A manual assembly line has six stations. The assembly time at each manual station is 60 sec….
A manual assembly line has six stations. The assembly time at each manual station is 60 sec. Parts arc transferred by hand from one station to the next, and the lack of discipline in this method adds 12 sec (Tr = 12 sec) to the cycle time. Hence, the current cycle time is Tc = 72 sec. The following two proposals have been made: (1) Install a mechanized transfer system to pace the line, and (2) automate one or more of the manual stations using robots that would perform the same tasks as humans only faster. The second proposal requires the mechanized transfer system of the first proposal and would result in a partially or fully automated assembly line. The transfer system would have a transfer time Tr = 6 sec, thus reducing the cycle time on the manual line Tc = 66 sec. Regarding the second proposal, all six stations are candidates for automation. Each automated station would have an assembly time of 30 sec. Thus, if all six stations were automated, the cycle time for the line would be Tc = 36 scc. There are differences in the quality of parts added at the stations; these data are given for each station in the following table for (q = fraction defect rate, in = probability that a defect will jam the station). Average downtime per station yam at the automated stations Td = 3.0 min. Assume that the manual stations do not expenence line stops due to defective components. Cost data: Cat = $0.10/min: Ca = $0.20/min; and Cas= $0.15/min. Determine if either or both of the proposals should be accepted. If the second proposal is accepted, how many stations should be automated and which ones? Use cost per piece as the criterion of your decision. Assume for all cases considered that the line operates without storage buffers, so when an automated station stops, the whole line stops, including the manual stations.
