SIMONA® Welding Rods are manufactured on state-of-the-art production lines. The raw materials used are carefully selected and always of premium quality. The granules are either ready-mixed or fed into the production lines by a gravimetric mixing and metering unit. The materials PE, PP, PVC, PVDF, E-CTFE and PETG are processed to form welding rods with various colours, dimensions and shapes, depending on customer requirements. 

In the manufacturing process the pre-dried granules are fed through a barrel by a multi- zone screw. They are heated and homogenised by friction and barrel heaters. Then the extrudate is pressed through the die. This is how the melt is given its final shape. When it has left the die, the continuous extrudate is fed to a take-off unit via a cooling section. When the welding rod has cooled down, it is either wound onto spools (2 kg, 10 kg, 25 kg) or cut to various lengths of rod. All bundles are weighed individually, categorised and packed. Quality assurance is performed daily by the company's own laboratory.

Applications in hot-gas welding

Hot-gas welding is one of the most important and oldest welding methods for thermoplastics. A very wide range of materials are processed such as PE, PP, PVC, PETG as well as the fluoropolymers PVDF and E-CTFE. The areas of use of the various SIMONA® materials are numerous, and they depend on factors such as operating conditions and temperatures, levels of chemical resistance and structural properties.

The methods used most frequently are hotgas string bead welding (for thin-walled components up to a maximum wall thickness of 10 mm) and hot-gas extrusion welding (as of a wall thickness of 5 mm). They are used to connect sheet blanks for constructing tanks, boxes, ducts, shafts, channels, linings (composite construction) and floor coverings. These methods are also used to connect pipes and piping systems, fittings for exhaust air, waste water and drinking water, as well as all types of profile.

The SIMONA® range of welding rods covers many different types of geometry in the various materials,

Fields of application of the various profile geometries

In the case of hot-gas string bead welding as per DVS Guideline 2207-3 a wide variety of profiles are used. Owing to the wide range of available die geometries and in view of its simple handling, it is the most well-known welding method on the market. The most proven method is to use round welding rods. They are used in sizes 3 mm, 4 mm and 5 mm depending on the cubic capacity of the welding joint and the geometry of the welding layer. The seam geometries are V-groove welds, double V-groove welds, bevel groove welds, double bevel groove welds and double fillet welds. Wall thickness is crucial when it comes to welding a seam economically. If the sheet thickness is greater than 10 mm, the method used normally is hot-gas extrusion welding because it is more economical and has a higher weld factor. Weld structure and structural design can be obtained by referring to the DVS Guideline.

In addition, triangular profiles (e.g. TA 80) are used for corner connections. The advantage of these geometries is that only one welding layer is required (depending on material thickness) to fill the welding joint neatly and achieve the required weld reinforcement. Other aspects are the minimal rework required, cost-effectiveness and perfect adaptation of welding joint geometry. A classic example of an application is a folded bracket. When round welding rods are used, at least two to three capping runs are required to fill the joint. This is time-consuming (preparation) and leads to an increase in material consumption. Triangular welding rods make it possible to perform the work more economically because the groove to be filled is only covered with one capping run.

Special types include three-core, oval and two-core rods which are used to connect thin-walled materials without any chamfer preparation (butt joint). They are only rarely used in Europe. The main fields of application are in the USA and Asia.

Influencing factors in welding

• Straightening of sheets being joined
• Standard-compliant chamfering (e.g. 30°)
• Dirt, grease, hand sweat and oxide layers must be removed by machining in order to obtain a high weld factor (scraper, plane)
• Avoid using detergents (acetone)
• Equipment (thermometer, air flow meter, oil and water separators)
• Bear in mind the influence of moisture, and pre-dry the rod if necessary
• To reduce stresses and strains in the welded seam, do not quench sheets but cool them down with air
• Warm the parts being joined evenly

Tips on plastic welding

All welding processes take place when the materials in the boundary areas of the surfaces being joined are in a ductile state. That is where the thread-like molecules of the parts being joined and pressed together link up and entwine themselves to form a homogeneous material bond. Only plastics of the same kind (e.g. PP and PP) can be welded to one another, and within these types only those with an identical, similar or adjacent molecular weight and the same density.