Light Machine Corp. Benchman XTr (retrofit)

wrightsh wrote: 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

The encoder in the motors is a Tamagawa "Singlesyn" or "Smartsyn" resolver that can't be used without the dedicated ASIC (also made by Tamagawa). It's a funny magnetic component with an "exciter" winding (Z) and 2 outputs A & B. The ASIC drives the resolver Z winding with a high frequency waveform and also does lots of processing on the resulting output signals. Several outputs are available including the simple pulse output that is used here. For permanent magnet motors where rotor position information is critical etc, it provides a 10 / 12 bit absolute position signal and that's normally why people install them. Seems a bit of overkill just to generate a speed / direction signal but it's a very good quality solution.

Basically, if you want to use this original (absolute position) encoder you will need to retain the interface board with its ASIC (AU6802). If you want a simpler solution, you may be better off removing the encoder and associated interface board and replacing them with a much simpler and conventional (speed) encoder.

Muzzer wrote: Basically, if you want to use this original (absolute position) encoder you will need to retain the interface board with its ASIC (AU6802). If you want a simpler solution, you may be better off removing the encoder and associated interface board and replacing them with a much simpler and conventional (speed) encoder.

Mesa offer a board that works _very_ nicely with resolvers.

Mesa 7i49

I like it so much that on my recent Lathe retrofit I removed an encoder and fitted a resolver

The 7i49 produces a very high quality velocity output, and it would be relatively easy to route that back to one of the analogue outputs on the board to get a velocity-proportional voltage.

I've recently got the 7i49 in stock.

JT

Before I tear into the Z axis, does anyone know how to adjust the Z axis on a Benchman? My unit is so loose that when the brake is deactivated the head just travels down on its own. This is a problem because the servo spikes on a downward move at about .006" error for a very short time before it corrects. I'm thinking I need to either counterbalance the Z axis or tighten the gibs to reduce the amount of "shock" from gravity. Any input would be appreciate.

There was an issue with the upper endstop in this machine, so I had to pull the head off. You may be able to see what you need without removing the head. Home the Z- axis. Remove the accordion dust cover, there are 4 allen head bolts on each side. That should expose what you need to see. If you cannot see what you need, then remove the head by removing the 4 - 3/8" allen heads from the headstock. I need to tram the head still, perhaps I will use duel touch probes.

As for the head falling, you may need some PID tuning or increase your allowable error. At this point, I have the zbrake turn off with the axes are enabled.

Steve, which spindle is on your machine?

andypugh wrote: Mesa offer a board that works _very_ nicely with resolvers.

Mesa 7i49

I like it so much that on my recent Lathe retrofit I removed an encoder and fitted a resolver

The 7i49 produces a very high quality velocity output, and it would be relatively easy to route that back to one of the analogue outputs on the board to get a velocity-proportional voltage.

Wow! Underestimated Mesa there. And 6 channels too. I stand (sit) corrected. My previous experience with Tamagawa was a PITA and this sounds like a slick solution.