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Motor tuning
« on: November 20, 2008, 08:42:48 PM »
My driver board maker recommends the following initial settings for motor tuning; Steps=400, velocity = 120, acceleration = 90 and step pulse = 1. This shows the motors to be in half step mode.

I am running a Rockcliff flying gantry, made of mdf, linear bearings, Keling 282 oz in motors with a 4 axis board, Y and A axis slaved. The motors are wired bipolar series @ 4.2 volts, 2.1 amps. I have a 24 volt power supply at 7.5 amps.

What do you think of these settings as an initial setting for getting it running? Should I start in 1/8th step mode? If so what do you recommend for steps, velocity and acceleration?

I am hoping to do my first cuts this weekend and would like your input.

Thanks,
John

Offline RICH

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Re: Motor tuning
« Reply #1 on: November 20, 2008, 10:44:19 PM »
JOHN,
Since he recommended them why not start off with them? You could also just start off at a much less velocity and increment up and see what happens ie; 20,40,80,100,120, 140 and should you start skipping steps at any point back off by say 20 to 30% leaving that as a margin of safety. Not having a motor curve which would delineate
the torque to rpm based on how they are wired at some voltage / current leaves with you with trial and error. Even if you had that you would probably still do the incremental increase trials before actualy trying to cut something. Then try cutting some of whatever your going to do and see if your margin you left for cutting is adequate.
RICH

PS: You don't go from 0 to 60 instantly in your car so give it a ramp and you can refine that also thru some trials.
Also you can use jog the motors to try them at different settings ini motor tuning. Make sure you save your settings and go out and come back into MACH. There is a MACH 3 tutoriial " setting up a basic three axis machine" in the downloads section and also  a fresh of the press MACH 3
software installation and configuration manual available for download.
« Last Edit: November 20, 2008, 10:51:58 PM by RICH »

Offline Hood

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Re: Motor tuning
« Reply #2 on: November 21, 2008, 12:40:55 AM »
Your Steps per Unit need to be calculated, if you are using the same motors/ballscrews/reduction as the recommended values as above then fine but if anything is different then you will need to set that differently.
Hood
Re: Motor tuning
« Reply #3 on: November 21, 2008, 09:07:34 AM »
Thanks Guys, that will give me a starting point to "play" with. I have downloaded all the tutorials and have looked at the videos, but the driver starting point seemed different from what I have seen others use, especially the steps.

I forgot to mention I am using 3/8 x 16 threaded rod for my lead screws with dumpster antibacklash nuts, how does that affect the steps calculation?

Thanks,

John

Offline Hood

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Re: Motor tuning
« Reply #4 on: November 21, 2008, 01:39:23 PM »
200 steps per revolution and you have 1/8 microstepping so that is 200 x 8 = 1600 steps per revolution.
You need 16 turns to move 1 inch so that is 16 x 1600 = 25,600 steps per inch or Steps per unit as they are called in Mach.
If you have any gearing then you will have to factor that in as well.
Hood
Re: Motor tuning
« Reply #5 on: November 21, 2008, 01:43:06 PM »
Thanks, that is more in line with what I have been seeing others use. I will try that and see how it goes. Hopefully I will start tuning in the morning and see how it goes.

Thanks for your help.

John