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Chapter 15

Chapter 15. 及時製造 (just-in-time manufacturing. Just-in-time philosophy. Elimination of all waste and continuous improvement of productivity Waste: anything other than the minimum amt of equipment, parts, space, mat’l, and workers’ time to add to the product

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Chapter 15

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  1. Chapter 15 及時製造 (just-in-time manufacturing

  2. Just-in-time philosophy • Elimination of all waste and continuous improvement of productivity • Waste: anything other than the minimum amt of equipment, parts, space, mat’l, and workers’ time to add to the product • No surplus, no safety stocks, minimum lead times

  3. Value • Satisfies the actual and perceived needs of the customer and does it at a price the customer can afford and considers reasonable • Means quality－meeting and exceeding customers’ expectations • Value starts in the marketplace－fig. 15.1 • Anything in the product cycle that does not add value to the product is waste

  4. Seven sources of waste • Process: • if the process is not being operated correctly, or if the wrong tools and fixtures are used • Methods: • wasted movement, time, or effort • Movement: • moving and storing components adds cost but not value • Product defects: • defects interrupt the smooth flow of work

  5. Seven sources of waste • Waiting time: • operator has no productive work to do or there are delays in getting mat’l • Overproduction: • Producing products beyond those needed for immediate use, resulting in unnecessary inventories • Inventory: • Inventory costs money to carry, and excess inventory adds extra cost to the product

  6. JIT environment • Flow mfg • Process flexibility • TQM • Total productivity maintenance • Uninterrupted flow • Continuous process improvement • Supplier partnerships • Total employee involvement

  7. Flow mfg VS functional layout and work cell layout • Functional layout can be improved by

  8. Process flexibility • Can react swiftly to changes in the volume and mix of their products • Operator and machinery must be flexible • Fig. 15.5 • System must be able to be changed over from one product to another

  9. Machine flexibility

  10. TQM • If the product is defective, customer will be dissatisfied • If a process produces scrap, it creates disrupted schedules that delay supplying • For mfg, quality does not mean inspecting the product to segregate good from bad parts • Must ensure that the process is capable of producing the required quality consistently and w/ as close to zero defects as possible • Quality at the source: doing it right the first time and if something does go wrong, stopping the process and fixing it

  11. Total productivity maintenance • Machinery must be maintained in excellent condition, not breakdown, to continue to produce the required quality • Can be achieved by a program of preventive maintenance • APICS: total productive maintenance is “preventive maintenance plus continuing efforts to adapt, modify, and refine equipment to increase flexibility, reduce mat’l handling, and promote continuous flow”

  12. Uninterrupted flow • Conditions to achieve it: • Uniform plant loading: • work done at each workstation should take about the same time • Pull system • starts at the end of the line and pulls product from the preceding operation as needed • Valid schedules • Schedule must be level • Mix of products should be the same • Fig. 15.6 + 15.7 • Linearity: scheduling to less than full capacity

  13. Level schedule • May create shortage in week 2 • An alternative schedule

  14. Continuous process improvement • Elimination of waste depends on improving processes continuously

  15. Total employee involvement • Successful JIT environment can be achieved only w/ the coordination and involvement of everyone in the organization • Operators: • improving processes, controlling equipment, correcting deviations, becoming vehicles for continuous improvement; PM, setup, data recording, and problem solving • Managers and supervisors: • Become coaches and trainers, develop capacity of employees, and provide coordination and leadership for improvement • Staff: • Become those of training and assisting line workers to do the staff duties (such as QC, maintenance, and record keeping) assigned to them

  16. Mfg planning and control in a JIT environment • Mfg planning and control is responsible for managing the flow of mat’l and work through the mfg process, not designing the process • Mfg planning and control is governed by the mfg environment －Fig. 15.8

  17. MPS in JIT mfg • MPS tries to level capacity, JIT tries to level the schedule based on capacity and mat’l flow－Fig. 15.9 • Shorter lead times reduce time fences and make the MPS more responsive to customer demand • JIT system requires a stable schedule to operate • Weekly time buckets are used－gives mfg an organizational buffer to plan and organize actual work flow

  18. MRP in JIT mfg • Time buckets can be reduced from usually one week to daily bucket • In a pure JIT mfg, no inventory on hand, make exactly what is needed • BOM can be frequently flattened in JIT, using the work cells and elimination of many inventory transactions

  19. Pull system • Not to preplan and generate schedule, but instead to react to the final customer order and produce only what is needed to satisfy demand and then only when it is needed • Will be ordering frequently, but in very small batches • Risk a stockout if the demand during the replenishment lead time exceeds expectations

  20. Kanban system • A system used to generate the reorder point signal • Info on Kanban: • Component part number and ID • Storage location • Container size (if the mat’l is stored in a container) • Work center (or supplier) of origin

  21. How the system works – two-card Kanban system • Types of cards: • Production card: • authorizing production of whatever part number is identified on the card in the quantity specified • Withdrawal card: • Authorizing the movement of the identified mat’l

  22. No movement since all cards are attached to full containers Steady state – no demand and no production How the system works – two- card Kanban system • A downstream process needs parts produced by WC #2 • “free” production card – authorizes production to replace withdrawn container

  23. The unattached production card is the signal to start WC #2 production Raw mat’l which is in front the WC w/ the move cards attached is used to replace the finished mat’l Raw mat’l container is now empty and the associated move card is unattached • The unattached move card authorized movement of mat’l to replace the mat’l that was used • That mat’l is found in the “finished goods” section of WC #1 • Container from WC # 1 moved to WC #2 • WC #2’s move card attached • WC #1’s production card removed and is now “free”

  24. WC #1 produces parts to refill container Production card attached to container Mat’l usage empties raw mat’l container and “frees” move card what was attached • This process continues upstream even to the suppliers

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