Unit 4 ppc

ppc

1. Unit 4- CONTENT Routing – Definition – Routing procedure –Route sheets – Bill of material – Factors affecting routing procedure. Schedule –definition – Difference with loading, Scheduling Policies – Techniques, Standard scheduling methods, Line Balancing, Aggregate planning, Chase planning, Expediting, controlling aspects.

2. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES

3. Routing: It means determination of the route to be followed by each part/component being transformed from input/raw material into final product.” Obviously where one single part/product is produced by fixed set of machines the job of routing becomes automatic or mechanized. In continuous production systems with line type or product type layout, no managerial effort is required for routing though different sets of machines may be utilized in manufacturing the products in such systems.

4. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES When one single part/product is produced by fixed set of machines the job of routing becomes automatic or mechanized. In continuous production systems with line type or product type layout, no managerial effort is required for routing though different sets of machines may be utilized in manufacturing the products in such systems.

5. UNIT 4- ROUTING AND SCHEDULING TECHNIQUES Functions of Routing: In all engineering industries, the steps in the direction of preparation for production of a product are more or less the same and occur as follows: The future product exists only as an idea in the mind of the inventor and he draws the sketch. (2) The possible product is deeply analysed, studied and developed to prepare the drawings. (3) The next step is preparation of working drawings which may include the parts and assemblies drawings. (4) Blue prints of the drawings with necessary technical details are prepared.

6. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES When the product is standardized and the work is repetitive, the drawings of the components/parts are prepared with following considerations: (1) The operations and processes required to manufacture the components. (2) The material required for manufacturing of the product. (3) The method of manufacturing.

7. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES In such cases the completed design prepared by the engineering division and received in production control department will include the following: 1. Blue print of each components 2. List of parts, assemblies and sub assemblies. 3.Complete specifications of material required for each product. 4. Limits and tolerances on each part. 5. Specifications of machining process by which the part is to be produced, 6.Sequence of operations to be performed. 7.Time allowances (set up and operation time) for each operation/process.

8. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Routing Procedure: Routing procedure consists of six decisions as mentioned below: (1) Make and Buy Decision: The product to be manufactured and as parts needed are thoroughly analysed to determine which parts/components are to be made and which are to be purchased in view of the following facts: (2) Cost comparison for making and buying. (3) Whether the available manpower can be utilized for the purpose of making within the plant. (4) Whether the existing machines which are idle can be utilized. (5) Whether the input materials and machines are available in the plant for manufacture or require procurement.

9. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Bill of Material: After proper analysis of the product the quality and quantity of materials required is determined and the bill of materials as shown in Fig. From this proforma the quantity of material required for each part is known and accordingly can be procured. Some firms prepare separate lists for finished components and raw materials. To know-how much material is to be purchased or procured the amount of materials in the stores should be known.

10. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES

11. ROUTING AND SCHEDULING TECHNIQUES Preparation of Route Sheet: The third step of routing procedure is the determination of operations required together with their sequence to manufacture the product. The routing decision establishes the operations necessary for processing the product and lists them in their sequence on route sheet or operation sheet. The operation or route sheet is shown in FIGURE.

12. UNIT 4

13. UNIT 4 Lot Size Determination: In case of mass or continuous production systems, the mathematical relations can be used to find out the lot size to be processed. The idea is to determine the number of units to be produced in one lot. If the product is to be produced to fulfil the consumer requirements, the question to determine the lot size does not arise.

14. UNIT 4 Determination of Scrap Factor: The amount of waste which depends on the scraping factors is estimated. The scrap factor is the anticipated normal scrap encountered during the course of manufacturing. As we know that the all components produced at various work stations do not meet the required standards and those which do not pass inspection are to be neglected as scrap. Moreover the total material taken for processing the product does not go into end product. Thus scrap factor determination is an important part of routing procedure. In determining the scrap factor, it should be known where the scrap is going to occur, whether it occurs progressively during the fabrication/production of parts, end assembly or all of sudden after a certain operation or after completion of assembly. If the scrap occurs at one point in the process, a single scrap factor may take care of the anticipated scrap at the point, but when scrap is progressive, cumulative scrap factor is essential to serve the purpose. It would be better to work out the material requirement back ward starting from the desired level of finished product. The usual practice should be to establish these factors from past experience, to determine the manpower, the essential machines/ equipment and the materials. Thus the scrap factor plays an important role in the determination of manpower requirements and loading of various machines.

15. UNIT 4 To Provide Necessary Information and Forms: In order to carry out routing as planned various forms and procedures are required which furnish necessary information for the purpose. Various forms used e.g. production order, job ticket, inspection ticket, move order, tool ticket and equipment ticket are shown in Figs. 7.4 to 7.8 are also prepared in this process

16. UNIT 4

17. UNIT 4 The type of forms used in each department depends upon the type of manufacture. Manufacturing order shown in Fig. 7.4 which contains name, no., description, quantity of the part to be produced. Serial no. and other information are invariably used in job manufacturing production.

18. UNIT 4

19. UNIT 4

20. UNIT 4 If the manufacturing process is simple many plant forms are combined into one sheet called the master Route Sheet. This is a multipurpose sheet which also considerably reduces the paper work. The type of forms used in each department depends upon the type of manufacture. Manufacturing order shown in Fig- 7.4 which contains name, number description, quantity of the part to be produced, serial no and other information are invariably used in job manufacturing production.

21. UNIT 4

22. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Advantages of Routing: (1) Effective utilization of available resources. (2) Reduction in production costs. (3) Quality improvement occurs. (4) Productivity of the system improves and (5) Provides a basis for loading & scheduling.

23. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Factors affecting routing procedure: 01. Type of Manufacturing Process/Technique Employed: It is the case of use of line type of layout where the production process is serialized according to the sequence of operations thus making routing automatic. Automobile industries adopt this type of layout. The set up requires change only when new models are introduced. The same type of routing may be adopted in batch production also.

24. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES 02. Plant Equipment Characteristics: The same product may be possible to manufacture on two or many machines available in the plant. In such cases the cheapest one should be selected, whether small, heavy and automatic or mechanized machine for routing purpose. In order to simplify the process, the routing division should prepare and place on file a machine data card for each and every machine giving characteristics of machine, special attachments (Jigs, fixtures and special tools) and the job range. Records of other facilities like material handling equipment available in the shop may also be useful.

25. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES 03. Availability of Plant and Equipment etc.: Recommended actions have to be taken in order to select that equipment or machines, which will help in production of parts at cheapest rate. But sometimes the services of such machines or processes may not be available due to machine load conditions, breakdowns or absenteeism of workers. In such conditions, the routing division must have alternatives available to keep the materials moving for manufacturing of the product. This alternative may be in the form of detours around the breakdown machines/operations or by changing the sequence of operations.

26. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES 04. Difficulties in Routing due to Non-Availability of Requisite Skilled Manpower: Manpower required in the plant may be highly skilled, semiskilled, or unskilled. On certain particular machines, where high precision work is done, only services of experienced highly skilled workers can be utilized. Routine work may affect the routing procedure in context to manpower are job incentives, lot size, light, heavy or medium sized work etc.

27. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Scheduling: Establishing the timing of the use of equipment, facilities and human activities in an organization Effective scheduling can yield Cost savings Increases in productivity OR Sequencing - determining the order in which jobs will be processed Job-shop scheduling Scheduling for low-volume systems with many variations in requirements

28. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Gantt chart - used as a visual aid for loading and scheduling.

29. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Loading: Infinite loading – Jobs are assigned to work centers without regard to the capacity of the work centre Finite loading – Jobs are assigned to work centers taking into account the work center capacity and the processing times Forward scheduling – Scheduling ahead, from some point in time Backward scheduling – Scheduling by working backwards from the due dates Schedule chart

30. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Hungarian Method: Method of assigning by a one-for-one matching to identify the lowest cost solution Refer Hungarian Method notes. Workstation : An area where one person works, usually with special equipment, on a specialized job.

31. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Priority rules: Simple heuristics used to select the order in which jobs will be processed. Job time: Time needed for setup and processing of a job.

32. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES FCFS - first come, first served SPT - shortest processing time EDD - earliest due date LPT –Longest processing time CR - critical ratio S/O - slack per operation Rush - emergency

33. Routing Routing is the first step in production planning and control. Routing can be defined as the process of deciding the path (route) of work and the sequence of operations. Routing fixes in advance: The quantity and quality of the product. The men, machines, materials, etc. to be used. The type, number and sequence of manufacturing operations, and The place of production. In short, routing determines ‘What’, ‘How much’, ‘With which’, ‘How’ and ‘Where’ to produce.

34. Routing may be either very simple or complex. This depends upon the nature of production. In a continuous production, it is automatic, i.e. it is very simple. However, in a job order, it is very complex. Routing is affected by the human factor. Therefore, it should recognize human needs, desires and expectations. It is also affected by plant-layout, characteristics of the equipment, etc. The main objective of routing is to determine (fix) the best and cheapest sequence of operations and to ensure that this sequence is followed in the factory. Routing gives a very systematic method of converting raw-materials into finished goods. It leads to smooth and efficient work. It leads to optimum utilization of resources; namely, men, machines, materials, etc. It leads to division of labor . It ensures a continuous flow of materials without any backtracking. It saves time and space. It makes the work easy for the production engineers and foremen. It has a great influence on design of factory's building and installed machines.

35. The   routing  defines a specific step-by-step method of manufacture necessary to take a component, or set of components, and produce a parent. For every parent item in the manufacturing process, a BOM and routing are maintained. The routing detail is arranged in the order or sequence of the single-level manufacturing process.

36. Each step is assigned a number or operation identifier. For each operation, the department and work center where the work is to be performed are identified; The expected hours of machine setup, equipment changeover, or cleanup time is described; and The expected time to complete the operation for a single item (or piece), known as the operation standard, is described. Additionally some routing files allow users to maintain other support information, such as The labor grade required to perform the work and Any tooling or fixtures required to support the operation process.

37. Routing and Scheduling in Production Planning and Control Routing may be defined as the selection of path which each part of the product will follow while being transformed from raw materials to finished products. Path of the product will also give sequence of operation to be adopted while being manufactured. In other way, routing means determination of most advantageous path to be followed from department to department and machine to machine till raw material gets its final shape, which involves the following steps: Type of work to be done on product or its parts. Operation required to do the work. Sequence of operation required. Where the work will be done. A proper classification about the personnel required and the machine for doing the work.

38. For effective production control of a well-managed industry with standard conditions, the routing plays an important role,  i.e ., to have the best results obtained from available plant capacity. Thus routing provides the basis for scheduling, dispatching and follow-up. Techniques of Routing While converting raw material into required goods different operations are to be performed and the selection of a particular path of operations for each piece is termed as ‘Routing’. This selection of a particular path,  i.e . sequence of operations must be the best and cheapest to have the lowest cost of the final product. The various routing techniques are:

39. Route card: This card always accompanies with the job throughout all operations. This indicates the material used during manufacturing and their progress from one operation to another. In addition to this the details of scrap and good work produced are also recorded Work sheet: It contains Specifications to be followed while manufacturing. Instructions regarding routing of every part with identification number of machines and This sheet is made for manufacturing as well as for maintenance.

40. 3. Route sheet: It deals with specific production order. Generally made from operation sheets. One sheet is required for each part or component of the order. This includes the following: Number and other identification of order. Symbol and identification of part. Number of pieces to be made. Number of pieces in each lot if put through in lots. Operation data which includes: List of operation on the part. Department in which operations are to be performed. Machine to be used for each operation. Fixed sequence of operation, if any.

41. 4. Move order: Though this is document needed for production control, it is never used for routing system. Move order is prepared for each operation as per operation sheet. On this the quantity passed forward, scrapped and to be rectified are recorded. It is returned to planning office when the operation is completed.

42. 1. Product analysis Product analysis is the first step in the routing procedure. This is done to find out what parts (goods) should be manufactured and what parts should be purchased. This depends mainly on the relative cost. It also depends on other factors such as technical consideration, purchase policies, availability of personnel, availability of equipment, etc. Generally, during less-busy periods; most of the parts are manufactured in the factory. However, during the busy period, many parts are purchased from outside. 2. Determine required materials Product-analysis is done again to find out what materials are required for production and their quantity and quality.

43. 3. Fix manufacturing operations The next step in the routing procedure is to fix (decide) the manufacturing operations and their sequences. The detailed production procedure is then scheduled (planned). Information required for this is derived from technical experience and by analyzing the machine capacity. 4. Determine size of batch The number of units to be manufactured in any one lot (group or batch) should be decided. This is done concerning customers' orders. Necessary provision should also be made for rejections during the production process.

44. 5. Estimate margin of scrap The amount of scrap in each lot, should be estimated. Generally, a scrap margin is between 2% to 5% of production. 6. Analyze the production cost Estimating the cost of manufactured goods is actually the function of costing department. However, the routing section provides necessary data to the costing department that enables it to analyze the production cost.

45. 7. Prepare production control forms Production Control forms such as Job Cards, Inspection Cards, Tool Tickets, etc. should be prepared. These forms should contain complete information for effective routing. 8. Prepare route sheet Route sheet is prepared on a production control form. It shows the part number, description of the part and the materials required. It is prepared by a route clerk. Separate route-sheet is required for each part of a customer's order.

46. Four main factors affecting routing procedure. The factors are : 1. Type of Manufacturing Process/Technique Employed. 2. Plant Equipment Characteristics. 3. Availability of Plant and Equipment etc. 4. Difficulties in Routing due to Non-Availability of Requisite Skilled Manpower.

47. Factor # 1. Type of Manufacturing Process/Technique Employed: It is the case of use of line type of layout where the production process is serialized according to the sequence of operations thus making routing automatic. Automobile industries adopt this type of layout. The set up requires change only when new models are introduced. The same type of routing may be adopted in batch production also.

48. Factor # 2. Plant Equipment Characteristics: The same product may be possible to manufacture on two or many machines available in the plant. In such cases the cheapest one should be selected, whether small, heavy and automatic or mechanised machine for routing purpose.

49. Factor # 3. Availability of Plant and Equipment etc.: Recommended actions have to be taken in order to select that equipment or machines, which will help in production of parts at cheapest rate. But sometimes the services of such machines or processes may not be available due to machine load conditions, breakdowns or absenteeism of workers. In such conditions, the routing division must have alternatives available to keep the materials moving for manufacturing of the product. This alternative may be in the form of detours around the breakdown machines/operations or by changing the sequence of operations.

50. Factor # 4. Difficulties in Routing due to Non-Availability of Requisite Skilled Manpower: Manpower required in the plant may be highly skilled, semiskilled, or unskilled. On certain particular machines, where high precision work is done, only services of experienced highly skilled workers can be utilized. Routine work may affect the routing procedure in context to manpower are job incentives, lot size, light, heavy or medium sized work etc.

51. Engineering Bill of Materials (EBOM) The engineering bill of materials (EBOM) defines the finished product as it was originally designed. It lists the items, parts, components, subassemblies, and assemblies in the product as engineering designed it. The EBOM is often created by the product engineers based on a CAD drawing. For a finished product, more than one EBOM may be created.

52. A precise and accurate EBOM is essential, especially for a new product, since this is the document that ensures the correct materials and parts—in the correct quantities—are available when the item is being manufactured. To ensure that the parts are available when required, the purchasing department needs information on what vendors to purchase items from and how much lead time is required for each ordered part. The purchasing department will negotiate to obtain the best price for each part in efforts to reduce the overall cost of the finished product. The ramifications of errors in the EBOM are serious. Incorrect quantities can cause production to be stopped. Any delay can lead to financial loss as the manufacturer attempts to find missing parts or postpones manufacturing to start a different production order.

53. Manufacturing Bill of Materials (MBOM) The manufacturing bill of materials (MBOM) contains information on all the parts and assemblies required to build a complete and shippable product. This includes all the packaging materials required to ship the finished product to the customer. The MBOM includes not only all the information required for manufacturing but also any processes that must be performed on the item before it is completed. When a materials resource planning (MRP) analysis is run, the details of the MBOM are used to calculate when materials need to be purchased and when the manufacturing order needs to start, based on the suggested delivery date to the customer.

54. Several elements are involved in creating an MBOM. For some companies, the MBOM must have a validity date range. For example, when new products are being tested, the manufacturer may want to restrict the MBOM's use to one or two months. If, after the test period, the product requires some modification to either key elements or to the packaging, the MBOM can be changed and a new validity date can be established. Alternatively, an entirely new MBOM can be created

55. Simple Sequencing Rules PROCESSING DUE JOB TIME DATE A 2 7 B 8 16 C 4 4 D 10 17 E 5 15 F 12 18

56. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES

57. Simple Sequencing Rules: SPT A 2 2 7 0 C 4 6 4 2 E 5 11 15 0 B 8 19 16 3 D 10 29 17 12 F 12 41 18 23 Job Processing Flow DUE TARDINESS SEQUENCE TIME TIME DATE Flow – dd (0 if negative) Sequence: A-C-E-B-D-F 41 108 40 Average flow time = 108/6 = 18 days Average Tardiness = 40/6 = 6.67 days Makespan = 41 days Average number of jobs at the work center = 108/41 = 2.63

58. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES

59. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES

60. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES Two Work Centre Sequencing: Johnson’s Rule : technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers. Minimizes total idle time Several conditions must be satisfied

61. UNIT 4 ROUTING AND SCHEDULING TECHNIQUES

62. Johnson’s Rule JOB PROCESS 1 PROCESS 2 A 6 8 B 11 6 C 7 3 D 9 7 E 5 10 C E A B D

63. Processing time(job work time) • Time required to process a job • Setup time + actual processing time Due date • Date at which a job is to be completed Flow time • Waiting time + processing time Job lateness • Time at which job is actually completed – scheduled finishing time • Flow time(days) – Job due date(days) Key Terminologies

64. 1. Minimize completion time Average completion time = sum of total flow time / number of jobs 2. Maximize utilization of facilities Utilization = total job work time / sum of total flow time Minimize work-in-process (WIP) inventory Average number of jobs in the system = sum of total flow time / total job work time 4. Minimize customer waiting time Average job lateness = Total late days / number of jobs

65. Apply the four popular sequencing rules to these five jobs

66. FCFS (First Come First Serve): Sequence A-B-C-D-E

67. SPT (Shortest Possible Time): Sequence B-D-A-C-E

68. EDD( Earliest Due Date) : Sequence B-A-D-C-E

69. Longest Processing Time (LPT): Sequence E-C-A-D-B

70. Sequencing N Jobs on Two Machines: Johnson’s Rule  Works with two or more jobs that pass through the same two machines or work centers  Minimizes total production time and idle time Johnson’s Rule 1. List all jobs and times for each work center 2. Choose the job with the shortest activity time. If that time is in the first work center, schedule the job first. If it is in the second work center, schedule the job last. 3. Once a job is scheduled, it is eliminated from the list 4. Repeat steps 2 and 3 working toward the center of the sequence

71. Johnson’s Rule Example Choose the job with the shortest activity time. If that time is in the first work center, schedule the job first. If it is in the second work center, schedule the job last.

72. WORK CENTER 1 Job WC1 Time in Time out Idle Time B 3 3 E 7 3 10 D 10 10 20 C 8 20 28 A 5 28 33 WORK CENTER 2 Job WC2 Time in Time out Idle Time B 6 3 9 3 E 12 10 22 1 D 7 20 29 2 C 4 28 33 1 A 2 33 35 Minimum elapsed time is 35