Plasma/Flame Cutting using CamSoft CNC Lite, Plus or Professional
There are a variety of torch height controls on the market for use with plasma cutting equipment. Each of these automatic THC's has a variety of functions and features. But all use the same basic elements to control position of the torch relative to the material being cut. This "torch to work" distance or "Torch Height" is critical to both cut quality and parts life. If the torch is too high or too low the quality of the cut will be impaired. The torch height control uses arc voltage (Tip Voltage) to maintain a consistent distance from the plate while the torch is cutting. This allows the system to maintain proper torch height regardless of variations in the material, or flatness of the cutting bed. The open circuit voltage is around 300vdc. While cutting it will range from 80vdc to 200vdc and that depends on the operating current and cutting height .
In CamSoft, the user can set the initial Pierce height. Once the torch has pierced the plate, motion of the cutting machine is enabled and the torch begins to move. Once cutting begins the THC monitors the tip voltage, filters it and divides it by 10 then compares it to the referenced voltage set by the Coarse and Fine adjustments on the control panel. Then adjusts the head up or down to control the voltage and therefore the height.
Each voltage setting corresponds to a specific height that optimizes the arc characteristics for a clean, straight cut. Torch height has the greatest affect on bevel angle of the plasma cut piece. Setting the voltage too high results in more material being removed from the top than the bottom. This causes excessive top rounding and positive bevel. Setting the voltage too low results in too much material being removed from the bottom of the plate. This causes undercutting or negative bevel
Torch height controls have many features and capabilities. But the most important is torch height control. Piercing at the right height will save you money on torch tips. Cutting at the right height will ensure good cut quality and minimize expensive rework operations. When properly used a torch height control pays for itself in a short time.
The power supply in the plasma machine will output about 300vdc open circuit. It is a constant current supply. In other words it regulates the current to what ever you have it set for. In order to do that it needs to change the voltage as the load changes. With the plasma cutting, the torch height determines the load and therefore the voltage . The current regulator lowers the voltage as the height moves lower and raises as it as the torch moves higher. The THC monitors the voltage and changes the torch height to keep the voltage at a set point. It is like a closed loop servo, in that you set the reference voltage through the front panel controls and it is compared to the divided down tip voltage. If the tip voltage is higher than the set voltage then THC moves the tip down, this causes the plasma current regulator to bring the voltage down. It works the same if the tip voltage is too low THC moves the tip up and the plasma current regulator brings the voltage up . The THC does have a window of voltage it works through. If it is less than or greater than the Fault set voltage then a Fault LED will come on.
Torch Height Controller
- User control panel dimensions - Height 3.5" Width 10" Depth 7.5 "
- Sensor Interface box
- Logic routines
- Plasma operator interface
- Power transformer
- High & Low voltage cables
- Ready to use with CNC Lite, Plus, or Professional software
**CNC Lite, Plus or Professional software, Motion card and Computer sold separately |
