I was thinking of using the pump with a stepper motor. Call it axis A,you could program in dispensing rates, suck-back, etc. You could also use parametric code to alter the flowrate along a run, ie ramp up and down.

I think I just came accross a neat solution.
My machine besides Mach3 also has a PLC incorporated.
What I´m testing at this very moment is to use the DIR pin of Z axis to control when to start and stop the pumping. I use the signal transitions from on to off and viceversa to start and stop the pump.
The pulses are generated by the PLC in my case.
My goal is to get something that will not require any hand codding at all. The GCode will come from Lazycam.

A PLC huh, that is cool.

I would do this then, I would send your Feed Rate across the modbus to your plc and use that value there as an Analog value to vary the dispense rate, the faster you go, the more your analog signal increases......   I would put a Max and Min feed rate limitation so you would have a High and Low end to your analog value.

scott

While testing this I run into another problem (yet another one in the hugelist).

I connected the motor driver PULSE and DIRECTION signals to PLC outputs and started making some tests.
I keep the DIR signal unchanged and send ON-OFF sequences to the PULSE pin to make the motor turn.

When doing this, first of all, the motor makes loud noises and shakes like somthing is about to brake each time it moves, this happens even if I send a single pulse to the driver. Also, if I send a series of pulses the motor turns a few steps in one direction and then it either misses a couple steps or it turns one or two steps in the opposite direction.(!?!?!?)

Of course the motor&driver works perfectly when it´s directly controlled by M3 through the PC parallel port.

I´m not sure what may be different between the pulses M3 creates and the ones from the PLC.

I found what was wrong.
The pulses out of the PLC were too wide (too much time) and that´s why the motor was not running smooth.

Now I only need to decide how to control the pump from Mach3.
I thought about using the Z axis direction pin, so when the Z axis go down the pump should start and when the Z axis goes up to stop. It´s like if this was a mill, when the tool goes down it means it´s working on the material.
The problem I also found is if I stop the program for some reason (or if I need to run it step by step), the pump will keep dispensing resin even when the axis are not moving.

Anybody used Mach3 for a laser cutting machine? there should be the same problem there to start and stop the laser beam.

For my laser I use M11P1 to turn the laser on and M10P1 to turn it off. (these commands are added to the existing GCode in place of the Z- and Z+ commands).

I have the same problem with stopping mid line, the laser remains on.

The cure for this is, I think, to add a new, VB, screen 'stop' button which issues the M10P1 and then activates the feed hold function. Something similar could possibly be done for the single step function.

Tweakie.

Why not just use a canned drilling cycle and by varying the drill depth (Z Axis) it would dispense varied amounts based on depth of Z. Doesn't it just fill a plunger of some type? Has some interesting applications.

Very nice George.
Well done !