WARNING Please treat your Plasma with care as the incorrect wiring of the THC or use of the Plasma may cause damage to MASSO or serious personal injury.
CAUTION: This document provides an overview of how THC works with MASSO, how to connect and how to test. Depending on what THC you are using you may need to wire it differently from the drawings shown below. Please consult your user manual.
Overview of the THC interface and Gcode
Under Torch Height Control on the MASSO F1 Screen select option 3 Proma Compact THC Controller 150
The MASSO THC interface uses 3 inputs and 1 output.
- Arc ok – This signals MASSO when the Plasma arc is struck to let it know that it is ready to continue with the cut.
- THC1 – Lets MASSO know that the torch is too low and needs to rise. Connects to the Up signal in the THC
- THC2 – Lets MASSO know that the torch is too high and needs to descend. Connects to the Down signal in the THC
A MASSO output is set as Plasma On/Off Signal and is used to turn the Plasma torch on and off as needed.
Gcode commands used with THC
M667 - This command is used to switched On the THC automatic Z axis control function.
You can specify a feed rate which sets the speed at which the Z axis moves while under THC control.
M666 - This command is used to switched OFF the THC automatic Z axis control function
M3 - Turn Plasma Arc on
M5 - Turn Plasma Arc off
Overview of Plasma operation
- Under Torch Height Control on the MASSO F1 Screen select option 3
- Proma Compact THC Controller 150 if you are using a THC.
- The THC must output Arc OK, Up and Down signals to be compatible.
- An M3 command is issued and the Plasma arc is struck
- The THC sees the arc and sends back an Arc ok signal to MASSO by changing MASSO the input from Low to High
- MASSO sees the Arc ok signal and lights the Plasma on button on the screen.
- If the Arc Ok does not show high within 15 seconds of the M3 a “NO ARC OK” alarm will present and the MASSO will stop running the program.
- The Plasma starts cutting as per the program but will ignore further input from the THC until the function is turned on in MASSO
- An M667 F## command is issued turning on the THC function at a feed rate of ## within MASSO
- On the first axis move the THC button lights up on the MASSO screen.
- As it moves the THC will send out Up and Down signals on the THC1 & THC 2 inputs
- If Input THC1 changes to High MASSO will move the torch up
- If Input THC2 changes to High MASSO will move the torch down
- If both inputs THC1 & THC2 are High MASSO will ignore the error and the torch will not move.
- If both inputs THC1 & THC2 are Low then the plasma is at the correct height and the torch will not move.
- MASSO will continue to adjust the torch height until it receives an M666 command to turn off the THC function on the next axis move.
- The MASSO Z axis cannot be jogged while the THC function is turned on.
- MASSO will ignore Gcode instructions to move the Z axis while the THC function is turned on.
- Use software version 3,47 of later to ensure no hesitation in motion when the THC is turned on or off. A motion command must be issued before the THC will turn on or off. eg G01 X150 Y246
- The M667 command allows for a Z axis feed rate to be specified. This will only affect the Z axis speed when in THC mode. The primary use of this feed rate is to slow down the speed of the z axis so that it does not move too fast and overshoot. Example: M667 F50. It does not affect the feed rate of the X or Y axis and the Z axis feed rate will return to the previous value when THC is turned off.
- The Z axis feed rate at power on is the rapid speed for your Z axis.
- Once a feed rate is set using M667 command the Z axis will remember this until it is changed or MASSO is powered off.
- If while cutting you find that the torch head bounces up and down in an uncontrolled manner you may need to adjust the THC voltage settings or slow down the Z axis feed rate specified in the M667 command. Example: M667 F50
Connection of the THC inputs to MASSO
INFORMATION: The following section explains 2 methods of connecting the THC and why one is preferred over the other. The actual connection of your Arc ok, THC1 & THC2 inputs to MASSO will depend on the THC unit that you are using and what type of outputs the unit uses. Please consult your user manual.
The diagram below is the recommended way to connect the proma Compact THC 150 to MASSO. The use of resistors from the positive of the MASSO power supply to the MASSO inputs will turn the Inputs on and the THC will switch MASSO ground to the inputs to turn them off. Because this logic is wrong for MASSO the inputs are inverted on the F1 screen so that they show Low in the normal state and High when the THC sends a output.
When there is no signal coming from the THC the input will be turned on which reduces the chance of noise entering the input and providing a false signal. When the THC sends a signal ground signal will turn the Input hard off and again the chance of noise entering the input is greatly reduced. By wiring it in this manner the inputs will have very high noise immunity. When wiring in this manner use 1/4W or higher resistors and do not leave them out and connect the +ve direct to the inputs or you will damage your THC and possibly MASSO. Actual resistance values may need to be decreased depending on the type of switch used in the THC. The final resistance value will depending on your setup, power supply voltage, mechanical or solid state switches within the THC.
Please consult your THC user manual for more details and the best method to connect your THC.
It is recommended a separate power supply is used to power the THC.
THC input settings. Note these are inverted.
INFORMATION: To invert the logic of an input select the input and press the space bar to reverse the logic.
Alternative wiring method
Another option though not recommended is to switch the Positive rail of the MASSO Power supply with a suitable sized resistor in series through the THC. This can create noise problems from the Plasma arc. When there is no signal coming from the THC it means the inputs have no signal on them at all. The length of wire between the THC and MASSO will act as an antenna, picking up all of the electrical noise generated by the plasma. If a high enough voltage is generated it will turn inputs on. This will create false inputs to MASSO and cause issues. While the wiring is easier there is a chance of problems from noise generated by the plasma arc. The actual resistance value will depend on the type of switch used within the THC. The purpose of the resistor is to limit the fault current in case a THC output is accidentally grounded. Using this method the inputs are not inverted.
Consult your user manual for more details and the best method to connect your THC.
It is recommended a separate power supply is used to power the THC.
THC input settings. Note these are not inverted
Setting up the MASSO output
- Assign the MASSO output of your choice as Plasma On/Off Signal. On the MASSO G3 this will be a TTL output and will connect to a TTL relay board such as the
- On the MASSO G2 you can use either a TTL relay as with the G3 on one of the 16 TTL outputs or you can use one of the 6 Relay outputs and connect a suitable relay direct to the output.
- Wire the normally open or normally closed contact from the relay to the Plasma unit in accordance with the manufacturers instructions. This is used to turn the torch on and off as needed under control of the M3 / M5 commands.
In the example below the normally closed contact is used and output 18 is configured as Plasma on / off.
- From the F1 screen go to Torch Height Control and select option 1 Without THC and Arc Ok Signal
- Click on the Plasma on button in the F2 screen to turn the plasma on, the relay will operate and the Plasma should strike an arc.
- Click on Plasma off, the relay will release and the Plasma will turn off.
- From the F1 screen go to Torch Height Control and select option 3 (Proma Compact THC controller 150)
Testing the THC signals
Your THC unit should have a test function built in to generate the Arc Ok , UP and DOWN signals needed to control MASSO.
Testing the wiring
- On MASSO go to the F1 screen and look at the 3 inputs. They should all show logic Low. If not highlight the inputs and invert the ones that show High in the idle state.
- Turn on the THC test function. This will be either automatic as with the Proma Compact THC and manual on some other THC units
- Check that as each output on the THC signal is sent the corresponding input on MASSO changes from Low to High
- If all inputs show the correct signals on the F1 screen your setup is correct. If not please check your wiring and retest.
- While looking at the F1 screen trigger the Plasma torch and strike an arc. Make sure you see the Arc Ok input change from Low to High. Please note that you may need to adjust voltage setting within the THC to get the Arc Ok signal on the THC. Your THC should have a light for each signal and if you are wired and setup correctly you should see the Arc light turn on at the THC and the Arc Ok input will go high on MASSO.
Testing the Masso THC function
- Put your THC into Test mode
- Go to the F2 Screen and press the Plasma on button.
- Within 15 seconds the THC must send an Arc ok Signal. For the Proma this is continually sent in test mode. On other THC units you may have to manually select and send the required test signal.
- The signal does not need to be continuous. Once it is received it is not needed again until the plasma is turned on again.
- On receipt of the Arc Ok signal the Plasma on light will immediately turn yellow and there will be no alarm indication.
- Click on the THC button on the screen to turn on the THC. (Note: The THC will move at the rapid speed you set for your Z axis so please ensure there is sufficient room for movement.)
- Send an up signal from the THC and the torch will rise
- Send a down signal and the torch will descend.
INFORMATION: On the Proma test function it sends the Arc ok signal continuously and alternate up and down signals automatically switching between Up & Down every second. On other THC units you may have to manually select and send the required test signal.
INFORMATION: If the above tests are successful the THC is correctly wired to MASSO and MASSO is configured right. Please be aware that your Gcode and THC settings will have an effect on how well the setup will work.
INFORMATION: If while cutting you find that the torch head bounces up and down in an uncontrolled manner you may need to adjust the THC voltage settings or slow down the Z axis feedrate specified in the M667 command. Eg M667 F150