow the post here.
http://camforum.autodesk.com/index.php?topic=5305.new;topicseen#new

How do we set the rapid in mach3 and how do we know if the acceleration is set correctly? Any other thoughts on what might be going on here??

This is our CNC kit
http://www.cncfusion.com/smallmill1.html

this stepper set up (ours is a KL23H2100-30-4B, not the 35 that is listed)
http://www.automationtechnologiesinc.com/products-page/g540-stepper-motor-kits/cnc-mogul-special-kit
« Last Edit: September 08, 2014, 12:13:20 PM by mjalaly »

Offline RICH

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Re: Mach3 motor rapid tuning
« Reply #1 on: September 09, 2014, 07:53:30 AM »
Set the max velocity at say 10 and just keep doubling it until the stepper skips. So if it skipped at say 200 then go back and set it at 100. Now with the the 100 max velocity,  setting start doubling the accel until it skips and set back at the one
highest that didn't skip. Lest say that 100 max vel and 10 accel seems fine, now you need to refine by trying machining of different material and at different feedrates and depth of cuts. You may also want to try some 3d code to test also.

You want max power from the motors and also reliability for the work that you will doing. You can use a motor curve 
if one is provided to start but still need to experiment. 30% down from the max velocity should leave you with enough
room to take care of different kinds of g code feedrates and materials.

RICH
Re: Mach3 motor rapid tuning
« Reply #2 on: September 09, 2014, 08:23:14 AM »
That is where the problem is... 90% of the time it doesnt skip... its just when i use the adaptive clearing feature in HSMworks which has aggressive moves. We cannot actually hear it skipping even now, we just measure the distance that has changed from the 0,0 location after the program has been run. I decreased the accel from 2 to 1.5 and it did make a big difference, only .010 off vs .100.

Offline RICH

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Re: Mach3 motor rapid tuning
« Reply #3 on: September 09, 2014, 07:08:28 PM »
You can also try lowering the max velocity.
You need torque to have good acelleration.
Post some of the code or the file.

RICH
Re: Mach3 motor rapid tuning
« Reply #4 on: September 10, 2014, 10:00:14 AM »
I went from an acceleration of 2 to 1 and no change. I am running the program now at a velocity of 20 from 30 to see what happens.

attached the code too

Offline RICH

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Re: Mach3 motor rapid tuning
« Reply #5 on: September 10, 2014, 05:24:20 PM »
You have some very small axis movements that must occur and to accomplish those movements in the time allowed you need adequate motor torque to do it. I think that is your problem in some cases. High stepper torque exists at lower motor rpm's and decreases as the rpm increases.
So lower  the max velocity, reduce feedrate, play with the acceleration  to see how it goes.

Sometimes you can't hear the axis skip and the axis recovers, but, it's position is not correct and may be a small or large amount.

You could put a dwell in the code to see if some part of the code is the cause provided you have an independant axis readout. I didn't have much luck with it as the exact skipping part of the code was not repeatable. PLus there was 1000's of lines of code.........

Anyway, play around and see how it goes. Yes this can be frustrating. I will add that manny times you don;t have a problem until you start doing 3d work
and this kind of thing shows up.

RICH