Note that is an ongoing project, and as thus be patient

When I do a new plasma build, I hookup and test various options in the order shown here:

  • Basic Torch Control

  • Floating Head

  • ARC OK Hookup

  • Torch Height Control (THC)

In this article we will be looking ate getting the ARC OK signal connected and configured on our plasma system.

Signal Hookup

In volumes 5 and 5B, you install a terminal block for the control cable connected to your plasma cutter. Here you will connect the ARC OK (OK to Move) signal to your CNC.

Step 1 - Connect Wires to Plasma Cutter Terminals

Start with two wires about 24” long. These wires can be any gauge, so you can use what you have on hand.

The wires are connected to the two middle connectors on the terminal black shown here.

Step 2 - Connect Wire to Ground

On the other end, connect one of wires to the ground buss terminal block located, just above the “AC IN” terminal block.

You can connect this wire to any of the terminals located on the top of the block, as shown here.

Rout the wire as needed around other objects.

Step 3 - Connect Wire to G540

Connect the other wire to position 2 on the G540 terminal block, as shown here.

This terminal is input #2, which we will setup in Mach 3.

Mach 3 Configuration

Step 1 - Load Plasma Screenset

In order to use the ARC OK signal, you need to use a screenset geared more towords plasma.

To load such a screenset, select the “Load Screens” option from the View menu shown here.

The screensets are located in the Mach3 directory.

Select the “Plasma11.set” file and hit the Open button.

Your Mach3 startup screen will look like this one.

Step 2 - Set ARC OK pins

You have to tell Mach3 what pin to look for in order to handle the ARC OK signal.

To do this select the Ports and Pins option from the Config menu, as shown here.

In the Ports and Pins dialog, select the Input Signals tab near the top of the screen.

Scroll down until you see the “THC ON” item. Change to the values shown here.

Once complete, hit the OK button to save everything.

Step 3 - Quick Test

To test both the Mach3 software and your wiring, you need to perform the following test.

With your plasma cutter powered off, short the two middle pins as shown here.

Select the Diagnostics tab and keep an eye on the “Torch On” indicator shown here.

Every time you short the two terminals the indicator should glow yellow, and go back to black when the short is removed.

If it does not change, go back and check all your wires and pin settings.

Testing the ARC OK Signal

Step 1 - Load the Test G-code

With the plasma cutter turned off, Mach3 loaded, and your machine powered up.

Load the “Washertest.txt” into Mach3.

You can get the Washertest.txt file here:

Washertest.zip

Take a piece of scrap thin sheet metal and place it on your slats as shown here.


Here I am using 26 gauge sheet metal that’s about 3-3/4” x 3-3/4” in size. This stuff is available at most home centers in the HVAC section.

Notice how I used some magnets to hold it in place.

Place the torch nozzle between two slats as shown here and zero both the X and Y axis.

This is where the center of the test washer will be cut.

Step 2 - Test with ARC OK Disabled

Important, your plasma cutter should be turned off.

Click the THC button until the indicator is dark. This means the ARC OK signal will be ignored.

This also means it will work exactly as it did before you added the ARC OK input to your machine.

Start the test by clicking the Cycle Start button shown here.

test2.jpg

You should see the torch outline the inside and outside of the washer.

Step 3 - Test with ARC OK Enabled

Click the THC button until the indicator is a bright green. This means the ARC OK signal will be monitored.

Mach3 should stall at the start of the first cut because it will never get the ARC OK signal, IE we have the plasma cutter turned off.

Start the test by clicking the Cycle Start button shown here.

Since Mach3 will never receive the ARC OK signal it will pause at the first cut and never continue until you short the ARC Start terminals or stop the job.

This is how it is supposed to work.


Step 4 - Cut with ARC OK Disabled

Important, your plasma cutter and downdraft should be turned on.

Click the THC button until the indicator is dark. This means the ARC OK signal will be ignored.

This also means it will work exactly as it did before you added the ARC OK input to your machine.

Start the test by clicking the Cycle Start button shown here.

The CNCCS will cut the part.

Looking at the part you can see that the machine did not wait long enough for the arc to start and transfer to the metal, so the inside cut was not complete.


Step 5 - Cut with ARC OK Enabled

Important, your plasma cutter and downdraft should be turned on.

Click the THC button until the indicator is a bright green. This means the ARC OK signal will be monitored.

Start the test by clicking the Cycle Start button shown here.

The CNCCS will cut the part.

The exact same cut with the ARC OK enabled waits or the arc transfer and completes the part.

While a little more tweaking needs to be done the part did cut correctly.

The tests in action

Not without issues

While I am very happy with the implantation of the ARC OK signal from the plasma cutter, There is one issue that came into play.

The plasma screenset, does not have an Auto Tool Zero button so you need to assign the floating head probe script to another button. This is not as big an issue for me as I have the probe script assigned to a pendant, but some of you may not have a pendant attached to your machine.

I have never used the Display Mode button located just under the G-code preview panel. This button can be assigned a script so is a good choice to manually activate the probe.

Just follow the instructions in volume 6, but use this button instead of the “Auto Tool Zero button”.

There are times when you may want some operations in the job to have ARK OK enabled, and other times you will want to have ARK OK disabled.

Comming up I will show you how to add a couple scripts and g-code snippets to SheetCam so you can do just that.