Whether prototyping or producing end-use parts, the goal is to work with a material that matches the final product as closely as possible. The range of materials for 3D printing continues to expand, and for German RepRap, includes Polypropylene (PP).

Recently, the X400 3D printer from German RepRap was instrumental in the prototyping of fans and ventilation components for Hürner-Funken GmbH, a company based in Mücke-Atzenhain near Gießen, Germany.

The engineers there have a need for rapid prototyping and small batch production.

Hürner-Funken manufactures fans and ventilation components for the chemical, semiconductor, pharmaceutical and electroplating industries. These products are made of plastic and can be used wherever fans, pipes, control flaps or volume flow regulators would corrode when around aggressive gases.

A typical product is a central exhaust air system for energy recovery, such as for university laboratories. The central element of these plants is a heat exchanger made from solid plastic installed in 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 pre-chilling.

Depending on the application, this also includes components such as filters, silencers, valves, chamber lighting for revision components, and so on. Free-standing centrifugal fans with optimized impeller efficiency and high efficiency motors are usually used to move the air.

“We have been using 3D printing and rapid prototyping for a long time now,” says Benjamin Wolf, head of the research & development department, “however, the stereolithography 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.”

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. They often use polypropylene (PP) as the principal material, which 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 with the 3D printing process. These are small batches of four to ten parts, and that need a 3D printer to produce hollow or only partly filled. “This firstly saves material and secondly weight – a critical factor in certain applications,” says Wolf.

Particularly in the area of prototyping, the ability to manufacture components oneself is worthwhile. “Previously, we often had to wait weeks until we received prototypes from the model builder,” says Wolf. “With the X400, this has been reduced to hours, sometimes days if we fully use the build envelope.”

3D printing is economical. “You can afford to make a reject,” Wolf adds, “and unusual solutions can be tried out without any problem.”

Wolf sums up: “The X400 from German RepRap has established itself here as an indispensable element of the development and production process. It is robust and reliable we can produce components in the original material quickly and economically. We save weeks in the prototype stage and can offer our customers more bespoke solutions – for us the X400 from German RepRap is a gain for the entire line.”