The Shop > CNC
Retrofit of an EMCO 120 CNC lathe
mukanico:
Since the original headstock motor had a maximum speed of 6000 rpm and the new engine only had 2850 rpm, I had to increase the diameter of the driving pulley so as not to lose too much top speed. In the end, I managed to have a maximum spindle speed of 4250 rpm.
I also had to change the headstock encoder. I chose an "omron" with a resolution of 1024 steps/rev (x4). Its support was machined in a small EMCO Compact 5 CNC lathe that I had at the time...
Beginning of the wiring
Wiring finished
And new vinyl decals (of course :headbang:)
mukanico:
And here is the finished lathe on its new custom made bench
And doing its job...
Overall, I am quite satisfied with the end result. The controller takes standard G code (USB or RS-232) and is quite simple to use. The mechanical part of the lathe does not seem to have much wear neither. The backlash in the ball screws is less than 2um and I can easily work within 0.01mm on mild steel.
The only annoyance I have is the lack of torque at low speed. I may need to reduce the belt pulley ratio and tweak the VFD settings to mitigate this.
I hope someone finds this project useful :wave:.
Cheers!
RotarySMP:
Nice clean retrofit. Thanks for sharing it.
Putting that 3.5hp DC motor back in would also solve your low torque but also high speed issue.
Mark
mukanico:
--- Quote from: RotarySMP on March 07, 2019, 08:32:01 AM ---Nice clean retrofit. Thanks for sharing it.
Putting that 3.5hp DC motor back in would also solve your low torque but also high speed issue.
Mark
--- End quote ---
Thanks.
Indeed, I felt bad for not using the original motor (it was a beast compared to the new one). Unfortunately I don't know much about electric motors and their drivers, so I decided to play it safe and go for the straightforward solution of a 3 phase motor + VFD, instead of messing around with the EMCO driver.
RotarySMP:
Wonder what the EMCO spindel motor driver interface was? Analog 0-10V?
To replace a DC motor with a AC motor, you normally need to go up significantly in power, not down.
Mark
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