Assuming the motor is out and on a bench.
Bear with me – I am recalling from memory. I should have taken pictures and notes – I do recall the things I did wrong, steps I skipped and errors made so that it goes smoother for you.
Tools:
-Small hex keys, 0.05"? but it is a 4-48 size screw I know that for sure - long story! Use the normal square end type not ball end and good quality.
-Sharpe scribe.
-A few cans of PLASTIC SAFE electrical cleaner.
-Soldering iron preferably with small pointed tip.
-Heavy paper like the card stock on the back of a note pad – big piece or several.
-A foot long or more length of 1 ½” PVC pipe, cut for or more slits inch length on one end, hack saw or band saw is fine.
-Roll of Electrical tape of any color you choose.
-copper, brass or aluminum shim thin enough to wrap once on shaft.
• Clean the outside carefully – Simple Green or your favorite brand, stiff brush and rag. Do not be too aggressive at encoder end. Do not hose off with high pressure water. Just a spritz with cleaner, scrub with stiff brush a quick spray rinse. Dry with paper towels. No need to be perfect just not completely gross.
• With a sharp scribe make match marks where covers and center body meet. I put two // on one end and one / on the other.
• Encoder is next – remove the cover, mind the wires!
Here’s where a bit of fun comes in.
For the Z axis I discovered that if you R&R the encoder then you will need to reset the tool change parameter (64?) to reset to proper height for the tool shuttle – but we are working Y. I don’t recall issue with my X, Y axis.
• There is a tiny coupling with two tiny set screws between the encoder and motor. Find them and choose a proper fitting key – don’t just guess be sure it’s an exact fit [insert my bad day here]. Now take the soldering iron [it is plugged in and warm now, yes?] Hold the tip on the set screw for a moment. What your doing is softening the Loctite. Quickly insert key and be sure it’s all the way in and just give it one or two turns. Repeat for other screw.
The coupling is in two parts, a ring with set screws and a close-fitting collar with slits. You should be able to gently move the encoder lengthwise on the shaft.
Remove the two screws holding the encoder and gently slide it off and set aside.
• Remove brushes
• Remove thru bolts. You did match mark the ends yes?
• The brush end should come right off. A gentle tap with a plastic mallet may be needed – GENTLE!
• Honestly you could stop right here and using air gun and the cleaner just get the commutator and brush cover clean and reassemble. I HIGHLY recommend it!
I’m a bit OCD so here’s how to go further..
• Take the paper and form a tube shape and slip it between the field and rotor, not tight we just want to protect the wiring. Use the electrical tape to close it tight to the commutator and wrap it well – protect the commutator and wires!
• Wrap the shaft in the shim and clamp the end in a bench vice – mindful that you want to pull strongly away from the vice yet not damage the shaft!
• Take the PVC pipe split end and shove it on the bearing at the brush end [should be towards you] - you’ll understand in a moment.
• Now what you are going to do is firmly grasp the housing and pull towards you. The magnet wants to pull back, try to do this in one smooth motion.. DON’T DROP IT!
You will understand now why all the trouble with the protective wrap and pipe.
Now take it all off and clean carefully – there are lumps of epoxy for balance and the insulating varnish is brittle – soft brush, air blast and or plastic safe solvent spray only! Now you may choose to polish the commutator – I recommend not to – the wrong abrasive can wreck it and I’m no expert here. If the grooves are free of dust your fine – tooth brush if needed.
Reassemble is reverse of above and the tube will be even more important - wrap it good as the field will jump to the rotor as soon as its near – a good strong grip is essential!
Check your brush cover carefully, rubbed wires solder joint damage..
New brushes are a good idea… but to just get going again for now not necessary, you can change later in place.
I mentioned the Y axis cover removal towards the front. What was I thinking, must have been the X cable. The Y cable is stationary and easy to get to.
I hope this does it and you gain the confidence to do the other two. None of it terribly hard, you just have to know how.
Good luck.