IE 131 Homework Problems due Jan 31, 2007
A new stamping plant must supply an automotive final assembly plant with stampings, and
the number of new stamping presses must be determined. Each press will be operated by one
worker. The plant will operate one 8-hour shift per day, five days per week, 50 weeks per year.
The plant must produce a total of 20,000,000 stampings annually. However, 400 different
stamping designs are required, in batch sizes of 5000 each, so each batch will be produced 10
times per year to minimize build-up of inventory. Each stamping takes 6 sec on average to
produce. Scrap rate averages 2% in this type of production. Before each batch, the press must be
set up, with a standard time per setup of 3.0 hours. Presses are 95% reliable (availability = 95%)
during production and 100% reliable during setup. Worker efficiency is expected to be 100%.
How many new stamping presses and operators will be required?
: Number of setups = 20,000,000/5,000 = 4,000 setups/yr
= 4,000(3.0) = 12,000 hr/yr
= 6 sec = 0.1 min
= 20,000,000(0.1)/0.98(60) = 34,013.6 hr/yr
Available time for setup
= 2,000(1.0) = 2,000 hr/yr per press
Available time for production
= 2000(0.95) = 1900 hr/yr
= 34,013.6/1,900 + 12,000/2,000 = 17.9 + 6 = 23.9 rounded up to 24 presses and 24
It has just been learned that a Boeing 747 transporting garments made in China crashed in the
Pacific Ocean during its flight to Los Angeles. Although the crew was saved, all cargo was lost, in-
cluding 3000 garments that must be delivered in one week. The garment company must produce
the order at its Los Angeles plant to satisfy delivery obligations. The number of workers must be
determined and workspace must be allocated in the plant for this emergency job. Standard time to
produce one garment is 6.50 min. The garments are then 100% inspected at a standard time of 0.75
min per unit. The scrap rate in production is 7%. However, all defective garments can be corrected
through rework. Standard time for rework is 5.0 min per unit reworked. It is not necessary to rein-
spect the garments after rework. Worker efficiency is 120% during production and 100% during
inspection and rework. The same production workers do the rework, but inspectors are a different
job class. How many workers and how many inspectors are required to produce the required batch
of 3000 garments in the regular 40-hour work week?