Re: [CAD_CAM_EDM_DRO] EMC Acceleration

ab2pn wrote:

>I have been fighting with EMC, My Mill, and My Cad software trying to
>get a decent PC Board or engraving out of it all.
>
>I would lose steps and the z axis would drift down while engraving or
>while making a pcboard.
>
>
>When TurboCNC runs you can hear the motors Ramp-up move then ramp
>down, unlike EMC where it is a fast move and steps get lost (because
>of inertia?).
>
>I have not been able to get a good cut out of EMC due to the Z axis
>drifting down, but would love to see it work since it suits my need
>better than TurboCNC.
>
>Please let me know if you find any more details or a solution.
>
>

Well, depending on the version of EMC, there is at least a global
acceleration
parameter in the [TRAJ] section. There should also be an acceleration
parameter
in each [AXIS_n] section unless you are using a very old version. In
the [TRAJ]
section there will be both MAX_ACCELERATION and DEFAULT_ACCELERATION
parameters. These will be in either inches per second squared or mm per
second
squared. I've always felt the default values were very high. In
inches, turn it
down to about 3 to start with, and listen for the acceleration ramp.
You should
definitely hear the ramping up and down with that setting. (For mm, try
50.)
Prove that the lost steps are no longer happening. Once you are
satisfied that
the reduced acceleration fixed the problem, then you can turn it up
until the
problem recurs. You should be able to hear the lost steps as a buzzing
or click
at the ends of the acceleration ramps when you are right on the edge.
Obviously,
turn the acceleration down by some safety factor once you determine what the
limits are.

If the parameters LINEAR_UNITS in the [TRAJ] section and UNITS in the linear
[AXIS_n] sections are 0.03937...... the user units are inches, if these
units are
1.0 then the user unit is mm.

You may be forced to limit your maximum velocity, too, if the
acceleration doesn't
fix it.

Jon