KOMADUR is made of thermoplastic materials. The sheets can be welded by means of familiar welding processes, such as hot-gas welding, heated-tool welding, folding and welding and friction welding, and using all pieces of equipment commonly available on the market.
Please always make sure before welding that the sheets in the welding zone have been properly cleaned with a cleaning agent or, better still, by machining.
After the welding process, and depending upon the kind of product and application, you have to decide whether the weld seams need finishing or not. Filing, planing, grinding or smoothing are suitable methods to finish the weld seams. In all cases, it is important to work with care in order to avoid notching.
Hot-gas welding (with welding rod)
When hot-gas welding with a welding tip, the sheet material and the welding rod are plasticised at the weld by means of heated gas (max. 0.3 bar, low- pressure blowers, e.g. from Leister, Wegener, Zinser, Forsthoff) and preferably oil and water-free compressed air, and are then joined under pressure.
The necessary welding rods are part of our production range; they are available as coils or as pieces in different lengths and with different profiles. Both manual welding and machine welding are possible. The market offers a wide range of different welding equipment and welding tips.
In particular, high-speed nozzles have proven themselves, enabling high welding speeds and producing good and reliable weld seams by evenly heating up the sheet and welding rod.
Semi-automatic welding units with mechanical feed are particularly suitable for series production runs.
The most frequent welds are the fillet weld, the single V and the double-V butt weld (see DIN 16930 and 16932). Thin sheets are joined by single-V butt welds, thick sheets by double-V butt welds. The latter should be produced by welding on both sides, alternately, to avoid warping and buckling. The standard values for the temperature of heated gas (measured in the nozzle) as shown in the accompanying table should be complied with in order to achieve weld seams with good welding factors.
Heated-tool welding (butt welding)
Another method of welding KOMADUR PVC sheets is the heated-tool welding procedure, in which tools of different shapes (circular, sword-shaped) are used. The perfectly smoothed-out and cleaned surfaces of the parts to be welded are heated up slightly by pressing them against the heated tool until they are plasticised. They are then pressed together.
This welding process is simple and time saving, and produces joints that are almost free of stress and capable of withstanding high stress.
As long as the welding conditions, which depend on the material (temperature of the heated tools, contact pressure against the tool, contact pressure when joining and immediate joining after plasticising), are adhered to, the strength of the welding seams is almost equal to the strength of the basic material itself. Please refer to the above chart for these heating and contact-pressure conditions.
The following parameters must be precisely adjusted and checked at regular intervals.
During the course of heating, the plasticised material forms a bead. Heating should be stopped when this bead is 1-2 mm thick. The contact pressure of the heated tool against the sheet must be set so low in order to avoid too much of the plasticised material being squeezed out of the plasticised zone.
Immediately after removing the heated tool from the sheet, the plasticised parts must be firmly pressed together until the material has hardened again.
Folding and welding
The folding and welding process is a modification of the butt-welding process. The sheet is resting on an even surface. The heated tool is placed on the sheet along the bending (folding) line as a cutting edge until it melts into the material.
The edge of the bar has an angle of 60° for rectangular folding. The bar should penetrate the sheet by up to 2/3 of its thickness, before it is raised again. Immediately on removing the bar, the sheet is folded and welded along the plasticised line.
In order to produce the necessary pressure at the heated bar, the angle between the edges to be welded must be 15° to 20° smaller than the folding angle wanted. If thick sheets have to be folded, the heating time can be reduced by milling a wedge-shaped groove into the welding line before applying the heated bar.
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