Just after some ideas.
What i would like to do is build a system that has an X gantry that attaches to the back end of a robot. When the robot travels forward at a set speed the X axis tracks backward and forward with a paint head or pen and draws line by line on whatever it is on.

The way I see it is there is an encoder on the rear wheels that tracks the Y movement, when Y = the specific trigger point the carriage prints a line on the ground and the pen or pain head fires where required. likely just a solenoid.

The X axis is the easy part however what I am not sure about is the encoder input and how to trigger it at that point.

Any suggestions would be most welcomed.   

I can not sync the forward motion with Mach3 as the controller for the robot has to be independent of Mach3, I can however have a single trigger output to tell the robot to STOP while the line is being printed.

Regards
Andrew

Hi there, I suggest maybe buying a large ink jet printer, it would have most of the features that I think you may be looking for.

Just a thought...

If you stood your robot on a platform that is driven by stepper motors, slaved to the Y axis then Mach3 could have complete control of the X - Y movement. This way the Impact / Laser plugin could be used to produce the pictures you require.

Some further reading...
http://www.machsupport.com/forum/index.php/topic,16446.0.html
http://www.machsupport.com/forum/index.php/topic,20490.0.html

Tweakie.