Calico,
   Could simply be a mechanical issue.
You mentioned in #18 that you have direct motor to screw  (couplings) I assume.
In #70 you mentioned a loose "spindle mount".
   I'd go through and double check that ALL coupling connections are very secure and in good condition.
What you are describing is precisely what can happen as a result of slippage of any of these components.
It runs OK in air with no load on the cutter or axis, introducing the load might be enough to cause the slip.
Just something else to check.
Russ

Hi All,

I had a problem (missted steps / stalling)  that always occured at the same point in a prog - and appeared to be a bug in the gcode / mach.... (YERRR RIGHT ;-)

After some time this was traced to the axis being juuuust a tiny bit stiff in a particular position in conjunction with that particular axis being a bit marginal in torque.
New motor and driver - problem solved.

ATB
Derek

Calico,
   Could simply be a mechanical issue.
You mentioned in #18 that you have direct motor to screw  (couplings) I assume.
In #70 you mentioned a loose "spindle mount".
   I'd go through and double check that ALL coupling connections are very secure and in good condition.
What you are describing is precisely what can happen as a result of slippage of any of these components.
It runs OK in air with no load on the cutter or axis, introducing the load might be enough to cause the slip.
Just something else to check.
Russ

I did check those couplings and they are good, that's the first time I thought.

Hi All,

I had a problem (missted steps / stalling)  that always occured at the same point in a prog - and appeared to be a bug in the gcode / mach.... (YERRR RIGHT ;-)

After some time this was traced to the axis being juuuust a tiny bit stiff in a particular position in conjunction with that particular axis being a bit marginal in torque.
New motor and driver - problem solved.

ATB
Derek

I change the X axis with new motor and driver already.

Calico,
Tend to agree with Derek and Russ in a general. Skipped steps is a rather loose term and "exact" reason can be very elusive. I think that you have mechanical / electrical mechanical  problems that are creating the skip.
Certainly can be wrong! Once you have a program that allows for repeating the problem then you have a means to narrow it down through disciplined observation and testing.


Here is a true practical example. Like you ,I have a problem with a mill that will not do 3D fine cutting without fault.
I machined  the same piece using my engraving machine and same code. No problem at all ( three tries / 20 hours of machining / and the engraving machine uses 253000 steps inch...but no problems ).
The mill was found to have an axis bearing problem such that normaly it would not show up, but after measuring the torque required to turn the screw, after some "manual similation" of code moves , i found it requires an additional 70 to 100 in-oz of motor torque and thus all my "freeboard" in motor tuning was used up and thus a fault. Varying config settings and other stuff mentioned will not cure my  problem.
The only fix is to modify that axis and do away with the problem. Finding the problem was very, very, very elusive. Now just need to get off my ask and fix it!

Forget about my problem though. Check your machine out and be confident that all is well, then apply the code to observe ( do post that code ).
You'll  find the darn cuplrit.

RICH
RICH

Rich,
Now you got m thingking of my Z ballscrew lead, it was the noise on that particular/diagonal gcode that bother me.
I don"t know how to check, specially below .

"but after measuring the torque required to turn the screw, after some "manual similation" of code moves , i found it requires an additional 70 to 100 in-oz of motor torque and thus all my "freeboard" in motor tuning was used up and thus a fault "

My ballscrew Lead onZ is like 1 inch, it's not smooth when I push up.

I wlil do like you said, later this week.
Will post the gcode.

Thanks you again guys for your help, now it's up to me.
Cheers
C