Cut Height and Its Effects


Let’s discuss what an Arc Voltage Height Controller (AVHC), sometimes referred to as a Torch Height controller, is. Basically, a height controller consists of several components designed to automatically maintain proper height while plasma cutting. There are many different brands, but all have similar components, though they may be called something else.

1. Human-Machine interface

This is the panel that allows the operator to input certain data such as initial torch height (pierce height) and Arc Voltage (cut height).

2. Voltage Divider Board

This device, usually mounted to the power source chassis, is used to do just as the name states, it monitors and divides the voltage signal from the power supply, sending a smaller, usable signal to the height control console during cutting.

3. Height Control Console

The control console receives input from both the operator via the control panel and voltage dividing board and sends output commands to the torch lifter motor.

4. Torch Lifter Motor

Moves the torch up or down based on the output signals received from the height control console.

Now, let’s discuss the importance of having a properly functioning Arc Voltage Height Controller to the performance of your consumables and CNC Plasma System.

The first advantage to having a working AVHC is to maintain a constant torch to work distance. Although the cutting surface of your table may seem to be flat, they rarely are. This causes the plate to not be level. The AVHC will prevent the torch from getting to high and breaking the arc or to low and crashing into the plate.

The second benefit to having a properly functioning AVHC is to maintain good cut edge quality. If the torch is too high there will be top bevel and to much dross. If the torch is too low, there will be under cutting (bottom bevel).

Next, proper height must be maintained in order to have correct kerf width, which affects the size of the part. Kerf is the metal that is removed by the circumference of the nozzle orifice. The kerf is calculated by the CNC control and is moved to the scrap allowing the part to be the proper size. If the torch is not the correct height, the arc will be out of position, causing the kerf calculations to be wrong.

Finally, with a properly functioning Arc Voltage Height Controller, arc stretch can be eliminated. The higher the torch, the longer the arc is stretched, relationally increasing the arc voltage. Consequently, the closer the torch is to the plate, the lower the arc voltage. Arc stretching can decrease the life of the electrode and nozzle causing premature failure.

All components are important for smooth operation with today’s modern CNC Cutting Systems. Not only is the Arc Voltage Height Controller one of the busiest components, but one that is vital to proper cutting, allowing for longevity of consumables, proper part sizing, prevention of torch crashing and good edge quality. Having a good, properly functioning, height controller will make your operator’s job easier and increase quality, longevity and production.

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