The three most prevalent methods for Initial Height Control of the plasma torch are the following:
The myCNC IHC system allows the user to work with all three of these systems, with the setup process being similar between all of them. Despite mechanical differences in these IHC systems, the way the controller performs the IHC procedure makes the IHC setup fairly universal.
Two out of three systems listed above (the Ohmic and the Probe Sensor) require the IHC system to only work before the cutting process starts. For the ohmic sensor, this is due to the fact that it must only register the voltage drops during the IHC process, while the probe sensor needs to be brought down/up before the cutting process as to not interfere with it. Therefore, these two systems require an INPUT from the sensor to the controller - the signal that indicates that contact has been made - and an OUTPUT from the controller to the IHC system housing those sensors, which indicates that these systems must be activated during the IHC phase.
On the other hand, the floating head system simply requires an INPUT to the controller to indicate that the button has been pressed. It does not need to be retracted or turned off when the cutting commences, so no OUTPUT from the controller is needed. Therefore, in order to set up the IHC system within the myCNC software, the user needs to assign at most two connections (or sometimes only one, in the case of the floating head mechanism).
The INPUT sensor will be assigned in the
pins.h file (found in Settings > Hardware > PLC > Hardware PLC) as
INPUT_IHC, while the OUTPUT connection will be assigned as
OUTPUT_PROBE. Then, the sequence will be the following:
This last step is where the difference between the three different potential systems becomes apparent, as their differences in position Z at which the input sensor is triggered must be accounted for. This is where the IHC Correction Height (found in the User Settings) is used:
(You can read more about the different settings in the diagram above in the THC manual).
This correction height allows the user to account for the machine height at which the IHC Sensor (our INPUT_IHC) gets triggered.
Below is a diagram that illustrates the idea behind the IHC Correction Height:
After the contact has been made, the machine will travel up by the IHC Ignition Height + the IHC Correction Height:
If, for example, a pneumatic probe system has been used, the IHC Ignition Height is equal to 6.0, and the IHC Correction Height is equal to 1.0, the system will go up by 7.0 mm after contact with the working surface has been made. It will then wait at this ignition height until it receives the Arc Sensor input, and will then proceed with the pierce and the THC sequence.
NOTE: This section is a cross-post from the MyCNC Plasma Setup Example (X1366P) manual.
In a typical configuration:
Both inputs should be configured in PLC Builder, in the pins.h file which can be accessed by going to
Settings > Config > PLC > Hardware PLC. Either of these can also be re-assigned to other input pins, 0 and 1 have simply been chosen out of convenience to have a default set of connections:
#define INPUT_ARC 0 #define INPUT_IHC 1
The video below shows the steps necessary to set up the IHC/Arc sensors in the X1366P plasma profile:
The following video illustrates the Initial Height Control process that takes place as the program begins to run:
The sequence will be the following: