I made some more progress this week. It was too darn cold in the garage to do any work so I got a friend to help me bring the gantry inside. Now it sits on my living room floor.
I got the bottom plate with the electronics bolted down and the power supplies mounted and wired in. Checked connections and everything seems to be OK. Eventually found two little issues. The stock board that the encoder on the X axis connects to and where the flex flat cables (FFC) terminate to before going to the arm had pins 26 to 30 on one of the two connectors ending in the board. This killed my 5v power to the gantry among other things. I jumped the connectors with some 32 ga wire and that fixed that. Second problem was the connection for the brushless motor on the Y axis. I got the pin order backwards. 1 was at 11 and 11 at 1. Luckily I was able to peel off the back spacer of the FFC and fold it over. I made up cables to connect the arm board to the carriage. I used those silicone wires I had posted about earlier. Pretty much the perfect length. I also made up a cable for the encoder, used some nice renishaw 12 conductor double insulated encoder cable that I picked up off ebay years ago.
I then made up a cable to connect the RJ45 serial connectors on the drives to the serial port on a laptop and installed the software for the drives. I managed to get the X axis tuned using the auto tune function, moves pretty quick with a resolution of .01mm per step. I dont have the encoder on the Y but managed to get it working in a low res mode where it reads the feedback from the motors hall encoder.
The Z axis motor was not so kind to me. Its a little maxon gear head motor. .18 amps at 45volts, 32 count encoder on the back, 24:1 gear box on it. First problem is the drive would not accept the single ended input from the stock encoder. Most drives have differential signaling built in and will take a single ended encoder input. Not these. I tried cheating and it almost worked but there was a whole lot of noise in the signal and it would not work right. So I needed to change the single ended input into a differential signal. Normally you would use a line driver but I didnt have one. What I did have was a mechanically bad encoder with line driver outputs. I took the board out and there was a line driver chip. I removed all the other components and took the bandsaw to the extra circuit board. I wired a connector to the inputs of the line driver IC and put a connector for the servo drive on the other end so the board is between the motor encoder and the servo drive. Finally the drive is happy.
Still problems though. Seems the motor draws less current than the drive really likes to see. This means the auto-tune is not happy. So I spent about 2 hours tuning the drive manually. Looks like this should work now.
Next up is trying to figure out how to mount the Y axis encoder scale and come up with a better mount for the Y servo motor. This one is just too floppy.
Here are a couple pics. One with the electronics mounted to the machine and the other with the machine guts exposed at night. I think I used too bright of LEDs!
Laser cutter electronics by
macona, on Flickr
Laser cutter at night by
macona, on Flickr