You are concerned that your company is understating its cycle time and throughput efficiency by measuring the cycle time for only those products completed without any defects. Products that are reworked or scrapped (because they cannot be made serviceable) are accounted for separately and removed from cycle time statistics. To understand the impact of this practice, you have decided to track the production of a typical product, Model DAD4700, over the course of four months. Sixteen different workgroups

(each composed of approximately 7 to 10 employees) work on different stages of the product (and simiChapter 7 Managing Quality and Time to Create Value 293 lar products). Each of three workgroups of eight employees do nothing but analyze and rework defective products (of all types) after the regular workgroups have completed them. You have gathered the following data on the DAD4700 over the past four months. (Note: These data can be more easily analyzed with spreadsheet software than by hand.)

Regular Workgroups January February March April Units completed without rework .....ccuccen 198 134 ne 189 Assembly time for good units... 1,809.70 1,293.60 1,105.60 1,714.20 Total cycle time for good units ....... ce 4,994.70 4,791.05 3,397.06 2,891.13 Regular Workgroups January February March April Units reworked successfully .....0....cccccceeeees 10 8 8 ale MES SOTADOe Cluewrenss eee Me emcee naiaccutt 1 0 2 O Rework time for all reworked units.........0...00 57.20 43.20 54.60 48.60 Total rework CyCle tiM@........ ccc eee 161.30 153.00 186.40 158.40 Required

a. Compute the average cycle time per unit and the throughput efficiency for good units produced by regular workgroups for each month and overall.

b. Compute the total cycle time and the throughput efficiency for units reworked successfully by rework workgroups for each month and overall. (Hint: Recall that these defective units were completed by regular workgroups first; an assumption is necessary.)

c. Compute the cycle times and the throughput efficiencies for each month for good and reworked products combined.

d. Prepare a group comment on the practice of computing separate cycle times and throughput efficiencies for good and reworked products.

e. What is your group’s opinion about having separate workgroups perform all rework of defective products?