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.

/()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

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