PDA

View Full Version : Todays Project, installing servo drive in my lathe.



macona
04-27-2008, 03:12 AM
Finally got the servo motor installed in my lathe today. I have been documenting the process here:

http://www.practicalmachinist.com/vb/showthread.php?t=154967

What a difference. The old drive system was good, but it pulled 20 amps at 240 out of the wall just idling!

Plenty of power. Took .25 of the diameter of a piece of 4140PH at .0065" per rev without straining it.

Couple vids of it working, before and after:

http://www.youtube.com/watch?v=ioS6_Qk1SoA

http://www.youtube.com/watch?v=si4MWsdGQpE

japcas
04-27-2008, 10:06 AM
Macona, that looks great. Did you build a gearbox to retain the factory back gear? We have one at work that was retrofitted with a servo motor and a vectorless drive. I didn't personally work on it so I'm not sure what the drive was but I believe they used a 7.5 hp servo motor on it. Anyway, we built an aluminum gearbox so we could retain the back gear. Our monarch is used on a wide variety of materials from aluminum and brass to Hastelloy and we need the back gear. We also have one that was rebuilt by monarch with the latest stuff in the late 80's. The servo drive works great and is smooth but the monarch rebuild seems to be a little smoother when going into the cut. I really think that the servo drive just needs to be tuned a little. The electrician that installed it knows very little about machine work so he didn't take a lot of time tweaking the settings in it. Management won't let us mess with it because it is intalled inside the factory cabinet on the back of the lathe and we aren't allowed in it. Thanks for posting the video.

Edited to add: I missed the link on the rebuild Macona and started typing before I seen it. Sorry about the long winded reply, your link answers my question.

lazlo
04-27-2008, 12:52 PM
Great job Macona! I've never seen a 10EE run -- that motor/generator is LOUD! :)

Does that Mitsubishi servo controller take step/direction inputs? If so, you're at least one step closer to CNC'ing the machine.

Jonathan: Macona is using a 2 KW (3 Horsepower) AC brushless servo motor. A sensorless vector drive is a VFD (inverter) used on a 3-phase induction motor. Monarch had a 7.5 Horsepower VFD upgrade available, which is a different way of getting to the electronic vari-speed like Macona has built.

japcas
04-27-2008, 02:11 PM
Great job Macona! I've never seen a 10EE run -- that motor/generator is LOUD! :)

Does that Mitsubishi servo controller take step/direction inputs? If so, you're at least one step closer to CNC'ing the machine.

Jonathan: Macona is using a 2 KW (3 Horsepower) AC brushless servo motor. A sensorless vector drive is a VFD (inverter) used on a 3-phase induction motor. Monarch had a 7.5 Horsepower VFD upgrade available, which is a different way of getting to the electronic vari-speed like Macona has built.

I wasn't sure on the drive but I was told by the guy that retrofit the new drive that he was using a servo motor, not a normal 3 phase motor. I would say it was some sort of Allen Bradley drive because thats what they like to use.

macona
04-27-2008, 02:43 PM
It may have been a 3 phase motor with an encoder on it and that is interfaced to a VFD. Better performance than a Straight flux-vector VFD with no feedback but not as good as a servo motor. With a AC servo you can run it past is rater HP for intermittent periods. How long depends on how well you can keep it cool.

Yes, this drive accepts step/direction input. Also has electronic gearing built in with native resolution of 4000 steps per rev. I also have three other mitsubishi motor/drive sets. 1.5kw (2HP), 400w (~.5hp), and 200W (~1/4 Hp.) THinking of useing the 1.5 to replace the spindle motor on the cnc mill, 400W on a ballscrew for the carriage on the lathe and make a servo driven rear toolpost on the lathe.