Abstract:
The objectives of the study are to solve the sink mark problem in the conveyer tray of the hard disk
drive reader and to increase the production efficiency. Nowadays, the sink mark causes the waste
about 40%. In the experiment, the finite element method by CADMOULD program was used to
analyze the molten plastic flow. The simulated results showed that the sink mark was developed
from the plastic freezing at the gate before the molten plastic packing in the cavity, so that the
holding pressure could not fill more plastic. After that, the runner systems were calculated to receive
the suitable runner sizes. The calculated results exhibited that the increasing size of the diameter
runners should be bigger than those of the previous one for 0.5 millimeter Therefore, the simulation
was tried again. It can be seen that the sink mark was reduced in some area. Due to the complicated
part of the samples, the runner systems were modified by increasing the number of the gates from 2
to 4. The sink mark was disappeared. The molds were improved and tried to inject the real samples.
The results showed that no sink mark on the samples that agree with the simulation result. The
investment cost was reduced for I,600,000 baht per year.