RE: Steppers and the .INI file

[Tim Goldstein <tgoldstein-at-mlh-services.com>]

> First off I can't figure out how set the direction 
> of movement
> for an AXIS. The X and Z are backwards.

Change the INPUT_SCALE sign (make it negative if positive and remove the
sign if negative) to change the direction the axis moves from an MDI or
program input. Change the JOGGING_POLARITY ( 0 or 1 ) if it is going the
wrong direction based upon a jog input

> Second of 
> all it looks
> like the steps per inch are correct but I couldn't see how to 
> set these up.

The INPUT_SCALE is the steps per inch. If you are using freqmod you have to
also set the OUTPUT_SCALE to the same value. If using stepppermod you can
leave the OUTPUT_SCALE at a value of 1

> My last problem is the steppers are losing steps.  During a 
> move the motors
> sometimes stall out and chatter for a split sec then take off 
> again.  It
> doesn't seem to be a matter of the speed.  I can jog one axis 
> at a time in
> manual mode and it's real smooth.  It seems to be worse when 
> I have more
> than one axis moving at a time, but I've seen it chatter 
> during a G0 on one
> axis even with the speed set to 20% of max.  I'm using a 
> Camtronics 5 Amp 3
> axis board with Vexta 3v 4a 550oz motors.  The Board is set 
> to put out 3a or
> 75% of max current.  I've removed the board and started 
> searching it for bad
> solder joints and solder bridges.  The signal lines to the 
> board are in
> shielded computer cable and grounded to the metal chassis.  I 
> do have the
> 36v unregulated power supply in the same case.  Any help 
> would be greatly
> appreciated this is my first project with a CNC machine and I'm still
> climbing up the learning curve.

Don't know which motion module you are using. If it is Freqmod you want to
change the PERIOD setting until the system is running as fast as you can go
without locking up. If steppermod you want to lower the CYCLE_TIME entries.
Also take a look at your acceleration parameters. THe default is a servo
value that is just too high for steppers. Try something like 1 or 2 and
slowly raise it to find the max.

Tim
[Denver, CO]