Quantified Surface Improvement Using Temperature Cycle Injection Moulding

Abstract In temperature cycle injection moulding (TCIM) of thermoplastics, the mould cavity surface is heated rapidly to a temperature close to the glass transition or crystalline melting point of the resin before melt injection, and then cooled after injection is complete. A range of important benefits of the process are listed, among which is surface improvement, and results are presented that quantify in detail the improvements achhieved. Weldline dimensions and surface roughness are determined using white light inteferometry, with a scale of inspection below 5 nm. For a qualitative comparison of the surface finish, photography and stereomicroscopy are used. Weld lines on conventional ABS/PMMA parts are up to 17 μm deep and 70 μm wide, hence clearly visible, whereas they are not detectable on TCIM parts. Surface roughness, Ra, on these parts is found to be 37 nm for conventional parts, reducing to 20 nm using TCIM. Surface roughness is compared for conventional and TCIM mouldings in chemically foamed A...