自动化课后答案ch16 transfer lines3esi.docx

1、自动化课后答案ch16 transfer lines3esiChapter 16AUTOMATED PRODUCTION LINESREVIEW QUESTIONS16.1 Name three of the four conditions under which automated production lines are appropriate. Answer: The four conditions listed in the text are (1) high product demand, (2) stable product design, (3) long product lif

2、e, and (4) multiple operations are required to produce the product.16.2 What is an automated production line? Answer: As defined in the text, an automated production line consists of multiple workstations that are automated and linked together by a work handling system that transfers parts from one

3、station to the next.16.3 What is a pallet fixture, as the term is used in the context of an automated production line?Answer: As defined in the text, a pallet fixture is a workholding device that is designed to (1) fixture the part in a precise location relative to its base and (2) be moved, located

4、, and accurately clamped in position at successive workstations by the transfer system.16.4 What is a dial-indexing machine?Answer: A dial-indexing machine is an automated system consisting of multiple workstations that process workparts attached to fixtures around the periphery of a circular workta

5、ble, and the table is indexed (rotated in fixed angular amounts) to position the parts at the stations.16.5 Why are continuous work transport systems uncommon on automated production lines?Answer: Continuous work transport systems are uncommon on automated lines due to the difficulty in providing ac

6、curate registration between the station workheads and the continuously moving parts.16.6 Is a Geneva mechanism used to provide linear motion or rotary motion? Answer: A Geneva mechanism provides rotary motion.16.7 What is a storage buffer as the term is used for an automated production line?Answer:

7、As defined in the text, a storage buffer is a location in a production line where parts can be collected and temporarily stored before proceeding to subsequent (downstream) workstations.16.8 Name three reasons for including a storage buffer in an automated production line? Answer: The text lists the

8、 following five reasons: (1) to reduce the effect of station breakdowns, (2) to provide a bank of parts to supply the line, (3) to provide a place to put the output of the line, (4) to allow for curing time or other required delay associated with processing, and (5) to smooth cycle time variations.

9、16.9 What are the three basic control functions that must be accomplished to operate an automated production line?Answer: The three basic control functions are (1) sequence control to coordinate the sequence of actions of the transfer system and associated workstations, (2) safety monitoring to ensu

10、re that the production line does not operate in an unsafe condition, and (3) quality control to monitor certain quality attributes of the workparts produced on the line. 16.10 Name some of the industrial applications of automated production lines.Answer: Applications listed in the text include machi

11、ning, sheet metal forming and cutting, spot welding of car bodies in final assembly plants, painting and plating operations, and assembly.16.11 What is the difference between a unitized production line and a link line?Answer: A unitized production line is an automated production line that consists o

12、f standard modules and is assembled in an appropriate configuration to satisfy the production requirements of the customer. A link line is a production line that consists of standard machine tools that are connected together by standard or special material handling devices.16.12 What are the three p

13、roblem areas that must be considered in the analysis and design of an automated production line?Answer: The three problem areas identified in the text are (1) line balancing the same basic problem as in manual assembly lines; (2) processing technology cutting tool technology, speeds and feeds, and s

14、o on; and (3) system reliability due to the complexity of an automated production line.16.13 As the number of workstation on an automated production line increases, does line efficiency (a) decrease, (b) increase, or (c) remain unaffected?Answer: (a). Line efficiency decreases because each additiona

15、l station increases the probability of a line stop.16.14 What is starving on an automated production line?Answer: Starving on an automated production line means that a workstation is prevented from performing its cycle because it has no part to work on. When a breakdown occurs at any workstation on

16、the line, the downstream stations will either immediately or eventually become starved for parts.16.15 In the operation of an automated production line with storage buffers, what does it mean if a buffer is nearly always empty or nearly always full?Answer: In the operation of an automated production

17、 line with storage buffers, if any of the buffers are nearly always empty or nearly always full, this indicates that the production rates of the stages on either side of the buffer are out of balance and that the storage buffer is serving little useful purpose.PROBLEMSTransfer Mechanisms16.1 A rotar

18、y worktable is driven by a Geneva mechanism with five slots. The driver rotates at 48 rev/min. Determine (a) the cycle time, (b) available process time, and (c) indexing time each cycle.Solution: (a) Tc = = = 0.020833 min = 1.25 sec(b) = = 72 Ts = = 0.01458333 min = 0.875 sec(c) Tr = = 0.00625 min =

19、 0.375 sec16.2 A Geneva with six slots is used to operate the worktable of a dial-indexing machine. The slowest workstation on the dial-indexing machine has an operation time of 2.5 sec, so the table must be in a dwell position for this length of time. (a) At what rotational speed must the driven me

20、mber of the Geneva mechanism be turned to provide this dwell time? (b) What is the indexing time each cycle? Solution: (a) = 360/6 = 60 Ts = = = 2.5 sec (given)N = = 0.2667 rev/sec = 16 rev/min(b) Tr = = 1.25 sec16.3 Solve the previous problem except that the Geneva has ten slots.Solution: (a) = 360

21、/10 = 36 Ts = = 0.60/N = 2.5 sec (given)N = 0.60/2.5 = 0.241 rev/sec = 14.4 rev/min(b) Tr = = 1.66 secAutomated Production Lines with No Internal Storage16.4 A ten-station transfer machine has an ideal cycle time of 30 sec. The frequency of line stops is 0.075 stops per cycle. When a line stop occur

22、s, the average downtime is 4.0 min. Determine (a) average production rate in pc/hr, (b) line efficiency, and (c) proportion downtime.Solution: (a) Tp = 0.5 + 0.075(4) = 0.5 + 0.3 = 0.8 min Rp = 1/0.8 = 1.25 pc/min = 75 pc/hr(b) E = 0.5/0.8 = 0.625 = 62.5%(c) D = 0.3/0.8 = 0.375 = 37.5%16.5 Cost elem

23、ents associated with the operation of the ten-station transfer line in Problem 16.4 are as follows: raw workpart cost = $0.55/pc, line operating cost = $42.00/hr, and cost of disposable tooling = $0.27/pc. Compute the average cost of a workpiece produced.Solution: Refers to Problem 16.4: Cpc = 0.55

24、+ 42(0.8)/60 + 0.27 = 0.55 + 0.56 + 0.27 = $1.38/pc16.6 In Problem 16.4, the line stop occurrences are due to random mechanical and electrical failures on the line. Suppose that in addition to these reasons for downtime, that the tools at each workstation on the line must be changed and/or reset eve

25、ry 125 cycles. This procedure takes a total of 15.0 min for all ten stations. Include this additional data to determine (a) average production rate in pc/hr, (b) line efficiency, and (c) proportion downtime.Solution: Refers to Problem 16.4:(a) F1Td1 = 0.075(4.0) = 0.3 minF2Td2 = 15.00/125 = 0.12 min

26、Tp = 0.5 + 0.3 + 0.12 = 0.92 min Rp = 1/0.92 = 1.087 pc/min = 65.22 pc/hr(b) E = 0.5/0.92 = 0.5435 = 54.35%, (c) D = 0.42/0.92 = 0.4565 = 45.65%16.7 The dial indexing machine of Problem 16.2 experiences a breakdown frequency of 0.06 stops/cycle. The average downtime per breakdown is 3.5 min. Determi

27、ne (a) average production rate in pc/hr and (b) line efficiency.Solution: Refers to Problem 16.2: (a) From Problem 16.2, Tc = To + Tr = 2.5 + 1.25 = 3.75 secTp = 3.75/60 + 0.06(3.5) = 0.0625 + 0.021 = 0.2725 min Rp = 1/0.2725 = 3.67 pc/min = 220.2 pc/hr(b) E = 0.0625/0.2725 = 0.2294 = 22.94%16.8 In

28、the operation of a certain 15-station transfer line, the ideal cycle time = 0.58 min. Breakdowns occur at a rate of once every 20 cycles, and the average downtime per breakdown is 9.2 min. The transfer line is located in a plant that works an 8-hr day, 5 days per week. Determine (a) line efficiency,

29、 and (b) how many parts will the transfer line produce in a week?Solution: (a) Tp = 0.58 + 9.2/20 = 0.58 + 0.46 = 1.04 min E = 0.58/1.04 = 0.5577 = 55.77%(b) Rp = 60/1.04 = 57.69 pc/hr Weekly production = 40(57.69) = 2307.7 pc/wk.16.9 A 22-station in-line transfer machine has an ideal cycle time of

30、0.58 min. Station breakdowns occur with a probability of 0.01. Assume that station breakdowns are the only reason for line stops. Average downtime = 8.0 min per line stop. Determine (a) ideal production rate, (b) frequency of line stops, (c) average actual production rate, and (d) line efficiency.So

31、lution: (a) Rc = = 1.724 pc/min = 103.45 pc/hr(b) F = np = 22(0.01) = 0.22(c) Tp = 0.58 + 0.22(8) = 0.58 + 1.76 = 2.34 min Rp = = 0.4274 pc/min = 25.64 pc/hr(d) E = = 0.248 = 24.8%16.10 A ten-station rotary indexing machine performs nine machining operations at nine workstations, and the tenth stati

32、on is used for loading and unloading parts. The longest process time on the line is 1.30 min and the loading/unloading operation can be accomplished in less time than this. It takes 9.0 sec to index the machine between workstations. Stations break down with a frequency of 0.007, which is considered equal for all ten stations. When these stops occur, it takes an average of 10.0 min to diagnose the problem and make repairs. Determine (a) line efficiency and (b) average actual production