8 tips to improve CNC plasma cut quality

By Hypertherm
Posted on 30/01/2019 in SPARK the blog, Plasma cutting

Though Hypertherm’s Technical Service Team is happy to troubleshoot issues and provide guidance, customers can often achieve better cutting outcomes on their own by running through the following questions:

1. Are you cutting in the right direction? With standard consumables, the plasma arc spins clockwise as the torch moves forward into the cut. The squarest cut angles will be on the right side of the arc. As a result, contour shapes are cut in a clockwise direction, while with internal features, the torch needs to travel in a counter-clockwise direction. Check and adjust the cutting direction, if needed

2. Are you following the cut charts? Refer to the cut charts in your system manual and select the appropriate process for your cutting application. Select the appropriate process for material type, material thickness, desired cut quality, and productivity goals. Based on these factors, the cut charts will list the consumables needed, with the appropriate plasma and shield gases. In addition, the cut parameters will list the appropriate gas pressures (or flow rates), torch-to-work distance, arc voltage, and cutting speed.

3. Are you using good consumables? Do a visual check to see if consumables are worn, dinged, or damaged. These are precision parts so any type of surface imperfections can impact system performance. Replace consumables when needed. Be sure to lubricate o-rings when changing consumables, but do not over-lubricate because that will impact system performance as well. Though less common, we also sometimes discover customers who have inadvertently received and put the wrong consumables in the torch. If you continue to have issues, we suggest ensuring the part numbers on your consumables match the numbers found in your owner’s manual.

4. Is your torch square to the workpiece? Check to see if the table and the workpiece are level, before squaring your torch to the workpiece. Keep in mind that if the metal is bent or warped, it might be impossible to square the torch and you might need to accept less than ideal cut quality.

5. Are you holding the right torch to work distance? Sometimes referred to as a “stand-off”, you’ll want to ensure your torch isn’t too close or far from the workpiece as this will cause angled and rounded cut edges. In addition, if the torch is too close, metal spatter blowing back onto the torch can seriously damage your torch and nozzle. Lastly, don’t forget to routinely adjust the torch to work distance as your consumables wear.

6. Are you cutting at the right speed? Dross is a great visual clue that lets you know if your cut speed is too fast or too slow. Low-speed dross is the bubbly or globular molten material that collects at the bottom of the cut edge. This kind of dross is easy to remove and flakes off the plate. To eliminate it on future parts, cut faster. On the contrary, high-speed dross causes a thinner bead of molten metal to collect at the bottom of the cut. Unfortunately, high-speed dross is harder to remove and so requires grinding. The solution is simple though. Reduce your cutting speed to give the arc time to catch-up with the speed of the torch.

7. How is your air or gas quality? If using an air plasma, make sure your air is clean and dry. The same applies to your gas when using an oxygen or multi-gas system. Always use pure, high-quality gas and the appropriately sized regulators and gas lines. If a manual purge is required, confirm that the purging cycle was completed. Check to see if the gas is leaking, or if the flow is restricted. Consult your gas distributor for help if needed.

8. Does your table need a tune-up? Is the table cutting at the specified speed? Is the torch secured tightly to the table gantry? How is your table motion? Is it vibrating? Often, plasma cutting issues have nothing to do with the plasma itself and instead are caused by poor motion or other table issues. If you’ve run through the preceding seven questions and are still having issues, this could very well be the cause, in which case you should consult your table manufacturer.