Speed change on Bridgeport CNC
20 Sep 2019 19:29 #145702
by arsenix
Speed change on Bridgeport CNC was created by arsenix
I have been using my Bridgeport R2E4 for many years now on LinuxCNC without spindle speed control and now trying to get it working "properly".
The machine has a Mesa 7i77/5i25 setup. The head is a standard "2J" head but with a pneumatic air motor driving the speed change pulley. It also has a two speed gearbox which has to be changed by human hand. The gear change has to happen with the spindle stopped, and the speed change pulley has to be changed when the spindle is running. I have a spindle encoder installed on the machine so linuxCNC should know the "true" rotation speed of the spindle. I also have the gear change lever hall sensor (which lets the control know the gear setting) wired up to a GPIO input. The pneumatic valves are hooked to GPIO outputs. So I believe all the hardware is ready for this to work properly!
I believe to get this to work correctly I'll need to remap either or both of the S? and M3/M4/M5 commands to properly request a gear change (when necessary) and run the air motor to change the spindle speed once the spindle is running again. Does that sound correct?
Thanks!
James
The machine has a Mesa 7i77/5i25 setup. The head is a standard "2J" head but with a pneumatic air motor driving the speed change pulley. It also has a two speed gearbox which has to be changed by human hand. The gear change has to happen with the spindle stopped, and the speed change pulley has to be changed when the spindle is running. I have a spindle encoder installed on the machine so linuxCNC should know the "true" rotation speed of the spindle. I also have the gear change lever hall sensor (which lets the control know the gear setting) wired up to a GPIO input. The pneumatic valves are hooked to GPIO outputs. So I believe all the hardware is ready for this to work properly!
I believe to get this to work correctly I'll need to remap either or both of the S? and M3/M4/M5 commands to properly request a gear change (when necessary) and run the air motor to change the spindle speed once the spindle is running again. Does that sound correct?
Thanks!
James
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20 Sep 2019 19:38 #145705
by arsenix
Replied by arsenix on topic Speed change on Bridgeport CNC
Additional note: We are using LinuxCNC 2.6.13 currently.
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25 Sep 2019 12:48 #146154
by andypugh
Replied by andypugh on topic Speed change on Bridgeport CNC
I don't think that you necessarily need a remap for this.
For the pneumatic speed control I would suggest using wcomp.
linuxcnc.org/docs/2.7/html/man/man9/wcomp.9.html
Connect motion.spindle-speed-out to a pair of "scale" componentsTo give +/- 5% speed tolerance
Then connect scale.0.out to wcomp.0.min, scale.1.out to wcomp.0.max. Connect the wcomp input to the actual spindle speed feedback and use the wcomp.0.over and wcomp.0.under outputs to operate the air valves.
To send a message to the operator to change gear I would use another wcomp that takes the spindle speed command as input, but which receives the max and min from a pair of mux2 components.
linuxcnc.org/docs/2.7/html/man/man9/mux2.9.html
The mux2 components would be switched by the input that reports the current gear selector position.
Then use the "message" compenent to alert the operator to change gear:
linuxcnc.org/docs/2.7/html/man/man9/message.9.html
There will probably need to be tweaks....
In practice you might need to use Mux4 rather than mux2. Then you would use mux.N.sel0 connected to motion.spindle.on to give very wide limits when the spindle is off, and sel.1 for the gear lever position.
wcomp.0.out can be used for motion.spindle-at-speed.
You probably want to interlock the spindle motor enable output to the message comp, to turn the motor off when a gear change is requested.
For the pneumatic speed control I would suggest using wcomp.
linuxcnc.org/docs/2.7/html/man/man9/wcomp.9.html
Connect motion.spindle-speed-out to a pair of "scale" components
net speed-command motion.spindle-speed-out
net speed-command scale.0.in scale.1.in
setp-scale.0.gain 0.95
setp scale.1.gain 1.05Then connect scale.0.out to wcomp.0.min, scale.1.out to wcomp.0.max. Connect the wcomp input to the actual spindle speed feedback and use the wcomp.0.over and wcomp.0.under outputs to operate the air valves.
To send a message to the operator to change gear I would use another wcomp that takes the spindle speed command as input, but which receives the max and min from a pair of mux2 components.
linuxcnc.org/docs/2.7/html/man/man9/mux2.9.html
The mux2 components would be switched by the input that reports the current gear selector position.
Then use the "message" compenent to alert the operator to change gear:
linuxcnc.org/docs/2.7/html/man/man9/message.9.html
There will probably need to be tweaks....
In practice you might need to use Mux4 rather than mux2. Then you would use mux.N.sel0 connected to motion.spindle.on to give very wide limits when the spindle is off, and sel.1 for the gear lever position.
wcomp.0.out can be used for motion.spindle-at-speed.
You probably want to interlock the spindle motor enable output to the message comp, to turn the motor off when a gear change is requested.
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