Tips and Tricks to Improve your CNC Plasma Cut Quality

The primary objective of all CNC machinists is to achieve high cut quality. Several factors are at play to obtain premium cut quality, such as the cut direction, cutting speed, referring to the right cut charts, and more. You must be able to single out and rectify the deterrents that might be impacting your CNC plasma cut quality.

Factors That Affect Cut Quality

Listed below are some factors that can impact the cut quality rendered by a CNC plasma cutting machine -

  • Torch Height – It is critical to ensure that the cutting machine retains the appropriate height, both for piercing and cutting.

  • Air Quality – The work environment must have clean and oil-free air since it impacts the cut quality and consumable life.

  • Consumables – Ensure that your consumables and torch segments are rid of any dirt and within spec. Check that the nozzle hole is round, with no debris on the swirl ring or the nozzle.

  • Cutting Speed – Perform tests using a stopwatch and tape measure to double-check that your cutting machine moves at the mentioned speed.

  • Vibration – Unnecessary vibration in your torch will affect cut quality, especially at higher speeds.

Tips and Tricks to Improve CNC Plasma Cut Quality

To ensure that your CNC cutting machine performs optimally and delivers high-quality cuts, implement these tips and tricks in your workshop -

Picking the Right Cut Direction 

The plasma arc rotates clockwise, which moves the torch forward into the cut when using standard consumables. Check that the squarest cut angles are on the right side of the arc. Due to this, machinists obtain contour shapes by cutting clockwise. If you are cutting internal features, remember that the torch must rotate in a counter-clockwise direction. 

Appropriate Cut Charts 

Check the cut charts in your system manual and pick the right process that suits your cutting application. The next step is to choose the appropriate process based on the material type, thickness, and required cut quality. These factors will then help you refer to the cut charts more effectively as they will state the necessary consumables and the suitable plasma and shield gases. 

Choosing the Right Consumables 

Visually inspect for any worn, damaged, or dinged consumables. Since these are precision components, any prevalent surface imperfections will affect system performance. Perform timely replacements of consumables and lubricate O-rings with just the right quantity. Some machinists often use the wrong consumables in the torch. To counter this issue, ensure that your consumables' part numbers match the ones present in your owner’s manual.

Square Your Torch to the Workpiece

Ensure that the workpiece and the table stay level, and then square your torch to the workpiece. However, if you discover that the metal is warped or bent beyond fixing, it is not feasible to square the torch, as it can degrade the final cut quality.

If you run a small-scale workshop and are on a budget, opt for a Bridgeport mill, as these are highly versatile and deliver premium cut quality.

Check the Torch-to-Work Distance

Sometimes referred to as stand-off, you must always ensure that your torch is not placed too close or distant from the workpiece since it leads to angled and rounded cut edges. Besides that, placing the torch too close will lead to the metal spatter blowing back onto the torch. This scenario can severely impair your nozzle and torch. You must also routinely correct the torch to work distance as your consumables exhibit wear and tear.

Cutting Speed 

Dross is a visual factor that tells you if your machine's cut speed is too fast or too slow. To give you a brief understanding, here are its two types -

  1. Low-speed dross - It is the globular molten material typically found at the bottom of the cut edge. Low-speed dross can get removed conveniently and flakes off the plate. Use higher cut speeds to eliminate it on future components.

  2. High-speed dross - It causes a thinner bead of molten metal, which is found at the cut's bottom. High-speed dross is not as easy to remove as low-speed dross and thus, requires grinding. To eliminate it, you must reduce your cutting speed so that the arc has enough time to catch up with the torch's speed.

Air/Gas Quality

Make sure that your air is clean and oil-free. If your air pressure is low, the final cut quality will suffer. It is advisable to use an inline filter and dryer to counter this issue.

Similarly, when using an oxygen or a multi-gas system, use clean, high-quality gas and the correct sized regulators and gas lines. Check for any gas leaks or restricted airflow. 

Motion and Table Issues

Often, plasma cutting issues do not involve plasma but instead occur due to poor motion or table-related issues. Check to see if your table needs a tune-up, if it is cutting at the appropriate speed, or indicating unnecessary motion or vibrations. You must also ensure that the torch is secured firmly to the table gantry.

Final Words

CNC plasma cut quality gets affected by several influential factors, including cut speed, air quality, consumables, or maintenance issues. It is advisable to perform routine checks on the plasma machine and replace worn-out parts. You must also keep your workshop clean and dust-free to obtain the best cut quality.

Last Updated on 2 years by Richard Boyer

  • June 8, 2022
Peter Jacobs

Peter Jacobs is the Senior Director of Marketing at CNC Masters. He is actively involved in manufacturing processes and regularly contributes his insights to various blogs on CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general.

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