Experimental research on the effects of cavity surface temperature on surface appearance properties of the moulded part in rapid heat cycle moulding process

The influences of the cavity surface temperature just before filling on part surface appearance and texture in rapid heat cycle moulding are investigated. It is observed that the cavity surface temperature just before filling has a very significant influence on part surface appearance. As the cavity surface temperature increases, aesthetic quality of the moulded part can be greatly improved by reducing surface roughness, increasing surface gloss and reducing weld mark. There is a critical cavity surface temperature just before filling for each plastic material. As the cavity surface temperature reaches the critical value, the part surface appearance will reach the optimal level with lowest roughness, highest gloss and without any weld mark. The critical cavity surface temperature on surface gloss and roughness is close to the Vicat softening point of the plastic material. The critical cavity surface temperature on weld mark is 10-20 A degrees C higher than that on surface roughness and gloss. The mechanisms for generating the rough surface of the part moulded with a low cavity surface temperature and improving part surface appearance by increasing cavity surface temperature are disclosed.