Okay, been offline for a while, lots to reply to... good!

Hi Hood:-

I thought of using a relay to 'dump' the step/dir signal so it never reaches the motor; thought it might be a problem because you can't guarantee to switch it if afterrather than during a pulse. Shame about not being able to switch an axis on/off when machine is running, like you say, but I was thinking of there being a macropump (thanks Tweakie) which just generates "G1 Z1" every time an input to mach 3 receives a logic 1. Would a pulse generator mean using a dc motor? Or do you mean altering mark/space ratio on a switch mode power supply to an AC motor? It on;y needs to be a tiny motor driving a screw thread. It has a motion control 35NCLA linear stepper at the moment, does very well.( 5V, 0.46A per phase, 4 wire)

Poppabear:-

I see your point on acceleration/ deceleration, but there is another 'axis' (A axis) that runs during plotting, that worka as an 'applicator'  by taking a dab of paint extruded from the syringe driven by the z axis, and 'tattooing' it onto the page. It runs at about 2000 cycles per minute; this is a real 'drag' on the X axis,: I wonder if a tiny Z axis move may not make any difference? as it involves the least hardware changes, I'm tempted to keep my fingers crossed and try it. The code below is want I have been running the machine off to test it. It works as my final code will, except that in this case THE Z COMMANDS ARE WRITTEN IN, rather than generated by a macro. It explains how the 'axes' A and Z work for me, though.




G01 F35000 X0.80 Z0.4 A-4                    (plotting begins here; A-4 means 'lift applicator to it's maximum height, so it picks up some paint from the extruder/syringe)
G01 X0.85 A4                                 (A4 means 'drop applicator down onto cpaper, so it leaves a dot of paint there)

G01 X0.9 Z0.7 A-4                            (Note the Z position increases by .03; this value gives good results, but still need constant pressure for best performance)
G01 X0.95 A4                   

G01 X1 Z1 A-4                 
G01 X1.05 A4                   

G01 X1.1 Z1.3 A-4             
G01 X1.15 A4                   

G01 X1.2 Z1.6 A-4             
G01 X1.25 A4                   

G01 X1.3 Z1.9 A-4             
G01 X1.35 A4                                 
G01 X1.4 Z2.2 A-4                            (plotting ends here)



Hood again:-

"Scott, yes that was my concern doing it that way, you would have to have the feed set so that switching on.off the pulse didnt stall the stepper which in turn would impact on the other axis."

This sounds important; but I don't quite know what you mean by "having the feed set...". If the stepper is only getting clean step/dir signals from the macropump when an input is present, does that conform to what you mean?

Tweakie:-

The plotter has no Z axis as such, I just happened to wire the extruder pump to that output on the ncPod controller; similarly, the A axis doesn't work as a positioning axis either, it just drives a little applicator thingy.

Stirling:-

Hadn't heard of THC before, sounds exactly what I'm looking for. Will it adjust my Z axis position in response to a logic input to Mach3, without interrupting other axe's moves? If so, great, assuming my ncPod supports this...

I was wondering if, although it sounds weird, I should just run my plotter in Mach3 plasma rather than Mach 3 mill; but then I noticed there are only 3 axes in Mach 3 plasma. Which is easier, adding another axis to Mach 3 Plasma, or adding the THC button to Mach 3 Mill? Also, where should I look for information on THC? Not much in this forum, only a little in the basic documentation, and no 'guide to using Mach3 plasma' either.

Kf2qd:-

The extrusion is controlled by Z axis. In my code, no plotting occurs when there is a "Y" axis move, all it does is straight horizontal lines. As you can see from the code, the A axis movement is 'tied' to the X axis movement. Currently the Z is, too but this is the bit that needs to change.

Thanks all,

Rich B

If all you are needing is to pump when a signal is seen and the actual pumping isnt too critical then I would think a small DC motor with a relay interrupting its supply would be suitable. Could  do it via a macropump but really if its an external signal then it would seem silly to take that signal to Mach then for Mach to pass it back out again, most logical would just be direct it straight to the relay..

If it needs to be more critically controlled then THC as Stirling mentioned may be the answer but afraid I have never used THC so cant comment on it.

Hood

Hi Hood,

I guess the important point is, how critical is the pump... not sure. If I hadn't already got a linear stepper on there that works well enough (but just needs a bit more control), then I would be pleased with the simplicity of your idea, and do it like that. Also it would free up another axis, which I may find useful at a later point. (I won't go into that here, yet). The extruder pump needs to withdraw fully on tool change ('syringe full of paint change' in my case), so needs to be under Mach control anyway. I could trip that from inside my tool change macro, or I may go with the THC or even just Z axis control, for now. Hopefully enough people out here you can guide me to the right resources.

Thanks for your advice,

Richard B

I think Mach's THC functions would do what you want but if you already have an arduino that may be the way to go. Also I don't know if your ncpod supports THC - I think for example the smoothstepper doesn't - whether that's of any relevance I don't know. I'm just thinking that by using the eeno you'd have complete programable control over the pump and be able to let Mach get on with the X Y interpolation which is what it does best.

FWIW - co-incidentally I'm currently working on an eeno based THC for Mach.

Ian

I don't have an Arduino at the moment, but they sound like fun. Why use the Arduino for THC if Mach already has it?
If smooth steper doesn't do THC, probably the ncPod doesn't either, but I'll ask them.

Rich B

Why use the Arduino for THC if Mach already has it?

Mach has THC software but you still need THC hardware to interface between Mach and the plasma cutter. A bit like Mach puts out step signals and reads input signals but you still need drivers for your motors and switches for your limits if that's not too crap an analogy. For example - if you *were* to use Mach's THC control of Z then it would "think" your pump sensor was the THC hardware sending a torch down request.

Ian

That makes sense...

Rich B