Lysholt Alle 8
DK – 7100 Vejle
Energy supply chains for three axes having different lengths2
Linear slide bearings
In flame cutting, the cutting machine consists of an annular hot nozzle and an oxy-fuel cutting nozzle located at the centre. The workpiece is heated to ignition temperature, then the gas supply is opened. The escaping oxygen oxidises the steel of the workpiece. The cutting slag has a lower melting point and is thinner. The slag is blown out of the joint by the gas, the burner carried on in such a way that the burner cannot introduce sufficient energy in the workpiece and is unable to melt it. The result is a clean kerf strongly demarcated from the base material. From the appearance of the kerf it can be seen whether the introduced heat and the feed rate are correct. As fuel gases, acetylene-oxygen or oxygen-propane mixtures are generally used.
Particularly steel, stainless steels and titanium and titanium alloys can be cut by flame cutting. Here the limits are above all set by the ignition temperature of the material. This must be lower than its melting temperature. In addition, the cutting oxygen has to have a minimum purity of 99.5%. The carbon content must be between 0.1 and 1.5%. Advantage of flame cutting is that it is very cost effective from a workpiece thickness of 30/35 millimetres. But, other methods are more suitable for thinner workpieces.
The plasma cutting method is used for cutting electrically conductive metals. Here an electrically conductive gas is used. A basic plasma arc cutting system is composed of a power source, an arc starting circuit and a burner. A high-frequency circuit is started between the nozzle and the electrode. The gas flows through the emerging arc. The resulting plasma arc is forced out by the gas flow and creates a pilot arc. The temperature of the plasma arc is approximately 30,000°C and melts the metal and penetrates the workpiece. The high velocity of the gas flow hurls out the molten material from the bottom of the kerf. The procedure is very inexpensive, and mild steel can be excellently cut with fine jet plasma. The quality of the cut with a plasma cutter is however not as high as in other methods. In addition a scale layer forms on stainless steel in some cutting machines, whereby the material is therefore unsuitable for a welding connection. With plasma cutting, any electrically conductive metal can be cut. However, the cut quality is not as high as in the case of laser cutting.
The work pieces are the least thermally stressed in laser cutting, because the heat is concentrated only on a very limited area of the workpiece due to the highly focused laser beam. Thereby only a short action time is required, which allows cutting at a high speed. In laser cutting almost any material can be machined (in addition to steel and leather, plastic, PVC, wood, glass, etc). With the method, the workpieces can be cut precisely with dimensional accuracy. Disadvantages of this method are a high energy consumption and high system procurement costs.
In water cutting - or water jet cutting - the workpiece is separated by a high pressure water jet. Thereby the nozzle shoots out the water with a pressure of up to 6000 bars and exit speeds of up to 1000 m/s. The material gets hardly heated compared to the three other previously described methods. There are basically two different types of water jet cutting: Cutting with pure water and cutting with abrasive agent. In pure water cutting only the beam energy of the water is utilised. The cutting performance is very limited in hard materials. But nowadays this also allows materials like aluminium of about four-millimetre thickness to be cut with a 6000-bar water jet without the use of abrasives. If a cutting agent is added to water (such as garnet or corundum) it is known as the water jet cutting with abrasive agent. Thereby harder materials can also be cut. In order to reduce the high pressure of the water, the jet must be trapped in a water basin. Thereby the temperature of the water in the basin increases. Advantage of water cutting is that it is free from thermal influences on the material to be cut. There is also no restriction in the thickness of the workpiece. Various materials such as wood, metal, aluminium, plastic, or food can be cut with it, here too the cutting edge quality is very good. But the cutting speed is relatively low and the moisture and the water contact in particular can be a disadvantage for some materials.
By the combination of various methods the advantages of the individual systems are bundled and reduces the possible disadvantages. The most frequently used are plasma flame cutting combinations. Thus, both thick and thin plates as well as massive steel parts can be cut.
Machines for plasma/water jet cutting are rare, because very few companies are able to combine both technologies. With this combination, the advantages of the very clean cutting with water are combined with the high cutting speed of plasma cutting.
The e-chain systems® and chainflex® cables from igus® can ensure high holding times in all cutting machines through a long service life. The energy supply and hose routing are ensured by the energy chains. Glass fibre cables and water supply lines can be installed even in a small space. Thereby the chain length can vary from system to system. Therefore: The cheapest solution that works technically is the right solution. For this reason, manufacturers of cutting systems can make energy chains specifically adapted to their size. In water cutting, it is also important that water and waste water are not contaminated with lubricants.
Less production complexity