Installing MASSO DTHC


The MASSO DTHC (Digital Torch Height Control) module is designed to provide digital arc voltage information from a plasma source. The module is designed to be mounted at the plasma source end then connect between the MASSO G3 controller and the plasma source. The Plasma source needs to provide a divider output.

It is important to mount the DTHC next to the Plasma source rather than the controller. The DTHC is optically isolated and mounting it at the source reduces the chance of noise entering MASSO.

The digital arc voltage data is used by MASSO to monitor arc voltage levels and to adjust the torch height while cutting parts.

Having full digital information about arc voltages, the user can easily set and adjust cutting voltages for jobs using gcode commands or on screen.

This makes it very flexible and easy for the user to set all the cutting parameters of a job in a gcode file as there is no requirement to set cutting voltages manually on an external THC.

Everything is automatically loaded in when the gcode file is loaded.

INFORMATION: The DTHC module is only supported with the MASSO G3 controllers as the old G2 model does not have the required interface electronics.

INFORMATION: The DTHC module requires MASSO G3 software v5.0 or above.


  • Requires 24v power - The unit can be powered using the MASSO Power supply or a separate 24v power supply.
  • Optically isolated interface - The unit provides optically isolated digital signals to MASSO for noise immunity and protection against high voltages from the plasma source.
  • Supports multiple arc voltage ratios - The unit can be used with a plasma source with the following voltage ratios: 50:1, 30:1, 20:1 or 16:1

Arc voltage rotary switch setting

  • Rotary switch position 0 - 50:1
  • Rotary switch position 1 - 30:1
  • Rotary switch position 2 - 20:1
  • Rotary switch position 3 - 16:1

LED status indication

The MASSO DTHC module has a Green LED which can tell you the status of your DTHC module.


INFORMATION: You can use the MASSO power supply or a separate one. If you use a separate power supply please ensure you connect the -ve of each power supply together or the DTHC will not work.

Setting up in MASSO

Configure MASSO DTHC

  • Once the system has been wired, go to the F1-Setup screen and set Input 9, and assign it the function MASSO DTHC Input.
  • Do not invert the input, ensure the invert column is set to No
  • The MASSO DTHC module data signal must be wired to MASSO Input 9 and assigned the function MASSO DTHC Input, or else the DTHC module will not work.


Enable plasma

  • Go to the Multi-Head Settings and select the Plasma Torch option as shown below by putting a tick in the Enable Plasma Torch box
  • Enter the plasma torch offset values in reference to the spindle location. If your machine is a plasma only machine the X Y & Z offsets will be left as 0
  • If the plasma head is one of several heads on your machine you will need to choose one head as the main head from which all other heads are offsets. On a combined Mill / Plasma combination machine the Main Spindle would normally be considered the main head. MASSO does not need to know which head is the main, it is up to the user to remember when configuring their machine.
  • Tick the Use MASSO DTHC module option to enable MASSO DTHC logic. You will not be able to put a tick in the Use MASSO DTHC module box if you have not purchased a MASSO DTHC. When you receive your DTHC you will also receive an upgrade to enable the DTHC in MASSO. Please ensure you download and update your software to enable the feature.


Probing inputs

  • MASSO has 2 sets of probing inputs Touch and Ohmic.
  • The Input logic can be inverted as required to suit your sensor. Both input logic should be LOW when not triggered and change to HIGH when triggered.
  • You can choose which you want to use for your probing and switch between them as required.

  • If using you select Ohmic and the sensor does not trigger before the touch sensor you will receive an alarm. It is therefore advised that a touch sensor be installed on your system or that the touch sensor input be included as part of the ohmic sensor in case it should fail.

Torch Breakaway

  • The Input logic can be inverted as required to suit your sensor. The input logic should be LOW when not triggered and change to HIGH when triggered.

Combined Torch Touch and breakaway

  • The Input logic can be inverted as required to suit your sensor. The input logic should be LOW when not triggered and change to HIGH when triggered.


  • On the Multi-Head Setting page for Plasma, there is the ARC Detect Voltage which must be set up before the Arc Detect will work.
  • There is an button that is used to calibrate the ARC Detect voltage.


WARNING: Make sure the torch is somewhere where it will not burn a hole in anything, as the Plasma will start during the setup process.

To set the ARC Detect Voltage simply press the Button and the Plasma arc will start.

Press the button again, the torch will turn off and the ARC Detect Voltage box will fill in the ARC Detect voltage for you.

Press and you will be ready to go.

  • The voltage in the box will auto-fill with the voltage MASSO will use as its Arc ok voltage.
  • MASSO will also create a log Auto Detect voltage test data and save it to the Flash drive.
  • This log file can be sent to MASSO for troubleshooting purposes.
  • The log file is located in the MASSO\Machine Setting folder and is called Plasma_Arc_Log-001.csv
  • Each time the Arc Detect rest is run a new Log file is created with an increasing number.
  • Arc detect should only need to be run once.

Plasma On/Off

  • The Plasma On/Off output is assigned to allow MASSO to remotely turn the plasma on and off.  

  • The plasma can be turned on by use of the M3 command or using the Plasma button on the F2 screen

Plasma Up/Down

The Plasma up/Down is used to move the plasma torch into position when used in a Multi-head configuration.

This output would not normally be used on a Plasma only machine.

The Touch would be mounted on a linear rail on a Common Z axis along with all the other heads such as spindle, scribe, laser.

The chosen Multi-Head is moved into position by a pneumatic cylinder or similar when tool 112 is selected and it moves up when another tool is selected.

The output is normally Low and changes to High when selected.

The output can be used for other purposes as decided by the user.

An example of how the Plasma Up/Down could be wired to operate a Pneumatic cylinder.

Plasma Up/Down Output

Example Plasma Up/Down Wiring

Plasma Tab

If you do not see the Plasma tab in the F2 screen please ensure that you have selected Tool 112

Ensure you have enabled Plasma in the Multi-head Plasma screen

In MDI type T112 M6 to change to the Plasma tool.

You will see 3 Tabs in the Gcode section of the screen.

F2 Screen

  • 7 Parameters are provided on the F2 Plasma tab to allow easy adjustment of the Plasma torch while it is cutting.
  • Each parameter box can be clicked on and a new value entered into the box.
  • Touch off and Piercing is automated in MASSO Plasma and will occur on each M3 command before moving to the cutting height and these are controlled by parameters 1 to 4
  • The THC voltage can be set directly on MASSO and changed either by entering a new value or using the Torch Up / Down buttons on screen which will change the voltage by 1 volt.
  • The THC feed rate can be adjusted as needed and this adjusts the speed of the Z axis when under THC control.
  • Feed rate Anti dive is a percentage of the X Y axis feed rate and should it fall below this value the Z axis will lock when under THC control to prevent the torch falling and touching the material.
  • Parameters 1,2,3,4,5 & 7 can be set as part of the Gcode file. Gcode command G200
  • Parameter 6 is set using Gcode command M667

  1. Touch off Feedrate 
  2. Piercing Height
  3. Piercing Delay
  4. Cutting Height
  5. Cutting Voltage
  6. THC Feedrate
  7. Feedrate Antidive (Under development)

Overrides Tab

Overrides Tab

How Plasma works

  • The Plasma-Up/Down output goes Low to move the Torch in to the up position when a different tool is selected.


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