Plasma

Things related to plasma tables... Under Construction...

Contents

1. Drive Systems

2. Finding the material top with Probe

3. Turning the Plasma Torch On and Off

4. Torch Height Controls

5. pyVCP Example showing the status of the torch

6. Getting the best performance from your plasma table

7. Misc. Plasma Stuff

1. Drive Systems

• I've used 80/20 with timing belt drive and stepper motors to run a plasma table. I can get speeds of 450 IPM with nema 23 steppers from [automationdirect] and Gecko [G203V] drives.

2. Finding the material top with Probe

If you have a floating head with a switch to detect the material top use a G38 straight probe to locate the material top prior to touching off the torch. To use a probe you have to "hook it up" using hal to motion.probe-input.

You can choose any input-mode parallel port pin--10, 11, 12, 13, or 15.

connect it in your hal file with a line like

net probe parport.0.pin-10-in => motion.probe-input

If the signal is inverted (starts at 5V when probe is not in contact, goes to 0V when the probe makes contact), then use the inverted version of the pin:

net probe parport.0.pin-10-in-not => motion.probe-input

3. Turning the Plasma Torch On and Off

• Use the M3 and M5 spindle control to turn on and off your plasma torch and control motion while the plasma torch is on. If the plasma arc stops the motion stops. The way to do this is to AND the motion.spindle-on and the parport.0.nn-not (arc stable from the plasma torch) to the motion.feed-hold.

• The basic steps are
  • Move to your start position
  • Tell the plasma torch to start the arc
  • Wait for Arc stable input from plasma torch
  • Start Motion as long as the Arc Stable input is on
  • At the end of the cut turn off the plasma

• An example using parport pin 10 in as the input from the plasma torch and parport 17 out as the start arc signal to the plasma torch. After some gentle prodding from Alex Joni and some guiding help in the correct direction I ended up with the following to make it work as it should.

• In your core_stepper.hal file place this line ahead of the hook functions to servo thread to create a two input AND gate

loadrt and2 count=1

• In the core_stepper.hal file place this line after the hook functions to servo thread to add the function AND2 to the servo thread

addf and2.0 servo-thread

• In the standard_pinout.hal file add the following lines

# This line connects pin 10 not & and2.0.in0 to plasma-arc-ok
net plasma-arc-ok parport.0.pin-10-in-not and2.0.in0
# This line controls the motion.feed-hold
net ext-feedhold and2.0.out => motion.feed-hold 
# This line turns on the pin 17
net plasma-start motion.spindle-on parport.0.pin-17-out
# This line connects plasma-start to and2.0.in1
net plasma-start and2.0.in1

• In your g code program something like this for example:

G0 Z1.000 
G0 X4.000 Y0.000 
G0 Z0.01 F50
M3 (Turn the plasma torch on)
G2 X4.000 Y0.000 I-4.000 J0.000
M5 (Turn the plasma torch off)
G0 Z1
G0 X0 Y0
M2

4. Torch Height Controls

5. pyVCP Example showing the status of the torch

6. Getting the best performance from your plasma table

When 2.3 is ready or if you are running 2.3 trunk you can take advantage of the G64Pn naive cam detector for short arcs and lines.

Just program a G64Pn P tolerance at the start of your file to get higher speeds for short moves when cutting.

7. Misc. Plasma Stuff