[Johns tool room]

I have 3 SEM MT30M4-28 servo motors that I need to change out teh encoders. Anybody know if the encoder can be hooked up directly to the commutator shaft where the tachometer would normally be ( hopefully I can take that out to no detriment). I'm just trying to save the hassle of making a new cover for that encoder. any help appreciated.

[Al_The_Man]

I have seen two types on the SEM, through shaft, which should be available from a few encoder manuf.. the other is a miniature shaft encoder with coupler, I believe Hengstler and Koyo have a alternative.
A photo of your set up may help.
Al.

[Johns tool room]

I have seen two types on the SEM, through shaft, which should be available from a few encoder manuf.. the other is a miniature shaft encoder with coupler, I believe Hengstler and Koyo have a alternative.
A photo of your set up may help.
Al.

Don't have photo of my servos yet but the encoder is the standard one that comes with the Ajax kit



they come for .25 .375 .5" and 6mm shaft sizes. Think I can mount this where the tachometer brushes get mounted? I have no idea what these look like on the bottom.

[cnckeith]

say.. you keep saying that ajax hasn't been to helpful and you can't even post a photo of the motor so we can see what it looks like? come on man put some effort in. The ajax photo album showing how to mount a new encoder on a Boss 9 SEM servo is fantastic, i don't see any other CNC control manufacture helping out customer with info like that. by your tone i'm sure what you expect when it comes to help with your encoder. with Ajax you have many choices for help. #1 Free email support via the ajax tech forum, #2 the best deal on CNC phone support at $1 per minute gets you a 20 year experience tech on the phone to solve YOUR problems. (this is incredible try to get that anywhere else for that price) #3 have one of our techs come over to your place and install the encoder for you. this is expensive, but you get fast expert service and your machine will be running in no time. So if you are going to ask for free help, at least post enough info that we can actually help you. otherwise you are just wasting everyone's time and being sour at the same time.

[cnckeith]

here is the new encoder retrofit on a old SEM motor slide show for everyone else to see.

[Al_The_Man]

Think I can mount this where the tachometer brushes get mounted?

Do you already have the encoders? as I would investigate as to what can be removed on the tach end, it almost looks like a compact design such as Renco or Us Digital might fit without remaking the end cover if the tach can be removed especially?
Al.

[Johns tool room]

It looks like the only way to get the conversation is to .................

[cnckeith]

ok. so you expect Ajax to have blue prints for every SEM motor every made? hunh? you are being unreasonable. SEM doesn't even have that!! Every retrofit will have its unique challenges. Ive taken motors off a machines of the same year, that had the same model number and they were completely different encoder mount. If you are not up to the challenge of adapting at rotary encoder to the rear shaft of an old servo motor then maybe retrofitting is not for you. We are hear to help, i've listed your support options. We can't help you without good information from you. Like i stated before. A good photo will go a long way in receiving that help. right now you are the only one BS'ing. The Ajax CNC control kit is a way for mechanically and electrically inclined folks to be able to install a state of the art CNC control at a fraction of the cost of buying that machine new or having a Retrofit company come in and perform the retrofit for them. Expecting free unlimited help on a motor that Ajax has nothing to do with is unreasonable. Not providing machine info, detailed photos of the encoder motor mount or (even a sketch drawing!) and then complaining about not receiving help is ridiculous. Ajax is here to help. you can get instant answers by calling the tech line, or post some photos and dimensions here so we can get the conversation started on how to retrofit an encoder on an old SEM motor.

[Johns tool room]

Here is the motor and the two connectors one for motor and tachometer with the big pins and the other for the encoder.


encoder lines go from encoder through the back cover into the box and out the rearward connector.

here are the power lines




Here is the encoder with the connector for the wires at about 1 O'Clock



Need some suggestions before I go beyond that as that jam nut I have never seen one like it before and and need suggestions about holding the spindle still?

Maybe I should go with vise grips and brass shim on the spindle? Use an impact wrench on the nut?

[Johns tool room]

Tachometer.



Now, there is a snap ring (can't find my snap ring pliers) there on the shaft followed by some kind of bushing that has set screws sticking out of it. If I remove that will the tachometer body come off too? At this point I would like to find some tubing from which I can make a spacer to use instead of using the encoder mounting plate and mount the encoder on the screws where teh tachometer "brush plate" ( don't know the name) is mounted? Fat part of the shaft is .669" I need to know what length the encoder takes up, not the diameter but the length.

[Al_The_Man]

The Tach armature on the ones I have removed, I had to press the armature off the shaft, but it appears yours may be easier to remove, remove the C clip and set screw and see where it leads, it may come off fairly easily, there are many compact, low profile through-shaft encoders that would probabally have fit onto a plate without the need to manuf. a rear cover.
Al.

[Johns tool room]

The Tach armature on the ones I have removed, I had to press the armature off the shaft, but it appears yours may be easier to remove, remove the C clip and set screw and see where it leads, it may come off fairly easily, there are many compact, low profile through-shaft encoders that would probabally have fit onto a plate without the need to manuf. a rear cover.
Al.

Big question is whether those lower profile encoders are well suppressed/encased against interference? I still need to know how much space the encoders I have shown require.

[Al_The_Man]

I still need to know how much space the encoders I have shown require.

The distance from the mounting plate to the set screws for the rotating scale should tell you, and overall the depth of the encoder body should tell you? it sounds like you have an encoder so you could measure it once you have the tach etc removed?
Al.

[Johns tool room]

The distance from the mounting plate to the set screws for the rotating scale should tell you, and overall the depth of the encoder body should tell you? it sounds like you have an encoder so you could measure it once you have the tach etc removed?
Al.

Don't have one. If I did I wouldn't be asking

From cover to adapter I will have to make to mount the encoder instead of tacho brush plate, I have 2.1" of free depth

[Johns tool room]

ok. so you expect Ajax to have blue prints for every SEM motor every made? hunh? you are being unreasonable. SEM doesn't even have that!! Every retrofit will have its unique challenges. Ive taken motors off a machines of the same year, that had the same model number and they were completely different encoder mount. If you are not up to the challenge of adapting at rotary encoder to the rear shaft of an old servo motor then maybe retrofitting is not for you. We are hear to help, i've listed your support options. We can't help you without good information from you. Like i stated before. A good photo will go a long way in receiving that help. right now you are the only one BS'ing. The Ajax CNC control kit is a way for mechanically and electrically inclined folks to be able to install a state of the art CNC control at a fraction of the cost of buying that machine new or having a Retrofit company come in and perform the retrofit for them. Expecting free unlimited help on a motor that Ajax has nothing to do with is unreasonable. Not providing machine info, detailed photos of the encoder motor mount or (even a sketch drawing!) and then complaining about not receiving help is ridiculous. Ajax is here to help. you can get instant answers by calling the tech line, or post some photos and dimensions here so we can get the conversation started on how to retrofit an encoder on an old SEM motor.

Forgot to ask, besides needing to know how much space the encoder takes place, has anyone ever managed to remove the shaft in a DC motor. I was thinking about turning the back down so it can fit an encoder where the tacho was mounted.

[cnckeith]

removing the shaft is not advisable. only a experienced motor repair shop should perform such a feat. what stage of the tear down are you at? looks like you are making some progress in tearing it down. try to post photos that are in focus, its really hard to see otherwise. all you have to do is make a place for the encoder to mount to, most guys do this by modifying an existing plate or making an new one. the encoder mounts with two 4-40 screws (sometimes 6-32) center the mounting holes so that they are concentric with the motor shaft. Position the plate on the motor body so the encoder slips onto the motor shaft completely. tighten the set screw. connect the wires and your are done. what is the diameter of the shaft now that you have it torn down? encoder come in common shaft sizes so you don't have to turn down the shaft of a motor in most cases.

[cnckeith]

https://picasaweb.google.com/1024433...16092199410818
take off stock plate.
https://picasaweb.google.com/1024433...16106950255362

make mount to hold plate in milling machine or drill press.

https://picasaweb.google.com/1024433...16122271921266

mount plate to mount
https://picasaweb.google.com/1024433...16144286487762

drill encoder mounting holes in stock plate. use instructions that came with encoder.

https://picasaweb.google.com/1024433...16172732173186

https://picasaweb.google.com/1024433...16277863831458

make spacer plate/ring to hold encoder at correct height.

https://picasaweb.google.com/1024433...16293474770018

[cnckeith]

encoder on spacer on stock plate.

https://picasaweb.google.com/1024433...16315674892594

[cnckeith]

start putting motor back together.

https://picasaweb.google.com/1024433...16333745726754

notice dust guard.

https://picasaweb.google.com/1024433...16350663118914

look at that.. encoder is going on..

https://picasaweb.google.com/1024433...16368386810754

nice..

https://picasaweb.google.com/1024433...16384406963298

feed new encoder wiring thru stock wire box and pathway to encoder in motor body.

https://picasaweb.google.com/1024433...16423045626658

solder wires together. follow diagram that came with ajax kit.

https://picasaweb.google.com/1024433...16476401448514

proper wiring positioning.

https://picasaweb.google.com/1024433...16549544925154

[cnckeith]

protect new encoder with new cap, or modified stock cap. some guys use a pc of steel or aluminum tubing as a spacer between the stock end cap and the motor.. others like Ken here. made his own.
https://picasaweb.google.com/1024433...16488926356050

either way.. no dust, chips, filings , oil or water can get in there, it will ruin the motor and the encoder. be sure to gasket it. make your own gaskets, cut out of cork or rubber gasket material, only use rtv if you have tested the motor and are sure everything is tight and good to go.