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The production processes of a cold heading steel wire plant
include pickling & coating, spheroidize annealing, and drawing.
There are about twelve products. The procedure of each product
is different. For example, the simplest production processes
(A1 product) need only pickling and spheroidize annealing. The
most complex production process (C4 product) must be through
seven processes, i.e. pickling, pickling and phosphate coating
twice, spheroidize annealing, process annealing , drawing, and
skin pass. Moreover, the raw material that comes from different
source can not be mixed into the same annealing furnace at the
same time. The P2 and P3 process can only be performed during
day-shift of pickling process. The different spheroidize
annealing pattern can't be mixed into the same furnace either.
The complexity of restrictions makes production scheduling a
difficult job. While pursuing 100% utilization of all
facilities in the past, the new scheduling method emphasizes
the shortest flow time. The process before bottle-neck facility
is scheduled using JIT (Just-In-Time), and the process after
bottle-neck facility is scheduled using push-type method. One-
month orders from cold heading steel wire plant are used as an
example. WIP has been chosen as a decision criterion for
comparison. Results show that the WIP inventory will be reduced
from 11369 pcs_day/month down to 4123 pcs_day/month when the
new scheduling method is used. Benefits include: (1) 25813 NT
dollars saved every month of the interest for capital. (2) 365
square meters saved. (3) 468 double handling of WIP decreased
every day.
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