This preview shows pages 1–2. Sign up to view the full content.
IE 131 Solutions for Problems due Feb 3 (Chs 2 and 3)
2.18 The standard time to produce a certain part in a workermachine system is 9.0 min. A rush
order has been received to supply 1000 units of the part within five working days (40 hours). How
many workermachine systems must be diverted from other production to satisfy this order? Each
machine must be set up at the beginning of production of parts for the order, and the setup time per
machine is 5.0 hours. Fraction defect rate is 5%, and worker efficiency is 100%. Availability is
expected to be 98% during setup and production. How many machines and machine operators are
required during the week?
Solution
: Production workload
WL
p
= 1,000(9.0)/60(1 – 0.05) = 157.9 hr/wk
Setup workload
WL
su
= 5.0
n
Total workload
WL
= 157.9 + 5.0
n
Available time (production and setup)
AT
= 40(0.98) = 39.2 hr/wk per machine
n
= (157.9 + 5.0
n
)/39.2
39.2
n
= 157.9 + 5.0
n
34.2
n
= 157.9
n
= 4.62 rounded up to 5 machines and 5 operators
2.25 In a workermachine cell, the appropriate number of production machines to assign to the
worker is to be determined. Let
n
= the number of machines. Each production machine is identical
and has an automatic processing time
T
m
= 4.0 min to produce one piece. Servicing time
T
s
= 12
sec for each machine. The full cycle time for each machine in the cell is
T
c
=
T
s
+
T
m
. The walk
time (repositioning time) for the worker is given by
T
r
= 5 + 3
n
, where
T
r
is in seconds.
T
r
increases with
n
because the distance between machines increases with more machines. (a)
Determine the maximum number of machines in the cell if no machine idle time is allowed. For
your answer, compute (b) the cycle time, (c) the worker idle time expressed as a percentage of the
cycle time, and (d) the production rate of the machine cluster.
Solution
: (a)
T
c
=
T
m
+
T
s
= 4.0(60) + 12 = 252 sec
Worker time per machine =
T
s
+
T
r
= 12 + 5 + 3
n
= 17 + 3
n
n
= 252/(17 + 3
n
)
n
(17 + 3
n
) = 252
17
n
+ 3
n
2
= 252
Setting this up to use the quadratic equation, 3
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Spring '08
 Groover

Click to edit the document details