Light Machine Corp. Benchman XTr (retrofit)

If the vfd is internally PID controlled, can I still run another PID?

Happy Caturday!

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Mac,
Just a wild guess but if you configure the VFD for torque mode then you can read the encoders and run an external PID. Configured on Velocity mode I believe it uses the internal PID settings. There is a "custom" configuration mentioned in the Benchman manual and I'm pretty sure that places the VFD in torque mode so the external PID can have an actual effect. I assume two PIDs would cause a conflict. Again it is just a guess but it seems logical. I'm still not there... I still need to run some wiring but I AM ready to run a quick cut file just to verify movement. Good luck!

Does anyone have in their stuff information about the spindle setup? I would like to see how it is assembled without pulling the whole thing apart.
Thanks,
M

Mac,
Can't really help you with that. I would be afraid to disturb too much so I have never had mine disassembled. About the only thing I can share is the motor number. It was on a really messed up label but I finally got the numbers. It's a 5k RPM according to the Benchman XT sheet. Model number LD-4030-Q-H00AA. Couldn't find a tech sheet on it but found an F model with the exact same number... Probably pretty close but only shows 4000RPM. Verified that it had a 2000 line per rev encoder. I'm assuming that a 2000 pulse per rev with an index and I will confirm that soon. Not much help and I would assume the drawbar is similar to what Tormach is using since they look close.
Otherwise, getting ever closer to making chips. I'm using an old test file and everything seems to run great. Just need to configure the spindle and wire the front panel. That will allow me to manually change the tools from the front panel. The tool changer will be my last task but having a basic running mill sans tool changer is probably just two weeks away. Fingers crossed.

Took the Flood pump out of my unit. Picture here.

It is a 230VAC submersible pump. Oil filled. Just FYI

Steve

A little update on the Benchman XT retofit. This week, the machine got a new encoder on the 4th Axis. The replacement part for the smw rt-5c rotary axis is a BEI MX216-50-1000. basically a 1/2" hollow shaft incremental 1000 counts per rotation quadrature encoder with an index channel. The hardest part was getting the connector to stay situated while putting it all back together.

So now the rotary axis is installed, rotating and counting properly. However, as in fashion with the other Axes, the PID tuning is making moving forward difficult. Anyone else happen to have their A axis going? I would like to know the max velocity and max accelloration.

Mac,

I have most of my machine up and running. The only part not currently working is the tool changer and that might take some time. Anyway, you are asking about the A axis which is the spindle. I was not able to use the Allen Bradley Ultra 100 internal settings since I could never find the software for it. I have it bypassed and sending it + and - 10 V signals for the drive so it can also rotate in reverse.
My PID settings are
P = 6,
I = .0015,
D = 800.
My max velocity is 10e6
acceleration is 250000.

A different controller from yours and probably not optimal tuning. (My philosophy was get it to work and tweek later.) but I'm cutting some pretty mice parts so far. I'm looking at about .001" accuracy but the machine is supposed to be capable of .0005"
So these numbers work for me... they might get you running but no guarantees. Good Luck!

Mac,

OOPS! I should have mentioned that my Spindle is a 5000 RPM style. If you have one of the other two, then my number won't work at all. Also, remember we compared PID numbers that were in the old software and virtually nothing worked in my new system. I even looked at it proportionally but there was no relation ship from the original numbers to what I ended up using.

Steve

Great forum guys!
Looks like motor 5000rpm on my XT is dead. Does any one know how to remove pneumatic drawbar ? It seems to get access to the motor belt/shaft.