1、1,JIT,ISQA 459 Mellie Pullman,2,Just-In-Time (JIT) Defined,JIT can be defined as an integrated set of activities designed to achieve high-volume production using minimal inventories (raw materials, work in process, and finished goods). JIT also involves the elimination of waste in production effort.
2、 JIT also involves the timing of production resources (e.g., parts arrive at the next workstation “just in time”).,3,The Japanese Approach to Productivity,Elimination of waste Efforts concentrated on shop floor Respect for people Quality improvement focus,4,Waste in Operations,(1) Waste from overpro
3、duction (2) Waste of waiting time (3) Transportation waste (4) Inventory waste (5) Processing waste (6) Waste of motion (7) Waste from product defects,5,JIT Demand-Pull Logic,6,Minimizing Waste: Focused Factory Networks,Coordination,System Integration,7,Traditional Conveyance,A,B,C,A,C,B,Sporadic an
4、d Infrequent Deliveries from Individual Suppliers,8,Mixed-Load Delivery,A,B,C,ABC,Regular and Frequent Deliveries from Many Suppliers,9,Minimizing Waste: Group Technology,Using Departmental Specialization for plant layout can cause a lot of unnecessary material movement.,Saw,Saw,Lathe,Press,Press,Gr
5、inder,Lathe,Lathe,Saw,Press,Heat Treat,Grinder,10,Minimizing Waste: Group Technology,Revising by using Group Technology Cells can reduce movement and improve product flow.,Press,Lathe,Grinder,Grinder,A,2,B,Saw,Heat Treat,Lathe,Saw,Lathe,Press,Lathe,1,11,Minimizing Waste: Uniform Plant Loading,Not un
6、iform Jan. Units Feb. Units Mar. Units Total1,200 3,500 4,300 9,000,Uniform Jan. Units Feb. Units Mar. Units Total3,000 3,000 3,000 9,000,Suppose we operate a production plant that produces a single product. The schedule of production for this product could be accomplished using either of the two pl
7、ant loading schedules below.,How does the uniform loading help save labor costs?,or,12,Mixed Batch Example,Company produces three products with a mixed model assembly line. Operates 16 hours per day for 250 days/yr. Determine the mixed model MPS for a daily batch. Determine minimum batch MPS and the
8、 mix schedule for a day.,13,Calculations,For every unit of #3 (minimum batch), we need twice as many #2 and 4 times As many #1 so for minimum batch: Produce during each day produce #1,1,1,1,2,2,3 - repeated 20 times,14,Mixed Batch Example,Company produces four products with a mixed model assembly li
9、ne. Operates 8hours per day for 250 days/yr. Determine the mixed model MPS for a daily and hourly batch . Determine mix schedule for a day.,15,Minimizing Waste: Just-In-Time Production,16,Minimizing Waste: Inventory Hides Problems,Example: By identifying defective items from a vendor early in the pr
10、oduction process the downstream work is saved.,Example: By identifying defective work by employees upstream, the downstream work is saved.,17,Minimizing Waste: Kanban Production Control Systems,Storage Part A,Storage Part A,Machine Center,Assembly Line,Material Flow Card (signal) Flow,Withdrawal kan
11、ban,Production kanban,18,Determining the Number of Kanbans Needed,Setting up a kanban system requires determining the number of kanbans (or containers) needed. Each container represents the minimum production lot size. An accurate estimate of the lead time required to produce a container is key to d
12、etermining how many kanbans are required.,19,The Number of Kanban Card Sets,k = Number of kanban card sets (a set is a card) d = Average number of units demanded over some time period L = lead time to replenish an order (same units of time as demand) S = Safety stock expressed as a percentage of dem
13、and during leadtime C = Container size,20,Example of Kanban Card Determination: Problem Data,A switch assembly is assembled in batches of 4 units from an “upstream” assembly area and delivered in a special container to a “downstream” control-panel assembly operation. The control-panel assembly area
14、requires 5 switch assemblies per hour. The switch assembly area can produce a container of switch assemblies in 2 hours. Safety stock has been set at 10% of needed inventory.,21,Example of Kanban Card Determination: Calculations,Always round up!,22,JIT Requirements: Design Flow Process,Link operatio
15、ns Balance workstation capacities Re-layout for flow Emphasize preventive maintenance Reduce lot sizes Reduce setup/changeover time,23,JIT Requirements: Improve Product Design,Standard product configuration Standardize and reduce number of parts Process design with product design Quality expectation
16、s,24,Respect for People,Level payrolls Cooperative employee unions Subcontractor networks Inverted pyramid management style Small group involvement activities,25,JIT Requirements: Total Quality Control,Worker responsibility Measure SQC Enforce compliance Fail-safe (Poke-yoke) methods Automatic inspe
17、ction,26,POKE-YOKEs address Mistakes,Damaged parts Missing parts Reversed parts Wrong parts Wrong size or shape Wrong chemical properties Wrong physical properties Wrong item shipped Wrong label Wrong package Damaged finished product,Omitting a part Omitting a process Performing a process incorrectl
18、y Performing a process on the wrong part Performing a process in improper environmental conditions Performing the wrong process Setting up equipment incorrectly Setting up a work piece incorrectly Adjusting equipment incorrectly Tooling set up incorrectly Tooling adjusted incorrectly Installing wron
19、g part Installing part incorrectly,DEFECTS,MISTAKES,27,JIT Requirements: Work with Vendors,Reduce lead times Frequent deliveries Project usage requirements Quality expectations,28,JIT Requirements: Reduce Inventory More,Look for other areas where inventory hides Stores Transit Carousels Conveyors,29
20、,MRP and JIT,MRP is a planning system that does not do detailed shop floor scheduling MRP requires fixed lead times which might actually vary with batch size JIT excels at rapidly moving small batches of material through the system,30,MRP Small Bucket Approach,MRP “buckets” are reduced to daily or h
21、ourly The most common planning period (time bucket) for MRP systems is weekly Planned receipts are used internally to sequence production Inventory is moved through the plant on a JIT basis Completed products are moved to finished goods inventory which reduces required quantities for subsequent plan
22、ned orders Back flushing based on the BOM is used to deduct inventory that was used in production,31,MRP Balanced Flow,Used in repetitive operations MRP plans are executed using JIT techniques based on “pull” principles Flows are carefully balanced with small lot sizes,32,MRP vs. The Supermarket,Items used by many products are held in a common area often called a supermarket Items are withdrawn as needed Inventory is maintained using JIT systems and procedures Common items are not planned by the MRP system,
