Modbus closed loop vfd spindle and rigid tap
- Charlieslasher
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08 Mar 2017 12:54 #89196
by Charlieslasher
Modbus closed loop vfd spindle and rigid tap was created by Charlieslasher
Has any one used modbus vfd spindle control with rigid tapping successfully?
Can a modbus vfd spindle control comunicate fast enough for closed loop pid spindle control.
Is closed loop pid spindle control in a lathe any better than open loop.
After a few weeks of testing modbus with rigid tapping g33.1 i think the modbus delay in reversing signal creates inconsistant reversal timing. Some times it over travels and machine stops at bottom of thread with no reversing.
I started with classic ladder modbus which was the worst for lag. Also have tested mb2hal which seems ok. Do i need to wire in reverse signal via pp output to get faster reversing?
Can a modbus vfd spindle control comunicate fast enough for closed loop pid spindle control.
Is closed loop pid spindle control in a lathe any better than open loop.
After a few weeks of testing modbus with rigid tapping g33.1 i think the modbus delay in reversing signal creates inconsistant reversal timing. Some times it over travels and machine stops at bottom of thread with no reversing.
I started with classic ladder modbus which was the worst for lag. Also have tested mb2hal which seems ok. Do i need to wire in reverse signal via pp output to get faster reversing?
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09 Mar 2017 13:32 #89253
by andypugh
Replied by andypugh on topic Modbus closed loop vfd spindle and rigid tap
I think that running a VFD with Modbus would worry me.
The LinuxCNC VFD controllers are all userspace components, and are subject to the same timing (and freezing) vagaries of any other software.
Classic Ladder itself runs in Realtime, but the Modbus part doesn't.
And then, if your Modbus output is via a USB dongle, that can have its own issues.
I run my lathe through modbus, and rely on the spindle-at-speed signal. I don't know if I would entirely trust it for rigid tapping, however.
Can your VFD be configured to take speed from Modbus and direction from a contact? I don't think mine can.
The LinuxCNC VFD controllers are all userspace components, and are subject to the same timing (and freezing) vagaries of any other software.
Classic Ladder itself runs in Realtime, but the Modbus part doesn't.
And then, if your Modbus output is via a USB dongle, that can have its own issues.
I run my lathe through modbus, and rely on the spindle-at-speed signal. I don't know if I would entirely trust it for rigid tapping, however.
Can your VFD be configured to take speed from Modbus and direction from a contact? I don't think mine can.
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- Charlieslasher
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09 Mar 2017 22:34 #89298
by Charlieslasher
Replied by Charlieslasher on topic Modbus closed loop vfd spindle and rigid tap
Yeah this i will try next modbus for hz/rpm and any other vfd data like spindle load and faults. And use a pp output pin to change fwd reverse. I ran out of outputs on the g540. So either upgrade to messa cards or add another pp.
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