Prototypes from Polypropylene: The German RepRap X400 in Operation at Hürner-Funken

Rapid prototyping and small batch production – 3D printer operation at Hürner-Funken is very typical of the sector and therefore a good example of the benefits that 3D printing can bring to the daily work of a development department.

Prototypes from Polypropylene: The German RepRap X400 in Operation at Hürner-Funken

Rapid prototyping and small batch production – 3D printer operation at Hürner-Funken is very typical of the sector and therefore a good example of the benefits that 3D printing can bring to the daily work of a development department. Since 2013 the X400 from German RepRap has been providing excellent service in the production of special series, function samples and prototypes for these specialists in fan and ventilation systems based in Central Hessen.

Hürner-Funken GmbH was founded in 1928 and has manufactured fans and ventilation components ever since. The main application areas include the chemical, semiconductor, pharmaceutical and electroplating industry, since Hürner-Funken products are made of plastic and can be used wherever fans, pipes, control flaps or volume flow regulators, would corrode due to the presence of aggressive gases. Hürner-Funken GmbH is a company based in Mücke-Atzenhain near Gießen, where around 95 employees work at its headquarters.

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Serial Production German RepRap X400

A central exhaust air system for energy recovery, such as for university laboratories is a typical product of this company. The central element of these plants is a heat exchanger made from solid plastic installed the integrated circuit system, which extracts valuable energy out of the exhaust air flow in the form of heat or cold and feeds it to the outdoor air for preheating or prechilling. Depending on the application, this also includes components such as filters, silencers, valves, chamber lighting for revision components etc. Free-standing centrifugal fans with an optimized impeller efficiency and high efficiency motors are usually used for conveying the air.

Benjamin Wolf, head of the research & development department recalls: “We have been using 3D printing and rapid prototyping for a long time now, however, the stereo lithography equipment available at the beginning was of no use to us due to the limited selection of materials – we wanted to print with a material that would match the final product as closely as possible.” While completing a project with a university Wolf then came across a 3D printer for the first time. The project participants were printing prototype parts for the project on their own 3D printer. “This went very well,” Wolf recalls. “We requested a bachelor thesis for the evaluation of a printer for our needs. The market analysis included the coverage of available materials, the build envelope and the price of the different devices and processes.” The clear winner of this study was the X400 from German RepRap, which according to Wolf’s assessments “stood out with the largest build envelope and an unbeatable price/performance ratio.”

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Clamping Element made of PP

The developers and designers at Hürner-Funken GmbH produce prototypes on the X400 – sometimes as scaled down models, but at full size if possible – as well as sample parts for their own tests or for customers and for producing small batches. Here the employees at Hürner-Funken very often use polypropylene (PP) as the principal material, which, however, tends to be considered as a rather exotic material for use in 3D printing.

“We have been working almost exclusively with PVC and PP since 1928 and therefore have a lot of know-how about handling the material,” Wolf explains. “Processing in the X400 with its closed build envelope is very straightforward. Printing in PP is very important for us as the standard 3D printer materials PLA and ABS materials are not resistant to chemicals. With PP we therefore have virtually the same material properties with the 3D printed prototype parts as in the injection molded series production.”

Hürner-Funken now manufactures specific parts only with the 3D printing process. These are firstly for small batches of four to ten parts and also parts, for which the ability of the 3D printer to produce hollow or only partly filled parts is an important factor. “This firstly saves material and secondly also weight – a critical factor in certain applications,” says Wolf.
Particularly in the area of prototyping, the ability to manufacture components oneself is worthwhile. “We often previously had to wait weeks until we received prototypes from the model builder,” Wolf explains. “With the X400 this has been reduced to hours, sometimes also days, if we fully utilize the build envelope.” 3D printing is also very economical if you compare the price for a prototype with the price structure of a model builder for manufacturing. “You can then also afford to make a reject,”  Wolf adds, “and unusual solutions can be tried out without any problem.”

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Benjamin Wolf, Head of Research & Development at Hürner-Funken GmbH