6 Tips and Tricks for Improving Your CNC Plasma Cut Quality
Plasma arc cutting is a process where you can constrict an open arc by passing through a narrow nozzle from the electrode to the workpiece. This process is straightforward, which leads to most people rushing through the plasma cutting without retaining quality.
Plasma cutters can be so easy to use that people do not follow any practices to increase the cutting efficiency, improve cut quality and ensure the longevity of the tool. Whether you use a plasma cutter in your shop or for DIY projects, motorsports, or arts, you must employ proper techniques to achieve better results.
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Tips and Tricks to Improve CNC Plasma Quality
Here are a few tips and practices to be mindful of when operating a plasma cutter to ensure that the final cut quality and texture is smooth and looks premium -
Pick the Right Plasma Cutter
When choosing a plasma cutter, consider crucial factors, like cutting speed, duty cycle, output power, input power, weight, and size. The type of jobs you will perform using the cutter will also influence your buying decision.
- Cutting speed: The cutting speed of the CNC plasma cutter is measured in inches per minute (IPM) and significantly influences production time. While one plasma cutter might take five minutes to cut 1/2-inch material, the other might take one.
- Duty cycle: The duty cycle is defined as the time a machine can cut within a 10-minute cycle until it overheats. A larger duty cycle is necessary to make long cuts and work in high productivity applications or hot environment setups.
- Output power: The desired output power is estimated based on the thickness and type of material to be cut. A CNC miller employs two standards: rated and sever cuts. A rated cut is the thickness of mild metal that an operator can cut manually at 15 inches per minute (IPM). A sever cut is the maximum thickness that a plasma cutter can easily handle.
- Input power: Input power is a crucial criterion to consider whether you need to use the cutter in a fixed location or plug it into different power sources. Buy plasma cutters that come with a range of power options. Certain plasma cutters can switch from 120 volts to 240-volt power.
- Weight and size: If you require a portable cutter, opt for hand-portable units that weigh less than 45 pounds. A bulky plasma cutter might deliver a higher efficiency for some use cases but will not provide portability.
Use Appropriate Cut Charts
Refer to the cut charts listed in your system manual and pick the appropriate process to perform your cutting application. Then, you must choose the relevant process depending on factors like the material thickness, material type, desired cut quality, and productivity goals.
After considering the above factors, the cut charts will mention the consumables required, along with the relevant plasma and shield gases. Moreover, the cut parameters also list the appropriate gas pressures, arc voltage, torch-to-work distance, and cutting speed.
It is advisable to pierce high and cut low. As per the rule of thumb, it is advisable to pierce at 1.5-2X the cut height or the maximum transfer distance. Piercing high helps avoid bridging, double arcing, and snuffing.
You can also use a creeping pierce if your CNC machine supports it. This feature helps slowly move the torch when performing the piercing operation, which leads to the “rooster tail” of molten material missing the front end of the torch.
Another handy tip is not to eyeball the pierce height. Consider using the initial height sensing if available. Avoid manual piercing since it is impractical for even the most experienced operators.
The final tip is to never pierce beyond system limits. The pierce rating typically stands at 1/2 the cut rating.
Monitor the Consumables
If the tip or the electrode sustains damage, the quality of the cut will deteriorate. Discard the tip hole when it becomes irregular or covered with spatter. Also, discard the tip of the electrode when it develops a pit.
The consumables are bound to show wear with each cut; however, atmospheric moisture, excessive cutting of thick materials, or engaging in poor technique will accelerate the deterioration of consumables.
Refrain from over-tightening the consumables retaining cup. The inside parts move to create an arc; therefore, only finger-tighten the cup.
Set Up the Cutter Appropriately
When setting up your newly bought plasma cutter, be sure to secure the ground clamp to clean metal only. Grind off rust or paint to prevent obstructions in the flow of electricity.
Place the ground clamp close to the cut, or have the clamp placed on the workpiece itself. Double-check the cables for worn spots, loose connections, or other factors that might inhibit the electricity flow.
To calibrate the amperage or heat of the cutting unit to optimum levels, perform some practice cuts on high amperage. Then, adjust the amperage down as per your travel speed. High amperage or slow travel speeds can lead to excessive heat generation and accumulation of dross.
Check the Travel Speed
Fast travel speeds on materials like aluminum will help achieve a cleaner cut. When cutting through thick material, calibrate the machine to ensure that it delivers full output. When dealing with thinner material, turn the amperage down and switch to a lower-amperage tip to maintain a narrow kerf.
Appropriate travel speeds ensure that the arc exits the material at a 15 to 20-degree angle opposite the direction of travel. If it is headed straight downwards, you need to speed up. If it sprays back, you need to slow down.
By adhering to the tips and tricks mentioned above, your plasma arc cutting unit can deliver premium finish cuts at high speeds, regardless of its size. You must also purchase the correct equipment for the job to obtain maximum productivity and lesser operating costs.
The technique you apply during plasma cutting is equally as pivotal as choosing the right equipment. You must also regularly monitor your machinery for wear and replace the worn-out parts immediately.
About the Author:
Peter Jacobs is the Senior Director of Marketing at CNC Masters. He is actively involved in manufacturing processes and regularly contributes his insights for various blogs in CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general.