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Can somebody tell me a thing or two about this AC servo/stepper motor (mitsubishi)? Answered

Hey I'm planning on building a mini/desktop-ish CNC milling machine, so I've started gathering materials for the building of it (when ever i stumple upon a great deal :) )

SO I've got this big Mitsubishi AC servo/ stepper motor (from a real industrial CNC machine) it's not working (that's why I got it for free)

I'm trying to disassemble it to see if it's something fixable (for me)...
It's divided into two compartments
the first "chamber" contains the elctronics; (looks like an optic sensor and some other stuff)... well IT WAS FILLED WITH OIL!?
that surprises me since my logic sense tells me that electronics and liquids don't mix? is it supposed to be filled with oil or could that be the reason why it doesn't work? (the electronics/ chamber 1 is pic 4-6)

I can't disassemble it any further... even thoug i can't se any more screws... has anyone done something like that before and can tell me how to proceed? (btw. I'm pretty sure the second (and last) "chamber" contains the stators and the actual motor parts..)

someone please help me... It would be a REALLY nice start of a hobby CNC milling machine project to get a strong, professional and WORKING stepper motor :D so come with all the inputs you can think of.
will be greatly appreciated! (sorry for the no so good pictures..)


I just assumed it was a stepper since a thought all motors on a CNC was a stepper motor... why would it be compicated/expensive to run for a home user?

I think steveastrouk is right about the seal leaking... especially because there's an optic sensor in there and I'm pretty sure they cant "see" throug oil

and the previous owner did not try to repair it/ didn't look for the problem so it's not because they couldn't repair it... so I hope I've got a chance :)

On real CNC machines, used for really cutting metal, stepper motors are NEVER used ! Either DC or AC servo motors are employed - they can accelerate much quicker, stop quicker etc etc,

The drivers for these AC servo motors are expensive and complex - look up the cost of buying one from Mitsubishi.....

BTW. I was thinking of using it as the spindle motor (for the cutting tools- not any of the axes) so it doesen't have to be controlled very accurate since it only needs to change RPM's for different tools, materials and such doesent matter that much if it runs at 1500 instead of 1200 or something like that... if that could make it easier to control?

That's not a stepper, its an AC servo motor. Completely different working principle, but a very valuable piece of kit if it would work. There shouldn't be oil in the end.....

Driving them is very complicated, and pretty expensive, for a home user.


Given the o-ring between the electronics and housing, I see it perfectly reasonable that it would be full of oil - maintenence free sort of thing. It's perfectly reasonable to immerse a LOT of electronics in oil for cooling.

As for this part - if the owner couldn't fix it, its probably WAY out of diy range/cost.

Its an INDUSTRIAL servo drive for a CNC machine. Its designed to be sealed in use, so no crud can get INTO it. Hence the seal. It leaked.