Plasma machines use a constant current power supply for cutting steel. The power supply can range from 10 to 400 amps (or more) selected from the plasma machine control panel. A constant current supply keeps the cutting current at the user selected value by changing the cutting voltage as the load changes. The load changes as the distance from the torch tip to the metal you are cutting changes. The HP105 Torch Height Control (THC) monitors this “Tip Voltage” and adjusts the torch height (by control DC motorized Z axis) to maintain Tip Voltage to within ±1V∽±5V ( adjustable) of the user Set Voltage.
When the distance between torch and cutting plate gets farther, the arc voltage increases and when torch comes close to the plate the arc voltage will decrease. HP105 plasma arc voltage height controller will constantly measuring the voltage change and will keep a constant distance between the torch and cutting plate using motor output to the DC Motorized Z axis.
- Working voltage: DC24±10% Isolated power, do not shared with others such as electronic valve!
- Lifting motor: DC24V DC motor (permanent magnet motor) lifting speed don't exceed travel speed 3000 mm/min (1500mm/min recommended for better accuracy)
- Lifting Motor Driving Mode: PWM
- Output current to lifting motor: 1A to 4A
- Working temperature: Height controller -10∽60℃
- Sensing voltage ratio: 100:1
- Accuracy: ±1V∽±5V，adjustable
- Protection class: IP64
- Weight: 0.8kg
- Installation position: Keep away from heat
Please for more informations go to download tab and download the datasheet of this product.
HOW Plasma Height Control THC Work
HOW DOES AN ARC VOLTAGE HEIGHT CONTROL WORK?
Plasma cutting uses a high temperature electric arc that is developed by applying DC current to an internal electrode (negative) and to the plate (positive). Gas flowing around the electrode is heated to its ionization temperature, which increases its electrical conductivity, allowing the DC energy to form a superheated electrical arc from the electrode to the plate. The arc is forced through an orifice in the plasma torch nozzle which controls the shape and velocity of this plasma arc, effectively controlling the energy and cut quality.
A DC voltage can be measured between the negative electrode and the positive plate during steady state plasma cutting . . . this voltage varies depending on the length of the arc between the electrode and the plate – longer arc reads higher voltage, shorter arc reads a lower voltage. In theory, this is a very effective method of gauging torch to work distance! A typical plasma system height control has a reference voltage that is set by the machine operator. This voltage is provided by the plasma torch manufacturer and is different for every type of material, every thickness, and every plasma process power level.
Once the plasma process starts cutting, the THC (torch height control) looks at the actual arc voltage (measured electronically between the electrode and the plate) and compares it to the operator set reference voltage, then the THC adjust the motorized Z-axis (up/down mechanical axis that holds the plasma torch) until the reference and actual voltage are the same, thus controlling the torch to work distance. Any warpage or flatness issues of the plate on the plasma cutting table are automatically adjusted by this height control process.
Torch Height Control Operation Sequence
Initial Position, the Plasma Torch is at some “retract” height above the work metal (see: Sequence 1).
Touch - off - Pressing Start on Mach3 (or similar CNC software) causes the torch to move to the requested X/Y position. The beginning G - code will perform a (Touch - off). The Z axis moves down and the “floating head switch” or ohmic sensor detects the work piece with the tip of the torch. The Z DRO will be set to “0”. We have now referenced the Z axis (see: Sequence 2).
Raising the torch - Mach3 (M3)(or similar CNC software) then turns on the TORCH light under Torch Height Control and tells the THC to fire the torch (Torch On signal). The THC triggers the Torch relay which sends the “torch on” signal to the plasma cutter. Gas flow (shop air in most cases) begins. The Z axis is still under G - code control (see: Sequence 3).
The Pierce Height is approximately 2 times the distance of the Cut Height. The torch is set to the Pierce Height when the torch is about to fire and pierce the metal to begin cutting. This extra distance help to prevent molten metal blowback from damaging the torch tip when the torch is fired and is piercing the metal. (see: Sequence 4).
Pierce Complete - Now Mach3(or similar CNC software) working with the THC moves the torch down to the Cut Height. The THC compares the Arc Voltage to the Set Voltage (Set Voltage is the number the user set in the THC by adjusting the optional en coder knob or the slider on the Mach3 screen ) and tells Mach3 to adjust the Z axis to compensate. Mach3 now tells the torch to move and start cutting (see: Sequence 5).
THC ON - As the torch moves and cuts the work piece the Tip Voltage may change if the metal warps or is not perfectly flat. This necessitates movement of the Z axis to maintain the proper cut height. The THC tells Mach3(or similar CNC software) to move the Z axis up if the Set Voltage is higher than the Tip Voltage or down if the Set Voltage is lower than the Tip Voltage. If they are equal, then no Z axis motion is performed. These actions are reflected in both the UP and DOWN lights on the modified Mach3 screen (see: Sequence 6).
Here you can download datasheet for HP-105