Chapter 11 Just-In In-Time and Lean Production
What is JIT? Producing only what is needed, when it is needed A philosophy An integrated management system JIT s mandate: Eliminate all waste
Basic Elements of JIT 1. Flexible resources 2. Cellular layouts 3. Pull production system 4. Kanban production control 5. Small-lot lot production 6. Quick setups 7. Uniform production levels 8. Quality at the source 9. Total productive maintenance 10. Supplier networks
Waste in Operations Figure 11.1
Waste in Operations Figure 11.1
Waste in Operations Figure 11.1
Flexible Resources Multifunctional workers General purpose machines Study operators & improve operations
Standard Operating Routine for a Worker Standard Operating Routine Sheet 1 Worker: Cycle Time: Russell 2 min Order of Operations time Operations :10 :20 :30 :40 :50 1:00 1:10 1:20 1:30 1:40 1:50 2:00 Pick up material Unload/ load machine 1 Unload/ load machine 2 Unload/ load machine 3 Inspect/ pack Figure 11.2
Cellular Layouts Group dissimilar machines in manufacturing cell to produce family of parts Work flows in one direction through cell Cycle time adjusted by changing worker paths
Manufacturing Cell with Worker Routes Cell 1 Worker 1 Worker 2 Worker 3 Figure 11.3
Worker Routes Lengthened as Volume Decreases Cell 1 Cell 2 Worker 1 Worker 2 Worker 3 Figure 11.4 Cell 3 Cell 4 Cell 5
The Pull System Material is pulled through the system when needed Reversal of traditional push system where material is pushed according to a schedule Forces cooperation Prevent over and underproduction
Kanban Production Control System Kanban card indicates standard quantity of production Derived from two-bin inventory system Kanban maintains discipline of pull production Production kanban authorizes production Withdrawal kanban authorizes movement of goods
A Sample Kanban
The Origin of Kanban a) Two-bin inventory system b) Kanban inventory system Bin 1 Kanban Bin 2 Reorder card Q - R R R Q = order quantity R = reorder point - demand during lead time Figure 11.5
Types of Kanbans Figure 11.6
Types of Kanbans Figure 11.6
Types of Kanbans Figure 11.6
Types of Kanbans Kanban Square Marked area designed to hold items Signal Kanban Triangular kanban used to signal production at the previous workstation Material Kanban Used to order material in advance of a process Supplier Kanbans Rotate between the factory and suppliers
Determining Number of Kanbans No. of Kanbans = average demand during lead time + safety stock container size where N = dl + S C N = number of kanbans or containers d = average demand over some time period L = lead time to replenish an order S = safety stock C = container size
Determining the Number of Kanbans d = 150 bottles per hour L = 30 minutes = 0.5 hours S = 0.10(150 x 0.5) = 7.5 C = 25 bottles dl + S (150 x 0.5) + 7.5 N = = C 25 75 + 7.5 = = 3.3 kanbans or containers 25 Example 11.1 Round up to 4 (to allow some slack) or down to 3 (to force improvement)
Small-Lot Production Requires less space & capital investment Moves processes closer together Makes quality problems easier to detect Makes processes more dependent on each other
Inventory Hides Problems
Lower Levels of Inventory Expose Problems
Components of Lead Time Processing time Reduce number of items or improve efficiency Move time Reduce distances, simplify movements, standardize routings Waiting time Better scheduling, sufficient capacity Setup time Generally the biggest bottleneck
SMED Principles 1. Separate internal setup from external setup 2. Convert internal setup to external setup 3. Streamline all aspects of setup 4. Perform setup activities in parallel or eliminate them entirely
Uniform Production Results from smoothing production requirements Kanban systems can handle +/- 10% demand changes Smooths demand across planning horizon Mixed-model assembly steadies component production
Mixed-Model Model Sequencing Example 11.2
Quality at the Source Jidoka is authority to stop production line Andon lights signal quality problems Undercapacity scheduling allows for planning, problem solving & maintenance Visual control makes problems visible Poka-yoke prevents defects
Kaizen Continuous improvement Requires total employment involvement Essence of JIT is willingness of workers to Spot quality problems Halt production when necessary Generate ideas for improvement Analyze problems Perform different functions
Total Productive Maintenance (TPM) Breakdown maintenance Repairs to make failed machine operational Preventive maintenance System of periodic inspection & maintenance to keep machines operating TPM combines preventive maintenance & total quality concepts
TPM Requires Management to: Design products that can be easily produced on existing machines Design machines for easier operation, changeover, maintenance Train & retrain workers to operate machines Purchase machines that maximize productive potential Design preventive maintenance plan spanning life of machine
Supplier Policies 1. Locate near to the customer 2. Use small, side loaded trucks and ship mixed loads 3. Consider establishing small warehouses near to the customer or consolidating warehouses with other suppliers 4. Use standardized containers and make deliveries according to a precise delivery schedule 5. Become a certified supplier and accept payment at regular intervals rather than upon delivery
Benefits of JIT 1. Reduced inventory 8. Better relations with suppliers 2. Improved quality 9. Simplified 3. Lower costs scheduling and 4. Reduced space control activities requirements 10. Increased capacity 5. Shorter lead time 11. Better use of 6. Increased productivity human resources 12. More product 7. Greater flexibility variety
JIT Implementation Use JIT to finely tune an operating system Somewhat different in USA than Japan JIT is still evolving JIT isn t for everyone
JIT In Services Competition on speed & quality Multifunctional department store workers Work cells at fast-food food restaurants Just-in in-time publishing for textbooks Construction firms receiving material just as needed