Agree 100% with Art.

I would also suggest, that it may very well be an acceleration issue
rather than a top speed issue.
Especially with steppers.

The way machines must be tuned, is for the worst case, rather than the
typical, or average, case.
This means that especially for stepper (direct) driven machines, you
need to use lower acceleration values and lower top speed values.

Because in the case where you are entering (leaving) material, while
moving, in some cases the load is larger than the current settings allow
.. thus leading to lost steps.

On 17/02/2015 13:40, art2 fenerty@... [mach1mach2cnc] wrote:
> >>The same code I tested 2x and worked fine. Then on tool change it
> start to
> >>hit the z-limit switch again
>
> This is almost textbook for a system with Z axis trouble. When the axis
> drives into the material, it struggles and steps get lost, this causes a
> most
> annoying and confounding type of problem, in the air all is fine, in
> material you hit the Z upper limit switch over time.

--
-hanermo (cnc designs)