Plasma cutting is undoubtedly the most popular CNC cutting technology. Taking advantage of the many years of experience of Eckert, we have decided to create a collection of plasma cutting tips based on the problems we encounter on a daily basis. We hope that they will make the work of cutting machine operators easier and encourage them to take better care of the machine.

Problems that can occur during plasma cutting

A common problem that leads to unplanned interruptions in the process is collisions between the torch and the workpiece, even though a height sensor is installed. These can have various causes, e.g. wear of wearing parts that lead to incorrect alignment of the torch height. In this case, the torch height must be corrected and the wearing parts replaced. However, there are methods that can easily eliminate the problem of collisions. The simplest method is to program the cutting of shapes so that the torch moves around the cut parts and not over them. The second solution, which has been used as standard in Eckert plasma cutters since 2010, is Intelligence Distance Control - a height adjustment system that ensures consistent cut quality and collision-free cutting even after 1000 piercings, as well as protection against torch damage caused by chipping. The system is an addition to the HD3000 and Vortex 3D plasma slides.

Torch mounting on plasma cutting machines

Another important point is the correct assembly of all torch components. This is necessary to ensure proper electrical contact and correct gas and coolant flow. When replacing parts, it is important to store the consumables correctly. Above all, they should be protected so that dirt and metal dust cannot contaminate the burner. When lubricating the sealing ring, please note that too much grease can clog the gas swirl element and contaminate the burner with metal dust. The burners must not be smeared with grease. This can lead to ignition inside the burner.

Time for replacing consumables

Operators, especially the less experienced ones, are not always able to determine the optimal time to replace consumables and perform this operation too early or too late. The use of excessively worn parts can lead to the destruction of the processed sheet metal, but also to torch failures, which are very costly to repair and cause an unnecessary interruption to processing.

The optimum time to replace parts can be determined in various ways:

• by analyzing the sound that accompanies the cut and the color of the sheet,
• noticing changes in the height of the flare,
• regularly checking the quality of the cut parts. 

If the operator records the service life of the parts, he can determine the time to check the parts and thus avoid a serious failure.

The appearance of excessive slag on a cut part can be the result of cutting too slowly or too quickly. If the speed is too slow, so-called "slow slag" can occur, which is deposited along the bottom edge of the workpiece. Another sign of this error is a cutting gap that is too wide and the appearance of excessive spatter at the tip. Conversely, if the cutting speed is too high, the edge will be cut at an angle and small and hard lumps of slag will accumulate along the bottom edge. This type of slag is particularly difficult to remove. The occurrence of any of the phenomena described should alert the operator to correct the cutting speed.

Influence of the amperage on the cutting quality

Does the amperage have an effect on the cutting quality? Of course it does. The cutting process and the wearing parts are negatively affected by current values that deviate from the optimum. The optimum current value is 95% of the nozzle output. Too low an amperage leads to a poor cut, while too high an amperage has a negative effect on the service life of the nozzle.

A major problem is insufficient coolant and gas flow. In the case of coolants, insufficient cooling of consumables leads to a shortened service life. Too high a flow, on the other hand, is the reason why the torch cannot ignite the arc even though all other conditions are met. It also leads to accelerated electrode wear. Particular care should be taken to ensure that there is no contamination from oil, moisture or particles.

One final piece of advice that can prove crucial and prevent many breakdowns is to carry out routine maintenance. Properly maintained burners can last up to several years.

The most important thing is that you follow a few rules:

• Make sure that the burner threads always remain clean
• Immediately remove any dirt, metal dust and excess grease that has settled on the sealing ring
• It is recommended to clean the burner with a cotton bud and electrical contact cleaner or hydrogen peroxide.

By following the above rules, the operator makes his work easier, protects himself from unplanned downtime and extends the service life of the cutting machine. A problem that is detected and rectified in good time also reduces the risk of incurring high costs for repairing the machine.