[LordyGordy]

I've helping a friend set up his new CNC plasma table. We can cut by manually activating the torch & jugging axes, or by running Gcode, but Mach3 doesn't consistently respond to the torch height adjustment commands from the Proma THC module. The module is giving Up and Down commands fine & in the Diagnostics tab I see that Mach3 in receiving them. I've emulated Up & Down inputs with keystrokes so I can find the problem without the Proma module and plasma cutter. The Z-axis doesn't always move when it's supposed to. One minute it will move the whole range, and the next minute Up and/or Down don't work or Down stops at some random point. Seems like Down may only move when Up just did. I see that it's detecting the Up & Down signals, but it's not moving accordingly. I've set THC Max and Min at 0 and -4.5 respectively, the same as the Soft Limits, though I'm not sure if that's what it should be set at so I've tried different values. For our purposes, the 0 (home) position is the uppermost point on the Z-axis and any lower position is negative.

When I jog the Z-axis the Current value in the THC pane doesn't change so I guess it doesn't know where the axis is positioned like it shows in the DRO. It will also go outside the limit of Max and Min. I've noticed that the difference between the values that Up and Down will stop at is equal to the difference between THC Max and Min. Also, the Z-axis position values in the Diagnostics tab will be unbalanced. Normally, for every axis, Current Position = Machine Coordinates - Work Offset - G92 Offset - Tool Offset, but with everything at 0 I can move the Z-axis Current Position with an Up or Down signal or by jogging to, say 2.773, and the equation will be 2.733 = 0 - 0 - 0 - 0. In the Program Run tab I can click 'Go To Zero' and the Z-axis will count up and/or down to the THC pane's Current value.

I have Mach3 installed on two other computers, all with the same settings, and THC behaves the same way. I've checked the box to "Allow THC UP/DOWN Control even if not in THC Mode" and Max Cl Mode is disabled (unchecked). What am I missing, or what else can I try?

[Torchhead]

You have the THC Corrections min and max set wrong. The Max is the highest you will let the Z travel while you cut above zero. Zero is supposed to be the top of the material (whereever that happens to be). Do not mess with tool offsets it makes no different on the plasma settings. Set your max to 1 (inch) unless you are confident that you will never have to let the Z move up that high due to material warp. If you get UP and Down signal to MACH and it refuses to move it is because some setting is preventing it. Enabling the "Use THC even when THC is off" opion is NOT for plasma cutting with THC. It is mostly used for manually adjusting the Z with no external THC like for oxy-fuel cutting . It will also not override the Min-Max settings if the THC is enable in MACH too.