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05 lean manufacturing and the jit philosophy

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Describes Lean related activities and links them to Just in Time

Publié dans : Direction et management
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05 lean manufacturing and the jit philosophy

  1. 1. Lean Manufacturing & the JIT Philosophy
  2. 2. Benefits of Lean
  3. 3. Concept of Lean
  4. 4. Lean, JIT Production Systems • Philosophy for optimizing the performance of a manufacturing system • Was designed by Taiichi Ohno • System is driven by more flexibility and smaller volumes per part using same equipment
  5. 5. Lean, JIT Production Systems • Settled on an effective strategy based on: • Kanban – based pull production • Elimination of waste as a guiding philosophy • Faith in the value and importance of quality • Kaizen • Belief in the value and utilization of human resources • Emphasis on reducing setup times for machines • Integration of suppliers and material acquisition into the corporate planning process • Efficient, cellular layouts with balanced material flow
  6. 6. Improving the Production Environment • Eliminating waste (TIM WOODS) • Employee Cross-Training and Job Rotation • Employee Empowerment and Involvement • JIT purchasing • Impact of reducing variability • Poka-Yoke • Economics of Setup Time Reduction • Technology of Setup Time Reduction
  7. 7. Value
  8. 8. TIM WOODS
  9. 9. TIM WOODS • T- Transport (Moving People, Products and Information) • I – Inventory (Storing parts, pieces, documentation ahead of requirements) • M – Motion (Bending, turning, reaching, lifting) • W – Waiting (For parts, information, instructions, equipment) • O – Overproduction (making more than is immediately required) • O – Overprocessing (tighter tolerances and high grade material use than are necessary) • D – Defects (Rework, Scrap and incorrect documentation) • S – Skills (underutilizing capabilities and delegating tasks with inadequate training)
  10. 10. TIM WOODS
  11. 11. The aim is to reduce the overall mileage or footprint a product / service accumulates as it moves through the organization, resulting in an increase in the proportion of the value – added activity. Transport is the unnecessary movement of a product, raw material, or documents. Moving items unnecessarily increases the risk of damage or loss, adds time and adds cost without adding value. Poor layout of the floor / office / work area, batching and lac of flow all contribute to this waste.
  12. 12. Inventory should be systematically reduced as holding stock hides problems in processes; reducing stock exposes issues and forces organisations to resolve them. In a service/administration environment it can be an accumulation of physical documents or electronic files, over an above what is required to satisfy the customer’s requirement. Holding excess stock represents a cost to the company, with no benefit to the customer. The waste of inventory results from poor design of the elements of the value stream, resulting in overproduction and imbalances in work flows.
  13. 13. Waste will be reduced by the implementation of a workplace organisation programme to re- organise the workplace ensuring processes are located closer to each other, that material delivery areas are at the point of use and tools and equipment are close to hand. The result of implementing such a programme will reduce the distance travelled by the person saving time and even “wear & tear” on the employee in the long term. This waste is similar to the waste of Transport, but refers to the time wasted by individuals moving around when they don’t need to, to collect parts or search for something they need to complete the job e.g. tools or equipment.
  14. 14. The ideal is to produce single piece at a time also referred to as single piece flow. This may not be always practical, but the goal is to reduce batch size, to reduce changeover time and waiting for parts between operations. This equally applies to operations where the output is not a physical item. Work should be scheduled in sufficiently small increments to allow the unit of work (e.g. a file, a report) to flow smoothly through the individual process steps to be delivered in a timely fashion. Waiting refers to the time an item spends between process steps, when no work is being performed and therefore no value added. For example, in manufacturing environments if batch production is practiced, individual products will wait between process steps while the remainder of the batch is processed
  15. 15. The remedy is to work to customer demand, improve flow through individual process steps to produce only what the customer needs when he needs it. It is also preferable that the ‘load’ on production be as consistent as possible to allow resources to be better planned thus minimising overtime costs. This waste is directly related to the waste of Inventory which is as a result of not responding to customer demand. Continuing to produce what is not required leads to an accumulation of stock between process steps and at the end of the process. Overproduction occurs when production runs ahead of demand; items are produced in greater volume than required, sooner than required or faster than required.
  16. 16. Overprocessing is eliminated by a thorough understanding of what exactly is required to fulfil customer needs and simplifying & standardizing the processes to deliver these expectations. This waste applies when more work is done than is required to meet customer expectations, performing wasteful steps that may not be required.
  17. 17. Defects can be reduced by ensuring that all work steps are highly specified with no ambiguity. All the required tools and equipment are present and in good working order (achieved through a workplace organisation programme). Instructions are clear, concise and photographs should be used as much as possible. Personnel must be trained in all aspects of the job. The result of implementing such a programme will reduce the distance travelled by the person saving time and even “wear & tear” on the employee in the long term. A concept called “Error-Proofing” is employed to reduce as much as possible the occurrence of defects. Error-proofing is a structured process which seeks to prevent errors through robust product and process design, to eliminate or immediately detect defects as they occur. A defect is the result of an error; it is a deviation from the product specification which leads to customer dissatisfaction. In a service environment, it could be data input errors, a report incorrectly filled out, an error in billing etc. Production defects lead to the cost of reworking. Reworking leads to a double handling of product which add costs and also exposes the product to further risk of damage.
  18. 18. Respect-for-people acknowledges their expertise, and challenges them to question old ways, gather real-time data and design creative solutions to resolve issues. This waste describes the situation where management functions within a company don’t fully utilize employees’ skillsets, the experience which people bring to their jobs, or develop over time in the performance of their jobs. It relates to the concept of “Respect for People”. The core of the Lean Production System is the relentless elimination of waste, however the culture of continuous improvement depends on all team members contributing ideas for possible improvement, also being in a position to implement and sustain such improvements once introduced.
  19. 19. Value Stream Mapping (VSM)
  20. 20. Value Stream
  21. 21. Value Stream Mapping • Visual tool used to illustrate how a process flow and information flow, transform a product as it moves through the value stream. • It’s purpose is to identify the source of waste and drive action plan to eliminate them. • VSM shows both the process and information flow, tracking the material’s progress from the raw material supplier to the end customer. • In service terms, a VSM typically details the process steps and the flow of a report or file through these steps • The timeline at the bottom of the chart compares the time where value is being added with the overall lead time to provide the product or service.
  22. 22. Value Stream Mapping There are three Value Stream Map variants: • The Current State (see overleaf for an example) or the current condition. • The Ideal State, which represents the long term vision, and • The Future State which represents an interim step toward the Ideal State, usually involving a series of improvements which are achieved within an agreed time period, through a defined action plan.
  23. 23. Value Stream Map (Geographically)
  24. 24. Value Stream Map
  25. 25. Employee Cross-Training and Job Rotation
  26. 26. Employee Cross Training • Enhances worker flexibility and enthusiasm • Workers trained over time to perform a variety of tasks within their work area • Rotation possible through cross training • Prevents boredom and monotony and does job enrichment • Minimizes fatigue and repetitive stress injuries • Increases manufacturing flexibility also.
  27. 27. U Shaped Cell • Results in short walking distances between machines and good visibility • Production rate of the machine can be adjusted easily • More appropriate where it is possible to deploy one person for two machines • Flexible enough to reduce or add workers as the need be
  28. 28. Employee Cross Training
  29. 29. Disadvantages of Cross Training • Too much cross training is detrimental • Workers may be tempted to stray from their primary jobs thus affecting productivity • Can be expensive where bottleneck operations will start building a queue • Workers can get in each others ways
  30. 30. Employee Empowerment and Involvement
  31. 31. Empowerment • Directed towards achieving quality and productivity improvement goals. • Includes minor investment and procedural changes to support continuous improvement. • Authority to stop and correct a production system that is not operating properly so as to reduce cost of making bad products. • Directed towards reducing the “Hidden factory” which is 10% of the capacity used for correcting a badly made product. • Can achieve the JIDOKA at workplace.
  32. 32. The Andon System for JIDOKA • Provide each line worker with a stop switch to stop the production line • Identify and solve the problem immediately as soon as it appears instead of the philosophy of “just ship it, we’ll fix it later” • One light will always be lit so as to display the status of that work station • Directed at reducing customer complaints as the problems are nipped in the bud.
  33. 33. SOPs as Performance Enhancers • Help in ensuring consistency in productivity and quality. • Employee involvement is a must in SOP development as they can envisage experiential problems and can help in building procedures more correctly. • Lesser resistance if employee involvement is there. • Implementation of 5S to systematically organize workplace leading to reduced customer complaints.
  34. 34. JIT Purchasing
  35. 35. Approaches to Decision • Sole Sourcing Versus Multiple Sources • Frequent Delivery of Small Lots versus Quantity Discounts • Flexible Ordering Versus Paperwork • Vendor owned and Managed Inventories
  36. 36. Impact of Reducing Variability
  37. 37. Reducing Variability • Technology providing benefits by creating genetic mutations leading to improvements in process. • In a thoughtfully designed production system, variability impedes efficiency • This gives rise to building up of safety stocks as customer delivery is of prime importance. • The efficiency of the production system can be increased by creating an optimized flow of material that matches with the availability of storage buffers between workstations.
  38. 38. Techniques for Mistake Proofing
  39. 39. A Change in the Die Design • In some operations (for example in stamping, drilling…), a die is necessary and can be placed incorrectly. That error can result in product quality issues and in damage done to the die. • How to avoid this? By making it impossible to place the die only in one way. This can be realized in many ways. An approach is to have guide pins of different sizes, so that they can only “fit” in one direction. There are many other approaches.
  40. 40. A Change in Fixture Design • This is relatively similar to point 1, with a key difference: the part being worked on can be placed the wrong way into a fixture, with resulting quality issues. • The fixture can be modified in order to make it impossible to place the part incorrectly. (Sometimes the design of the part itself has to be changed, for the same effect.)
  41. 41. Sensors That Prevent Processing Under Certain Conditions The most common sensors are listed below: • Limit switch – convenient when a part is in contact with a tool/fixture. • Proximity sensor – a good solution when a part is/might be at a certain distance. • Infrared sensor – appropriate for checking presence from a distance.
  42. 42. A Vision System • In simple terms, a vision system captures images, analyzes them, and triggers an action in pre-determined cases. It does not require contact with the product. • For example, it might detect that a part is poorly positioned, that a component (or labeling element) is missing, that a step was done before another, etc. As a response, it might sound an alarm, or it might make it impossible to proceed (often by stopping a piece of equipment) until a positive change is made. • This approach appeared in the 1980s in a simple form and has kept improving since them. • With the advances of artificial intelligence / machine learning, vision systems will get better and better. Remember, a Tesla car can pretty much self-drive based on cameras alone!
  43. 43. A Checklist • By any standard, a checklist is one of the weakest mistake proofing techniques. It does help a lot when no other approach listed above is possible and when operators are trained and careful – think pilots in a plane. • The more a checklist’s elements are integrated into the work content, the better. Think of color codes where a checklist step matches a certain tool. Or a form to fill out that contains the steps in the right order.
  44. 44. Design Thinking • Poka yokes are a science but also an art. Think this way and you will see many opportunities that will take different shapes depending on the application. • For example, let’s say some parts move on a conveyor. A few of them have a defect and are taller. The “obvious” countermeasure is a sensor that detects that abnormality. But a better approach is to place a stick that will block the way to all defective parts and push them into a red container on the side of the conveyor. It is faster and cheaper to implement, it is easier to maintain, and it immediately acts on its findings!
  45. 45. Points to Ponder
  46. 46. Technology of Setup Time Reduction
  47. 47. Design Parts for Manufacturability • Manufacture with reasonable tolerances • Use as much Standard tools as possible • Control Tooling changeovers
  48. 48. Develop Standard Methods • Do Industrial Engineering through man machine charting of processes • Improve and redesign processes to standardized and recognized level
  49. 49. Divide Setup Activities into Internal & External Tasks • Obtaining Tooling, reading blueprints, prepositioning fixtures for easy roll onto the machine are external activities. • Move as many activities as possible from Internal to External
  50. 50. Design Procedures to Perform Setup Tasks in Parallel • By performing internal setup tasks in parallel, total idle time of the machine for setups is reduced.
  51. 51. Utilize Family Tooling to Minimize the Need for Setups • Construction of family fixture • Setting up of Tool magazines • Use of modular fixtures • Use of Standard Clamps
  52. 52. Locally Stored Tools and Tooling Kits • Tools to be stored near assembly line • Develop methods such as standard height carts or conveyors for quicker tool change
  53. 53. Standard sized Intermediate Workholders • Tooling even if not the same size, may be expedient to design the tooling with similar characteristics • Semiconductor industry has adopted this method of quick changing for handling wafers
  54. 54. Eliminating Adjustments • Foolproof the set up process. • Self diagnostic machines should be more utilized • Add Limit switches to aid in alignment tooling or setting stroke lengths with specific parts
  55. 55. Use of Power Clamps • Use of Hydraulic or Pneumatic power clamps instead of manual screwed ones. • Use of items like washers to reduce the tightening and loosening mechanism.

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