A novel adaptive process control for injection moulding of BMC and CIC polyester compounds

Abstract

The formulation of unsaturated polyester Bulk Moulding Compounds (BMC) or Continuously Impregnated Compounds (CIC) induces a variation of their reactivity or viscosity, which reflects the heterogeneity of the material batches produced. This experimental study has pointed out the benefits brought by an advanced process control of the injection moulding holding stage (feedback control on the polymer pressure in the mould cavity with automatic set up of holding time) compared to a regular process control (feedback control on the hydraulic pressure). The advanced process control actually leads to the reduction of the scattering observed on bulk (weight, specific gravity), surface (porosity, roughness) or mechanical properties (Charpy impact strength). It allows smoothing the thermal perturbations induced by a manufacturing start-up, as well as the rheological perturbation due to the material batches heterogeneity that are frequently encountered in the unsaturated polyester compound injection moulding industry. This scattering decrease, centred on the mean value of the target properties, directly involves significant quality and productivity improvement.