Wednesday night I decided to dig in. My goal was to finish it by sunday as I need it for work this week. I put it on rollers and slid it away from the wall.
Thursday I gutted the machine. Pulled out anything to do with the servos, transformers, drives, scales, contactors. Yanked of the servos and pulled off the pulleys. Bored out the pulleys to 24mm and broached a 8mm keyway for the motors.
Y axis motor installed without a hitch. Did have to use a rotary file to remove a little more of the motor mount casting but I expected that. It bolted right into place. The Z motor was similar. Mounted in place of the old one. The X axis was a little more painful, literally, I managed to get myself really nice like while trying to get the pulley off. Since the new motors have a larger face on them I had to mount the X axis to the sides of the casting.
Friday I did the motor and encoder wiring. Ran all over town to try and find the wire I wanted, ended up getting stuck with MTW. The machine has sealed cable carriers and I managed to get the new motor cables and encoder cables in them to the control box. The Z axis encoder had to go externally. It was just too fat to fit through the conduit.
Saturday I mounted the drives and support pieces. I wired in mains power to the drives breakers, contactors, and finally to the drives. The newer drives control the buss power and shut it down if there is a fault. I finished the connections to the motors and encoders. The Z axis encoder amphenol was a pain. Must have been about twenty wires. Differential A,B,Z plus hall tracks for UVW. X wasnt so bad, by that time they went to a serial interface encoder and there are only a handful of wires. I tied the motors into the drives and the encoder cables as well. I got initial power to the Z drive and was able to jog the motor from the test mode.
Originally the machine was ran off 4 wire 208 so it had 120v off the lines. I did a no-no and was using the ground as a neutral. With the extra space I installed a .5kva 240 to 120v control transformer to run the computer, contactors, and lube pump.
That night I also got the cables ready. I reused the drive cables that came out of the molder. They have 50 pin MDR connectors on one size and 40 on the other. I took one of the cables and put the 36 pin connector for the MR-J drive on the end for the Z axis. While doing this I found a mistake on the board. So I cut that trace and jumped to correct it.
So, finally, this morning I did the control wiring. I needed to mount the interface boards. For some reason I neglected to put in mounting holes so I had to add those. I too a piece of 3/8" white PVC sheet and made a plate to mount the three boards to. This mounted next to the drives. I wired up the contactors and estop interlock for the drives.
I went into the computer cabinet and yanked out the old pixie boards. I reused the analog signal wires for step and direction signals.
Finally it was time to make it move. Powered everything up, grabbed the pendant, and turned it. Nothing. Huh. Eventually after some probing I found I had mislabeled the silkscreening on the interface boards. I connected the signal wires to the correct spots and X and Y moved! But Z didnt. On the newer drives you can enable the drive in the parameters. I had forgotten that the old drives have to be hard wired. Jumped that and still nothing. Oh yeah, left and right stroke inhibit. Jumped those. Now it moved.
But it moved very slowly with the native encoder resolution the X and Y were at 81920 pulses per inch. The Z axis was 64000 pulses per inch. I used the internal electronic gearing to divide those numbers by 8 on the X and Y and 5 on the Z. Much better.
All while messing around with it I managed to get it to run through the Z bottom tie rods on the balance cylinder. The had been welded together from shorter screws. I repaired one, still need to do the other two. I also made a couple other mods, installed a SSR running off the computers 5v line to kill power to the servo contactors when the computer is off. Also tied the Z axis servo-on line to the e-stop loop. The older drives dont have a dedicated e-stop line like the newer ones.
So far it looks like it is going to work great. The Z (Knee) is a whole different creature now. Moves quick. I had to have the old motor's acceleration all the way down to 3 in/sec/sec. I can easily run the new motor at 50.IMG_0939
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