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Author Topic: Tool dash and Z axis problem  (Read 4176 times)

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Tool dash and Z axis problem
« on: July 19, 2008, 10:01:03 AM »
Hi All,
We have been using Mach3 from the last month. The setup consists of the following:

1.   A retrofitted heavy duty lathe with ball screws and timing pulleys
2.   Servo motors+ drive unit + breakout board which take step and dir signals
3.   Mach 3 (Version R2.0.065) to drive the setup.

In the last ten days, the tool crashed into the job 2 times while executing the program below. In both the cases, the crash occurred when a rapid traverse command was issued to Z axis.

These are some more observations regarding the issue:
1. The problem is never faced when executing G01, G02 or G03 commands.
2. It only occurs during execution of the rapid traverse, and that too when the Z-axis is moving rapidly
3. The crash doesn’t occur at any specific place
4. The Z axis skips pulses (or stops which is not very clear as the tool plunges into the job leaving no room for investigation)
5. To probe this issue in greater depth, I opened the drive unit - There is an LED on both the motor drives, which indicate a situation when the drive is 90% loaded. Every time a rapid traverse is issued to the Z-axis, I see the led glowing momentarily while the axis is accelerating and then the LED stops glowing, indicating normal service
6. It is an extremely rare occurrence - about once in 200 cycles – but when this happens, as expected, there is a considerable damage done to the tool and the job

My queries are the following:
1.   Assuming that the motor is skipping/stopping due to overload, why does it not occur frequently?
2.   As a precautionary measure, I have now reduced the max acceleration (about 33%), max velocity (about 25%) and increased the step pulse to 25 micro secs for the Z axis. Now the “max load” LED doesn’t glow anymore, indicating that the z axis motor is not stretched to its capacity. But will that really help?

I have attached the program and the profile herewith
Please advise.

Offline Hood

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Re: Tool dash and Z axis problem
« Reply #1 on: July 19, 2008, 09:26:16 PM »
Try a later Rev of Mach.
Hood