Re: [CAD_CAM_EDM_DRO] Re: Z-Axis problem - Not Enough Torque?

Your explanations have been very helpful and it did clear up a lot of
questions in my mind regarding my first experience with CNC.

As you have pointed out, I guess I know beforehand the consequences when I
used the very coarse pitch ballscrew and not even using a belt/pulley
reduction. As I am still experimenting on how CNC works, I did not bother to
get the proper or correct parts which will entail importing them and have to
make do with what is available locally.

Time to consider doing refinements one at a time. Pulley reduction will be
the first and then possibly finer (5mm) pitch ballscrews later on. I think
the stepper motors may have enough power to drive the X and Y axis. Z axis
stepper motor may be a suspect.

Thanks for the kind advise.

Best,
WT

----- Original Message -----
From: caudlet
>
1. Microstepping does not gain true resolution and actually
decreases torque somewhat. Microstepping smooths out moves at lower
speeds and reduces resonance problems. It may decrease upper speeds
but it adds no torque.

2. Your ballscrews are way too course. You don't have enough torque
in the design.

3. Lifting a heavy load is a lot more work that shoving it. You can
easily shove a 200 lb weight on a level surface with moderate levels
of friction and many times that with low coefficents of fricton.
It's harder to left it vertically.

4. Not holding position means that the motor does not have enough
holding torque with the given screw to maintain the down position.
There are a lot of forces in milling depending on the type cutter,
the feedrate, the material and the cutter type and size.

Your solution is what you probably already suspect: (much) bigger
motor, disable drive "standy" current reduction, finer pitch
ballscrew or added belt reduction between motor and screw. It may
take one or all depending on the ratio of change.