looking to replace these motors

[Boltz]

Hi, my Multicam has these older and rather rare servo motors on it. They are coupled to 10:1 gearboxes.

Does anybody know of a more common motor which would work with my Electro-Craft BRU-series drives?

Which manufacturers should I be looking at for a motor with these specifications, and how would I know if this is a "low inertia" motor?

thanks,
-Jim Hart

[Al_The_Man]

My experience with BRU drives indicated that the encoder had a commutation sync pulse that was unique to the compatible motor.
At the time I could not find any details on the sync pulse required.
Al.

[Boltz]

I have the drive manual. This is from the "custom profile section". Is this the info you're referring to?

thanks,
-Jim Hart

[Al_The_Man]

The one I experimented with, BRU-200 did not have hall commutation unfortunately.
Al.

[Boltz]

I have full documentation in my manual, including cable pinouts and a step by step procedure for creating custom motor profiles, and I also have the Ultramaster software.

Aside from the color of the case, my BRU-series are identical to the Allen-Bradley 1398 drives, so any motor which works with an AB1398 will be useable.

Am I wasting my time with brushless DC, or is it a technology which still has some life left in it? Should I convert to AC?

thanks,
-Jim Hart

[Al_The_Man]

I have been using BLDC for a while now, I am using Galil Motion and simple AMC analogue drives in torque mode, the encoder I have on the present application gives 80000 counts/inch resolution and I can position within 1 count.
I have seen posts here than claim they cannot work on CNC??
Al.

[Woody111]

Jim is the motor bad? I have a great servo repair guy that can remag the motor and rewind them if needed. He would need all the info on the motor name tag to see if he can fix yours. He is located near Pittsburgh Pa. Woody

[Boltz]

Hi, I sent one of the junk box motors I got with the machine to NC Servo in Michigan. It's taking several weeks for them to order in a suitable replacement encoder, and they're charging about $850 for the rebuild, including remag and all that.

The real problem here is that Minarik is more like Bodine than Fanuc, which is to say that they don't seem to have been extensively involved in motion control and machine tool building. A search of Ebay for "Minarik" turns up a couple hundred variable speed drives for BLDC motors, and just a couple of servo motors with encoders.

It looks there are quite a few servo motors currently in the Allen-Bradley lineup which can be driven with my 1398DDM-009 drives, but none of them even come close to the nameplate torque specs on the Minariks.

Still trying to get my head around the difference between a brushless DC servo motor and an AC servo motor. One article seemed to say that the motors themselves are the same, but the drives and method of driving them are different.

Mind boggled, at least for now!

I could easily pay somebody a couple hundred dollars to spec out a substitute with the money I'd save by switching to a readily available motor.

[Al_The_Man]

Still trying to get my head around the difference between a brushless DC servo motor and an AC servo motor. One article seemed to say that the motors themselves are the same, but the drives and method of driving them are different.

The difference is in the commutation, the BLDC is usually trapezoidal power to two windings at a time, whereas AC use sinusoidal to all three windings which is superior, but I have had excellent results in spite of warnings that BLDC cog at low rpm, it seems that the controller makes the difference as I have used them direct to ball screw without sign of cogging.
http://users.tinyworld.co.uk/flecc/4...otor031102.swf
And also in spite of comments to the contrary, I have found them absolutely silent in operation.
Al.

[Boltz]

Definitely a different approach you use, Al...

Although I'm old enough to remember when AC servos were rare and expensive, they're now easy to get and don't seem that expensive, I'm curious why you like the BLDC approach...

-Jim Hart

[Al_The_Man]

I'm curious why you like the BLDC approach...

-Jim Hart

A couple of reasons, they work for me.
And I can pick them up fairly cheap, the AMC drives I use with Galil take a bit more cost and integration using AC sinusoidal.
I do generally stick with 8 pole motors though.
Al.

[Boltz]

Okay, I've been reading spec sheets until my eyes glaze over, and I haven't found a motor which is rated for the peak torque on the nameplate of my Minarik (1450 in-oz) which can be driven with my existing DDM-009 drives.

So, I've been pricing out DDM-019's and I've been wondering a few things.

1. Aside from the fact that I'd have to inventory 2 sizes of spare motors, is there any reason not to ugrade the drives and motors which do the hardest job, moving the gantry in the x-axis? Do the motors and drive on all 3 axes need to be the same?

2. Are all DDM-019's truly interchangeable? Including the AB 1398 versions, the DDM-019x indexing versions? Are there any firmware gotchyas to watch out for, or can any of these drives be flashed to suit?

Thanks for any insights.

-Jim Hart