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Plastik Welding

Hot Gas Welding

A hot gas (usually air) is passed to connect the films which are plastically at this point. By pressing together the films and cooling, the molecular chains of the films network and the connection is established. The disadvantage of the hot gas welding is the high energy losses and the resultant low efficiency.

 

Contact Or Pulse Welding

The contact welding is performed with the aid of forceps-shaped contact rails. To be welded, the films are placed between the contact bars, and by the closing of the forceps, the required heat and the pressure exerted. If the duration of the heating can be adjusted on the welding machine, it is called pulse welding.

Contact welding is called discontinuous welding process, since only small areas can be welded and the welder has to be placed new for each welding process.

The disadvantage of the contact welding is that the films are heated directly only on the outer sides, even though the heat is actually used on the inside. This results in loss of energy, and efficiency decreases.

 

RF Welding

When high-frequency welding, the chemical structure of some plastics is exploited. One distinguishes the neutral plastic types (without dipoles), such as Polyethylene (PE), polypropylene (PP) and polystyrene (PS), of the polar plastic materials (with dipoles), such as Polyvinyl chloride (PVC), polyamides (PA) and acetates. As dipoles two opposite electric or magnetic poles are designated.

To be welded, the films are exposed in this process to a high-frequency alternating electromagnetic field, whereby the dipoles of the plastics can be excited. By this excitation, it is coming to heat, and by the subsequent application of pressure, the films are joined together.

The advantages of this method are firstly the fact that there is a continuous welding process and larger areas can be edited without removing the welding machine. On the other hand, you can work with this method very accurate, because only the areas have to be heated, which are really have to be connected.

A disadvantage is the limited applicability because only plastics can be welded with dipoles.

 

Ultrasonic Welding

In this method, ultrasonic waves generate heating by an inner friction in the films. Both, the inside and the outside cause the same temperature so that no losses occur. By pressurizing the warmed surfaces are then bonded together. Ultrasonic welding is, such as the high-frequency welding, a continuous welding process.

 

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