Process Improvement of Knives Production in a Small Scale Industry

摘要

Small scale industry that produces several kinds of knive should increase its capacity due to the demand from the market. Qualitatively, this case study consisted of formulating the problems, collecting and analyzing the necessary data, and determining the possible recommendations for the improvement. While the current capacity is only 9 (nine), it is expected that 20 units of knife will produced per month. The processes sequence are: profiling (a), truing (b), beveling (c), heat treatment (d), polishing (e), assembly (f), sharpening (g) and finishing (h). The first process (a) is held by out-house vendor company while other steps from (b) to (g) are executed by in-house vendor. However, there is a high dependency upon the high skilled operator who executes the in-house processes that are mostly held manually with several unbalance successive tasks, where the processing time of one or two tasks require longer duration than others since the operation is merely relied on the operator's skill. The idea is the improvement or change of the profiling and beveling process. Due to the poor surface quality and suboptimal hardness resulted from the laser cut machine for profiling, it is considered to substitute this kind of process with wire cut that is capable to obtain good surface quality with certain range levels of roughness. Through simple cutting experiments on the samples, it is expected that the generated surface quality is adequate to omit the truing process (b). In addition, the cutting experiments on one, two, and four test samples resulted the shortest time that was obtained through four pieces in one cut. The technical parameters were set according to the recommendation of machine standard as referred to samples condition such as thickness and path length that affected the rate of wear. Meanwhile, in order to guarantee the uniformity of knife angles that are formed through beveling process (c), a grinding fixture was created. This kind of tool diminishes the dependency upon the operator's skill as well. The main conclusions are: the substitution of laser cut with wire cut machine for the first task (a) could reduce the operation time from 60 to 39.26 minutes with good result of surface quality and the truing process (b) could be omitted; the additional grinding fixture in beveling process (c) is required and two workstations have to be assigned instead of one as in previous condition. They lead to improvements including the guarantee of the uniformity of knifes' angle, the reduction on the operators' skills dependency, the shortening of cycle time from 855 to 420 minutes, and the higher number of productivity from 9 units/month into 20units/month.