These pages detail my progress in converting an old Bridgeport Series II Interact 2 mill to EMC2 CNC Software based CNC PC control.
I bought it from a local seller who placed a Craigslist ad (see pictures from the ad). He advertised a Bridgeport CNC mill with a non-working display. The price was $500, plus $500 for a large quantity of toolholders. I figured that the price was right and bought it. At that price, the worst case scenario would be that I would be unable to restore the mill and would part it out. I would probably get my money back from toolholders alone (35 of them). While searching for more information about this mill, I save some pictures of other similar milling machines. An additional impetus to act quickly was this thread from CncZone, where a potential buyer was asking questions about the same mill that I was looking at.
I rented a low boy trailer. Pick up was relatively uneventful and the mill looked okay. I had help from Machinery Movers Chicago. The trip back, unfortunately, was not without a disappointment. I was stopped by the police and accused of exceeding weight allowed by my drivers license. I was told my trailer will be towed until I get a Class C license. Fortunately, I had a laptop with me and looked up and showed them the Illinois statute, which permitted me to drive up to 25,000 GVWR vehicles. I was still fined for lack of some stupid sticker, but was let go. So, now I say, beware of Sugar Grove, IL police department.
I was extremely fortunate, because my friend generously offered me to use his warehouse to hold the mill until I clean up my garage enough to place the milling machine. I dropped it off there.
Since the mill was taller than my garage door, I had to remove the head and chip guard from the mill. I documented every single wire that was disconnected.
A mere six weeks later:), I rented a car hauler trailer and took it home. Again, my friend, his son and his son's buddies helped me a lot. All faces in pictures are blurred for privacy.
Check out some pictures of servo motors and their guts and original look of inside the control cabinet. Also check out the Bridgeport Series II Interact 2 Schematic. Those, like me, desperate to get a manual, look no further: Bridgeport Series II Interact 2 Maintenance Manual PDF and more manuals.
An attempt to diagnose problems with the original control, pointed the finger to Hendenhain TNC151 control. A CNC control is like a PC and, as you know, PCs go bad after a few years. I was quoted some outrageous amount for fixing this control (3,000-5,000 USD). I figured that even if I fix this control, all I will have is an old control, and next time another capacitor leaks I would again have to pay thousands. At this point I decided to junk my control, took out the control and servo drives. I sold those parts (with proper disclosure) on eBay and recouped the cost of the mill from just that stuff.
My first undertaking was building of a homemade CNC power supply. I made it from a toroid donut transformer, a capacitor and a rectifier. It was easy and pleasant. I was reusing mounting brackets from servo drives.
After removing stuff from inside of the cabinet (see emptied out cabinet, I started wiring the control cabinet anew. I tried very hard to have all wiring labeled and to go through wiring channels.
Being a computer programmer, I tried to do one thing at a time: for example, first I tried powering a servo motor with a DC power supply. Next, I wired in a servo drive and connected a DC servo to it. That way I could test stuff and get myself familiar with the operation of this machine and its components.
At that point, more fun began: I purchased a PPMC drive from Jon Elson's PICO Systems. This an interface between computer on one side, and servo drives, encoders and control buttons on the other. It was not dirt cheap, but well worth the money and Jon provided excellent product support. I also bought three E5 Optical Encoders from US Digital. The model I selected provided 4,000 pulses per revolution, which amounts to resolution of one pulse per 0.000025 inch move (this does not directly translate into accuracy of the machine, just shows that there is plenty of resolution).
I made adapter plates to mount new encoders to the existing servo motors. That was somewhat painful, because I had to drill a large 43/64 hole for the motor shaft, and I could not do it accurately enough. My solution was to drill the big hole approximately where it should be, and then re-zero my coordinate system relative to the big hole. I really wished that I had a CNC mill working. It was time consuming, but I made all the plates.
Then something exciting happened and I hooked up a Linux PC to the mill. Being a long time Linux user since 1995, I was very happy to use the OS with which I am most familiar.
After a day of not understanding of what is going on, the PC connected to the PPMC device and was able to read encoder readings and send signals to the motor. For testing purposes, I unhooked a belt from the Y axis motor (which I could easily see when sitting near the cabinet), so there was no danger from the motor moving, even when it was moving uncontrolled, in a wrong direction, could not stop etc. A lot of time was then spent wiring limit switches, E-STOP, and home switches.
I also wired the computer for Ethernet and added a webcam.
Finally, I could move the axes from a GUI. I programmed my first G-Codes and voila, the table MOVED exactly as programmed!
Finally I started writing some perl scripts that generate G codes and wrote a G code file to drill bolt holes. YouTube video.
After the mill became functional, I spent some time looking at the Troyke CNC rotary table that I bought on eBay for $149. It is currently a completed project. The table has a resolver instead of an encoder, and so it needs to have a resolver to encoder converter.
The next mini project was to mount a nice 17 inch monitor that was thrown away at my employer's place, and therefore I had to CNC a set of monitor mounting brackets.
One sunny August day, I stopped by a garage sale and purchased a new in box Saitek P880 joypad that I set up with EMC2. I can use this joypad now to jog the mill in a super convenient way. It is even better than the original jog control, which I intend to restore to full function anyway.
This is how the mill looked in September.
My last and, possibly, final project for this mill is to motorize the knee, in order to provide a greater vertical "envelope", in order to accommodate short, as well as long, tools.