Vacuum Assisted Multipoint Moulding – A Reconfigurable Tooling Technology for Producing Spatially Curved Single-item CFRP Panels

Abstract

Carbon fibre reinforced plastics (CFRP) are widely used in all scales from single items to mass products mainly due to their lightweight properties. However, manufacturing of CFRP single items and small batches is highly resource extensive. Mould making is one of the main cost factors. Multipoint tooling replaces the commonly used solid mould with an array of individually adjustable pins to create a desired shape. This shape is then smoothened by an elastic sheet to create a viable tooling surface. This technology has been adapted to various applications from metal stretch forming to thermoforming. In this paper the principal design parameters for multipoint tools are identified and therefrom a concept for CFRP prototype manufacturing is derived. This vacuum assisted multipoint moulding concept modifies the multipoint tooling concept to meet the specific demands of the composite manufacturing process. The general idea behind the technology is to introduce a vacuum to pull the elastic sheet onto the pin array. By evacuating the space underneath the interpolation layer it is pushed on the pin array and therefore enables the creation of convex and concave surfaces in an open mould configuration. To validate the concept, a prototype is built and first moulding tests are conducted. The influence of the interpolation layer in surface quality is evaluated qualitatively. It is found that its thickness has great influence and over a threshold value defect free surfaces can be created. The technology shows the potential to create numerous shapes and enable cost efficient manufacturing of CFRP panels.