Cut quality is the key point of concern when it comes to plasma cutting and if you’re facing any problems with the cut quality, a few steps of troubleshooting such as adjusting the power levels, adjusting the cut height and speed, using the correct consumables, etc. can help to resolve any problem related to the cut quality.
A very common problem that occurs in plasma cutting is that the holes may be out of round or they may have a taper. So, if you’re having problems with achieving the proper quality of holes, here are some tips that can help. Here are some ways by which the quality of the hole cut can be improved:
Maintain Proper Pierce Height
Apart from piercing the workpiece at the proper height, you should also stick to the recommended pierce delay time. This will help in reducing the amount of molten metal that is blown back on the nozzle’s orifice and the torch shield. If you pierce very close to the workpiece or move the plasma torch before the piece is completed, this will cause the orifice to get damaged and alter the cut quality.
Use a Lead-in
While cutting, make use of a lead-in which comes very close to the centre of the hole as firstly, there is a puddle of slag on the workpiece and if the puddle remains on the contour of the hole, the plasma arc will waver and cause a divot in the hole. Secondly, if the lead-in is longer, the plasma arc has time to stabilise as the energy and the pressure take some time to ramp up. This also allows the height control to adjust to the cut height before it gets to the contour of the hole.
Adjust the Cutting Speed
The cutting speed on the holes should be around 60% of the speed used to cut the outside contour of the workpiece. While this may create low-speed dross at the bottom of the workpiece, the taper in the hole will be minimised. Some plasma cutting systems and CAM software can do this automatically on holes with a diameter of less than 1.25 inches. You may have to manipulate the G-code of other software to achieve this. Nevertheless, cutting at a high speed will increase the taper of the hole.
Use Anti-Spatter Spray
If you run the plasma torch over the pile of slag which was produced while piercing, it will affect the roundness of the hole. Using an anti-spatter spray on the workpiece before cutting can help to eliminate the spatter that is produced when piercing and also minimises the arc wobble on the holes. Using anti-spatter spray on the front of the plasma torch also helps to prevent the build-up of spatter on the nozzle and shield. It is recommended that you use a water-based spray. Using an anti-spatter spray can go a long way in improving the cut quality.
Use Consumables as Per the Material’s Thickness
This can help to reduce the cutting speed and provide good results. It is recommended that you use 45-amp shielded consumables for materials of thickness between 0.1875 – 0.375 inches and 65-amp consumables for materials of thickness between 0.375 – 0.625 inches. Making use of higher power levels will cause more taper in the holes.
Ensure that the shield and nozzle orifices are perfectly round and do not have any craters, dings or nicks. If the round is not perfect, then you can use these consumables for contour cutting or hand cutting which are not critical. The orifice shapes the plasma arc and this affects the quality of the cut. If you pierce too wide or too close, the nozzle orifice will get damaged.
By following the above steps, you can ensure that you get high-quality cuts at all times and the key to getting best cut quality is to make use of high-quality consumables, which are inspected regularly to ensure that they are not worn out.