Equipment for mass manufacturing of carbon parts

February 17, 2014 7:16 am

  RTM presses offer short cycle times and high part quality
Carbon fibre-reinforced plastics (CFRPs or simply carbon) have been used for the manufacturing of cars for several years now. As the ultra-light, extremely rigid material is much more expensive than steel or aluminium; however, it is rarely used in mass manufacturing processes. Schuler now offers lines which can economically produce CFRP parts – even in large volumes.
For the manufacturing of carbon parts, Schuler uses the RTM (Resin Transfer Moulding) process in which woven carbon fibre mats are placed in a die, filled with resin and hardened by applying heat and the pressure of the press. “High-pressure RTM presses not only enable shorter cycle times for complex parts with high requirements regarding geometry and rigidity, but also deliver consistently high part and surface quality,” says Product Manager Raimund Zirn. This virtually eliminates so called voids, i.e. resin-free vacuum pores or gaps within the part or along its edges.
In the high-pressure RTM process, resin is injected as quickly and smoothly as possible into the vacuum mould which is opened by just a few tenths of a millimetre. This gap injection process enables the resin to spread over the mat with far less flow resistance and thus with low injection pressure. It then quickly infiltrates the mat before polymerisation is started by heat induction.
The curing process begins with the wetting of the last fibres“The vacuumising, fast resin injection, high resin pressures and tempered dies mean that the gelling process virtually begins with the wetting of the last fibre,” explains Raimund Zirn. Curing takes 4-8 minutes – the thicker the part, the longer, as the reaction heat cannot be led as easily into the die. Depending on the part, the necessary resin pressures also vary between 30 and 150 bar. Large-surface exterior panels with clamping areas of 3,600 mm x 2,400 mm require total press forces of 36,000 kN or more.

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