[DICKEYBIRD]

Question for you when you get a sec:

Is there a combination of adjustments on the KB controller that would help stabilize the motor speed a bit? I added a manual switch in the circuit so I can manually set the speed from the 5K pot when threading (no influence from Mach3/C11 BOB) but I still get a cyclic variation of about 5 - 20 rpm around the set speed. I don't worry about it for normal lathe work but it causes threading worries sometimes. You can hear the sound of the Z axis varying in time with the spindle speed fluctuation when just cutting air so I know it can't be helping things when it's under load. It cuts threads OK on easy stuff but gets out of whack when the going gets tougher.

Oh, this is a KBCC-125R reversing unit (has the KBMM speed controller). A while back, I added a tach generator on the the Baldor 3/4 hp motor but it was actually a bit worse so I disconnected it. Maybe an adjustment I missed setting it up, dunno. It was supposed to be more precise with the tach installed.

If I was rich I'd put a 1kw servo motor & control on it but I ain't.

[TroyO]

I'm not Al, but I think that is called "cogging". Reducing the IR compensation pot might help.

[DICKEYBIRD]

Thanks Troy, that makes sense. I'll give it a shot this weekend.

[DICKEYBIRD]

Like my Pappy used to say: "First, you have to RTFM." I pulled up the KBMM .pdf manual and I found this in the tach generator instructions:

Notes: 1. The correct value Plug-In Horsepower Resistor® must be installed for the IR Compensation to
operate properly. Calibration of the IR Trimpot is normally not required when the proper Plug-In Horsepower
Resistor® is installed. 2. Excessive IR Compensation will cause the motor to become unstable, which causes
cogging. 3. For tach-generator feedback applications, set the IR Trimpot fully counterclockwise.

I'd forgotten that little tidbit and when I disconnected the T/G I most likely guessed at re-setting the IR pot & may have adjusted it too high. Hopefully a tweak downwards will smooth out the wobblies without causing an excessive speed drop under load.

[Al_The_Man]

Yes I would look to the IR adjustment first, also the resistor value should be confirmed, I have even gone up a HP size on the resistor.
I have had success with the KBCC but since using these (KB) drives I favour the PWM ones for somewhat better performance.
Al.

[DICKEYBIRD]

I favour the PWM ones for somewhat better performance.

Thanks Al. If I can't get the KBCC to work well enough I'll have to look around for a PWM type control. I saw them when I was looking initially but came across the killer deal on the KBCC. The PWM styles at that time were generally much higher in price.

Is there such a thing as a servo drive that would work with my 3/4 hp Baldor brushed motor with an encoder grafted on? Probably big bucks if there is, huh.

[Al_The_Man]

One of the suitably sized A-M-C line that come up on ebay often will run it, both DC brushed and BLDC will run a DC motor.
You don't necessarily need the encoder, there is a tach option on most though.
There is also Copley-controls and Aerotech.
Al.

[DICKEYBIRD]

Thanks again Al, I'm learning every day! New stuff to study up on yet again.

I have a Servo-Tek 7v per 1000rpm tach generator already mounted on the back of the motor so that should work with some of the drives you listed. Just need to find a bargain.

In the mean time after re-RTFM'ing, I think I'll hook the T/G back up to the KBCC and give it another shot. KB claims 1% of set speed with a T/G. I had a lot of things going on at the same time with the lathe when I last tried it and may have missed something on the adjustments.

[DICKEYBIRD]

Hi Al, I wanted to thank you for your input on servo manufacturers.. After some research, I got a good deal on a NIB AMC BE25A20AC and it's on the way from a seller in Canada. It'll probably be a while before I get it installed & working but I will let you know how it works out

Cheers!
Milton

[Al_The_Man]

Good luck.
Al.