Light Machine Corp. Benchman XTr (retrofit)

any ideas on a make and part number?

If I recall correctly, we went through several manufacturers/suppliers while I was there.
You could call tech support and see if they have any or if they can give you the length, diameter, and strength with which to look elsewhere.
Don

It has been a few years since we purchased and I do not have the contact.
I have an old one here that says SpringLift gas springs Attwood Corp Lowell Mi 49331
the numbers on the side are
0206CC 0267N 176/04 A 5
SL36-60-1

Thanks a bunch TGTROPIC. After a quick review of the Attwood online catalog, the only gas strut they had with a similar number was SL36-60-5. A call to the help line revealed that it is the same strut as you listed above, and the -5 indicates the item is individually packaged for retail. As of today, the price with shipping was $23.18.

Today there was a series of successes on PID tuning the BenchmanXT. Error on the xyz are down to 0.0001". This can be improved, but decided to move on. After lunch, I decided to move on to working on the spindle, which has produced frustration. Since the Allen Bradley Ultra 100 drive had input-1 set to torque-mode-selection, I am assuming the original machine was configured in torque mode. I tried one method of increasing FF0 until it produced a stable RPM, then increase I until it hits the desired RPM. It did not work as expected. At a commanded 100rpm, the spindle would not break static. I turned by the time I got the spindle to break static with a commanded 100rpm, the result was over 700rpm. After a few hours of messing around with the numbers, it was time to try moving on to a traditional PID tuning. FYI a small amount of P and I go a long ways. If you are reading this before attempting to tune your spindle, be cautious and start out VERY LOW and work your way up. This time the idea was to start out with a little higher rpm, 500rpm. Once P was high enough to stabilize at ~500rpm, the commanded 600rpm ended up making me shut it down because it started to accelerate to very high numbers. After a while of trying these out for a bit, it was time for a break and ask for some advice. If anyone of you have manually tuned the spindle in your BXT, please give up some tips!
Thanks,
MAC

A spindle PID will typically be mainly FF0 and IGain.
Choose a middle-ground speed (probably one you expect to use a lot, rather than an arithmetic average) and set the FF0 to make that exactly right. Then choose a speed nearer your anticipated limits, and set Igain such that it corrects to that speed without overshoot or oscillation. Then set to the opposite end and see what you get. if there is an overshoot (or reversal) then consider limiting the maxerrorI (google for I-term windup).
That's basically it. You could add some PGain to make response faster, but you might not need it. In this context P-gain will act more like D-gain.
You won't be wanting any D-gain.