The accuracy of a plasma cutter is vastly superior to that of any previous method of doing the job, and CNC is more accurate than handheld, but there are still limits.
Factors that affect accuracy include the thickness of the material to be cut, the efficiency of the torch height control and the condition of the consumables: worn nozzles and electrodes result in less accurate work, so in addition to using the best machine available, it is essential to keep it well maintained.
Real World Tolerances by Material Thickness
If you are working with 3mm mild steel, you are likely to achieve better results than with 20mm or 30mm, purely because there is less resistance to deal with, and yet you should be aiming for a very similar level of success. In many cases it is a question of stepping up the skill with which your operators use your chosen equipment.
As a guide, with material less than 20mm thick you can expect ±0.5mm and the following:
20-50mm: ±75mm
50-100mm: ±1.0mm
100+mm: ±1.5mm
Machine Design vs Plasma Source: What Actually Controls Accuracy
The plasma source could be thought of as the muscle of the operation, the part that creates the plasma arc, while machine design would be the brain, controlling the precision, speed and accuracy. Without the plasma source there is no cutting, of course, but in the stellar world of CNC plasma cutting, it is the precision that makes the crucial difference.
The quality of the machine overall also has a direct influence on results. When buying machinery for plasma cutting work it is important to identify the level at which you wish to pitch your business and your budget should be set accordingly. While everyone in the engineering and manufacturing business might like to think they offer a superb service (or at least good for the prices they charge), even the best operators on the workshop floor are restricted by the equipment they are given to work with.
Having a plasma cutter is rather like having a car: it’s a step up from a horse or a bicycle, but it has competitors within its own field, and a low-cost runabout will not give the performance of a luxury model.
An entry level machine will typically not have automatic torch height control, which works to combat the effects of wear on consumables. With a better machine which does feature this, the operator has better control of cut angles and quality. Hole diameter is a factor here too, with smaller holes having a negative effect. Imperfections can include taper and bevel, resulting in a cone-like shape rather one that is the same diameter from top to bottom. There can also be divots and bumps, while very small holes can also be prone to dross appearing on the bottom edge.
Given a good rigid, lightweight gantry giving stability to the operation, a skilled operator using top equipment can focus on the plasma power source rather than worrying too much about drive systems and height control. The better the equipment, the more it will look after itself as regards the quality of the finished product. This applies to backlash too: the “play” in the system that wastes time in changing direction to make angles etc. Good nesting software optimises material usage to minimise waste and thereby reduces costs.
What is the True Test of a CNC Plasma System?
Perfect bolt holes, slots, and plough-bolt holes are the true test of a CNC plasma system, especially for structural steel and mining components. This is because it is essential for a hole to be bolt-ready without additional finishing, saving time and ensuring a smooth process. To learn more, visit Plazmax today.