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would like some advice
« on: March 04, 2011, 09:51:53 PM »
i have built a cnc router with 4 nema 23 motors, a g540 and a 48v power supply . it is rack and pinion on x and a 5 start 1/2" acme lead screw for y and z axis i would like to have a smooth running machine as be well balance in speed and tork would you pleas look at these screen shots and advise on what is best
thanks
ghostlx

Offline Tweakie.CNC

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Re: would like some advice
« Reply #1 on: March 05, 2011, 02:55:03 AM »
Everybody will have their own views on this one but here is my 2 cents.

This is pretty much a trial and error thing which will depend on your steppers, their driver circuits and the amount of loading each axis puts on the stepper in it's resistance to movement.
I increase the Velocity and Acceleration to the maximum figure that the motors will sustain then reduce the velocity by some 20% or so and then reduce acceleration so the machine does not jerk or rock (it is on castors). Then carry out some practical tests with GCode to make sure everything is reliable, does not stall under load or miss steps etc.
I am more concerned with accuracy and reliability than I am with speed so I always opt for the lower settings.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: would like some advice
« Reply #2 on: March 05, 2011, 08:16:02 AM »
thanks tweakie
i found a earlier post on the subject that ritch posted.
i'll start their
ghostlx

i found this from ritch




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Re: motor tuning
« Reply #2 on: February 24, 2011, 06:36:33 AM »
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how to tune the motor

- Pick a start velocity , leys say 10 ipm and an accel of 1 , jog the machine, will assume it didn't skip
- Now double the velocity and accel....20 vel / accel 2,             "                           "
- keep doubling the velocity an accel until it skips ie,  40/4, 80/8, 160/16 willl assume it skips
- now lower to say 120 / 12, assume it ships
- now use 100 / 10 and assume it doesn't skip
- so  now increase by 10 to 110 / 11........lets say it skips
- so lower by 30% or more , say 75 / 8 , i like to be conservative and leave enough "headroom" for machining tasks so that the axis will
  not skip for the maching tasks that i will do.
- At this point you play some with the accel by jogging in smaller moves

Doing the above, you have found the max velocity and acceleration when doing a rapid where the machine will not skip. By reducing the values
you are trying to make sure that your machine will be reliable when  machining. You should test  the final setting some by jogging in small and long moves and by actualy cutting different materials.

How fast you can accelerate and decelerate depends on how your axis system will react to the load it is trying to move or stop. A velocity of 0 to max  & from max velocity to  a stop in a some distance.

Hope this helps,
RICH
« Last Edit: March 05, 2011, 08:33:49 AM by ghostlx »

Offline RICH

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Re: would like some advice
« Reply #3 on: March 05, 2011, 08:54:57 AM »
Note the following:
The max velocity in motor tunning is limited by the available pulses / Kernel Speed:
KERNEL SPEED / STEPS PER UNIT X 60= MAX IPM
IE; 25000/20000 x 60= 75 IPM max so if you want more velocity you will need to increase your Kernel Speed given the axis steps per unit shown

RICH
Re: would like some advice
« Reply #4 on: March 05, 2011, 02:04:03 PM »
Note the following:
The max velocity in motor tunning is limited by the available pulses / Kernel Speed:
KERNEL SPEED / STEPS PER UNIT X 60= MAX IPM
IE; 25000/20000 x 60= 75 IPM max so if you want more velocity you will need to increase your Kernel Speed given the axis steps per unit shown

thank you very much
i'll set my ipm to75 and my velosity to 8 and see what happens
thanks
ghostlx

RICH
Re: would like some advice
« Reply #5 on: March 07, 2011, 10:55:57 PM »
rich
changed my motor tuning to 100imp and 8 in acceleration
wow does my machine sound smother
thank you for the advice
ghostlx