Threading on a lathe
- yoshimitsuspeed
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09 Sep 2015 13:52 - 09 Sep 2015 13:52 #62305
by yoshimitsuspeed
Threading on a lathe was created by yoshimitsuspeed
I have toyed with the idea of converting my old lathe to CNC. Not something I'm real serious about but it did start me wondering about turning. My old 1940s straight cut gears are insanely loud and I was thinking it would be cool to drive the Z axis with a stepper motor. This would work great for turning but it occurred to me that it wouldn't work for turning threads without something more.
My first thought was maybe having an encoder on the Spindle.
Would it be possible to do this with Linuxcnc accurately enough to turn threads?
If so are there any cheaper encoders that would work?
Or are there any other solutions aside from mechanically tying the spindle to the Z axis?
Possibly running the Spindle on a servo motor like this?
www.ebay.com/itm/New-1kW-AC-servo-motor-...?hash=item2ee11a3efd
My first thought was maybe having an encoder on the Spindle.
Would it be possible to do this with Linuxcnc accurately enough to turn threads?
If so are there any cheaper encoders that would work?
Or are there any other solutions aside from mechanically tying the spindle to the Z axis?
Possibly running the Spindle on a servo motor like this?
www.ebay.com/itm/New-1kW-AC-servo-motor-...?hash=item2ee11a3efd
Last edit: 09 Sep 2015 13:52 by yoshimitsuspeed.
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09 Sep 2015 14:07 #62306
by yoshimitsuspeed
Replied by yoshimitsuspeed on topic Threading on a lathe
To get a little crazier would linuxcnc have the capability to run a combo machine that bolted a Gantry CNC on to a lathe bed?
Basic idea would be similar to a CNC A axis but instead would use the lathe as the A axis. Then if the CAM and linuxcnc both had the capability could then perform milling and turning operations all at once.
Something like this but attached to a lathe instead.
www.automation-drive.com/EX/05-14-14/6%2...%255C20076201575.jpg
Basic idea would be similar to a CNC A axis but instead would use the lathe as the A axis. Then if the CAM and linuxcnc both had the capability could then perform milling and turning operations all at once.
Something like this but attached to a lathe instead.
www.automation-drive.com/EX/05-14-14/6%2...%255C20076201575.jpg
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09 Sep 2015 23:08 #62329
by andypugh
Replied by andypugh on topic Threading on a lathe
Both things you have suggested are possible.
Electronic Leadscrew doesn't need LinuxCNC, you can do it easily with an Arduino.
It doesn't make it any easier to do imperial threads with a metric leadscrew and vice-versa, whereas a full-CNC conversion can do absolutely any thread that takes your fancy.
With an electronic leadscrew you will still be disengaging the nut at the end of the pass, so the system does not know where the carriage is when you re-engage.
I guess that a "wind-back" button could reverse the leadscrew by a pre-set and exact amount to work around this problem.
But, once you have motorised one axis, you might as well do them both. (Actually, this statement isn't entirely true, the X axis is typically much more difficult to modify, space is much more limited)
Electronic Leadscrew doesn't need LinuxCNC, you can do it easily with an Arduino.
It doesn't make it any easier to do imperial threads with a metric leadscrew and vice-versa, whereas a full-CNC conversion can do absolutely any thread that takes your fancy.
With an electronic leadscrew you will still be disengaging the nut at the end of the pass, so the system does not know where the carriage is when you re-engage.
I guess that a "wind-back" button could reverse the leadscrew by a pre-set and exact amount to work around this problem.
But, once you have motorised one axis, you might as well do them both. (Actually, this statement isn't entirely true, the X axis is typically much more difficult to modify, space is much more limited)
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- yoshimitsuspeed
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12 Sep 2015 03:02 #62478
by yoshimitsuspeed
Replied by yoshimitsuspeed on topic Threading on a lathe
So do you think it would be better and or cheaper to put an encoder on the spindle? Or put something like a stepper/servo motor to run it?
Knowing where everything is when you re-engage is the main concern I have.
But if the computer knows where the spindle is in it's 360 degree rotation then it could start the next pass as the exact same point of rotation.
With an encoder this should be easy. With a direct drive stepper.servo it should work well also.
My lathe is belt drive and this makes things a little more complicated. Any slippage would be unaccounted for. Also if your drive ratio were just a tiny bit off it could change quite a lot over many rotations.
Knowing where everything is when you re-engage is the main concern I have.
But if the computer knows where the spindle is in it's 360 degree rotation then it could start the next pass as the exact same point of rotation.
With an encoder this should be easy. With a direct drive stepper.servo it should work well also.
My lathe is belt drive and this makes things a little more complicated. Any slippage would be unaccounted for. Also if your drive ratio were just a tiny bit off it could change quite a lot over many rotations.
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