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752 PRODUCT, PROCESS, AND SCHEDTIIEDESIGN
an assembly chart, ao operations p1'ocess chart, and a
precedence diagram for thisrecipe so that someone could fbl1ow the
recipe without additional instl'uctions.
2.11 Take the parts 1ist, bill ol materials, route sheet,
assembly chart, operations processchart, ancl prececlence diagrarn
from Problem 2.10 and give it to another individual un-farniliar
$,ith the recipe. Have this inclividual decompose these charts into
a writtenform of the recipe. Examine how close this derivecl recipe
is to the original.
SECTION 2.42.1.2 A computer recycler sel1s computer enclosures
to a computer remanufacturer. To meet
monthly expected demand. the remanufactLuer needs 2,000
enclosures. The lecyclerutilizes a four-step clisassembly process
$.ith scrap rates given as follows: ch- 0.08,cl2: 0.05, r$: 0.05,
and d,,:0.03. Hou.'many compLlters mLlst the reclcler receiveeach
month in order to meet the remanufacturer's demand?
2.13 Consider a simple three-step rlanr-rflacturing process as
illustratecl in the given figure.Assuraing that den-rand is 1,000
units, what is the required input to meet demanci?You'1l note that
the required input is the same if the scrap rates are reversed
fot'processes 1 and 3. Assune that the scrap cost is $5 at process
1. S10 at process 2, and$15 at process 3. The defectlve rates are
3o/0,50/0, and 7ol0, respectively. Compute the to-lai sclap cost
fbr the given system and the system q,here the scrap rates are
reversed.Which system would be preferred?
U2- J/a u?-//a
2.14 Considel Problem 2.13 q,'here, in this case, each process
is capable of reu'ork. Giventhe infolmation in the follor.ing
table, what is the input required to satisty a demand of1,000
units?
Si-rppose that scrap costs a1'e negligible, and re1l'ork costs
are S2, $3, and $4, respec-tivelv. Calcr:late the rev,.ork cost for
producing the 1,000 units. r&hal happens to the re-work cost if
the scrap rates on processes 1 and 3 are reversecli Does this
resuil agleewith that of Problem 2.13?
2.L5 Part X reqr-rires machining on a miliing machine
(operations A and B are required).Fincl the number of machines
required to prochrce J000 parts per week. Assume thecompany will be
operating five clays pel w-eek. 18 hours per dav. The follon'ing
infbr-mation is knoq,-n:
Process1
2
3
OperaticlnAFt
I)efect Rate3o/o
5o/o
7o/o
Rerv'ork Rate60o/o
7 5o/o
[300/o
Standard Time3 min5 rnin
Efficiency Reliability95a 9)o/o9ia 90o/o
Defect Rate2o/o
5o/a
Note: The milling machine requires tool changes and preventive
maintenance afterer..ery lot of 500 parts. These changes reqr:ire
30 minutes.
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/()Pt:fil O]1e DEF]NING REQLIREMENTS
2.16 Given the figure belorr,, operntiolr 4 represents a ren ork
operation ()n parts that fail in-spection upon completion of
operation 2.
5000 Units
dt: 27"How- rlany units lttlrst the process start v!,ith in
order to meet the reqr-iirecl output of5000 nnits?
2.17 Given the infirrmation in lrrr>blen-r 2.16 and the
infonnation in the talrle belorl', hovr'many machines are neecled
to perltrrm each operation (rouncl r-rp to nearest integer)?Assurne
operati()ns 1, 2. ancl 3 run tor 16 hours per ciay, five days per
neek. Macl-rine4 is available for eigl-rt hours per c1av, five
clays per v''eek.
Operation Stanclarcl Tinre Elliciency Reliability1 3 min 1009'0
giak2 2 min 95ari 904/o3 5 mln 702a/a 90o/o4 10 rnin 90on 9iVo
Assr,uning that macl'rines 7-3 are parl ()f a declicatecl
m:inufacturing ceil. that operation4 is perfbrn'red bv a
generai-purpose machine that is usecl specifically fi>r
reu,'ork, zLndthat macl-iines neecled for operation 4 are located
s
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772 PRODUCT, PROCESS, AND SCHEDULE DES]GN
part x routing is machine A. then B, and then c; 100,000 pafis
are to be prodr-rced peryear. Part Y routing is machine B, then A,
ancl then c; 200,000 pafts are to be producedper year. setup times
for pafis X ancl Y afe 20 minllles and 40 minutes,
respectively.
2.2O ParlA ls producecl on machine 1 and tiren machine 2. One
unit of Part A is assembledrn,irh threl units of Part ll, which is
produced on machine 3, in assembl]'station 4. Ma-chine t has a
scrap factor of 2oa/0, and machine 2has a scrap factor of 10%. The
as-sembly process has a scrap factor of 15%. Anothet pafl, Paft c,
is produced onmachine 5 and 1.ras a scrap
"rtirrut" ol 250/0. Part c and the subassembly comprison of
part A ancl part B are assemblecl at assembl-v station 6 into
the completed product.Each day, 15,000 units of the completed
pioduct ale required to meet demand As-suming ihat machine 3 and
assembly station 6 have scrap factors of 3oo/o each, whatare the
requirements for Parts A, B, and C in orcler to meet the daily
demand for thecornpleted product?
2.21 Suppose that in Problem 2.2O,each process n'as able to
reduce its scrap estimate bylyo. what would t1-re percent change in
the requirement for each input be? w'hat signif-icance can this
have on the process clesigner's decision making process? (Hit'tt:
Thereare ts,.o ways of bokil-rg at this problem, either fiom the
estimation pelspective or fromthe continuous improvement
perspective')
2.22 Consider Problems 2.20 and 2.21. Assume for operation 4
that the assembly oPelationhas a standard time of four minutes,
reliabilitv of 950/0, and efficiency of 9Bo/0. Computethe number of
assembly machines required for each scrap leve1. Vhat is the impact
ofthe scr.ap percentage on the nllmber of machines? Wh-v might a
facilities planner u''antto be involved in the requirements
definition process?
2.23 Duringone eigl-rt-hour shift, 750 nondefective pafis ale
desired from a fabrication op-eratio;. The standard time for the
operation is 15 minutes. Because the machine oper-ators are
gnskilled, the actual tin-re it takes to perform the operation is
20 minr-rtes, and,on average, one-fifth of the parts that begin
fabrication are scrapped. Assuming thateach of the machines usecl
for this operation will not be available for one hour of eachshift,
determine the numbel of machines required'
2.24 Sr:ppose that a final assembly is produced by assembling
tEo components. The firstcomponent, component A, is produrced
in-house and proceeds through three processsrep;, blanking,
forging, and machining, with scrap estimates of 1096, 7)0/0, ar,d
25a/a, re-spectively. nor everl, tiree units ol component A
produced, tB'o are used in the final as-slmbly, and one is set
aside to meet spare parts requit'ements. The second
component,component B, use