On XPTHC's operation panel,  there're UP/DOWN LEDs to show the up/down function of THC. please always watch the ON/OFF state when you have torch up/down problem,

 1. When THC auto mode is working,  the auto height control function adjust torch up/down according to plasma arc voltage change,   UP/DOWN LEDs would not turn on.

 2. The UP/DOWN LEDs would only turn on when the command signal is from external of THC control module,  like Manual press up/down on THC operation panel, or up/down signal from CNC controller. So you can check accordingly where the signal from and find the reason.

 3. Another Up signal from is collision ( Torch retaining cap IHS or Proximity Switch IHS function), you can see often on THC’s panel,  the collision LED turns on first, then Up LED turns on for a while.
This is IHS function,  any conductive material touch retaining cap, or activate the proximity switch for IHS, torch would lift up a pierce height (repeat an IHS process, programmed in THC.) It is used as kind of anti-collision protection.
So sometimes if the dross stick on retaining cap,  or proximity switch installation gets loose,  you can see the collision LED is on all the time, then UP led is on at the same time, and torch is up until the limit.

  4. Another situation of torch keeps lifting up is,  it installed proximity switch for IHS, but the SW2 switch on IHS circuit is OFF. In this situation, torch keeps lifting up when you power on THC.

Some customers said their torch can follow the cutting when the cutting surface is getting higher and higher( cut a warp plate,  torch go up first along with plate, then go down),  but the torch not goes down when the plate height decreases.
That’s because the THC’s auto mode not activated.
During manual mode, when torch touches steel, it lifts up right away( IHS function), so user see torch follow cutting go higher to the top of plate,  but not follow cutting when the plate height goes down.

5.  Up signal has priority against Down,   If the CNC's down signal short connected with THC's Down signal input,  you will see torch down, touch steel, collision signal lift torch up,  CNC order torch down again, touch steel.....repeat the process....then you see torch is shaking all the time.  ( In this case,  Down, Collision, Up LEDs all ON.)

6. THC sensitivity too high can cause torch shaking too.  Usually set a straight line cutting, see if torch shaking ( On auto mode,  but UP, DOWN LED should not turn on. as it is auto mode sensitivity too high.)  

Also, lifter's mechanical problem could torch shaking,  like the lifter's bearing slips, or lifter is not enough to carry the weight...