Case Summary Toshihiro Nakamura, manufacturing engineering section head, examined the prototype assembly process heet for the newest subnotebook computer model. When every new model was designed, considerable attention was directed toward; * reducing the numbers of components, * simplifying parts production and * assembly requirements. This new computer’s production was scheduled to begin in 10 days. Initial production for new model was to be at 150 units/day, increasing to 250 units/ day the following week. Eventually production should reach 300 units/ day. Assembly Line Model type: varies Lot size : 10 – 100units Assembly line : 14. meter conveyor Total station: 10 Workers: 8 – 12 assembly workers + 1 supporter Operating hour: 7. 5 hours (450min) Question 1: What is the daily capacity of the assembly lime designed by the engineers? From the time roadmap, Unit1 reach end assembly (done shock test) at min 21. Thus, 1st 20min of production hour, there is no output. Remainder production hour = 450min – 20min = 430min If 1 unit notebook is assembled at every minute, there will be 430 units notebook. But since there is only 1 notebook at every 2min, thusDaily capacity is = 430 / 2 = 215 unit notebooks
Question 2: When it is running at maximum capacity, what is the efficiency of the line? Formula: Efficiency = Sum of Task time (T) Actual no. of workstation (N) x Workstation cycle time (C ) Sum of Task time (T) = 21 min Actual no. of workstation (N) = 10 stations Workstation cycle time (C) = Production time per day Current output per day (in units) C150 = 7. 5 hr x 60min = 3. 0 min/unit 150 units (initial prod. ) C215 = 7. 5 hr x 60min = 2. 09 min/unit 215 units (engineer design) C250 =7. 5 hr x 60min = 1. 80 min/unit 250 units (following week) C300 = 7. 5 hr x 60min = 1. 50 min/unit 00 units (target) Thus, at max capacity, the line efficiency is =Sum of Task time (T) Actual no. of workstation(N) x Workstation cycle time(C ) Line efficiency at 150 output = 21min = 0. 7 (70%) 10 station x 3min/unit Line efficiency at 215 output = 21min= 1. 00 (100%) 10 station x 2. 09min/unit Line efficiency at 250 output = 21min= 1. 17 (117%) 10 station x 1. 80min/unit Line efficiency at 300 output = 21min= 1. 4 (140%) 10 station x 1. 50min/unit Question 3: How should the line be redesigned to operate at the target 300units/day, assuming that no overtime will be used?
What is the efficiency of your new design? Current operator Layout; Since the current assembly line layout should achieving 100% line efficiency when running at maximum capacity of 215 units. Thus, to operate at target 300 units/day, the current assembly line needs to redesign. Proposed new operator Layout; New sum of Task time (Tnew) = 21 min (new designed assembly line) New no. of workstation (Nnew) = 7 stations Current workstation cycle time (C215) = Production time per day Current output per day (in units) C215 = 7. 5 hr x 60min 215 units C215 = 2. 09 min/unit New redesigned line efficiency =Sum of Task time (Tnew) Actual no. f workstation (Nnew) x Workstation cycle time (C215) =21min 7 station x 2. 09min/unit =1. 44 (144%) Question 3 (cont’) Thus, expected daily out from redesign line = Efficiency x Daily capacity = 1. 44 x 215 = 309. 6 = 309 unit notebooks Summary, new re-design assembly line proposed is able to operate at target 300 units per day with assuming current cycle time remain 2. 09min/unit. Question 4: What other issue might Toshihiro consider when bringing the new assembly line up to speed? A) If the current assembly line was to redesign to 7 stations, Toshihiro need to consider for; 1)additional space at the other side of the conveyor needed. )task time need re-calculate, in order to obtain real production task time. 3) restudy the movement of supporter around the assembly line, to ensure no effect on his/her supporting role/quality. B) If the current assembly line to remain with 10 stations, Toshihiro need to consider for; 1)current station task time improvement in term of operator; – Re-train those slow performances operator – Operator re-position – to station higher performance operator at critical task station. 2) current station task time improvement in term of process; – tasks arrangement for optimal total task time. – tools upgrade/improvement