Abstract:
The aim of this research is to increase the output of 7 × 1- inch self- tapping screws made of
SWRCH18A steel wire. The problem discovered in this case study was that the surface hardness of the
self-tapping screw and the core were inappropriate. Based on the analysis of the process capability, the
hardness of the surface and the core has a Cpk value of 2.27 and 0.44, respectively. The latter value
indicates that the core hardness has a Cpk value lower than the specified level, which is 1.33, resulting
in the occurrence of waste in the production process. This study was carried out to investigate both the
problem and the relevant and appropriate factors affecting the hardness value. There were 4 factors:
carburizing time, carbon potential, tempering temperature, and tempering time. Taguchi technique was
used to develop an experimental plan and the outcomes were examined using the response surface
method. According to the study's findings, the ideal surface and core hardness values were obtained with
a hardening process time of 35 min; a 0.95 percent carbon potential, and a tempering temperature of 310 degree celsius.
At a tempering process duration of 40 min, the Cpk of the surface and core hardness values were equal
to 3.16 and 1.90, respectively which were the most appropriate values. When the aforementioned factor
level was applied throughout the production process, the Cpk was found to be greater."