THC Mach2 Files

     Downloads

Download the THC300 Zip File here (contains all of the files listed below in a single zip file) updated 8-7-05

• THC300 set updated 8-7-05
• THC300 XML file   Pin settings for both ports

     THC300 Set File

 The THC300 .set file has three extra DROs added to enter setup values for you machine.

1. Pierce Gap:  sets air gap between the material and the torch tip to start piercing material.

2. Lost Motion Z:    Lost motion in the floating head between where the head touches the metal and where the  touch-off switch trips.

3. Pierce Delay Sec: The delay after Good Arc signal is received.  This allows the torch to fully penetrate the material before motion is started.

In order to use the “THC300.set” and the M3 macro provided you will need a floating head setup on the Z axes. I used a 6” section of THK rail mounted to the Z axes and a bearing mounted to the back of the torch mounting plate. You may need some springs to make it operate properly. Mount a micro switch or a proximity switch so it will trip when the Z axes moves down and strikes the material surface. There is some dead space or lost motion between when the head touches the surface and when the switch trips. This distance is entered in the Lost Motion DRO from the THC300 run screen. See a screenshot.

     M3 Macro code:

rem modified 02/04/2004 by Jim Cullins
Option Explicit
Dim TorchHeight, SwitchTravel, PierceDelay,TCutHeight
PierceDelay = getUserDRO (1001)

code "g31z-1"
While IsMoving()
wend
TorchHeight = GetUserDRO(1000)
SwitchTravel = GetUserDRO(1002)

TCutHeight = (getUserDRO (1003) + SwitchTravel)
code "G92Z0"
code "G1Z" & (SwitchTravel + TorchHeight)
While IsMoving()
wend
DoSpinCW()
code "G4 P" & (PierceDelay)
code "G1Z" & (TCutHeight )
TorchHeight = 0
SwitchTravel = 0

• The idea is to start the PROBE command G31 Z-1. The Z axes will move down until the touch-off switch closes or to –1 inch which ever is first. You can change the M3 macro, first line, to G31 Z-3 or what – value your machine requires.

• Once the X,Y axes moves to the point to start a cut the following sequence of events happens:

1. G31 Z–1 sends the Z axes down until the Touch-off switch closes.

2. Z reverses up to the Touch off switch opens.

3. Reads the user input torch height and the dead space for the touch-off switch.

4. G92Z0 zeros the Z axes

5. G1Z  & lossz + adder moves the z to the proper height to start the pierce.

6. Waits for an ARC GOOD signal from the THC300 hardware.

7. G4 sets the delay to allow the torch to cut all the way through the material (user input).

8. Start motion

• If you have a favorite SET file that you prefer, all you need to do to use the M3 macro is copy the 1000,1001 and 1002 DROs from the THC300.set file and paste them into your set file via screen designer and copy the M3 macro into the macro sub. Make sure to make a back up copy of both the standard M3 and the M3 used with the THC.

• I hope this will help all those who are, or are planning to use a plasma cutter.  

     Alternate method:

This is an alternate method to use the THC300. This method was provided by Tom Caudle. His post processor is modified to include the G28.1 Z .5 code. Here is the way he uses it.

G28.1 Z .5 says to rapid down until you hit .5 then use the Reference speed to move to the Touch Off switch mounted on the floating head. Once activated it zero's the DRO and rapids back to .5 (with .5 showing on the DRO). If you have some method of making sure the Home is at true material zero then from that point MACH2 always knows where it is. The pierce height is a constant that I have plugged into my post processor as well as the beginning cutting height.

The head moves to the XY pierce position, moves to the Z pierce height (.185 above the surface) and fires the torch. When the Arc Good releases the code the very next thing in the program is a Z move down to .125 followed by XY movement so we first pierce then with the flame cutting move the tip closer and start cutting. The reason for piercing high is the fact that as the arc penetrates the metal the molten steel has no place to go but back towards the surface. Sort of like turning a hose on a bowl. That condition only lasts until the flame breaks through then all of the molten stuff goes down.

If you pierce too close the blow-back tends to clog the tip and cause premature failures. If you pierce too far away the flame is less concentrated and either takes too long to pierce, or burns too big a hole in doing so.

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