Effects of process parameters on warpage of rapid heat cycle moulding plastic part

LIU Dong-lei(刘东雷)^{1, 2}, XIN Yong(辛勇)¹, CAO Wen-hua(曹文华)¹, SUN Ling(孙玲)¹

(1. College of Mechanical and Electrical Engineering, Nanchang University, Nanchang 330031, China;
2. National Engineering Research Center for Application Plastic Processing Technology (NERC-APPT),
Zhengzhou University, Zhengzhou 451002, China)

Abstract:The effects of process parameters in rapid heat cycle moulding (RHCM) on parts warpage were investigated. A vehicle-used blue-tooth front shell (consisting of ABS material) was considered as a part example manufactured by RHCM method. The corresponding rapid heat response mould with an innovational conformal heating/cooling channel system and a dynamic mould temperature control system based on the J11-W-160 type precise temperature controller was proposed. During heating/cooling process, the mould was able to be heated from room temperature to 160 °C in 6 s and then cooled to 80 °C in 22 s. The effects of processing conditions in RHCM on part warpage were investigated based on the single factor experimental method and Taguchi theory. Results reveal that the elevated mould temperature reduces unwanted freezing during the injection stage, thus improving mouldability and enhancing part quality, whereas the overheated of mould temperature will lead to defective product. The feasible mould temperature scope in RHCM should be no higher than 140 °C, and the efficient mould temperature scope should be around the polymer heat distortion temperature. Melt temperature as well as injection pressure effects on warpage can be divided into two stages. The lower stage gives a no explicit effect on warpage whereas the higher stage leads to a quasi-linear downtrend. But others affect the warpage as a V-type fluctuation, reaching to the minimum around the heat distortion temperature. Under the same mould temperature condition, the effects of process parameters on warpage decrease according to the following order, packing time, packing pressure, melt temperature, injection pressure and cooling time, respectively.

Key words:rapid heat cycle moulding; plastic part; process parameters; warpage