Lecture 20 - Production Activity Control (Revision). The contents of this chapter include all of the following: Production activity control, gantt chart, critical ratio scheduling, finite loading, scheduling, assignment method, sequencing slack, Johnson''s rule, monitoring, advance planning and scheduling, scheduling procedure, employee scheduling.
Lecture 20 Production Activity Control (Revision) Books • Introduction to Materials Management, Sixth Edition, J. R. Tony Arnold, P.E., CFPIM, CIRM, Fleming College, Emeritus, Stephen N. Chapman, Ph.D., CFPIM, North Carolina State University, Lloyd M. Clive, P.E., CFPIM, Fleming College • Operations Management for Competitive Advantage, 11th Edition, by Chase, Jacobs, and Aquilano, 2005, N.Y.: McGrawHill/Irwin • Operations Management, 11/E, Jay Heizer, Texas Lutheran University, Barry Render, Graduate School of Business, Rollins College, Prentice Hall Objectives • • • • • • • • • • • • • Production activity control Gantt chart Critical ratio scheduling Finite loading Scheduling Assignment method Sequencing Slack Johnson's Rule Monitoring Advance planning and scheduling Scheduling procedure Employee Scheduling Production Activity Control • PAC in the MPC System – – • Production Activity Control Techniques – – – – • Shop Floor Control Vendor Scheduling Basic Data Gantt Charts Priority Scheduling Finite Loading Process Design Impact on Scheduling – – Batch Manufacturing – Work Orders Repetitive Manufacturing – JIT Production Activity Control in the MPC System Basic Data Routing Data and Operation Setback Chart Gantt Charts The incoming orders at Tom's Sailboard follow different routes through the shop but all orders must stop at each of the three work centers in the plant. The table below shows all tasks for four jobs that arrive over 5 days and need to be scheduled at the company. It is currently November 10 and Tom works a sevenday week _ Arrival Job/WC Processing time (days) Order date routing WC 1 WC 2 WC 3 (B)iff Nov. 10 132 1 3 1 (G)riffin Nov. 10 231 2 2 2 (H)erbie Nov. 12 321 3 1 2 (K)errie Nov. 14 213 1 3 1 Assume that the new material for all orders is in stock and that a firstcome/firstserved sequencing rule is used at all work centers. All three work centers are idle as work begins on orders B and G on November 10 Tom’s Sailboard a Construct a Gantt chart depicting the processing and idle times for the three work centers for these four jobs Order (B)iff (G)riffin (H)erbie (K)errie Arrival Job/WC Processing time (days) date routing WC 1 WC 2 Nov. 10 132 1 3 1 Nov. 10 231 2 2 2 Nov. 12 321 3 1 2 Nov. 14 213 1 3 1 WC 3 Tom’s Sailboard b How many days does each job wait in queue for processing at work center 2? The determination of how long jobs wait at work center 2 is as follows: B and G are processed immediately at work center 2, order K must wait 1 day (11/14) and order H waits 4 days (11/12, 11/13 at WC3) and (11/16 and 11/17 at WC2) Priority Sequencing Rules First Come, First Served • Shortest Operation Next • Earliest Due Date • Order Slack: (Time Remaining until Due Date – Sum of Remaining Setup and Run Time) • Slack per Operation • Critical Ratio: (Due DateNow)/(Lead Time Remaining) Lead Time Remaining includes setup, run, move and queue time for all remaining operations • Excel for Input/Output Control User inputs planned and actual values Excel calculates deviations and backlog Advanced Planning and Scheduling Systems • • Infinite scheduling assumes infinite capacity – Loads without regard to capacity – Then levels the load and sequences jobs Finite scheduling assumes finite (limited) capacity – Sequences jobs as part of the loading decision – Resources are never loaded beyond capacity Advanced Planning and Scheduling Systems • Advanced planning and scheduling (APS) – – – – Addins to ERP systems Constraintbased programming (CBP) identifies a solution space and evaluates alternatives Genetic algorithms based on natural selection properties of genetics Manufacturing execution system (MES) monitors status, usage, availability, quality Advanced Planning and Scheduling Theory of Constraints • • • • • Not all resources are used evenly Finite scheduling approach Concentrate on the” bottleneck” resource Synchronize flow through the bottleneck Use process and transfer batch sizes to move product through facility DrumBufferRope • Drum – • Buffer – – • Bottleneck, beating to set the pace of production for the rest of the system Inventory placed in front of the bottleneck to ensure it is always kept busy Determines output or throughput of the system Rope – Communication signal; tells processes upstream when they should begin production Synchronous Manufacturing A B C D B3 C3 15 D3 B2 C2 10 D2 B1 C1 D1 10 Key: i Ij k l Item i Operation j of item i performed at machine center k takes l minutes to process Synchronous Manufacturing Demand = 100 A’s Machine setup time = 60 minutes MACHINE MACHINE MACHINE B1 B3 C2 Sum 10 22 * Bottleneck B2 C3 D2 15 26* C1 D3 D1 10 17 Synchronous Manufacturing Setup Machine C2 Setup B1 B3 1002 1562 2322 Idle Setup Machine C3 B2 12 1512 Machine Setup C1 200 Setup D2 1872 2732 Setup D1 Idle 1260 D3 1940 Completion time 2737 Employee Scheduling • • • • Labor is very flexible resource Scheduling workforce is complicated, repetitive task Assignment method can be used Heuristics are commonly used Employee Scheduling Heuristic Let N = no. of workers available Di = demand for workers on day i X = day working O = day off Assign the first N D1 workers day 1 off. Assign the next N D2 workers day 2 off. Continue in a similar manner until all days are have been scheduled If number of workdays for full time employee