ThinKing April 2020: Even steel can be lightweighted: New method is resource-efficient, cost-effective and suitable for series production



German manufacturing company MIMplus has redesigned its air conditioning flange from scratch, thereby improving it in several areas: The flange’s alternative material, resource-efficient design and functional optimization all lead to better energy efficiency of the air conditioning system. 

In addition, the company manufactures the component using the metal injection moulding method, thus ensuring competitive component pricing and making the manufacturing process highly suitable for large-scale production.

The Development Agency for Lightweighting Baden-Württemberg presents this innovation in its April 2020 edition of ThinKing. Under this label, Leichtbau BW GmbH provides a platform every month for new innovative lightweighting products or services from Baden-Württemberg.

At a glance:
- Smaller and lighter, therefore better
: Function-oriented, material-efficient design reduces weight by 20 percent
More cost-efficient, as machining stainless steel would be too expensive – the move from aluminium to stainless steel only becomes possible through metal injection moulding
More energy-efficient, as the air conditioner uses less electricity

“It wasn’t actually the thought of lightweighting that motivated us,” Sales Director Thomas Klein openly admits. “Initially, we were more concerned with the material: We needed the air conditioning flange to be made of stainless steel so that it could be welded to the corrugated hoses of the air conditioning system for a good seal.” An air conditioning flange is a component in CO2-based air conditioning systems in cars – the demand for such systems is expected to increase in future, especially for electric vehicles. The new, small and lightweight stainless-steel flange measures 35x18x10 millimetres and replaces a machined component made of aluminium. The nature of the latter material meant that considerable effort was needed to join the outlet of the component to the steel corrugated hoses.

However, simply changing the material would not have worked – because the stainless-steel component is about 60 to 70 percent more expensive to machine than its aluminium equivalent. The team at MIMplus therefore decided to use the manufacturing method known as Metal Injection Moulding (MIM). With this method, the quantity of material used determines the subsequent component costs. In a joint project with an automotive supplier, the air conditioning flange was therefore optimized with regard to mass accumulation in the component. “We have reversed the way of thinking in product design: MIM design requires additive thinking, optimum material use is at the centre of this process,” Thomas Klein explains. This allows for the lighter components to be competitively priced due to lower parts costs.

The new stainless-steel component, manufactured by metal injection moulding and designed to be resource-efficient, is now around 20 percent lighter. The height of the prototype has been reduced by around 50 to 60 percent, thus requiring less installation space. Using this extra space, the tubes can then be assembled for optimal flow, allowing the air conditioning system to operate more efficiently due to an improved flow rate – all thanks to the new lightweight component.

“The metal injection moulding process itself allows for complex geometries that almost correspond to the possibilities offered by plastic injection moulding,” Thomas Klein explains. As this is an injection moulding process with comparatively short cycle times, it is particularly suitable for the cost-effective production of large quantities. The process comprises four steps: compounding, injecting, debinding and sintering.

“I am convinced that, for about 30 percent of all constructed metal components, this method can be used to reduce the amount of material needed, and thus the weight of the component,” Thomas Klein says. Following this recent project, he sees a lot of potential in lightweighting – even in other areas of application. “The important aspects that need to be considered here are function integration and material optimization. For our air conditioning flange, we are now looking for a partner to commence series production of this component.”

About MIMplus Technologies GmbH & Co. KG
MIMplus Technologies GmbH & Co. KG offers innovative freeform production technologies, designing and producing sophisticated components or assemblies for various industries. The company’s focus lies on materials with complex geometries that are difficult to machine. It forms part of the family-owned company OBE Holding GmbH, which is based in Ispringen, Germany, and operates internationally. Another of the companies belonging to this holding is OBE GmbH & Co. KG, one of the leading suppliers of hinges and safety screws for the eyewear industry.

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