SEM Servo Question

[astr]

I'm retrofitting my Boss 8 mill to run with Mach3. I'm keeping the original SEM servos but replacing the encoders with the AMT102 capacitive units. The shafts on the servos are too large in diameter to accept the AMT encoders so I was planning to turn them down. It looks like it may be possible to turn the shaft down without disassembling the servo completely however it would be much simpler process if I just pulled the armature.

I read that with stepper motors disassembly is not recommended as loss of the magnetism will result. Is there any such problem with disassembling servos? Is there anything else that I should be concerned with?

[Al_The_Man]

I have never experienced a problem with disassembling servo's, the thing to watch for however is as soon as the armature shaft leaves the bearing it is rapidly attracted to the magnets so care must be taken to prevent a crack or other damage to the magnet.
There was a post here some years ago on removing the encoder disc and bore it out in a lathe, I have done this also.
Al.

[astr]

Thanks Al for the info. I did a search but couldn't locate the thread you referred to. Do you by chance what the title of it was?

[Al_The_Man]

It was ages ago, but I seem to think it was a post from Art Eckstein, IIRC.
I don't seem to locate any of his posts as I am not sure what he used as a forum name?
But essentially he used a 3 jaw chuck with no run out or use a four jaw and accurately centre the encoder hub.
I used a collet chuck which is best of all.
Then just bore them out using a fine boring tool.
I have never used the capacitive encoders, just the glass or mylar optical disk.
Al.

[CASTLEVILLE]

i ran into the same problem when i retrofitted my bridgeport with SEM servos. i didn't disassemble the servo. i chucked it up in the lathe holding on to the shaft. dialed it in then hooked up a strap to hold the body of the servo from spinning. turned down the end of the shaft where the encoder went(didn't turn it very fast) and finished it to final size with a file. worked out pretty good. i have been running the mill for 4 yrs of hobby use with the servos.

[astr]

These encoders seem to be highly recommended http://products.cui.com/CUI_AMT102-V...df?fileID=7573. Sparky_NY used them in his retrofit that I'm using as my guide: V2E3 retrofit build. He has high praises for this encoder. The encoder comes with shaft adapter from 2mm to 8mm but even the largest is too small for thhe SEM shaft so I was planning on turning down the servo shaft to either 8mm or 1/4".

[astr]

i ran into the same problem when i retrofitted my bridgeport with SEM servos. i didn't disassemble the servo. i chucked it up in the lathe holding on to the shaft. dialed it in then hooked up a strap to hold the body of the servo from spinning. turned down the end of the shaft where the encoder went(didn't turn it very fast) and finished it to final size with a file. worked out pretty good. i have been running the mill for 4 yrs of hobby use with the servos.

That is my fall-back approach. I've already removed the old encoder and the tach generator along with the magnets that are in the tach section of the servo since I won't be needing the tach generator any more.

Did you use the AMT encoders? What drives did you use?

[CASTLEVILLE]

I bought the ajax kit. so i got the encoders that ajax sells. i think they are made by dynapar. can't remember the modal number thought. if i remember right i think i had to turn my shafts down to .375".