Need encoder recommendation

[Swede]

Some background - my friend is retrofitting a cherry BP series one CNC mill with a new control. The original motors (NEMA 43-sized) used a very low resolution encoder, which we want to replace with a more modern optical encoder. The motor shaft, which extends from the rear of the motor, was originally threaded 10mm. Our plan is to fit a stub shaft over the threaded portion, extending the shaft and creating basically any diameter... probably to either 10mm or 3/8".

The motor has 3 mounting holes in a standard NEMA43 pattern for the encoders. We are looking for a recommendation on an encoder which can be directly mounted, or adapted.

Needed: Quadrature encoder for NEMA 43 mount, 1000 line, 5V, channels A/A~, B/B~, w/ index, ungated. I've always used Renco encoders up til now but their encoders are too small! Any hints/pointers to a suitable encoder would be appreciated, hopefully not ones which seem to cost $350+ each.

Thanks guys!!

added: These are brushed S.E.M. motors with tach. We won't be using the tach at all. Again, TY all.

[duluthboat]

Many choices here.
http://www.usdigital.com/products/
Gary

[Al_The_Man]

Swede, Did you want a through hole type? Also what is the current mounting bolt circle? Was the original mounted by through screws or external 'servo' mount type where you can slacked and rotate the encoder?
I have several sources, it would depend on some of the above answers.
When you say Renco are too small, in what way?
Al

[Swede]

Wow guys thanks for the fast replies. I should have been more specific.

The motors have, on the rear, a stub shaft which has a 10mm shoulder, and perhaps 12mm of thread. The original encoder disk was secured against the shoulder via a nut. Our plan is to turn adaptor stubs to create an unthreaded section of shaft extension which will probably be dia. 10mm to 1/2", although we can neck it down smaller if necessary.

The original encoder mounted on 3 ea tapped holes on a 2.61" bolt circle. I suspect this is a typical pattern for a NEMA 42 motor, as the HS22 encoders from B.E.I., among others, would bolt right on. If necessary, we can create an aluminum plate adaptor disk which would allow the mounting of say a RENCO 15 or 21 series of encoder. The rear of the motor cannot be drilled and tapped, we need to live with the 2.61" 120 degree pattern.

The price on the BEI encoders was a bit of sticker shock. S.E.M, the motor maker, hasn't been helpful at all. We are trying to keep the cost for 4 encoders reasonable. Thanks!

[Al_The_Man]

That bolt circle is pretty much standard for the 'Synchro' mount type for the typical 2.25 dia. encoder, where the mounting screws are separate from the encoder and use a eccentric ring washer that engages in a slot in the encoder, this was to enable a 360 deg rotation of the encoder if neccessary. If you are buying new, probally the cheapest is going to be Renco in qty 5. The price really drops for 10 (you could but the other six on ebay), The 21 series that have the dual encoder/commutation track have this kind of mounting. I have a policy now that if I buy encoders on ebay, I make sure they are new as I have ended up a few dud used ones. A through hole type is obviously going to be the most compact. Unless you have a lot of room to put a shaft encoder with coupling.
Al

[Swede]

Thanks, Guys. That is pretty much what we came up with. I've always liked Renco modular encoders. It'll just be a matter of adapting them.

What puzzled us a bit is given the large number of these motors used by BP, you think there'd be a market for new encoders which are a direct replacement for the old.

[Al_The_Man]

I know S.E.M. used some pretty odd ball encoders, I have some that use a miniature shaft encoder inside the back cover of the motor, about 1" in dia. I guess there is no make/model on your old one?
Al

[Swede]

Al, sorry for my slow reply, I was out of town! I'm glad to hear you've encountered some with retrofitted encoders. The original has a model number - not available at the moment - but we're going to go with Renco RM15 or RM21's, as I am comfortable with these encoders and their wiring.

If they don't fit in the original encoder case, we plan on "extending" the case off of the rear of the motor with a section of turned aluminum tube. The tube would act as a standoff for the original cover, rather than trying to machine an entirely new cover, or worse leaving the Rencos exposed to swarf and coolant.

I appreciate the suggestions.

[HillBilly]

Ajax CNC has one they use on these motors @ $125 each.
http://ajaxcnc.com/cnc_components.htm

HillBilly

[greggv]

Again, US Digital, and you might look at automation direct. I know they have some inexpensive encoders, too.