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Author Topic: Minimum Feed rate in Mach3?  (Read 11236 times)

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Minimum Feed rate in Mach3?
« on: May 16, 2013, 09:57:34 AM »
Hello,

i have a micro stage with each axis run by a NEMA 08 stepper motor.
I currently use the Pololu boards with a CNC4PC breakout board to control the movement through Mach3.
For the application that i use, i would need the axis to move at a very low feed rate; something like 5microns per second or 0.3 mm/min and lower.
I had some problems with my experiments and i was wondering if the axes were moving faster than they say they are moving?
It is very important that the axes move at a speed lesser or equal to 0.3 mm/min.
Currently i was giving the feed and the axis movement in the MDI screen itself.
It moves very slowly but i am not sure what the capability of the software is?
Please let me know if it can be run at very low feed rates.

http://www.zaber.com/products/product_group.php?group=LSA&tab=Series%20Specs#tabs
Re: Minimum Feed rate in Mach3?
« Reply #1 on: May 16, 2013, 10:33:42 AM »
I believe Mach will feed as slowly (and smoothly) as you want, provided the resolution of your motor tuning is fine enough.
I temporarily set my steps per very high and added 8 decimal places to the axis dro, then commanded f .0005" feedrate and can see the dro incrementing normally.
It's all math and pulses, so I'd say you're fine.

Highest resolution I can actually achieve, direct coupled is 50,000 ppr x the pitch of the screw.
I toyed with the idea once to make a stage similar to yours using a micrometer head coupled to the 50,000 ppr motor.
40 tpi x 50,000 = 2,000,000 steps per inch.
This is what I used for simulation.

Russ
« Last Edit: May 16, 2013, 10:43:09 AM by Overloaded »

Offline RICH

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Re: Minimum Feed rate in Mach3?
« Reply #2 on: May 17, 2013, 07:08:00 AM »
Quote
It moves very slowly but i am not sure what the capability of the software is?
Please let me know if it can be run at very low feed rates.

I have never timed slow movements and have run at slow rates in the range of .1 to .01 IPM or even slower.
One of the problems is confirming the  actual feed rate based on time and distance.
My engraving machine uses around 253000 steps per inch and to check movement a calibrated micro slide reference along with
a mounted 400x microscope on the axis was used. Confirming the number of steps is even more difficult.

So yes you can run at slow feedrates, but to confirm is difficult and time consuming.
I would need to do some testing ( which I have no desire to do) to be more difinitive.

FWIW,
RICH