Abstract:
Based on the study of thermoforming machine in Rajamangkala University of
Technology North Bangkok, there are many incomplete parts after thermoforming
process which are both incomplete shape and side-thickness (less than 85% of original
thickness). A reason for this is that there is no standard setting for vacuum
thermoforming machine. This research aims to determine the optimal setting of vacuum
thermoforming machine which generates the complete shape with the side-thickness not
less than the specification. There are 6 factors in this experiment, namely, temperature,
heating time, vacuum time, air-blow time, type of mold, and mold alignment. This
research uses polyethylene 0.4 millimeter of thickness for all experiments. Since there
are limited materials, a 2k-1 fractional factorial design is then conducted in order to
determine the optimal setting of the six factors. The experiments are analyzed at
significant level of 0.05. The result shows that at 190 Celsius degree of heating
temperature, 22 seconds of heating time, 17 seconds of vacuum time, 12 seconds of
air-blow time, and use male mold and horizontal alignment, the shape of part is
complete and the thickness of part is not less than 0.34 millimeter which is not less than
85% of the original thickness as expected.