Kompendium

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What worth to know about plasma cutting?

Plasma cutting is surely the most popular CNC cutting technology. Due to many years of our experience in machine construction and manufacturing we decided to present some advices for plasma cutting. Our base were problems which we met in daily work. We hope they can make easier machine operators work and will incline to better caring for cutting machine.

They are frequent problems unplanned process pauses. Their reason can be for example collision of torch and cut material. It can happen even if machine is equipped with height sensor. One of the possibilities is too long lasting spare parts exploitation that leads to disadjusting of torch height. In this situation there is necessary to make correction of torch height and exchange of spare parts. But there are few ways which can eliminate collision problem. The simplest method is programming shapes cutting in order to move the torch around cut parts instead above them. There is also second solution. It works since 2010 and works as standard in plasma Eckert cutting machines as Intelligent Distance Control. This is system of height adjusting that ensures constant cut quality and lock of collision even after 1000 piercings. It also protects from torch damages because of splashes. System is complementar part of plasma HD3000 supports and it is available even for Vortex 3D cutting head.

Another important thing is suitable assembling of all torch elements. It is necessary for achieving of needed electrical contact and flow of gas or coolant liquid. You should remember about suitable exploitation part storage during spares exchanging. They should be secured to prevent from torch pollution or metallic dust. Grease shouldn’t be put directly on torches. It can be reason of ignition inside torch.

Operators, especially less experienced, are not always able to define optimal time for spare parts exchanging. They do this too late or too early. Using of too used spares parts can lead to cut plate damaging or to torch accident that will be expensive for repair and will make unplanned pause of cutting process. Optimal time of parts exchanging can be specified for few ways:

  • analysis of sound and arc colour during cutting,
  • changes of torch height,
  • periodic checking of cut parts quality.

If operator makes suitable notes about spare parts durability, he is able to define moment when he should control them and then avoid an accident.

If there is excessive amount of slag on cut details, it can be consequence of too slow or to fast cutting. During to slow cutting there can be generated “slow-moving slag”. It settles along lower cutting edge. Other sign of this problem is too wide cutting gap or excessive amount of splatter on top. In the opposite situation - if speed is too high, edge is beveled and along lower edge there gather small and hard slag drops. This slag kind is especially hard for removal. Appearance of any of described occurrence should note operator to make correction of cutting speed.

Does electricity voltage have influence for cutting quality? Of course. Voltage values, if they are different from optimal, have negative influence for cutting process and spare parts. Optimal voltage value is about 95% of nominal value of nozzle. Too low voltage results weak cutting but too high voltage has negative influence for nozzle durability.

Big problem is incorrect flow of gas and coolant liquid. In case of coolant liquid, inadequate spare parts cooling results their lower durability. Too strong flow is reason of situation when torch is not able to ignite arc despite fulfillment of  all other terms. There fallow also faster electrode consumption. It is especially important to avoid pollution from oil, moisture or dust.

The last advice can come key and prevent from many accidents. We mean routine conservation actions. Suitable maintained torches are able to work many years. But it is important to follow some rules:

  • pay attention if torch treads stay clean,
  • immediately remove all pollution, metallic dust and excess grease from sealing ring,
  • use cotton pledget and contact cleaner or hydrogen peroxide for torch cleaning.

Following mentioned above rules, operator makes his work easier and protects himself from unplanned pauses and extends cutting machine lifetime. Every problem that is immediately observed and defused, reduces also risk of bearing of cost of machine repair.