tblough wrote: ↑Mon Jul 11, 2022 5:53 pm
OP isn't really doing rigid tapping since the spindle speed and feedrate are not synchronized. My advice is instead of wasting time trying to adjust the spindle speed in Fusion, or adjusting the retract height, or fudging the thread lead, or any other work-around, is to fix the spindle encoder. Then, you can do away with the tension/compression holder and not worry about speed adjustments.
I have decided after banging my head against the wall for hundreds of hours and many forum posts wasting all yall's time that
yeah, you guys are absolutely correct
basically i tried to do a clever, non standard solution, and it ended up taking way more time and way more farting around than if i just did as yall recommended.
How we got here:
I have a PM-30 and replaced the standard brushless motor with a 6 pole brushless servo. I happened to have one from the early 2000's that fit the exact same bolt pattern and shaft size as the stock one, except with way more torque and speed.
What is neat about the servo driver, is that it has a virtual encoder output. Basically it is supposed to output a quadrature signal matching the motor's encoder.
The idea was this was going to be real slick, drop in the motor, run an encoder cable from the servo drive to acorn to not have to mount an encoder, real plug and play upgrade.
Then the problems started:
1: it is an early 2000's driver. ALL tuning is done with potentiometers and jumpers. no fancy vfd controls (think Giddings & Lewis)
2: the encoder output of the drive was a different pinout than acorn. I had to make my own encoder cables
3: the encoder cables used differing wire color codes, and DB9 pinouts are hard depending on if plug or pin side
4: the spindle driver is in a separate enclosure from everything else because it was an after thought, meaning running lots of cables
5: with all this cable running i have been fighting tons of EMI/EMF interference in the encoder cable
6: the motor encoder isnt 1:1 with the spindle, so had to figure out the ratio off of pulley size, which were all weird numbers
Basically the motor runs fine. the acorn to driver to motor works great. i set it to 3000 rpm, it goes 3000 rpm, verified with a tachometer.
Only problem is from the motor to acorn, it thinks the motor is turning faster than it actually is by about 120 rpm (divisible by 60hz, hmmm).
Ive just got to ditch the idea of using the servo driver for an encoder, and figure out how the heck i am going to mount an encoder to my mill, which is why i have been trying to avoid it.
Here is pictures of my mill, and my idea of how im thinking of mounting an encoder. Feedback would be appreciated.
I am thinking of 3D printing the pulley for the encoder to perfectly match the 6 groove micro V belt pulley on the spindle. I cant find a matching pulley anywhere so ill just 3d print one. I can get belts though and would just use the low range pulley on the spindle for the encoder, since i never switch out of high range
Would this encoder work?
https://www.automationdirect.com/adc/sh ... 0r1n1024vd
auto direct doesnt have many medium duty ones in stock that go 5k rpm. Want a medium duty one so can use encoder shaft to mount pulley too (can take radial loads)
