Jeff Epler <[EMAIL PROTECTED]> wrote: 

> If you hook the laser intensity to the Z or A axis (instead of to the 
> spindle speed), and set the acceleration and velocity for that axis to 
> very large values, maybe you will get better results because this 
> synchronization between each move will go away. 

The problem with using another axis is that the change in laser
intensity will be spread over the entire move.  For example,
assume you are using Z for the laser intensity:

G0 X0 Y0 Z0    initial position, laser power zero
G1 X1 Y0 Z1    moves to (1,0), while ramping laser from 0 to 1
G1 X2 Y0 Z2    moves to (2,0), while ramping laser from 1 to 2

If you want the laser power to be constant during the moves,
you would need to do:

G0 X0 Y0 Z0    initial position, laser power zero
G0 Z1          raise laser power to 1 as quickly as possible
G1 X1 Y0       move to (1,0), laser power remains at 1
G0 Z2          raise laser power to 2 as quickly as possible
G1 X2 Y0       move to (2,0), laser power remains at 2

If you are willing to write that kind of g-code, this approach
is quite feasable.  However, you still won't get step changes
in the laser power level - the rate of change will be controlled
by the Z axis velocity limits.  In essence, you are turning your
two-dimensional part program into a three dimensional one, with
the third dimension being laser power.  In addition, the program
above will _still_ stop the X axis while the Z axis (laser power)
changes.  (The first program does _not_ stop X, but the Z axis
change is spread out over the entire X move, instead of happening
quickly when the X value passes 1.0.

It sounds like what you really want is motion synchronized I/O.
That means analog and/or digital outputs that are controlled
by G (or M) codes, and change in sync with the motion.  Such 
I/O has been planned for years, and was partly implemented in
EMC1 (other parts of it were commented out years ago and never
worked).

At the moment I can't even find out what G or M-codes were
intended to be used for synchronized I/O.  (I'm away from my
Linux box and don't have the ability to quickly search thru
the source code.)

This should probably be moved to the emc-developers list. It
may be possible to implement synchronized I/O in time for 
the version 2.1 release.

Regards,

John Kasunich


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