PNCconf error

John:

I left calibrate, and have gone back to pncconf. I tried running the test/tune, and I am having a problem with the mechanical linkage between the stepper and the ball screw. The ball screw is a hollow shaft with a split in the end, the stepper motor shaft inserts into the shaft and then I tighten down on a split collar. The instructions said to put thread lock on the assembly, but I didn't want to do that until I knew things were working. I need to pull the steppers and clean up the shafts and put some threadlock on them. Hopefully that will solve this problem. Right now it is only on the X axis, but I think I'll go ahead and do the Y axis also. There is lot more drag on the X axis than the Y axis. I would say it's 2-3 times the force to move X rather than Y. I know the tighter (less backlash) I have on the X axis the more "drag" and more force it takes to move it. As I load the thrust in the bearing with a cupped washer, the "drag" increases, but I want to eliminate as much backlash as possible. Trying to find a happy medium.

Should I be trying to test/tune in pncconf now, or moving on to something else???

thanks,
Ken

Andy:

Good call. The linkage is good. I guess the stepper is "missing steps". Best I can describe it the motor is trying to turn but isn't, just "bumping". I can grab the hand wheel and help it along. I tried lowering the velocity from 100in/min to 50in/min. Didn't seem to make much difference. Also noticed that it is occurring much more frequently near the end of the X axis than in the middle.

I ran the X axis from one end to the other 2X. I've been pumping the oil system several times each pass down the axis. The motor is warm, probably 120 degrees, I can hold onto it comfortably.

Is it missing steps due to velocity, step timing, or the amount of torque needed to turn the ball screw??? Don't know if I should be playing with velocity/timing or trying to figure out how to reduce the torque without adding a lot of backlash???

thanks,
Ken

test/tune should work - I thought it did a few messages ago.
Test/tune is for testing the acceleration and max velocity of steppers.

It seems you need a secret decoder ring to figure out how to get the calibration program to pick up all the values in the INI file.
I gave up trying.

Chris M

BigJohnT wrote:

customcutter wrote:

Should I be trying to test/tune in pncconf now, or moving on to something else???

thanks,
Ken

The only thing you need to test is your math and that the scale is correct. If you command a 1" move does it move exactly 1"? If not your scale is wrong.

As for tuning the maximum acceleration and velocity are all that is left to discover. It looks like the test part of pnconf is not working but you can jog and see what different settings give you and they will be saved to your config.

John

The only thing I can do in test/tune is jog. The enable button is hot, but the run button is not. Don't know how to "command a 1" move yet. G-code, cad/cam will be a whole other ball of wax. Or should I say, another pie too eat.

I'm pretty sure scale is correct.

thanks,
Ken

cmorley wrote:

test/tune should work - I thought it did a few messages ago.
Test/tune is for testing the acceleration and max velocity of steppers.

It seems you need a secret decoder ring to figure out how to get the calibration program to pick up all the values in the INI file.
I gave up trying.

Chris M

Chris:

From pncconf I can run test/tune. I can make the enable button hot, but the test button is not. I can only jog, I can't tell it to move 1", hit the test button, and check my indicator to see how far it moves.

If you can't get the calibration program to run I know I won't be able too. Is there something I need to manually move from the INI file to another file?

andypugh wrote:

customcutter wrote:

Is it missing steps due to velocity, step timing, or the amount of torque needed to turn the ball screw?

It could be velocity, drive current set too low, or supply voltage too low (possibly transiently, due to inadequate PSU current capacity)

However, the first thing I would try would be lower acceleration settings.

Andy:

I lowered the velocity from 100 to 50, didn't seem to notice any change.

Just now I lowered the acceleration from 2 to 1, and same thing it runs very well most of the time, but starts missing steps about 5" from the end of the + or - end of the table travel, on the X axis. Also the motor is getting warmer, probably 140 degrees, I can still hold it.

I'm thinking I will tell it OK and move onto the Yaxis. If I don't encounter a problem there, I'm thinking it is due to amount of required torque?

thanks,
Ken