Coolant for the Wet Machining of Fibre Injected Plastic

Reducing the weight of moving masses is one of the primary future goals in the automotive and aviation sectors. Due to their outstanding weight-related stiffness, fiber-reinforced plastics (FRP) offer enormous potential for achieving this goal. Despite near-net-shape FRP production by RTM or prepreg processes, the edges of the parts must be trimmed after curing (e.g. removal of pure resin areas at the edges of the parts). Furthermore, joints as well as cut-outs and apertures are made. In the majority of processing companies, this trimming is carried out on CNC machining centres - i.e. machining. Currently, the industrial use of cooling lubricants (KSS) in the machining of FVK plays only a minor role. However, dry machining has some serious disadvantages:
- Glass or carbon fibres are very hard and lead to high tool wear and the resulting very high tool costs
- FVK dusts are a hazard for process and machine safety. Furthermore, there is uncertainty in Germany about possible health hazards. The use of coolant lubricant offers an advantage here, as the dust is bound directly to the cooling lubricant. An energy-intensive extraction system, which can never completely capture the dust, is therefore not required.

The aim is to use cooling lubricants to reduce tool wear and increase productivity and thus reduce costs in finishing operations, while at the same time improving occupational safety and machine safety.

The focus of the research project is on the development of a cooling lubricant tailor-made for FVK machining and a machining process adapted to it. By means of laboratory tests, the compatibility with plastics, adhesive and paintability, as well as sliding friction coefficients in combination with selected FRP materials are analysed. Based on the results of the laboratory tests, the composition of suitable basic coolant concentrates is carried out. These are evaluated in machining tests with regard to their effect on tool life, machining quality and machining performance. In feedback with laboratory tests on machined FVK samples the iterative fine composition is carried out. In parallel, the requirements for the filtration degree of the coolant are determined. In addition, suitable wet tools are to be identified which, in interaction with the optimum coolant, lead to longer tool life at increased machining speed.

Cooperating Research Association: Carbon Composites Leichtbau gGmbH