Max acceleration - for motor or driver?

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cparsons
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Junior Member

30 Aug 2016 09:46 #79711 by cparsons

Max acceleration - for motor or driver? was created by cparsons

I have my home made set up working and am doing some fine tuning?

Nearly time to mount it in a case and bolt the motors on the mill

My X axis is a direct drive, 1:1 and Y and Z are using toothed pulleys 1:2

I have found that the default acceleration and velocity values in stepconf cause the
Y motor to stall (and make a strange noise) so I have used the 'test axis'
to lower this to a value that seems to work without problems but am wondering
how to work out the correct values - is this related to the driver board (a home
built one based on a 6064AH chip and kit) or the actual stepper motor
(an FL86STH80-4208A-H from motioncontrolproducts.com)

The X axis values are set much higher without problems which I am guessing
is due to the 1:1 ratio?

The step timings are shown below - based on the settings from the Linistepper
which uses the same 6064AH chip - although the Gecko settings work too?

Step time 2300ns
Step space 2300ns
Direction hold 4600ns
Direction setup 1000ns

Thanks in advance

Chris Parsons

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tommylight
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Moderator

30 Aug 2016 10:36 #79712 by tommylight

Replied by tommylight on topic Max acceleration - for motor or driver?

Set the step time and all others to at least 5000, test again. Do you get latency warnings when running Linuxcnc? If so raise the base period to max ( in stepconfig 50000 is max) until you do not get warnings, then test again.
Acceleration is very dependent on weight of the parts being moved, drives power supply, motors inductance, etc, but your best bet is to test with your actual setup. Also check for binding on all moving parts, if you notice the force required to move any part of the machine varies, fix that first, binding makes for a very unreliable machine.
Now you can use stepconf to find the max velocity and acceleration, and lover them by at least 20%, so you have a bit of overhead. This should be done under full load of the machine, so apply pressure by hand, or use a piece of wood or whatever you intend on milling.
With a bit of trial and error, you can quickly have a working machine and be fairly sure it is going to perform good.

The following user(s) said Thank You: cparsons

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andypugh
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01 Sep 2016 16:28 #79840 by andypugh

Replied by andypugh on topic Max acceleration - for motor or driver?

cparsons wrote:
is this related to the driver board (a home
built one based on a 6064AH chip and kit) or the actual stepper motor

Both. And the drivetrain, and the mass of the moving parts, and the lubrication.
It is a function of the entire system. Don't forget to test with a heavy workpiece if that moves, too.

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