Surface roughness effects on melt flow in injection molding

• Main Author: Ang, Nicholas Kheng Tiong
• Other Authors: Ong Nan Shing
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Manufacturing
• Online Access: http://hdl.handle.net/10356/16823
• Institution: Nanyang Technological University

Injection moulding is commonly used for the cost effective mass production of plastic parts. Cavity surface roughness which is insignificant in conventional injection moulding may play an important role in micro injection moulding. Although the roughness effects in micro injection moulding have been discussed in some research, they were neither investigated in detail nor understood clearly. This report aims to facilitate future research on roughness effects on cavity filling in injection moulding through the design of a mould which is capable of producing micro thickness parts. A rectangular mould insert consisting of two halves of different roughness is also fabricated such that the distance (Δd) between the roughness mean line of the rougher half of the insert and that of the smoother half is negligible. Experimental investigations were also carried out to evaluate the difference in the height of the mean planes between the two rectangular halves of the core insert using the Talyscan 150 dual gauge system. Two-dimensional surface roughness profiles of the core insert and the rectangular moulded parts were measured to determine the Δd value. If the distance between the mean line of the rougher half of the core insert and that of the smoother half is negligible, the differences in the filling flow areas in either half are mainly caused by the difference in roughness between them. The difference in height of the mean lines will affect the volume of the cavity and hence the flow on the two halves. Lastly, polymer filling into a rectangular-shaped cavity mould was performed. Short shots are intentionally produced to visualize the flow pattern. The partial filled parts of various sizes are obtained by varying the injection rate within a short range.