Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: kenserdar on April 03, 2010, 08:11:40 PM
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For some reason my lathe doesn't like G0 rapids? I can replace all G0's with G1's and the code will run OK.
The code has a F12 to set the feed rate. But the rapids still try to go much faster?
Jog works OK - I have the jog set to ~12% to keep the ipm below 12.
The really strange thing is my motor tuning parameters: Velocity - 85, Acc - 20.
How do I get my rapid speed down without changing motor tuning parameters?
Ken
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Ken you must set the motor tuning first there are examples in the member docs section
Phil
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Ken you must set the motor tuning first there are examples in the member docs section
Phil
Huh??? If I didn't set the motor tuning parameters ... How could I post them here????
Ken
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Huh??? If I didn't set the motor tuning parameters ... How could I post them here????
Ken
Yes but as you cannot use G0 they are set incorrectly
Phil
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Ken,
Set the velocity at 20 and an acceleration at 2, then try 30 and an accel of 3, keep working your way up until they skip , then back off by 30 %. use that velocity as the max. Now start increasing just the acceleration with that max velocity.
G00 - is a rapid movement at the max velocity you have set in motor tuning
I assume they are steppers.
RICH
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Ken,
Set the velocity at 20 and an acceleration at 2, then try 30 and an accel of 3, keep working your way up until they skip , then back off by 30 %. use that velocity as the max. Now start increasing just the acceleration with that max velocity.
G00 - is a rapid movement at the max velocity you have set in motor tuning
I assume they are steppers.
RICH
RICH ... Have you got a filter for my stupid questions?
Man, your answers are always right on.
With your answer, I realized, that I was testing my motor tuning with a 13% "jog" command. IE 85 (VEL) * .13 = 11.05 ipm. Not a G0 rapid command. To stop this in the future. I cranked the jog to 100%.
Turns out my MAX Velocity is 16. Thus, 16 - (.3*16) = 11.2
I already knew, I couldn't run these motors faster then 12 ipm. I just couldn't see how the "85" velocity was working.
Thanks again
Ken
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kEN,
Glad you figured it out.
That 30% of max is just a ball park figure. The motor torque decreases as the speed increases. So by reducing the
max velocity you are allowing some "headroom" so you have some torque left when cutting or in the case of a an X & Z
move ie; G01 X..Z.. F15 ( if one of the axes was able to go faster ) it would limit the move to the slower of the pair.
I am rather conservative and have my max velocity set at 50% on my lathe ( 60IPM vrs 120IPM ) since when threading for instance i won't
try cutting a thread at a feedrate where there is not enough torque to accomplish the task and that velocity just happens to get the max
power ( where speed x torque = power ) out of the stepper. Over time or via testing you will find what velocity and acceleration settings works such that YOUR motors won't skip when running a program. If you have a motor curve / spec sheet for the motor you will have some data to get you in the ballpark rather quickly.
Others may have a different opinion, but that's my nickle on it. ;)
RICH