Two=part plastic component mfr. - involves premoulding 1st part placing in tool cavity, introducing further polymer into cavity void and compressing to prevent sink marks in 2nd part

摘要

Mfg. a component, comprising two individual parts which are integrally combined, involves (i) premoulding the first part; (ii) locating first part in a tool cavity corresponding to the final prod. shape; (iii) feeding melt through a channel to fill a void between the first part and the cavity walls; and (iv) closing off the feed channel, compressing the melt in the cavity void and cooling to produce a single component comprising two combined parts. Process equipment comprises (i) first and second tool halves; (ii) a cavity in the tool corresp. to final prod. profile and having an end section forming a void fed with melt through a channel; (iii) a bore directly entering the hollow void and housing a pressure pad pushed to and fro by a piston to compress melt fed into the void. The second part of the product is pref. produced from a thermoplastic melt e.g, copolymer of styrene-ethylene, butyl and styrene, rubber modified polypropylene. USE/ADVANTAGE - For mfg. a prod. with long main part and a combined end piece e.g for fitting to vehicle bodywork. Prevents sink marks in the end pieces during cooling and also prevents gaps between the two parts, therefore improves appearance.