Light Machine Corp. Benchman XTr (retrofit)

They are generally just to hold the axes when the power is off.
This can be especially useful for the Z axis if there is a danger of the head dropping on to the table.

Brakes can also prevent position-loss when the power is off and the encoders are not counting.
(this works better with absolute single-turn devices like resolvers, though)

Ok I am Back. After a long robotics season and reworking a plasma table I can finally give much needed time to this project. I AM using the kflop and I am suffering for it, but I believe the mechanics of this machine will still be useful to anyone working with one of these in Linux with a Mesa. SO far, I delivered 24V to the z axis brake, and the spindle started to drop rapidly until I pulled the 24V and it locked up. Pretty cool!
I tried to leave as much of the wiring intact as I could so I am using what's there to make my connections so as not to disturb the original wiring. Because there are smoothing circuits on the original control boards, I elected to buy a 72V power supply and just gut and replace the main toroid 72v supply and the main control PCAs when that time comes. Right now, I just have the power supply sitting on a work table behind the Benchman. I ordered some male ribbon cable connectors and used the ribbon cable to breakout the encoder signals and wire them into the Kflop/Kannalog unit. I WISH I had a Mesa, but the wiring seems to be the same in terms of what the signals are. I used the Copley amplifier manual and wired the X axis in the torque mode ( more on that in a minute) and used the 1.5V battery suggestion... MOVEMENT!
A quick note... the Kflop/Kannalog documentation STINKS! I've been stumbling through it all, but today, Success! I can control the x axis and the encoders are actively giving position and I am able to control the movement. Next comes tuning. If I can get this X axis to work, the others will be easy.
Got a question for you gurus out there. Something strange. I THOUGHT the Copleys were set up in Velocity mode... but I don;t see where they are getting a Tachometer reading. Is it the index pulse from the encoders? Did I miss an actual brush tachometer? Also, the Manual defines component values (appox) for Torque and Velocity modes.... these seem to be set up as BOTH. CH11 has a zero ohm resistor (a short) that you would see in torque mode instead of a small cap... and CH9 is supposed to be blank for torque mode but instead has a 220PF cap installed like you would see in Velocity mode. Coupled with the missing Tach I'm totally confused. Anyone have any ideas on this? My first thought is to convert the Copleys to Torque mode to avoid a conflict with the controller that thinks it is controlling everything.
I will post drawing of my connections as soon as I actually draw them.

So on my ProLight (which I think is pretty much the same machine) there's a board that takes the encoders as an input and runs through several logic chips to produce a tachometer output. At one point I tried tracing out all of these components and found datasheets for them and got a schematic but if I remember correctly I would have needed a few more supply voltages then just +5 and +24. I think each of the LED's below and to the left of this tachometer board correspond to each of these supply voltages which are fed from the box that houses the computer. I ended up just getting rid of that board and running the servos in torque mode and have been happy with it. I can look up the tuning values that I used if you want.

-Shawn

Thanks Wrightsh! That board is similar but I think there are some differences. It IS pretty close though and I'm sure your explanation is the right one. I have the original tuning values, they are listed in an earlier post on this thread but if you have other values I would love to see them. Tuning is supposed to be the hardest part and I suspect the values I should use for this new controller are either the same or some numeric ratio. Anyway, if you can post those without too much trouble I would appreciate that.

So my X & Y run pretty well with this but I do need to do some more work on the Z because I recently added a plate between the spindle and the carriage that the spindle mounts to in order to shift the Z axis up by a couple inches & the added weight needs some compensation. At least on my ProLight if you bring the Z all the way down the spindle nose is basically in the table. Which isn't very helpful if you only have 9" of Z travel and are always going to have at least ~2" of tool holder and tool + however tall your vise is


You'll also need to put the amp into torque mode

Thanks for the numbers wrightsh. I played with mine today but they are pretty different by the time it was all said and done.
I have two axis running and have decided that for E-Stop I will disable all the Copley Servo Amps. There is quite a bit of residual power stored in the smoothing caps of my DC supply SO I think the motors will continue to move a small amount after an E-Stop. I have to supply ground to pins 11, 12 and 13 and by disconnecting the ground I can completely stop any movement. Making some pretty good progress.