Hardware requirements for G76 Utilization
30 Aug 2013 22:24 #38249
by Anappa
Hardware requirements for G76 Utilization was created by Anappa
Hi Everyone,
I'm new to LinuxCNC (liking it very much by the way) and I could use a little direction if someone has a minute on the hardware requirements for threading function G76. I currently have a mini-lathe retrofitted with stepper motor controls (working very nicely), the spindle is manually switched on and there is currently no feedback or indication to the PC that there is a spindle or even that it's on.
My question specifically is: Can I use a 100ppr encoder with an index pulse and synchronize via software with the actual spindle rpm or do I need some method of direct spindle speed control like a VFD?
Thanks folks, I really appreciate the guidance!
I'm new to LinuxCNC (liking it very much by the way) and I could use a little direction if someone has a minute on the hardware requirements for threading function G76. I currently have a mini-lathe retrofitted with stepper motor controls (working very nicely), the spindle is manually switched on and there is currently no feedback or indication to the PC that there is a spindle or even that it's on.
My question specifically is: Can I use a 100ppr encoder with an index pulse and synchronize via software with the actual spindle rpm or do I need some method of direct spindle speed control like a VFD?
Thanks folks, I really appreciate the guidance!
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30 Aug 2013 23:07 - 30 Aug 2013 23:08 #38253
by ArcEye
Replied by ArcEye on topic Hardware requirements for G76 Utilization
Hi
That should work fine.
I have an index pulse via a hall effect switch triggered by an embedded magnet in the spindle pulley
There is a 120ppr optical disc on the spindle shaft for the pulses.
I try to make it easier for the software, by having a spindle speed and pitch that are proportional to each other, or at least easily divisible and having a lead-in which is a multiple of the pitch.
eg
S450 Pitch 1.5mm Lead-In 15mm
S300 Pitch 1mm Lead-In 10mm
In theory you could have any old values, but why have fractional remainders when you don't need to
regards
That should work fine.
I have an index pulse via a hall effect switch triggered by an embedded magnet in the spindle pulley
There is a 120ppr optical disc on the spindle shaft for the pulses.
I try to make it easier for the software, by having a spindle speed and pitch that are proportional to each other, or at least easily divisible and having a lead-in which is a multiple of the pitch.
eg
S450 Pitch 1.5mm Lead-In 15mm
S300 Pitch 1mm Lead-In 10mm
In theory you could have any old values, but why have fractional remainders when you don't need to
regards
Last edit: 30 Aug 2013 23:08 by ArcEye.
The following user(s) said Thank You: Anappa
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31 Aug 2013 09:35 #38275
by andypugh
You can actually do it with just a single pulse per rev: You set up a counter-mode encoder with a shared A and Z pin and use position-interpolated from the encoder to the motion controller. This works better with a big, heavy, powerful lathe where the spindle speed doesn't vary rev-to-rev.
On a Mini-lathe a pulse wheel plus index is a lot more satisfactory. Choose the number of pulses to suit the base-thread period and the maximimum speed you want to track spindle position at.
Replied by andypugh on topic Hardware requirements for G76 Utilization
My question specifically is: Can I use a 100ppr encoder with an index pulse and synchronize via software with the actual spindle rpm
You can actually do it with just a single pulse per rev: You set up a counter-mode encoder with a shared A and Z pin and use position-interpolated from the encoder to the motion controller. This works better with a big, heavy, powerful lathe where the spindle speed doesn't vary rev-to-rev.
On a Mini-lathe a pulse wheel plus index is a lot more satisfactory. Choose the number of pulses to suit the base-thread period and the maximimum speed you want to track spindle position at.
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