Midterm I Review CH 3 Manufacturing Metrics and Economics EXAMPLE 3.3 Bottleneck Model A small machine shop has six machine tools of four different types used to produce five different part styles. Part-mix fractions, batch quantities, stations, number of servers per station, setup times, and cycle times are listed in Table 3.2. Operation sequence for each part style is in the order of station number. Determine: (a) Which station is the bottleneck? Do the same thing for Then, next, calculate WL EXAMPLE 3.3 Bottleneck Model A small machine shop has six machine tools of four different types used to produce five different part styles. Part-mix fractions, batch quantities, stations, number of servers per station, setup times, and cycle times are listed in Table 3.2. Operation sequence for each part style is in the order of station number. EXAMPLE 3.3 Bottleneck Model A small machine shop has six machine tools of four different types used to produce five different part styles. Part-mix fractions, batch quantities, stations, number of servers per station, setup times, and cycle times are listed in Table 3.2. Operation sequence for each part style is in the order of station number. (a) Total production rate of all five parts, (b) Production rates of each of the five-part styles, EXAMPLE 3.3 Bottleneck Model A small machine shop has six machine tools of four different types used to produce five different part styles. Part-mix fractions, batch quantities, stations, number of servers per station, setup times, and cycle times are listed in Table 3.2. Operation sequence for each part style is in the order of station number. (a) Utilization of each server at each station, .00 (b) Average utilization of the machine shop. EXAMPLE 3.3 Bottleneck Model A small machine shop has six machine tools of four different types used to produce five different part styles. Part-mix fractions, batch quantities, stations, number of servers per station, setup times, and cycle times are listed in Table 3.2. Operation sequence for each part style is in the order of station number. Ch 14 Single-Station Manufacturing Cells Determining Workstation Requirements A total of 13,000 sheet metal stampings must be produced in the press department during the next three days. Manually operated presses (one operator per press) will be used to complete the job and the cycle time is 27 sec. Each press must be set up with a punch-and-die set before production starts. Setup time is 2.0 hr, and availability is assumed to be 100%. How many presses and operators must be devoted to this production during the three days, if there are 7.5 hr of available time per machine per day? Solution: The workload consists of 13,000 stampings at 27 sec per piece WL = 13,000(27/60 min) + 2(60)n = 5850 + 120 n (min) = 97.5 + 2n (hr) Time available per press during the three days AT = 3(7.5) = 22.5 hr 22.5n = 97.5 + 2n 20.5n = 97.5 n = 97.5/20.5 = 4.76 rounded up to 5 presses and operators Where: = number of workstations = available time on one station in the period (hr/period) WL = Workload = + �= �� �� =10/60 hr =20(45)=900 part Time setup=2.5 hr =20(2.5)=50 hr = 40-hr week = + = 200 hr �= �� �� = 200 40 =5 ���h�� A total of 900 parts must be produced in the lathe section of the machine shop during a particular 40-hr week. The parts are of 20 different styles, and each style is produced in its own batch. Average batch quantity is 45 parts. Each batch requires a setup and the average setup time is 2.5 hr. The average machine cycle time to produce a shaft is 10 min. Availability on the lathes is 100%. How many lathes are required during the week? Given that each lathe is available 40 hr/wk, Solution In this case the number of setups required during the week is known because the number of batches is known: 20. Total workload for the 20 setups and 20 production runs is given by: =20(2.5)+20(45) (10/60)=200 Determining Workstation Requirements Ch15 Multi-station Manufacturing systems: Manual Assembly Lines Example: A problem for line balancing Given: The previous precedence diagram and the standard times. Annual demand=100,000 units/year. The line will operate 50 wk/yr, 5 shifts/wk, 7.5 hr/shift. Uptime efficiency=96%. Repositioning time lost=0.08 min. Determine (a) total work content time, (b) required hourly production rate to achieve the annual demand, (c) cycle time, (d) theoretical minimum number of workers required on the line, (e) service time to which the line must be balanced. No. Work Element Description Tek (min) Must be Precede d By 1 Place frame in work holder and clamp 0.2 – 2 Assemble plug, grommet to power cord 0.4 – 3 Assemble brackets to frame 0.7 1 4 Wire power cord to motor 0.1 1, 2 5 Wire power cord to switch 0.3 2 6 Assemble mechanism plate to bracket 0.11 3 7 Assemble blade to bracket 0.32 3 8 Assemble motor to brackets 0.6 3, 4 9 Align blade and attach to motor 0.27 6, 7, 8 10 Assemble switch to motor bracket 0.38 5, 8 11 Attach cover, inspect, and test 0.5 9, 10 12 Place in tote pan for packing 0.12 11 Example: Solution (a) The total work content time is the sum of the work element times given in the table Twc=4.0 min (b) The hourly production rate (c) The corresponding cycle time with an uptime efficiency of 96% (d) The minimum number of workers: w* = (Minimum Integer 4.0 /1.08=3.7)=4 workers (e) The available service time Ts=1.08-0.08=1.00 min �� = 100,000 50(5)(7.5) =53.33 units/ hr �� = 60(0.96) 53.33 =1.08min � �� =∑ �=1 �� ��� �� = �� 50�� ��h �� = 60 � �� �∗= ��� �� �� =��−�� Line Balancing Algorithms – Heuristics 1. Largest candidate rule 2. Kilbridge and Wester method 3. Ranked positional weights method, also known as the Helgeson and Birne method In the following descriptions, assume o
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