JIT and Lean Operations

JIT/Lean Production Just-in-time (JIT): A highly coordinated processing system in which goods move through the system, and services are performed, just as they are needed, JIT   lean production JIT  pull (demand) system JIT operates with very little “fat”

Goal of JIT The ultimate goal of JIT is a balanced system. Achieves a smooth, rapid flow of materials through the system

Summary JIT Goals and Building Blocks Figure 14.1 Product Design Process Personnel Elements Manufactur- ing Planning Eliminate disruptions Make the system flexible Eliminate waste A balanced rapid flow Ultimate Goal Supporting Goals Building Blocks

JIT Building Blocks Product design Process design Personnel/organizational elements Manufacturing planning and control

Product Design Standard parts Modular design Highly capable production systems Concurrent engineering

Process Design Small lot sizes Setup time reduction Manufacturing cells Limited work in process Quality improvement Production flexibility Little inventory storage

Benefits of Small Lot Sizes Reduces inventory Less storage space Less rework Problems are more apparent Increases product flexibility Easier to balance operations

Personnel/Organizational Elements Workers as assets Cross-trained workers Continuous improvement Cost accounting Leadership/project management

Manufacturing Planning and Control Level loading Pull systems Visual systems Close vendor relationships Reduced transaction processing Preventive maintenance

Pull/Push Systems Pull system: System for moving work where a workstation pulls output from the preceding station as needed. (e.g. Kanban) Push system: System for moving work where output is pushed to the next station as it is completed

Traditional Supplier Network Figure 14.4a Buyer Supplier

Tiered Supplier Network Figure 14.4b Supplier Buyer First Tier Supplier Second Tier Supplier Third Tier Supplier

Comparison of JIT and Traditional Table 14.3 Factor Traditional JIT Inventory Much to offset forecast errors, late deliveries Minimal necessary to operate Deliveries Few, large Many, small Lot sizes Large Small Setup; runs Few, long runs Many, short runs Vendors Long-term relationships are unusual Partners Workers Necessary to do the work Assets

Transitioning to a JIT System Get top management commitment Decide which parts need most effort Obtain support of workers Start by trying to reduce setup times Gradually convert operations Convert suppliers to JIT Prepare for obstacles

Obstacles to Conversion Management may not be committed Workers/management may not be cooperative Suppliers may resist Why?

JIT in Services The basic goal of the demand flow technology in the service organization is to provide optimum response to the customer with the highest quality service and lowest possible cost. Eliminate disruptions Make system flexible Reduce setup and lead times Eliminate waste Minimize WIP Simplify the process

Benefits of JIT Systems Reduced inventory levels High quality Flexibility Reduced lead times Increased productivity

Benefits of JIT Systems (cont’d) Increased equipment utilization Reduced scrap and rework Reduced space requirements Pressure for good vendor relationships Reduced need for indirect labor

CHAPTER 15 Scheduling

Scheduling Scheduling: Establishing the timing of the use of equipment, facilities and human activities in an organization Effective scheduling can yield Cost savings Increases in productivity

High-Volume Systems Flow system: High-volume system with Standardized equipment and activities Flow-shop scheduling: Scheduling for high-volume flow system Work Center #1 Work Center #2 Output

Scheduling Manufacturing Operations High-volume Intermediate- volume Low-volume Service operations Build A A Done Build B B Done Build C C Done Build D Ship JAN FEB MAR APR MAY JUN On time!

High-Volume Success Factors Process and product design Preventive maintenance Rapid repair when breakdown occurs Optimal product mixes Minimization of quality problems Reliability and timing of supplies

Intermediate-Volume Systems Outputs are between standardized high-volume systems and made-to-order job shops Run size, timing, and sequence of jobs Economic run size:

Scheduling Low-Volume Systems Loading - assignment of jobs to process centers Sequencing - determining the order in which jobs will be processed Job-shop scheduling Scheduling for low-volume systems with many variations in requirements

Gantt Load Chart Figure 15.2 Gantt chart - used as a visual aid for loading and scheduling

Loading Infinite loading Finite loading Vertical loading Horizontal loading Forward scheduling Backward scheduling Schedule chart

Sequencing Sequencing: Determine the order in which jobs at a work center will be processed. Workstation: An area where one person works, usually with special equipment, on a specialized job.

Sequencing Priority rules: Simple heuristics used to select the order in which jobs will be processed. Job time: Time needed for setup and processing of a job. Everything is #1 Priority

Priority Rules FCFS - first come, first served Table 15.2 FCFS - first come, first served SPT - shortest processing time EDD - earliest due date CR - critical ratio S/O - slack per operation Rush - emergency Top Priority

Example 2 Average Number of Jobs at the Work Center Table 15.4 3.24 9.67 22.17 CR 2.68 6.33 18.33 EDD 2.63 6.67 18.00 SPT 2.93 9.00 20.00 FCFS Average Number of Jobs at the Work Center Average Tardiness (days) Average Flow Time (days) Rule

Two Work Center Sequencing Johnson’s Rule: technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers. Minimizes total idle time Several conditions must be satisfied

Johnson’s Rule Conditions Job time must be known and constant Job times must be independent of sequence Jobs must follow same two-step sequence Job priorities cannot be used All units must be completed at the first work center before moving to second

Johnson’s Rule Optimum Sequence List the jobs and their times at each work center Select the job with the shortest time Eliminate the job from further consideration Repeat steps 2 and 3 until all jobs have been scheduled

Scheduling Difficulties Variability in Setup times Processing times Interruptions Changes in the set of jobs No method for identifying optimal schedule Scheduling is not an exact science Ongoing task for a manager

Minimizing Scheduling Difficulties Set realistic due dates Focus on bottleneck operations Consider lot splitting of large jobs

Scheduling Service Operations Appointment systems Controls customer arrivals for service Reservation systems Estimates demand for service Scheduling the workforce Manages capacity for service Scheduling multiple resources Coordinates use of more than one resource

Cyclical Scheduling Hospitals, police/fire departments, restaurants, supermarkets Rotating schedules Set a scheduling horizon Identify the work pattern Develop a basic employee schedule Assign employees to the schedule

Service Operation Problems Cannot store or inventory services Customer service requests are random Scheduling service involves Customers Workforce Equipment

Overview—United Airlines Service Scheduling SSU1 Overview—United Airlines

United Airlines Flight Schedule Service Scheduling SSU2 United Airlines Flight Schedule

Painting Example (Washburn Guitar) Schedule PS8 Painting Example (Washburn Guitar)