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Author Topic: Ballbar test  (Read 2597 times)

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Offline sml

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Ballbar test
« on: April 12, 2010, 10:04:58 AM »
Hi
Does i need ballbar test for my cnc milling machine? or motor tuning is enough ?
Does i need ballbar test for using motor tuning?
Please tell me more
Thank you.

Offline Hood

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Re: Ballbar test
« Reply #1 on: April 12, 2010, 11:26:35 AM »
Motor tuning should be enough.

Hood

Offline sml

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Re: Ballbar test
« Reply #2 on: April 12, 2010, 11:41:44 AM »
Thank you Hood
So why other cnc machine need ballbar test? Does it haven't motor tuning?

Offline kf2qd

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Re: Ballbar test
« Reply #3 on: April 12, 2010, 03:50:50 PM »
A ball bar test the accuracy of a machine, or to certify the positional accuracy of a machine. Unless you have some need to prove teh accuracy of the machine you won't need the ball bar. You will want to test all axis against a good dial indicator at first, you may find that you are a step or 2 off based on whether you are using english or metric screws/gear racks/etc. and you may find that you have to make small adjustmants on each axis because minor inaccuracies in you system.

What kind of machine are you running, and what are you trying to do with it?

Offline kf2qd

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Re: Ballbar test
« Reply #4 on: April 15, 2010, 11:36:31 AM »
Another reason for the ballbar test is to adjust the servo perameters on a true servo based machine. Using steppers the performance is different because we are using steps to position, not torque and feedback. In otherwords - on  a true servo based system the exact position is controlled by adjusting the speed of the motor by changing  voltage current, and the motor has no position that it will stop exactly like a stepper. On a true servo based system the gain and accel values have to be adjusted to minimize over/undershoot on positioning moves. With steppers we send the stepper a specific number of steps and the motor locks in positin based on which coil(s) is/are energized.