4th axis questio

[Bell 430]

hello folks its me again.
I;m trying to set up a SOBO cnc rotary table. in Mach 3 if I enter g0 a10 the table moves about 75 degrees. I've slowed the step rate down to 5000 and the stepper stalls. in mach 3 where it states the axis will move "1 unit" I assuming(I hate that word) it means 1 inch on the rotary table just like the other three?
Help please

[ger21]

1 degree.

[Bell 430]

I cannot get 1 degree with the number of steps in the "Motor Tuning" thats been my problem

[HuFlungDung]

What is the actual gear ratio of the rotary table, assuming it is a worm drive? However many steps it takes to turn the worm one revolution should most likely be the unit? Worth a shot anyway

[ger21]

In motor tuning, you need to enter how many steps it takes to turn 1°.

[neilw20]

Typical steppers are 200 steps per rev. That's 1.8 degrees
For a worm that does 40 turns per revolution you need 8000 steps per rev.
Multiply motor steps per rev by worm ratio.

Number of starts on worm times teeth on worm wheel gives ratio. Say 1 x 40.

Not much point trying different value. Calculate the correct one.

You need to slow the max speed of A axis in motor tuning until it does not slip.
Find the that limit then back off, say another 20% to allow for hot stepper motor.

Don't expect it to move really fast unless you are running a really high performance, high voltage stepper driver.

[cnc_timmi]

hi neilw,
having the same problem, after one hour of moving, one of my (used) stepper motors becomes warm or hot...
than suddenly it skippes steps, and startes stalling...
no problems when I start (and the motor is cold...) but within one hour it becomes warmer... and then it could loose steps of nearly 1/8 inch.... and works on... (-:
should I reduce the max speed by 20% or should I go for a new motor with more oz/inch (Nm) ?

thanks
timmi

[michaelthomas]

Originally Posted by neilw20 Typical steppers are 200 steps per rev. That's 1.8 degrees For a worm that does 40 turns per revolution you need 8000 steps per rev. Multiply motor steps per rev by worm ratio. Number of starts on worm times teeth on worm wheel gives ratio. Say 1 x 40. Not much point trying different value. Calculate the correct one. You need to slow the max speed of A axis in motor tuning until it does not slip. Find the that limit then back off, say another 20% to allow for hot stepper motor. Don't expect it to move really fast unless you are running a really high performance, high voltage stepper driver.

I believe the above is correct, but it needs to be further divided by 360 to get steps per 1 degree as Gerry mentioned. 8000/360=22.22 steps per degree. Multiply that number by the microstep unless you are set to full step.

[neilw20]

I should also mention that the acceleration may need to be reduced by the same proportion, if it was ever set correctly.

[neilw20]

Originally Posted by cncmakers001 Can the Mach 3 be set to correct it?

YES. That is where it must be done.
Config/motor tuning & setup
Acceleration. Velocity. See driver requirement for pulse width control.