Are you new to plasma cutting? Do you want to avoid the common mistakes people make when operating a CNC plasma cutter? Well, you’ve come to the right place.
Mistakes in plasma cutting can damage the consumable and shorten your plasma table’s life. Poor quality cuts and interruptions can also result in wasted materials, costly downtime in the workshop, and potentially lost sales.
Fortunately, most CNC plasma cutting mistakes are completely avoidable. Here’s a breakdown of the common mistakes people make and some ways to prevent them. (P.S. Even professional fabricators can benefit from reviewing some operating procedures and proper cutting techniques).
1. Using the Wrong Consumables
Randomly choosing consumables is a recipe for disaster. Not only does it lead to lower cut quality, but it can also shorten the life of your parts. Always select consumables based on the thickness of your material, plasma gas used, and the required amperage (amperage set to 95% of the nozzle’s rating usually delivers the best cut quality). The owner’s manual that came with your CNC plasma cutter should inform you about the appropriate consumables for your machine.
2. Using Severely Worn Consumables
Using worn out consumables can ruin even the best metal and cause extensive torch damage. To avoid this, check whether any sound is coming from the arc or if parts have any coloring. The reduction of torch height is another indication of deteriorated consumable parts. Establish baselines for the expected lifespan of these parts and use them to understand the ideal time to order a replacement.
3. Not Assembling the Torch Correctly
Before fabricating the metal piece, ensure all parts of the plasma torch are assembled correctly and fit together snugly. This is crucial to achieving good electrical contact and proper flow of coolant and gas through the plasma torch. Additionally, cleaning is important to prevent dirt or metal dust from contaminating the plasma torch. Use a clean rag to reduce dust and oil to lubricate parts, but avoid over-lubricating the O-rings as that can cause the swirl ring to clog and result in an uncontrolled arc.
4. Piercing too low
Good operators know the distance between the material being fabricated and the torch’s tip affects the cut’s quality. Piercing too low may cause the molten metal to spatter – something you want to avoid. Use ATCH (automatic torch height control) to make precision cuts and avoid materials wastage.
5. Cutting Extremely Fast or Slow
Cutting too slow or too fast can result in faster utilization of the consumable and also cause other issues. For example, cutting too slow may result in a large accumulation of trash along the bottom edge of the metal piece. This may also cause excess top spatter and a wider kerf. Cutting too fast, meanwhile, causes lag back in the kerf, leaving rollover dross or a small hard bead of uncut material at the bottom edge of the cut piece. To perform clean edge cutting with minimal dross, follow the operator’s manual and set the cut speed accordingly.
6. Using Bottled Nitrogen
Operators often pick bottled nitrogen over bottled air because A) it’s cheaper B) it exhibits less oxidation. However, most plasma cutters use a hafnium electrode that eventually evaporates, causing them to misfire and leave behind dross until they stop functioning. Ideally, you should use compressed air because it helps hafnium electrodes last longer, which translates into a longer lifespan for the cutter.
7. Elongating the Arc
Another common mistake is ignoring the situation where the plasma cutter’s arc stretches to find the material you are cutting. This typically happens when a fabricator begins to cut the material or at the end of the cutting process. The arc stretching could cut the side walls of the nozzle beyond repair, costing you money in the future.
To avoid elongating the arc, point the nozzle opening directly over the surface of the metal you are cutting. Additionally, you can time the arch off signal and program the lead out to avoid arch stretching.
8. Poor Grounding
Working the CNC plasma cutter for a long period can result in the aging of the circuit, leading to poor grounding. If there’s an insulating layer on the ground wire, it will limit the standard function. The plasma cutter should have a separate grounding tool, and the operator should check the wiring for aging lines before use. Timely replacement of aging lines is key to achieving efficient grounding.
Above are some of the common mistakes to avoid with CNC plasma cutting. Remember that your CNC plasma machine is also a critical part of the process, so make sure to get the best fit for your project. If you’re yet to purchase a machine, we invite you to consult with our experts here at Squickmon’s before making your final decision. We’d love to learn about your project and recommend the best CNC plasma cutter for your work. Call us today!