Q&A Hero

Question

16) A work cell is required to make 200 computerized diagnostic assemblies (for installation into hybrid automobiles) each day. The cell currently works an eight hour shift, of which seven hours is available for productive work. What is takt time for this cell?

Answer: Takt time = 420 minutes / 200 units required = 2.1 minutes

17) A work cell is scheduled to build 120 digital light processor (DLP) assemblies each week. These assemblies are later installed into home theater projection systems. The work cell has 7.5 hours of productive work each day, six days per week. What is takt time for this cell?

Answer: The cell has 7.5 x 6 = 45 hours (or 2700 minutes) of work time each week. Takt time = 2700 / 120 = 22.5 minutes.

18) A work cell is required to make 80 computerized diagnostic assemblies (for installation into hybrid automobiles) each day. The cell currently works an eight hour shift, of which seven hours is available for productive work. These assemblies require five operations, with times of 1.0, 0.8, 2.4, 2.5, and 1.4 minutes each. What is takt time for this cell? How many workers will be needed?

Answer: Takt time = 420 minutes / 80 units = 5.25 minutes. Total operation time is 1.0 + 1.8 + 2.4 + 2.5 + 1.4 = 9.1 minutes. Workers required = 9.1 / 5.25 = 1.73 or 2.

19) A work cell is required to make 140 computerized diagnostic assemblies (for installation into hybrid automobiles) each day. The cell currently works an eight hour shift, of which seven hours is available for productive work. These assemblies require five operations. Standard times for these operations are: Operation A, 3.0 minutes, B, 1.8 minutes, C, 2.4 minutes, D, 2.5 minutes, and E, 1.4 minutes. What is takt time for this cell? How many workers will be needed to achieve this schedule? Use the grid below to construct a work balance chart for this cell.

Answer: Takt time = 420 / 140 = 3 minutes/unit. Total operation time = 3.0 + 1.8 + 2.4 + 2.5 + 1.4 = 11.1 minutes. A minimum of four workers are required (11.1 / 3 = 3.7), but to balance at 3 min./unit requires five. The balance chart appears below.

20) An airport is trying to balance where to place three airlines. The distance between terminals and the number of trips that travelers make between airlines per day are listed. Find the assignment that minimizes the distance travelers must walk.

Answer: There are 6 possible assignments and the distance traveled for each scenario is 110(Distance A-B)+195(Distance C-B) + 180(Distance A-C)=total distance

A(1)-B(2)-C(3)=110(4000)+195(6000)+180(5000)=2510K

A(1)-B(3)-C(2)=110(5000)+195(6000)+180(4000)=2440K

A(2)-B(1)-C(3)=110(4000)+195(5000)+180(6000)=2495K

A(2)-B(3)-C(1)=110(6000)+195(5000)+180(4000)=2355K

A(3)-B(2)-C(1)=110(6000)+195(4000)+180(5000)=2340K

A(3)-B(1)-C(2)=110(5000)+195(4000)+180(6000)=2410K

Airline A should be assigned terminal 3, Airline B terminal 2 and Airline C terminal 1 to minimize the distance travelers must go.

21) Brandon's computer shop has hired a consultant to help apply operation management techniques to increase profits. Currently the shop sells most of its computers to a high-end customized online retailer and sales are steady at 250 per month. A single work cell produces the computers. To produce the computer three operations are required. First the parts must be assembled, next software must be installed, and finally the computer must be safely packed and labeled for shipping. These operations take 2 hours, 5 hours, and 1 hour respectively. If there are 6 available work hours each day and the shop operates 20 days per month find:

A: The takt time

B: The number of workers Brandon should hire

Answer: Takt time = (6 hours/day * 20 days/month)/(250 units/month)=.48 hours per computer.

Total operation time = 2+5+1=8hours. Workers required = Operation time/Takt Time = 8/.48 = 16.67 = 17 workers required.

22) A manufacturing work cell has a takt time of 7 minutes and is staffed by 10 workers. If the work cell delivers 68 units each day find

A. The total operation time

B. The amount of time worked during the day for all 10 workers combined

C. If the plant is open for only 8 hours per day, can the staff meet demand?

Answer: Total operation time = Workers required * Takt time = 10(7 minutes) = 70 minutes

Time worked = Takt time * Units Delivered * # workers = 7minutes*(68)*10 =4760 minutes = 79.33 hours

10 workers * 8hours/day = 80 hours per day are available. From B only 79.33 are required, so the workers can meet demand.

23) A company is trying to balance production between 3 workstations on an assembly line. Currently there are 5 tasks that need to be performed. These tasks, ABCDE, have required times of 2 minutes, 4 minutes, 1 minutes, 3 minutes, and 10 minutes respectively. The assembly line needs to produce 40 units per day to meet demand and can work for up to 8 hours each day.

A. What is the required cycle time?

B. What is the theoretical minimum # of workstations?

C. Assign the tasks according to shortest task time.

D. Is there a better way to divide the work than in Part C?

Answer: Required cycle time = Production time available / Units required = 8 hours * 60 minutes / 40 units = 12 minutes

Minimum # of workstations = Sum of task times / Cycle time = (2+4+1+3+10)/12 = 1.667 stations = 2 stations

Workstation A would be assigned Task C for a total of 1 minute, Task A for a total of 3 minutes, Task D for a total of 6 minutes, Task B for a total of 10 minutes. Task E cannot be assigned because 10+10 > 12 minutes. Therefore Task E would be assigned to station B for a total of 10 minutes. Station C would have no assignment.

The assignment method of Part C creates the optimum assignment (2 workstations = theoretical minimum). The company would be wise to eliminate the third workstation or to up production so that cycle time decreases and each workstation would be needed.

24) An assembly line is assigned as follows. Station A- task A, B, and C. Station B- task D. Station C- task E and F. The task times are 7, 3, 2, 9, 4, and 5 minutes respective to A, B, C, D, E, and F. (Assume that there is no precedence relationships between the tasks, ie they can be accomplished in any order)

A. Calculate the efficiency.

B. What would the assignment of tasks to stations be using shortest processing time (assuming the current maximum station time remains the cycle time)?

Answer: Efficiency= Sum of task time / (# Stations * Longest Station duration) = (7+3+2+9+4+5)/(3*12)= 83.3%

Station A would be assigned task C for a total of 2 minutes, task B for a total of 5 minutes, Task E for a total of 9 minutes. Task F cannot be assigned because the total would be 14 minutes which is greater than the 12 maximum. Therefore Station B would be assigned task F for a total of 5 minutes and task A for a total of 12 minutes. Finally station C would be assigned task D for a total of 9 minutes.