I did not want to hijack JD's thread any further. I am starting a conversion of my stepped pulley J-head Bridgeport mill to CNC. At the same time I am converting a Taig lathe to CNC. I got a lot of information from JD's thread and much of what I plan to do will be similar to his. I don't really have a good reason for the conversion other than the entertainment and educational value of the project.
I purchased my mill about 8 years ago for $500. It was pretty worn out. I had to shim the Y-axis gib to get it close to being useable. I could get the slop in the table down to .002, but then it would be tight at either end of the travel. I could get decent result if I locked the table in the direction I was not milling. So, to start this project I sent the table, saddle, and knee out to a machine rebuilder to have them ground, scraped and fitted. No point in starting a project like this if the mill is this worn.
I am not going to install ball screws at this time. The machine rebuilder guarantees I can get .002" backlash when he is done (and less than .0005 slop in the table). I can take care of this with software. If it turns out that I am not getting the results I would like, I can always add them later.
I am really starting from scratch. I found 5 60VDC motors at Triangle machine (on of the places that the "MythBusters" shop). It took about three days to get all the specs, but I think they will work for this project. They have no encoder or shaft for an encoder so I will have to add that. The brushes and bearings were shot on most of the motors. The bearings are standard R10ZZ. I found the brushes at Arrowhead Electric Company.
http://www.carbonbrush.com/brushes.htm
They were about $6 each and it takes 4 per motor. I paid $50 each for the motors, $120 for all the brushes, $40 for bearings and $54 each for three encoders.
The first picture is my mill stripped and waiting for the parts to return from the machine rebuilder.
#2 is boring the hole for the encoder shaft in the end of the motor shaft.
#3 shows the armature before I turned it.
#4 is turning the armature.
#5 is the finished armature.
To bore the hole in end of the motor shaft I mounted the motor in my lathe and centered it as best I could. Then I added power to the motor and used and end mill in the tail stock to bore the hole. I did this before I replace the bearings in case I caused them stress from the procedure. Next I pulled the bearing and turned the armature. After turning the armature you have to undercut the armature sections so there is a little gap between them. I installed new bearings, assembled the motor, installed new brushes and tested them. They all worked great. Today I am going to work on installing the encoder shafts and mounting the encoders.
A word on encoders. I purchased some Renco encoders, but after talking to Mariss at Gecko, I found that they drew too much current. The Gecko’s can only deliver 50 mA to the encoder. These Rencos required 125 mA. I purchased some US Digital E5S encoders that will work with the Gecko 320.
Vince