The process of cutting steel, stainless steel, aluminum, brass, copper, and other electrically conductive metals using an accelerated jet of hot plasma is called plasma cutting. Plasma cutting with is widely used in manufacturing, industrial construction, automotive repair and restoration, scrapping, salvage, and other industrial CNC applications due to its high speed, precision, and low costs. Compressed gases contact electrodes and ionize to create pressure. This creates plasma which is pushed towards the cutting head and applied to the workpiece.
The components used in CNC plasma cutters, called consumables, are present in the cutting torch. The consumables include a swirl ring, nozzle, electrode, and retaining and shield caps. All the energy is focused on these consumables. Hence, it goes through gradual wear and tear over time, requiring them to be replaced at intervals. It is necessary to be wary of such wear and tear to ensure that the consumables are maintained well for the parts to last longer. This blog aims at providing you with an understanding of the symptoms and factors that reduce the life of consumables and ways to elongate the life of the parts.
Factors that Reduce Part Life
The most common symptom of reduction in the life of consumables is the premature failing of the electrode and nozzle. This will deteriorate the quality of the cut, cause failure to pierce, or lead to loss of arc amidst a cut. The first step is to match your industry requirements to the machine features such as duty cycle, amperage, material type, speed, cutting capacity, weight, and other features before investing in the most suitable CNC plasma machine. Here are a few factors that lead to the reduction in the life of the parts of CNC plasma cutters:
1. Consumable Set
Using the wrong set of consumables even if the parameters are correct will also shorten the life of the consumables.
2. Current Setting
Unlike automatic systems, setting the current manually, if done incorrectly, can damage the nozzle. Operators need to be cautious about setting the current when it is done manually.
3. Cutting Parameters
It is important to feed the correct settings concerning kerf width, arc voltage, gas pressure, and flow rates, cut speed and amperage, pierce time, etc., in CNC plasma cutting machines. This can simply be done by using a built-in database for setting the parameters.
4. Gas Flow
The plasma gas constricts the arc when it flows through the nozzle orifice and cools the nozzle.
The boundary layer of cool gas prevents the nozzle from melting. Insufficient gas flow will heat the nozzle and result in its melting.
5. Coolant Type
Wrong coolants will reduce electrode life. Using the right kind of freeze protection, coolant mixes, and the right mix with water is necessary to maintain the life of consumables.
6. Coolant Flow
When an electrode emits lots of power, it generates heat. Lack of adequate coolant fluid flow will result in the failure of electrodes. Replacing electrodes, nozzles, electrode holders, gas baffles, and other parts damaged in the process can reduce this risk.
7. Running off the Plate Edge
The arc tends to snap off if the torch is driven off the edge of the plate. This causes electrodes to wear more and damage the orifice. The best practice is to initiate the proper shutdown sequence by shutting off the plasma in the scrap area.
8. Pierce Height
A large amount of piercing spatter is released when a plasma torch pierces. Piercing when the height between the torch and plate is close will end up in the spatter contacting the shield or nozzle, resulting in melting or double-arcing. A plasma height control system sets correct piercing heights and prevents this.
9. Torch Damage
The plasma torch can be obstructed, causing it to crash if the plate pops, is tipped, or has slag on top of it. Contact of the nozzle with the plate while cutting causes double-arcing or orifice damage.
10. Contaminated Gas or Water
Damages to nozzles can also occur when the plasma gas has impurities that deposit inside the nozzle. The same applies to impurities in water injection nozzles.
Ways to Extend Plasma Cutting Machine Consumption Parts’ Life
A few ways to extend the life of CNC Plasma cutting machine consumables are as follows:
- Ensure the maintenance of the correct air pressure and flow of the plasma
- Select a reasonable distance between the workpiece surface and the cutting nozzle so that the power consumption, penetrating ability, and electrode consumption is maintained correctly
- The thickness of perforation should not be more than the thickness of cutting to protect the cutting nozzle
- The plasma cutting machine should not be overloaded
- Do not cut too quickly, too slowly, or at the wrong distance; your workpiece will quickly wear out
- Install the components/consumables correctly, including matching the tolerances of the consumables
- Keep track of the components used and their wear to prevent premature degrading
CNC plasma cutters are gaining more popularity due to their application and advantages. Its importance to industries has made the question of long-life consumables a feature that helps plasma machines stand out. Manufacturers are increasingly focused on technological innovation to consumables, advanced thermal modeling technology, special manufacturing processes, and the application of new materials. To prolong the life of consumables, you must choose the right plasma machine, automate the system, reduce slag buildup, pilot time to transfer, use proper coolant type, inspect the flow, and carry out regular maintenance. Increasing the service life of consumable parts will significantly reduce the operating costs of your manufacturing process.
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.