Linear axis for precision, clearance-free welding seam bend testing device

• What was needed: drylin® SHT-linear system, drylin® W-linear guide
• Requirements: High positioning accuracy, as clearance-free as possible, robust, durable, lubrication-free, insensitive to dirt
• Industry: Plastics machinery
• Success for the customer: The bending test device for weld seams can test bending samples in accordance with DVS 2203-5 up to a plate thickness of 15 mm or a maximum force of 5,000 N. All lubrication- and maintenance-free and durable. What started out as a trainee project then went into series production.

Munsch plastic-Schweißtechnik GmbH stands for quality and reliability in tank and landfill construction. Simple handling and sophisticated design make the company's hand welding extruders a professional and uncomplicated tool for welding thermoplastics. Quality is the top priority in the development, production and testing of the products. For example, all devices must also function under difficult climatic conditions.
As part of their training at Munsch, two industrial clerks, four cutting machine operators and one technical draughtsman and one industrial mechanic formed a project team. The aim was to design a bending test device that could test the quality of a plastic weld seam in accordance with the relevant regulation, DVS 2203-5. This is a destructive test, the measurement results of which must be recorded or documented. When welding a wide variety of plastics, the bending device should test the quality of different weld seams, such as extruder or butt weld seams, and record the data.
The main criteria for the actual measuring process are the positioning accuracy and the zero clearance of the testing device. In addition, the topics of lubrication and maintenance-free operation, robustness and long service life of the entire machine, which will mainly be used on construction sites, are particularly important.

A spindle-linear system from the drylin® SHT range realises the format adjustment of the bending die in the bending test device. This is a lubrication-free linear axis that can be driven either with a trapezoidal or steep thread or a toothed belt. From lightweight all-plastic units to solid stainless steel solutions, the user will always find a customised solution. The stroke length can be freely selected for all systems and the drive can be optionally realised via hand wheel or motor.
Munsch specifically favours a standard solution with trapezoidal thread and motor. The shaft diameter of the linear unit is 12 millimetres. Hard anodised aluminium is used as the shaft material.
The three spans specified by the DVS are realised with a drylin® W linear guide. The cost-effective and pre-assembled linear rail with carriage allows maximum flexibility in design and easy assembly. To achieve the best friction and wear results, rail material made of hard-anodised aluminium is used. Particularly important for use on the construction site: as the drylin® SHT-linear axis completely dispenses with external lubrication, the system is extremely resistant to dirt. In the bending test fixture, the round double rail with housing bearing proves its robustness when quickly locking and absorbing the forces of the respective plastic test specimens. In addition to the two linear guides, an energy chain made of plastic is also used in the test fixture to measure the pressure of the test plunger. The test device was so convincing overall that the system subsequently went into series production at Munsch.

We worked closely with Munsch to develop a solution from our product range based on the technical specifications of the testing device. Once the ordered sample parts had been installed and the system was working, the two linear products were initially ordered in quantities of 1.
The project team's testing device was convincing and subsequently even went into series production. Regardless of the material, the machine can test bending samples in accordance with DVS 2203-5 up to a plate thickness of 15 millimetres or a maximum force of 5,000 newtons with a travel of up to 90 millimetres. The bending device is suitable for both workshop and construction site use and, at just under 29 kilograms, is also easy to transport. The test is carried out inside the supplied transport case, so that the device is well protected from dust, dirt and moisture.