When it comes to the advantages of plasma cutting systems, users can count on versatility, speed, safety and precision, among other benefits.
By adhering to the following best practices, users can ensure they’re getting the highest quality cut possible from their plasma cutting system.
The three most common causes of substandard cut quality are poor air quality, overused consumables, and bad voltage readings.
5 Best Practices for a Precise Cut
1. Use clean, dry shop air
Regularly clean and check your shop’s air filters to ensure good air quality. In addition, use an air compressor with a desiccant or refrigerated air dryer (or combination of both) to eliminate humidity.
Check for humidity by unplugging the air line from the plasma and connecting an air gun. Using a white paper towel or a small mirror, spray air onto the surface. If any moisture is present, the air being used for the machine is too humid.
Another way to check for humidity is to examine the bottom of the electrode, where the rod of hafnium is, or inside the nozzle. If you see swirl marks — similar to if you wash a wine glass in the dishwasher and see swirls afterward — it is an indication of moisture or hard water in the line.
2. Don’t overuse consumables
Worn out or overused consumables result in poor cut quality. Thicker material wears out consumables faster, as well as pierces vs. continuous cuts. The experts at AKS recommend checking the consumables each time a new sheet is put on.
As a general rule, the electrode should be replaced once the rod of is worn down 1/16th of an inch.
3. Grease O-rings
Most consumables — such as the water tube, retaining cap, nozzle and swirl ring — have small O-rings on them. Each time you change consumables, rub in a rice grain-sized amount of O-ring grease or lube on your fingers until it is rubbed in and your finger is shiny, then use that to coat your O-rings. Ungreased O-rings wear out consumables faster and could cause leaks. Conversely, do not overcoat the lube, as this could result in clogs.
Make sure you use Hypertherm’s O-ring lubricant. It is made to handle the high flashpoint of plasma. Any O-ring lubricant used that does not meet the flashpoint of a plasma torch will result in damaging or melting your torch.
4. Don’t overuse slats
When cutting with plasma, many people overuse their slats. This results in a buildup of molten metal drops, which degrade cut quality. In addition, this buildup can interfere with the ground reading, which is important for height control.
An indication of this problem could be an incorrect voltage reading. For example, if it should be reading 132 volts, you might see a reading of 138 or below. This is the head trying to compensate — and it will move up and down, causing taper and/or wavy edges on the parts. It is common to see voltage fluctuations, but a consistent reading above or below the setpoint is an indicator of overused slats or consumables.
There are two quick tests you can perform. If you are getting poor cut quality and you are not sure if it is your slats, put new consumables in your torch and try a cut. If your cut quality is still poor, you now know it is not your consumables. If your slats look overused, take a jumper cable or ground wire and piggyback it from the ground bolt on your table directly to the material you are cutting, then try another cut. If your cut quality is better, it is most likely your slats that are causing a bad voltage reading and effecting your cut quality.
Perform a visual check to learn when it’s time to change out the slats. They’ll have drops all over the tops and sides and generally appear overused.
5. Check air pressure
Low air pressure can potentially cause the same kind of issues with an incorrect voltage reading. To determine whether the issue is the ground or air pressure, perform the same test you did for checking the ground reading through the slats. Connect jumper cables to the ground where the plasma is connected and piggyback it directly to the material.
Next, perform a test cut. If cut quality is still bad, but your slats and consumables are good, the cause must be the air. Check your air pressure and make sure it is able to hold the minimum required pressure while cutting. This can be accomplished by performing a gas flow test through your plasma unit or unplugging the air line going into your plasma, connecting an air gun to it and holding the trigger down for three minutes while watching your pressure gauge.