Solution Manual for Automation, Production Systems, and Computer-Integrated Manufacturing, 5th Edition

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Chapter 1INTRODUCTIONREVIEW QUESTIONS1.1What is a production system?Answer: As defined in the text, a production system is a collection of people, equipment,and procedures organized to perform the manufacturing operations of a company.1.2Production systems consist of two major components. Name and briefly define them.Answer: The two major components given in the text are (1) facilities, which consist of thefactory, the equipment in the factory, and the way the equipment is organized; and (2)manufacturing support systems, which are the procedures used by the company to manageproduction and to solve the technical and logistics problems encountered in orderingmaterials, moving the work through the factory, and ensuring that products meet qualitystandards. Product design and certain business functions are included among themanufacturing support systems.1.3What are manufacturing systems, and how are they distinguished from production systems?Answer: A manufacturing system is a logical grouping of equipment in the factory and theworker(s) who operate(s) it. Examples include worker-machine systems, production lines,and machine cells. A production system is a larger system that includes a collection ofmanufacturing systems and the support systems used to manage them. A manufacturingsystem is a subset of the production system.1.4Manufacturing systems are divided into three categories, according to worker participation.Name the three categories.Answer: The three categories are (1) manual work systems, (2) worker-machine systems,and (3) automated systems.1.5What are the four functions included within the scope of manufacturing support systems?Answer: As identified in the text, the four functions are (1) business functions, (2) productdesign, (3) manufacturing planning, and (4) manufacturing control.1.6Three basic types of automation are defined in the text. What is fixed automation and whatare some of its features?Answer: Fixed automation is a system in which the sequence of processing (or assembly)operations is fixed by the equipment configuration. Each operation in the sequence isusually simple, but the integration and coordination of many such operations in one pieceof equipment makes the system complex. Typical features of fixed automation are (1) highinitial investment for custom-engineered equipment, (2) high production rates, and (3)relatively inflexible in accommodating product variety.1.7What is programmable automation and what are some of its features?Answer: In programmable automation, the production equipment is designed with thecapability to change the sequence of operations to accommodate different part or productconfigurations. The operation sequence is controlled by a program,which is a set ofinstructions coded so that they can be read and interpreted by the system. Some of the

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features of programmable automation are (1) high investment in general purposeequipment, (2) lost production time due to changeovers of physical setup andreprogramming, (3) lower production rates than fixed automation, (4) flexibility to dealwith variations and changes in product configuration, and (5) most suitable for batchproduction.1.8What is flexible automation and what are some of its features?Answer: Flexible automation is an extension of programmable automation. A flexibleautomated system is capable of producing a variety of parts (or products) with virtually notime lost for changeovers from one part style to the next. There is no lost production timewhile reprogramming the system and altering the physical setup. Accordingly, the systemcan produce various mixes and schedules of parts or products instead of requiring that theybe made in batches. Features of flexible automation are (1) high investment for a custom-engineered system, (2) continuous production of variable mixtures of products, (3) mediumproduction rates, and (4) flexibility to deal with product design variations1.9What is computer-integrated manufacturing?Answer: As defined in the text, computer-integrated manufacturing (CIM) denotes thepervasive use of computer systems to design the products, plan the production, control theoperations, and perform the various information-processing functions needed in amanufacturing firm. True CIM involves integrating all of these functions in one system thatoperates throughout the enterprise.1.10What are some of the reasons why companies automate their operations?Answer: The reasons give in the text are (1) increase labor productivity, (2) reduce laborcost, (3) mitigate the effects of labor shortages, (4) reduce or eliminate routine manual andclerical tasks, (5) improve worker safety, (6) improve product quality, (7) reducemanufacturing lead time, (8) accomplish processes that cannot be done manually, and (9)avoid the high cost of not automating.1.11Identify three situations in which manual labor is preferred over automation.Answer: The five situations listed in the text are the following: (1) The task istechnologically too difficult to automate. (2) Short product life cycle. (3) Customizedproduct. (4) To cope with ups and downs in demand. (5) To reduce risk of product failure.1.12Human workers will be needed in factory operations, even in the most highly automatedoperations. The text identifies at least four types of work for which humans will be needed.Name them.Answer: The four types of work identified in the text are (1) equipment maintenance, (2)programming and computer operations, (3) engineering project work, and (4) plantmanagement.1.13What is the USA Principle? What does each of the letters stand for?Answer: The USA Principle is a common sense approach to automation and processimprovement projects. U means “understand the existing process,” S stands for “simplifythe process,” and A stands for “automate the process.”1.14The text lists ten strategies for automation and process improvement. Identify five of thesestrategies.

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Answer: The ten strategies listed in the text are (1) specialization of operations, (2)combined operations, (3) simultaneous operations, (4) integration of operations, (5)increased flexibility, (6) improved material handling and storage, (7) on-line inspection, (8)process control and optimization, (9) plant operations control, and (10) computer-integrated manufacturing (CIM).1.15What is an automation migration strategy?Answer: As defined in the text, an automation migration strategy is a formalized plan forevolving the manufacturing systems used to produce new products as demand grows.1.16What are the three phases of a typical automation migration strategy?Answer: As defined in the text, the three typical phases are the following: Phase 1: Manualproduction using single-station manned cells operating independently. Phase 2: Automatedproduction using single-station automated cells operating independently. Phase 3:Automated integrated production using a multi-station automated system with serialoperations and automated transfer of work units between stations.

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Chapter 2MANUFACTURING OPERATIONSREVIEW QUESTIONS2.1What is manufacturing?Answer: Two definitions are given in the text. The technological definition is thefollowing: Manufacturing is the application of physical and chemical processes to alter thegeometry, properties, and/or appearance of a given starting material to make parts orproducts. Manufacturing also includes the joining of multiple parts to make assembledproducts. The economic definition is the following: Manufacturing is the transformation ofmaterials into items of greater value by means of one or more processing and/or assemblyoperations.2.2What are the three basic industry categories?Answer: The three basic industry categories are (1) primary industries, which are those thatcultivate and exploit natural resources, such as agriculture and mining; (2) secondaryindustries, which convert the outputs of the primary industries into products; they includemanufacturing, construction, and power generation; and (3) tertiary industries, whichconstitute the service sector of the economy; examples include banking, retail,transportation, education, government.2.3What is the difference between consumer goods and capital goods?Answer:Consumer goods are products that are purchased directly by consumers, such ascars, personal computers, TVs, tires, toys, and tennis rackets. Capital goods are productspurchased by other companies to produce goods and supply services. Examples includecommercial aircraft, mainframe computers, machine tools, railroad equipment, andconstruction machinery.2.4What is the difference between a processing operation and an assembly operation?Answer: A processing operation transforms a work material from one state of completionto a more advanced state that is closer to the final desired part or product. It adds value bychanging the geometry, properties, or appearance of the starting material. An assemblyoperation joins two or more components to create a new entity, called an assembly,subassembly, or some other term that refers to the joining process.2.5Name the four categories of part-shaping operations, based on the state of the starting workmaterial.Answer: The four categories are (1) solidification processes, (2) particulate processing, (3)deformation processes, and (4) material removal processes.2.6Into which of the four basic categories of part-shaping operations does each of the followingbelong: (a) powder metallurgy, (b) plastic molding, (c) drilling, (d) forging, and (e) grinding?Answer: (a) Particulate processing, (b) solidification, (c) material removal, (d) deformation,and (e) material removal.2.7Assembly operations can be classified as permanent joining methods and mechanicalassembly. What are the four types of permanent joining methods?

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Answer: The joining processes are (1) welding, (2) brazing, (3) soldering, and (4) adhesivebonding.2.8What is the difference between hard product variety and soft product variety?Answer: Hard product variety is when the products differ substantially. In an assembledproduct, hard variety is characterized by a low proportion of common parts among theproducts; in many cases, there are no common parts. Soft product variety is when there areonly small differences between products. There is a high proportion of common partsamong assembled products whose variety is soft.2.9With what type of production is a job shop usually associated?Answer: Low production of specialized and customized products. The products aretypically complex, such as experimental aircraft and special machinery.2.10Flow line production is associated with which one of the following layout types: (a) cellularlayout, (b) fixed-position layout, (c) process layout, or (d) product layout?Answer: (d) Product layout.2.11What is the difference between a single-model production line and a mixed-model productionline?Answer: A single-model production line makes products that are all identical. A mixed-model production line makes products that have model variations characterized as softproduct variety.2.12What is meant by the termtechnological processing capability?Answer: Technological processing capability of a plant (or company) is its available set ofmanufacturing processes. It includes not only the physical processes, but also the expertisepossessed by plant personnel in these processing technologies.2.13Define the termproduction capacity.Answer: Production capacity is defined as the maximum rate of production that a plant canachieve during a given period (such as a week, month, or year) under assumed operatingconditions (e.g., direct labor manning levels, number of shifts per week, hours per shift,etc.).PROBLEMSAnswers to problems labeled(A)are listed in the Appendix at the back of the book.2.1(A)A manufacturing plant produces three product lines in one of its plants: A, B, and C.Each product line has multiple models: 5 models within product line A, 3 models within B,and 4 within C. Total annual production quantity of all models of product A is 2000 units,1500 units for product B, and 800 units for product C. Determine the number of (a) differentproduct models and (b) total quantity of products produced annually in this plant.Solution: (a) The total number of different product models produced isP= 5 + 3 + 4 =12 different models(b) The total production quantity of all products made in the factory isQf= 5(2000) + 3(1500) + 4(800) = 10,000 + 4500 + 3200 =17,700 unitsannually

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2.2Consider product line A in preceding Problem 2.1. Its five models have an average of 27components each, and the average number of operations needed to produce each componentis 4.5. All components are made in the same plant. Determine the total number of (a)components produced and (b) operations performed in the plant annually for product line A.Solution: (a) Total number of components produced is given by Equation (2.7).PQ= 2000 productsnpf=PQnp= 2000(27) =54,000 components(b) Total number of operations performed annually in the plant is given by Equation (2.9).nof=PQnpno= 2000(27)(4.5) =243,000 operations2.3A company produces two products in one of its plants: A and B. Annual production ofProduct A is 3000 units and of Product B is 2000 units. Product A has 25 components andProduct B has 36 components. For Product A, 40% of the components are made in the plant,while 60% are purchased parts. For Product B, 30% of the components are made in the plant,while 70% are purchased. For these two products taken together, what is the total number of(a) components made in the plant and (b) components purchased?Solution: (a) The total number of components produced in the plant can be determined usingEquation (2.3), adjusting it for the proportions of each part made in the factory:npf=3000(25)(0.40) + 2000(36)(0.30) = 30,000 + 21,600 =51,600 partsmade in plant(b) Letnpp= the total number of parts purchased:npp= 3000(25)(0.60) + 2000(36)(0.70) =45,000 + 50,400 =95,400 purchased parts2.4(A)A product line has two models: X and Y. Model X consists of 4 components: a, b, c, andd. The number of processing operations required to produce these four components are 2, 3,4, and 5, respectively. Model Y consists of 3 components: e, f, and g. The number ofprocessing operations required to produce these three components are, 6, 7, and 8respectively. The annual quantity of Model X is 1000 units and of Model Y is 1500 units.Determine the total number of (a) components and (b) processing operations associated withthese two models.Solution: (a) The total number of components can be determined using Equation (2.3):npf=1000(4) + 1500(3) = 4000 + 4500 =8500 componentsAlternatively, Equation (2.7) can be used, first computing the average values forQandnpusing Eqs. (2.6) and (2.8).Q= (1000 + 1500)/2 = 1250 unitsnp= (1000(4) + 1500(3))/(2×1250) = 3.4 components per unit productnpf= 2(1250)(3.4) = 8500 components(b) The total number of processing operations can be determined using Equation (2.4):nof=1000(2 + 3 + 4 + 5) + 1500(6 + 7 + 8) = 1000(14) + 1500(21) =45,500 operationsAlternatively, Equation (2.9) can be used, first computing the average values fornpandnousing Eqs. (2.8) and (2.10).The value ofnpwas calculated above:np= 3.4 components per unit productno= (1000(2 + 3 + 4 + 5) + 1500(6 + 7 + 8))/3.4 = 5.353 operations per componentnof= 2(1250)(3.4)(5.353) = 45,500 operations

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2.5The ABC Company is planning a new product line and a new plant to produce the parts forthe line. The product line will include 8 different models. Annual production of each model isexpected to be 900 units. Each product will be assembled of 180 components. All processingof parts will be accomplished in the new plant. On average, 6 processing operations arerequired to produce each component, and each operation takes an average of 1.0 min(including an allowance for setup time and part handling). All processing operations areperformed at workstations, each of which includes a production machine and a humanworker. The plant operates one shift. Determine the number of (a) components, (b)processing operations, and (c) workers that will be needed to accomplish the processingoperations if each worker works 2000 hr/yr.Solution: (a) Number of components produced in the plant:npf=PQnp= 8(900)(180) =1,296,000 components(b) Number of operations performed in the plant:nof=PQnpno= 8(900)(180)(6) =7,776,000 operationsin the plant per year(c) Total operation timeTT=nofTp, whereTp= time for one processing operation.TT= 7,776,000(1.0) = 7,776,000 min = 129,600 hr of processing timeAt 2000 hours/yr per worker, number of workersw= 129,600/2000 = 64.8 workersThis should be rounded up to65 workers.2.6The XYZ Company is planning a new product line and a new factory to produce the parts andassembly the final products. The product line will include 10 different models. Annualproduction of each model is expected to be 1000 units. Each product will be assembled of300 components, but 65% of these will be purchased parts (not made in the new factory).There are an average of 8 processing operations required to produce each component, andeach processing step takes 30 sec (including an allowance for setup time and part handling).Each final unit of product takes 48 min to assemble. All processing operations are performedat work cells that include a production machine and a human worker. Products are assembledat single workstations consisting of one worker each plus assembly fixtures and tooling. Eachwork cell and each workstation require 25 m2of floor space and an additional allowance of45% must be added to the total production area for aisles, work-in-process storage, shippingand receiving, rest rooms, and other utility space. The factory will operate one shift (the dayshift, 2000 hr/yr). Determine (a) how many processing and assembly operations, (b) howmany workers (direct labor only), and (c) how much total floor space will be required in theplant.Solution: (a) The number of products isQf=PQ= 10(1000) = 10,000 products/yrTherefore, the number of final assembly operations =10,000 asby ops/yrTotal number of partsnpf= 10(1000)(300) = 3,000,000 components, but 65% of these arepurchased, so the number made in the plant will be 0.35(3,000,000) = 1,050,000Number of processing operationsnof= 1,050,000(8) =8,400,000 proc ops/yr(b) Total processing timeTTp=nofTp, whereTp= time for one processing operation.TTp= 8,400,000(0.50) = 4,200,000 min = 70,000 hr/yrTotal assembly timeTTa=QTa, whereTa= assembly time for each product.TTa= 10,000(48) = 480,000 min/yr = 8000 hr/yrNumber of workersw= (70,000 + 8000)/2000 =39 workers

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(c) With 1 worker per workstation for processing operations and 1 worker per assemblyworkstation,n=w= 39 workstations.Total floor spaceTA=nAw(1 +AL), whereAw= area of each work cell or workstation, andAL= allowance for aisles, storage, etc.TA= 39(25)(1 + 0.45) =1413.75 m2(~15,217 ft2)2.7Suppose the company in Problem 2.6 were to operate two shifts (a day shift and an eveningshift, a total of 4000 hr/yr) instead of one shift to accomplish the processing operations. Theassembly of the product would still be accomplished on the day shift. Determine (a) howmany processing and assembly operations, (b) how many workers on each shift (direct laboronly), and (c) how much total floor space will be required in the plant.Solution: (a) Number of final assembly operationsPQ= 10(1000) =10,000 asby ops/yrTotal number of partsnpf= 10(1000)(300) = 3,000,000 components, but 65% of these arepurchased, so the number made in the plant will be 0.35(3,000,000) = 1,050,000Number of processing operationsnof= 1,050,000(8) =8,400,000 proc ops/yr(b) Total processing timeTTp=nofTp, whereTp= time for one processing operation.TTp= 8,400,000(0.50 min) = 4,200,000 min = 70,000 hr/yr total for two shiftsTTp= 70,000/2 = 35,000 hr/yr total for each shiftNumber of processing operation workers per shiftwp= 35,000/2000 = 17.5 rounded up to 18parts production workers per shiftTotal assembly timeTTa=QTa, whereTa= assembly time for each product.TTa= 10,000(48) = 480,000 min/yr = 8000 hr/yrNumber of assembly workerswa= 8000/2000 = 4 assembly workersNumber of workers on day shiftw= 18 + 4 =22 workersNumber of workers on evening shiftw=18 workers(c) The floor space must be based on the number of day shift operations, which includesprocessing and assembly operations.Total floor spaceTA=nAw(1 +AL), whereAw= area of each work cell or workstation, andAL= allowance for aisles, etc.TA= 22(25)(1 + 0.45) =797.5 m2(~8584 ft2)Comment: This is a savings in floor space of ~44% compared to the one-shift operation inthe previous problem.

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Chapter 3MANUFACTURING METRICSREVIEW QUESTIONS3.1What is the cycle time in a manufacturing operation?Answer: As defined in the text, the cycle timeTcis the time that one work unit spendsbeing processed or assembled. It is the time between when one work unit begins processing(or assembly) and when the next unit begins.3.2What is the difference between sequential batch production and simultaneous batchproduction?Answer: In sequential batch production the parts in the batch are processed one after theother, resulting in a batch time =Tsu+QbTc, whereTc= cycle time per part. Insimultaneous batch production, the parts in the batch are all processed at once, resulting ina batch time =Tsu+Tc, whereTc= cycle time to process all of the parts in the batch.3.3What is a bottleneck station in a production line?Answer: The bottleneck station is the slowest workstation in a production line, and thereforeit limits the pace of the entire line.3.4What is availability and how is it defined?Answer: Availability is a reliability metric that indicates the proportion of time that a piece ofequipment is up and working properly. It is defined as follows:A= (MTBF–MTTR)/MTBFwhereA= availability,MTBF= mean time between failures, andMTTR= mean time torepair.3.5What is workload?Answer: Workload is defined as the total amount of time required to complete a givenamount of work. In production it refers to the total amount of time to produce a givenquantity of work units, for example in sequential batch production,WL=QTp, whereTp=Tsu+QTc.3.6What is production capacity?Answer: Production capacity is the maximum rate of output that a production facility (orproduction line, work center, or group of work centers) is able to produce under a given setof assumed operating conditions.3.7How can plant capacity be increased or decreased in the short term?Answer: As listed in the text, the two ways that plant capacity can be increased or decreasedin the short term are (1) add workers, (2) change the number of work shifts per week, and (3)change the number of hours worked per shift.3.8How can plant capacity be increased or decreased in the intermediate or long term?

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Answer: As listed in the text, the two ways that plant capacity can be increased or decreasedin the intermediate or long term are (1) increase or decrease the number of work centers in theplant or (2) increase the production rate of the work centers by making methodsimprovements or using more productive processing technologies.3.9What is meant by the termpart mix?Answer: The term part mix refers to the relative proportions of different part styles made in aproduction facility. The symbolpj= the proportion of part style j out of a total ofPdifferentpart styles,pj= 1, 2, . .P.3.10What is utilization in a manufacturing plant? Provide a definition.Answer: Utilization is defined as the proportion of time that a productive resource, such as amanufacturing plant, is used relative to the time available under the definition of plantcapacity.3.11What is manufacturing lead time?Answer: Manufacturing lead time is the total time required to process a given part orproduct through the plant, including any lost time due to delays, time spent in storage,reliability problems, and so on.3.12What is work-in-process?Answer: Work-in-process (WIP) is the quantity of parts or products currently located in thefactory that are either being processed or are between processing operations. WIP isinventory that is in the state of being transformed from raw material to finished product.3.13How are fixed costs distinguished from variable costs in manufacturing?Answer: Fixed costs remain constant for any level of production output. Examples includethe cost of the factory building and production equipment, insurance, and property taxes.Variable costs vary in proportion to the level of production output. As output increases,variable costs increase. Examples include direct labor, raw materials, and electric power tooperate the production equipment.3.14Name five typical factory overhead expenses?Answer: Table 3.2 in the text lists the following examples of factory overhead expenses:plant supervision, applicable taxes, factory depreciation, line foremen, insurance,equipment depreciation, maintenance, heat and air conditioning, fringe benefits, custodialservices, light, material handling, security personnel, power for machinery, shipping andreceiving, tool crib attendant, payroll services, and clerical support.3.15Name five typical corporate overhead expenses?Answer: Table 3.3 in the text lists the following examples of corporate overhead expenses:corporate executives, engineering, applicable taxes, sales and marketing, research anddevelopment, cost of office space, accounting department, support personnel, securitypersonnel, finance department, insurance, heat and air conditioning, legal counsel, fringebenefits, and lighting.3.16Why should factory overhead expenses be separated from corporate overhead expenses?

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Answer: A manufacturing company may operate more than one factory, and each factoryhas its own overhead expenses that are different from the expenses at other factories. Onthe other hand corporate overhead expenses are applied to all factories operated by thecompany. Also, in matters of analyzing costs, corporate overhead would simply inflate theoperating costs so they should not be included in the cost analyses, but at least some of thefactory overhead costs should be included. In pricing decisions, both factory and corporateexpenses must be included.PROBLEMSAnswers to problems labeled(A)are listed in the Appendix at the back of the book.Cycle Time and Production Rate3.1(A)A batch of parts is produced on a semi-automated production machine in a sequentialbatch production operation. Batch quantity is 300 units. Setup takes 55 min. A worker loadsand unloads the machine each cycle, which takes 0.75 min. Machine processing time is 3.46min/cycle, and tool handling time is negligible. One part is produced each cycle. Determine(a) average cycle time, (b) time to complete the batch, and (c) average production rate.Solution: (a)Th= 0.75 min,To= 3.46 min, andTt= 0Cycle timeTc= 0.75 + 3.46 =4.21 min(b) Batch timeTb= 55 + 300(4.21) = 55 +1263 min=21.05 hr(c) Average production timeTp= 1263/300 = 4.21 min/pcProduction rateRp= 60/4.21 =14.25 pc/hr3.2In a sequential batch machining operation, setup time is 1.5 hours and batch size is 120 units.The cycle time consists of part handling time of 30 sec and processing time of 2.85 min. Onepart is produced each cycle. Tool changes must be performed every 10 parts and this takes 2.0min. Determine (a) average cycle time, (b) time to complete the batch, and (c) averageproduction rate.Solution: (a)Th= 30/60 = 0.50 min,To= 2.85 min, andTt= 2.0/10 = 0.20 minCycle timeTc= 0.50 + 2.85 + 0.20 =3.55 min(b) Batch timeTb= 1.5(60) + 120(3.55) = 90 + 426 =516 min= 8.6 hr(c) Average production timeTp= 516/120 = 4.3 min/pcProduction rateRp= 60/4.3 =13.95 pc/hr3.3The setup time in a sequential batch production operation is 2.0 hours, and the actualprocessing time of 1.60 min per cycle. Three parts are produced each cycle. No tool handlingtime is included in the cycle. Part handling time each cycle is 45 sec. It consists of the workerobtaining two starting work units from a parts tray, loading them into the machine, and thenafter processing, unloading the completed parts and placing them into the same tray. Eachtray holds 24 parts. When all of the starting work units have been replaced with completedparts, the tray of completed parts is moved aside and a new tray of starting units is movedinto position at the machine. This irregular work element takes 4.0 min. Batch quantity is2400 units. Determine (a) average cycle time, (b) time to complete the batch, and (c) averageproduction rate.

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Solution: (a)Th= 45/60 sec = 0.75 min/cycle,To= 1.60 min, andTt= 0. The irregular workelement of replacing the parts trays is an additional component of work handling time thatmust be done every 24 parts or 24/3 = 8 cycles:Th2= 4.0/8 = 0.5 minCycle timeTc= 0.75 + 1.60 + 0.5 =2.85 min(b) Batch timeTb= 2.0(60) + (2400/3)(2.85) = 120 + 2280 =2400 min= 40 hr(c) Average production timeTp= 2400/800 = 3.00 min/cycle = 1.0 min/pcProduction rateRp= 60/1.0 =60 pc/hr3.4An automated production line consists of eight workstations. Work units are moved betweenstations with a transfer time of 12 sec. The automated operations performed at the eightstations take 40 sec, 52 sec, 43 sec, 48 sec, 30 sec, 54 sec, 53 sec, and 49 sec, respectively.Determine (a) cycle time for the line, (b) time to process one work unit through the eightworkstations, (c) average production rate, and (d) time to produce 25,000 units.Solution: (a) The longest processing operation time, MaxTo= 57 sec at station 6. It sets thepace for the rest of the line.Tc= 12 + 54 = 66 sec =1.1 min(b) Time to process one work unit through the eight workstations = 8(1.1) =8.8 min(c) Production rateRp= 60/1.1 =54.55 pc/hr(d) Time to produce 25,000 units = 25,000/54.55 =458.33 hr3.5Simultaneous batch production is used in a heat treating operation. The batch size that fits inthe furnace at one time is 12 parts of a certain type. A total of 500 of these parts are to be heattreated. Loading of 12 parts into the furnace takes 3.0 min. Unloading time at the end of heattreatment is 1.5 min. The cycle time to heat treat each batch is 25 min. How many hours arerequired to process the 500 parts?Solution: Assuming the furnace has been heated to the proper temperature in advance ofproduction, the time to process each batch of 12 parts = 3.0 + 25 + 1.5 = 29.5 min. Thenumber of batches = 500/12 = 41.67. This would have to be rounded up to 42 batches.Accordingly, total time for 500 parts = 42(29.5) = 1239 min =20.65 hr3.6(A)The proportion uptime of a certain piece of production equipment is 97.5%. When abreakdown occurs, the mean time to repair is 45 min. Determine the mean time betweenfailures of this equipment.Solution: From Equation (3.9),A(MTBF) =MTBF–MTTR0.975(MTBF) =MTBF– 45/60 =MTBF– 0.750.75 =MTBF– 0.975(MTBF) = 0.025(MTBF),MTBF= 0.75/0.025 =30 hr3.7Setup time on a certain production machine is 3.0 hours. Batch size is 36 parts, and operationcycle time is 2.5 min. Parts are processed sequentially. The reliability of this machine ischaracterized by a mean time between failures of 47 hours and a mean time to repair of 48min. (a) If availability is ignored, what is the average hourly production rate of the machine.(b) Taking into account the availability of the machine, determine its average hourlyproduction rate. (c) Suppose that availability only applied during the actual run time of themachine and not during the setup time. Determine the average hourly production rate of themachine under this scenario.Solution: (a) Batch timeTb= 3.0(60) + 36(2.5) = 180 + 90 = 270 min

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Tp= 270/36 = 7.5 min and production rateRp= 60/7.5 =8.0 pc/hr(b) AvailabilityA= (47 – 48/60)/47 = 0.983 = 98.3%Production rate including effect of availability =ARp= 0.983(8.0) =7.86 pc/hr(c) If availability only applies during run time, thenTb= 3(60) + 36(2.5/0.983) = 180 + 91.56 = 271.56 minTp= 271.56/36 = 7.54 min and production rateRp= 60/7.54 =7.95 pc/hrWorkload and Production Capacity3.8In a certain week, a production schedule for a certain department shows the following partsbeing produced: 540 parts of type A, 1200 parts of type B, 490 parts of type C, and 780 partsof type D. The respective production times for these parts are the following:TpA= 5.28 min,TpB= 2.86 min,TpC= 4.65 min, andTpD= 3.22 min. Determine the workload for thisdepartment in hours per week.Solution:WL= 540(5.28) + 1200(2.86) + 490(4.65) + 780(3.22)WL= 2851.2 + 3432 + 2278.5 + 2511.6 = 11,073.3 min =184.56 hr/wk3.9(A)A mass-production plant has eight machines and currently operates one 8-hour shift perday, 5 days per week, 50 weeks per year. Each machine produces the same part at a rate of 24parts per hour. (a) Determine the annual production capacity of this plant. (b) If the plantwere to operate three 8-hour shifts per day, 7 days per week, 52 weeks per year, determine theannual percentage increase in plant capacity?Solution: (a) From Table 3.1,Hpc= 2000 hrAnnual plant capacity using 50 weeks/yrPCy= 2000(8)(24) =384,000 pc/yr(b) From Table 3.1,Hpc= 8736 hr.Annual plant capacityPCy= 8736(8)(24) = 1,677,312 pc/wkThis is an increase of 1,677,312/384,000 – 1 = 3.368 =336.8%Comment:This problem illustrates the significant effect that hours of operation can haveon plant capacity.3.10One/half million parts of a certain type are to be manufactured annually on dedicatedproduction machines that run 16 hours per day, five days per week, 50 weeks per year. (a)The cycle time to produce one part is 1.8 min. If availability and utilization are each 100%,and setup time is neglected, how many of the machines will be required to satisfy demand?(b) Solve part (a) except that availability = 95%.Solution: (a) Total workloadWL= 500,000(1.8 min/60) = 15,000 hr/yrFrom Table 3.1, hours available/machine = 4000 hrNumber of machinesn= (15,000 hr)/(4000 hr/machine) = 3.75rounded up to4 machines(b) AtA= 90%,n= (15,000 hr)/(4000×0.95) = 3.95 rounded up to4 machines3.11A factory produces cardboard boxes. The production sequence consists of three operations:(1) cutting, (2) indenting, and (3) printing. There are three machines in the factory, one foreach operation. The machines are 100% reliable and operate as follows when operating at100% utilization: (1) In cutting, large rolls of cardboard are fed into the cutting machine andcut into blanks. Each large roll contains enough material for 4,000 blanks. Production cycletime = 0.03 minute per blank during a production run, but it takes 35 minutes to change rolls

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between runs. (2) In indenting, indentation lines are pressed into the blanks to allow theblanks to later be bent into boxes. The blanks from the previous cutting operation are dividedand consolidated into batches whose starting quantity = 2,000 blanks. Indenting is performedat 4.5 minutes per 100 blanks. Time to change dies on the indentation machine = 30 min. (3)In printing, the indented blanks are printed with labels for a particular customer. The blanksfrom the previous indenting operation are divided and consolidated into batches whosestarting quantity = 1,000 blanks. Printing cycle rate = 30 blanks per min. Between batches,changeover of the printing plates is required, which takes 20 minutes. In-process inventory isallowed to build up between machines 1 and 2, and between machines 2 and 3, so that themachines can operate independently as much as possible. Determine the maximum possibleoutput of this factory during a 40-hour week, in completed blanks per week (completedblanks have been cut, indented, and printed)? Assume steady state operation, not startup.Solution: Determine maximum production rateRpfor each of the three operations:Operation (1) - cutting:Tb= 35 min. + 4000 pc×0.03 min/pc = 35 + 120 = 155 min/batchRp= 4000 pc/batch/(155 min/batch) =25.806 pc/min =1548.4 pc/hrOperation (2) - indenting:Tb= 30 min. + 2000 pc(4.5/100 min./pc) = 30 + 90 = 120min/batchRp= 2000 pc/batch/(120 min/batch) = 16.667 pc/min =1000 pc/hrOperation (3) - printing:Tb= 20 min. + 1000 pc/(30 pc/min) = 20 + 33.33 = 53.33 min/batchRp= 1000 pc/(53.33 min/batch) = 18.751 =1125 pc/hrBottleneck process is operation (2).Weekly output = (40 hr/wk)(1000 pc/hr) =40,000 blanks/wk3.12A machine shop has ten machines in its automatic lathe section. Setup time on an automaticlathe is 5 hours. Batch size is 100 for parts processed through the section. Cycle time per partis 9.0 minutes. Under shop rules, an operator can be assigned to run one or two machines.Accordingly, there are five operators in the section for the ten lathes. In addition to the latheoperators, there are two setup workers who only perform machine setups. These setupworkers are busy the full shift. The section runs one 8-hour shift per day, 5 days per week.Scrap losses are negligible and availability = 100%. The production control manager claimsthat the capacity of the section should be 2000 parts per week. However, the actual output isonly 1600 units per week. What is the problem? Recommend a solution.Solution: Hours/week = 40 hrTp= (5 + 100×9/60)/100 = 20 hr/100 pc = 0.20 hr/pc,Rp= 5 pc/hrProduction capacity of automatic lathe section:PC= (40 hr/wk)(5 pc/hr)(10 machines) =2000 pc/wkBut the actual output = 1600 pc/wk. Why? Consider the workload of the setup workers.Number of setups per week = (2 setup workers)(40 hr/wk)/(5 hr/setup) = 16 setups/wk = 16batches/wk. At 100 pc/batch, total pc/week = 16×100 =1600 pc/weekThe problem is that the setup workers represent a bottleneck. To solve the problem, hire onemore setup worker. With three setup workers, number of batches per week = 3(40)/5 = 24batches/wk. At 100 pc/batch, total output could be 24×100 =2400 pc/weekComments: (1) There are 10 machines but with 2 setup workers each setting up during the40-hr week, this means that only 8 machines are producing parts at any given moment. Thustwo of the five machine operators only have one machine to tend at any given moment. To

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maximize worker utilization, each machine operator should be tending two machines at alltimes. An ideal situation would be to have 12 machines, in which two machines are being setup at any given time, and 10 machines are producing, so that there are two machines for eachof the five machine operators.(2) In order to increase output and balance the workloads between the machine operators andsetup workers, the shop should consider purchasing two additional automatic lathes. Threesetup workers would be capable of (3)(40 hr/wk)/(5 hr/setup) = 24 setups/wk. Each batchtakes 20 hr, so each machine can complete 2 batches/wk. Total batches with 12 machines is24/wk or 24 setups/wk.Bottleneck Model3.13(A)A job shop has three workstations, each with multiple servers. It operates 80 hours perweek and produces four different product styles: A, B, C, and D. Part-mix ratios, batchquantities, part routings, machines, servers, and production times are given in the tablebelow for the four product styles made in the shop. Operation sequence for product style isin the order of station number. Determine (a) which station is the bottleneck, (b) totalweekly output of all four products, (c) weekly output of each of the four product styles, (d)utilization of each server at each station, (e) average utilization of the machine shop. Setuptimes are accounted for in theTpvalues.Part style (j)ABCDPart mixpj0.240.180.310.27Batch quantitiesQb15201012Stations(i)ServerssiTpA(hr)TpB(hr)TpC(hr)TpD(hr)130.550.400.380.42240.620.750.520.38320.380.280.450.24Solution: (a) Computations were performed on a spreadsheet calculator with the resultsshown in the table below. Workloads are calculated by Equation (3.20). For example,WL1= 0.24(0.55) + 0.18(0.40) + 0.31(0.38) + 0.27(0.42) = 0.435 hr/pc. The bottleneck station isidentified in bold characters:station 3with two servers.Part style (j)ABCDPart mixpj0.240.180.310.27Batch quantityQb15201012Stations(i)ServerssiTpiA(hr)TpiB(hr)TpiC(hr)TpiD(hr)WLi(hr)WLi/s(hr)Rp*(pc/hr)Userver130.550.400.380.420.4350.1450.839240.620.750.520.380.5480.1370.792320.380.280.450.240.3460.1735.781.0(b) Total production rate of all five parts = 5.78 pc/hrWeekly output = 5.78(80) =462 pc/wk(c) Production rates of each part style:RpA= 1.39 pc/hr,RpB= 1.04 pc/hr,RpC= 1.79 pc/hr,andRpD= 1.56 pc/hrWeekly outputs for A = 1.39(80) =111 pc, B =82 pc, C =143 pc, and D =125 pc

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