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ENX300 Manufacturing Systems Design

ENX300 Manufacturing Systems Design. REVISION Module Leader: Ken Robson, St Peters Campus. What we covered. UNIT 1 Lesson 1 JIT/Lean Philosophy Lesson 2 JIT Techniques Lesson 3 Manufacturing Layout Lesson 4 Layout Design Techniques/ Line-balancing

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ENX300 Manufacturing Systems Design

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  1. ENX300Manufacturing Systems Design REVISION Module Leader: Ken Robson, St Peters Campus

  2. What we covered UNIT 1 Lesson 1 JIT/Lean Philosophy Lesson 2 JIT Techniques Lesson 3 Manufacturing Layout Lesson 4 Layout Design Techniques/ Line-balancing Lesson 5 Layout Design Techniques /Production Flow Analysis Lesson 6 JIT Planning & Control / Push vs Pull.Kanban UNIT 2 Lesson 9 &10 Maintenance Strategies Lesson 11 OEE Exercises UNIT 3 Lesson 12 Improvement Approaches CI & BPR

  3. Unit 1 lesson 1 -Just in Time Philosophy THE 7 WASTES - The elimination of waste in all its forms (see Slack pages 524-525 (470) ) for more detail • Overproduction • Waiting time • Transport • Process • Inventory • Motion • Defective goods

  4. Unit 1 lesson 2 - JIT Techniques Nine Areas • Flow Layout • The basic working practices of JIT • Design for Ease of Processing • Emphasize Operations Focus • Small Machines • Total productive maintenance (TPM) • Reduction of Set-Up Times • Ensure Visibility • JIT purchasing

  5. High Dependency Theory One explanation of the JIT approach to operations management is called the high dependency theory. It derives partly from the logic of low buffer inventories. With high inventories the production stages are ‘insulated’ and the dependency on one another is low. Conversely, if the inventory is removed then mutual dependency significantly increases. This has the effect of empowering ‘shop floor’ staff and makes the organization dependent on their actions. One might argue by doing so the responsibility is being shifted from management to the shop floor. Other examples of high dependency strategies: • Internal customer/ supplier concept • Total Productive Maintenance • Supplier development policies

  6. Unit 1 lesson 3 - Layout and Flow Layout decisions have to be carefully thought out: • Size and complexity of equipment involved • Cost • Resource and time • Disruption to production and customer service • Complex production flows achieved as a result of poor design.

  7. Unit 1 lesson 3 - Layout • Product volume and variety dictate the process type selected. • Areas of overlap exist where more than type could be applicable – in this case operational objectives are used to make decision: cost, flexibility, known future areas of growth etc. • There are four broad layouts • Fixed position • Process • Cell • Product

  8. Effect of bottlenecks on Product and Process layouts • The type of layout that is deployed in manufacturing plants is dependent on the demand for products i.e. the volume variety mix. • When the volume demand is high and product variety low a ‘flow line’ configuration is often the best approach because it is able to produce large volumes of standard product virtually continuously.

  9. Effect of bottlenecks on Product and Process layouts • In the Product layout the resources or machines are aligned specifically for the manufacture of the product. In this case the sequential nature of the process makes any bottleneck significant because all of the products have to be processed through the ‘bottleneck’ and this then dictates the overall cycle time and therefore the number of products produced in a given period.  

  10. Effect of bottlenecks on Product and Process layouts • In the case of a “process layout” products are routed through grouped resources and “bottlenecks” become less influential on cycle time because of the regular filling and refilling of the different products through the process.

  11. Effect of bottlenecks on Product and Process layouts • The time it takes to “fill” a process line with one product is likely to be significantly longer than the duration of the ‘bottleneck’ activity. This means that any improvement to the ‘bottleneck’ has limited impact on the overall production cycle time.

  12. Effect of bottlenecks on Product and Process layouts • In “process” layout configurations the main challenge to manufacturing practitioners is not so much the identification and removal of bottlenecks but rather the identification of inefficiencies in a relatively complex process where products are difficult to track and manage.

  13. Lesson 4 Layout Design Techniques: Line Balancing

  14. Unit 1 lesson 4 - Product Layout • Transforming resources located for the convenience of the transformed resources • Product/customer/information follow a pre-arranged route • Sequence of activities matches the sequence in which process’s have been located • The bottleneck dictates the cycle time that can be achieved

  15. Some definitions – (ch4 Slack) • Cycle time – the average time for units of output to emerge from the process • Throughput time – the time for a ‘unit’ to move through the process • Work Content – the total amount of work required to produce a unit of output • WIP – work in progress

  16. Detailed Design - Product Layout • Key decisions are concerned with ‘what to place where’ – in terms of what to allocate to each of the workstations. • This is termed line balancing • Other key questions are: • What cycle time is needed? • How many stages are needed? • How should the layout be balanced? • How should the stages be arranged?

  17. Line Balancing Cycle time = time available No.of units to be processed • Suppose a bank is designing an operation to process mortgage applications. The number to be processed per week= 160 and the time available for processing = 40 hours Cycle time = 40 = 1 hr = 15 minutes 160 4

  18. Line Balancing Number of stages req. = work content required cycle time Suppose the back in the previous example calculated the total work content to process a mortgage application to be 60 minutes. Cycle time = 15 mins Number of stages = 60 = 4 stages 15

  19. Line Balancing • The previous example assumed that 15mins. of work time was allocated equally to each of the 4 stages. • This can be almost impossible in practice and some imbalance results • The effectiveness of the line balancing is measured by ‘balancing loss’ • Balancing loss - is that proportion of the time invested in processing the product or service which is not used productively • Can lead to excessive stations being required

  20. Calculation of Balancing Loss An ideal ‘balance’ where work is allocated equally between the stages But if work is not equally allocated the cycle time will increase and ‘balancing losses’ will occur 3 Cycle time = 2.5 mins Cycle time = 3.0 mins 3.5 2.5 3 3.0 2.5 2 2.5 Load 2.3 2.5 2.2 2.2 3.0 2.3 2 Load 1.5 1.5 1 1 0.5 0.5 0 0 1 2 3 4 1 2 3 4 Stage Stage Work allocated to stage Calculating balancing loss: Idle time every cycle =(3.0 - 2.3) + (3.0 - 2.5) + (3.0 - 2.2) = 2.0 mins Balancing loss = 2.0 4 x 3.0 = 0.1667 = 16.67% Idle time

  21. Element - -De-tin and trim 0.12 mins a Element - Reshape with off-cuts 0.30 mins b Element - Clad in almond fondant 0.36 mins c Element - Clad in white fondant 0.25 mins d Element - Decorate, red icing 0.17 mins e Element - Decorate, green icing 0.05 mins f Element - Decorate, blue icing 0.10 mins g Element - Affix transfers 0.08 mins h Element - Transfer to base and pack 0.25 mins i Total work content = 1.68 mins 0.17 mins e 0.25 mins 0.30 mins 0.05 mins 0.25 mins a b c d f g i 0.12 mins 0.36 mins 0.10 mins 0.08 mins h Element listing and precedence diagram for Karlstad Kakes

  22. 0.17 mins e Stage 1 Stage 2 Stage 3 Stage 4 0.25 mins 0.30 mins 0.05 mins 0.25 mins a b c d f g i 0.12 mins 0.36 mins 0.10 mins h 0.08 mins Cycle time = 0.48 mins Idle time every cycle= (0.48 - 0.42) + (0.48 - 0.36) + (0.48 - 0.42)= 0.24 mins Proportion of idle time per cycle = 0.24 = 12.5% 4 x 0.48 Allocation of elements to stages and balancing loss for Karlstad Kates

  23. Line Balancing Example (May 2010) • A manufacturer wishes to create a flow line which will produce 1895 products/day (24 hr / day). The assembly information for the product is outlined in Table Q2 below. • Calculate the maximum cycle time (3) • Calculate the theoretical minimum number of work stations (3) • Produce the precedence diagram (6) • Produce the line design which achieves the required cycle time (8) • Calculate the idle time/cycle and the output level based upon the new cycle time. (5)

  24. Line Balancing Example (May 2010)

  25. Line Balancing Example (May 2010) Max cycle time required =24*60*60/1895 = 45.59 secs therefore 45sec (A solution of 46 secs is incorrect (3 marks) Minimum Number of workstations required =191/45 = 4.24 therefore 4 or 5 workstations (3 marks)

  26. Line Balancing Example (May 2010)

  27. Line Balancing Example (May 2010) Possible solution (key points are that logic and max cycle time are not compromised) (8 marks ):

  28. Line Balancing Example (May 2010) Idle time/cycle = (34/(5*44))*100 = 15.45 % . Actual output based upon new 44 sec cycle time = 24*60*60/44 =1963 units/day. ( these may vary based upon the student’s design and will be marked accordingly) (5 marks)

  29. Lesson 5 Layout Design Techniques: Production Flow Analysis

  30. Cellular Design • We have looked how flow-lines can be designed and analysed using the line balancing technique. • If we want to design a manufacturing cell to produce a specified set of components we can use a variety of techniques. • One of the most commonly used methods is ‘Product Flow Analysis’(PFA) e.g. Rank Order Clustering

  31. Product Flow Analysis(PFA) • PFA uses the resources needed to manufacture components as the basis of identifying cellular groupings. It has a number of advantages and disadvantages these can be considered as: • ADVANTAGES; • Quick and simple to perform • Low cost method as no specialist equipment or training is needed. • No need for resource or product technical expertise

  32. Product Flow Analysis(PFA) DISADVANTAGES • It does not consider the number of resources available - separate capacity calculation have to be carried out to determine the number of each resource type needed in each cell. • It does not consider the geometry / features of parts – this may prove problematic when material handling devices and transport systems are considered. • Resource and routing data has to be verified or the output for the process is meaningless

  33. Cellular Design • PFA. A technique for planning to change from a process (functional) layout to one which is more focussed on the product i.e. a hybrid (work cell) • Achieved by identifying families of products which need to be processed by the same resources creating ‘islands of product layout, in a sea of process layout’ Waters (1991) • Rank Order Clustering (ROC) is a common technique used for this purpose. It uses binary numbering to give each row and column an identity or value. • This allows them to be sorted in descending order • From the ordered matrix produced, clusters and patterns can be seen, which allow the boundaries of potential ‘work cells’ to be identified

  34. ROC Discussion • Remember the output from the ROC process is just an indicator, an initial part of the overall analysis that would be needed. • Other issues to consider include: • Capacity – i.e. how many resources of each type are needed. [Important as any particular cell may be to large] • Bill of materials (BOM) relationship, how the product is constructed Resource restrictions: • Space • Health & Safety • Cost of resource duplication

  35. Product Flow Analysis Tutorial Example 1. Sort the given matrix using the ROC technique 2. What cells are you suggesting and why 3. Are there any issues which require additional consideration

  36. 16 8 4 2 1 24 23 21 20 22 Product no 4 10 11 12 14 1 22 1 1 1 2 9 1 1 3 22 1 1 1 4 22 1 1 1 5 1 1 6 31 1 1 1 1 1 Resource 7 9 1 1 8 18 1 1 9 22 1 1 1 10 22 1 1 1 11 9 1 1 12 22 1 1 1 13 1 1 9 14 9 1 1 Product Flow AnalysisTutorial Example

  37. 1 1 1 1 16 8 4 2 22 1 24 23 21 20 22 Product no 4 10 11 12 6 31 1 1 1 1 1 3 22 1 1 1 4 22 1 1 1 9 22 1 1 1 10 22 1 1 1 Resource 12 22 1 1 1 8 18 1 1 2 9 1 1 7 9 1 1 11 9 1 1 13 1 1 9 14 9 1 1 1 5 1 Product Flow AnalysisTutorial Example– Rows sorted 14

  38. Product Flow AnalysisTutorial Example – Sort columns Product no 4 10 11 12 14 1 6 31 1 1 1 1 1 2 1 1 1 1 22 4 3 22 1 1 1 8 4 22 1 1 1 16 9 22 1 1 1 32 10 22 1 1 1 64 Resource 12 22 1 1 1 128 8 18 1 1 256 2 9 1 1 512 7 9 1 1 1024 11 9 1 1 2048 13 1 1 9 4096 14 9 1 1 8192 1 5 1 255 7937 127 255 16129

  39. Product Flow AnalysisTutorial Example –Columns sorted To process products 10 & 14 both cells need the use of resource 6 ! Product no 11 4 12 10 14 1 6 1 1 1 1 1 2 1 1 1 1 4 3 1 1 1 8 4 1 1 1 CELL 2 16 9 1 1 1 32 10 1 1 1 64 Resource 12 1 1 1 128 8 1 1 256 CELL 1 2 1 1 512 7 1 1 1024 11 1 1 2048 13 1 1 4096 14 1 1 8192 1 5 127 255 255 7937 16129

  40. Product Flow AnalysisTutorial Example

  41. Self Assessment Questions

  42. Product Flow AnalysisTutorial Example

  43. Product Flow AnalysisTutorial Example – Sort rows

  44. Product Flow AnalysisTutorial Example – Columns

  45. Product Flow AnalysisTutorial Example – Sort Columns CELL 1 CELL 2

  46. Unit 1 lesson 6 -JIT Planning and Control • Pull and push • Drum, buffer rope

  47. JIT Planning and Control • There are many approaches to the planning and control of products through a process. • The main issue is to ensure inventory timing is predictable. (parts arrive on time) without excessive build up of inventory • The following methods will be considered: • ‘Push’ and ‘Pull’ systems – the two main approaches to planning and control. (Chapter 10 – p347 (309)gives a useful account of these two systems). • Will also consider the elements of ‘Theory of constraints’ proposed by Eli Goldratt (1984) • Levelled scheduling

  48. Push philosophy of planning and control PUSH CONTROL FORECAST CENTRAL OPS. PLANNING AND CONTROL SYSTEM OR Instruction on what to make and where to send it Work centre Work centre Work centre Work centre DEMAND • Activities are scheduled centrally • There are always errors in the forecast – Why? • Each work-centre produces work irrespective of whether the next centre needs it or not • This inevitably leads to queues and inventory build up

  49. Pull philosophy of planning and control PULL CONTROL Request Request Request Request Work centre Work centre Work centre Work centre DEMAND Delivery Delivery Delivery Delivery • The customer determines what is produced at what frequency • The customer’s request pulls work through the system. • Can be used to link both suppliers and customers into an organisation’s control system. • Less likely to allow inventory build-up. • JIT uses the pull system

  50. Levelled Scheduling • Attempts to ensure mix and volume are even over time. • Plans regular runs of the full range of components, i.e. every day rather than once/month. • Requires that batch sizes are reduced and therefore set-up times must be reduced also ----why?

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