A siphon, as used in sanitary facilities in every household today, is a simple but effective solution for preventing unpleasant odors from the sewer system. Specially shaped pipe systems accumulate water in such a way that an odor trap is formed. Otto Haas KG in Nuremberg has developed a patented trap system that can be easily adapted to existing conditions, especially for renovation and replacement work.
For decades, Otto Haas KG in Nuremberg has been involved in the development and production of rubber and plastic products, which are sold in the sanitary, heating and air conditioning trade, as well as in medical technology, mechanical and automotive engineering and the wind power and solar industries. The company has also established itself as a problem solver. The patented suction siphon in Image 1 was developed for the replacement and renovation market. It complies with the relevant DI standards and can be infinitely adjusted in height by up to 65 mm. This avoids time-consuming work in the brickwork, even when changing the manufacturer of the sanitary ceramics. All ceramic manufacturers usually have different connection dimensions and distances. According to Otto Haas KG, the siphon therefore saves a lot of time, trouble and money.
Technically and economically, the implementation of the required functions is an outstanding achievement. In addition to the standardized connection sizes, fixing lugs are required on the assembly to ensure easy installation. Finally, smooth and tight height adjustment must be ensured so that the assembly is watertight and airtight at the end. In order to meet all these requirements, a minimum two-part construction is necessary, as the mechanism for adjusting the height is realized via two tubes that run into each other. Manufacturing the two individual parts in a single injection molding process is not feasible due to the geometry and numerous undercuts. As a result, the assembly has to be manufactured from four individual parts.
The joining methods available were adhesive bonding, laser welding or hot plate welding. Due to the significantly poorer process reliability and the space required, the components cannot be bonded. In addition to the short cycle time, laser welding of the four different assemblies was chosen due to the small space requirement of the joining process and the high level of cost-effectiveness. Compared to the alternatives, the tool costs for a laser welding process are comparatively low. Thanks to the high flexibility of the system technology, it is also possible to carry out both required welds on one welding system.
Another advantage of laser welding is the mechanical accuracy that can be achieved, which is particularly important with regard to the roundness of the individual parts of the siphon. Due to the very small heat-affected zone during laser processing, tight tolerances can be maintained here. Finally, the good possibilities of online process monitoring, the high achievable weld seam strength and the fact that no filler materials are required also spoke in favor of using laser technology.
Laser processing for material consistency
Laser welding involves joining a laser-transparent plastic with a laser-absorbing plastic. The laser beam is focused through the laser-transparent molded part onto the absorbent joining partner, causing it to melt on the surface. When the two parts are pressed together, heat is transferred to the laser-transparent plastic part. This melts both joining partners in this area of laser activity and creates a stable, materially bonded connection without major mechanical component stresses. The required joining pressure is applied from the outside by the clamping device. It is required in order to achieve the best possible gap-free contact between the components over the entire joining surface. As with all welding processes, the joining pressure must also be maintained during the cooling phase of laser welding in order to counteract the volume contraction of the plastic. In this way, defects in the form of blowholes, which impair the weld seam quality, can be avoided.
Quasi-simultaneous welding is used for the assembly processed here. In this variant, the laser beam is guided along the welding contour at very high speeds of up to 10 m/s using galvanometric mirrors. The aim is to scan the contour several times so quickly that the weld seam is heated and melted almost simultaneously. This makes it possible to bridge part tolerances by means of a joining path.
PP was selected as the material due to the mechanical requirements and high chemical resistance. In particular, the high resistance to cleaning chemicals was the decisive factor. The two black base bodies are each dyed black absorbent by adding pigment carbon black. Uncolored natural PP is used for the two laser-transparent lids. Taking into account the functional and production-specific boundary conditions, the design of the plastic parts was adapted to the requirements of the welding process. A processing zone that is easily accessible for the laser beam and the option of fixing the individual parts in a holder should be emphasized.
siphon (O. Haas KG)
The core element of the system is the laser with subsequent beam shaping and guidance. The beam is guided into a dynamic mirror system (galvanometer scanner) using a special optical setup. The scanner is followed by a plane field optic that focuses the beam into the processing plane. In order to process the complex shape of the weld seam, the laser beam scans it several times in succession. A special feature of welding the siphon is the 2.5-dimensional welding geometry, i.e. although the welding zone can be reached from above with the laser, it is not completely in one plane. However, this is not a problem during the process due to the large depth of field that is set optically.
Another module that is essential for production is the positioning and clamping unit for the two components to be joined. Interchangeable, component-specific fixtures and clamping techniques ensure exact positioning of the components before the welding process. As soon as both parts to be joined are in the correct position, the entire device is automatically moved into the welding position. Clamping is then carried out using a pneumatic cylinder in order to control the forces required for the welding process. During the welding process, online process control is carried out by means of joining path monitoring. Surface defects and soiling of the laser-transparent components can be detected with a pyrometer. This guarantees that 100% of contaminated components inserted into the system can be ejected.
Summary
The production of the siphon at Otto Haas KG shows that laser welding is an extremely economical process that can also be used for everyday products. Experience in series production – both with the process of laser welding plastics and with the welding system used – has been consistently positive. The clean and robust process guarantees a high output, even with the given fluctuations in the material and the complex component geometry. The system demonstrates high availability with extremely low follow-up costs. The low-maintenance laser and the reliable mechanical and electrical components contribute to this.
Do you have any further questions or would you like a personal meeting? Then please contact us on +49 9131 – 4088 – 1029 (Mr. Holger Aldebert) or send us an e-mail to sales@evosys-laser.com.
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