OPER10500A Operations Management Design of Work Systems © DEPARTMENT OF LOGISTICS AND OPERATIONS MANAGEMENT, 2021 Conceptual Map Conceptual Map Time Study: Calculating NT and ST Observed time (OT) Performance rating (PR) Normal time (NT) NT = OT x PR / 100 Allowance factor (AF) (as % of task time) Standard Time (ST) ST = NT x (1 + AF) Example Casing Sausages From Work Measurement to Capacity Management Cycle time Production rate of a workstation Bottleneck Utilization rate of a workstation Utilization rate of a worker Sequential vs parallel processes Continuous improvement Production rate of a process Cycle Time Interval of time between the exit of two consecutive units at a stage, or at the end of a process Standard Time Cycle Time = # of resources assigned to the stage (task) Production Rate of a Workstation Number of units produced per unit of time, generally in hours (if one expresses the cycle time in hours per unit, the rate per hour is equal reciprocal of the cycle time: units per hour) Rate = (units/hour) 60 minutes Cycle Time OR (in minutes) Example: • Cycle time = 15 minutes or 0.25 hour • Rate = 4 units/hour (60/15 or 1 / 0.25) 1 hour Cycle Time (in hours) Sequential versus Parallel Processes SEQUENTIAL PROCESS PARALLEL PROCESS Process where a work is divided in a series of specialized tasks. Employees are assigned to a specific part of the process Process where each employee realizes all tasks, independently for the others. 1 2 3 4 1 3 2 4 1 3 2 4 1 3 2 4 1 3 2 4 Bottleneck Acting on the Bottleneck Acting on the Bottleneck Identifying the Bottleneck Acting on the Bottleneck Operation 1 2 3 4 5 Rate (Units/hr) 15 10 18 9 12 Where is the bottleneck? 1 2 3 4 5 Production Rate of a Process Number of units produced during one unit of time (e.g. 1 hour) by the process. CALCULATION • Sequential process: The rate of the process is equal to the rate of the bottleneck • Parallel process: The rate of the process is equal to the sum of rates of each working station (performing all the tasks) of the process Cette photo par Auteur inconnu est soumise à la licence CC BY-SA Example Production Rate of a Process A process is composed by 5 activities whose standard times are: 1) 17 min 2) 18 min 3) 15 min 4) 16 min 5) 17 min Calculate the production rate of: • a sequential process in which each of the five employees specializes in performing one of the five activities, and • a parallel process in which each of the five employees performs the process from activity # 1 to # 5 ANSWER Sequential process Parallel process 22/05/09 16 Utilization Rate of a Workstation Sequential process: Production rate of the bottleneck Utilization rate of the = workstations of a stage Production rate at this stage Utilization rate of the = workstations of a stage Cycle time of the stage Cycle time of the bottleneck Bottleneck Exercise Sequential Process B A C B D C B S.T 2 min S.T. 9 min S.T. 5 min Task Standard Time # of workers A B C D 2 9 5 1 1 3 2 1 Production Cycle Time Rate (un./hr) 2,0 30 3,0 20 2,5 24 1,0 60 S.T. 1 min Utilization rate 66,7% 100,0% 83,3% 33,3% Exercise What is the Production Rate of this Parallel Process? A C A B D C A B D • Total st = 2+9+5+1=17 • PR = 60/17 = 3,53 units/h • PR = 3,53*7=24,7 units/h C A B D C A B D C A B D C A B D C B D Utilization Rate of a Worker When part of an operation is done by a machine, the utilization rate of a worker is the proportion of time worked by the employee versus the total standard time of the operation. (Total standard time – Machine time) Total standard time Exemple Exercise What is the utilization rate of the employee? • (49,48,05)/49,34 = 84% Continuous Improvement • Removing one bottleneck will create a new one. • It is not advantageous to push the nonbottleneck resources to produce at full capacity. • In order to improve the utilization rate of resources, we must try to balance, as much as possible, the capacity of each workstation Exercise Increasing the Production Rate? B A C B D C B S.T 2 min The capacity of the line is limited by task B S.T. 9 min S.T. 5 min Task Standard Time # of workers Cycle Time A B C D 2 9 5 1 1 3 2 1 2,0 3,0 2,5 1,0 Production Rate (un./hr) 30 20 24 60 S.T. 1 min Utilization rate 66,7% 100,0% 83,3% 33,3% Solution Balancing B A C B D C B S.T 2 min Capacity as increased to 23 units/h S.T. 9 min S.T. 5 min Task Standard Time # of workers A B C D 2 9 5 1 1 3,5 2 0,5 Production Cycle Time Rate (un./hr) 2,0 30 2,6 23 2,5 24 2,0 30 S.T. 1 min Utilization rate 76,7% 100,0% 95,8% 76,7% Continuous Improvement • Eliminating waste • Reducing standard times • Reducing set-up times (Single Minute Exchange Die, SMED) Majo statt Senf and licensed under the Creative Commons Attribution-Share Alike 4.0 International license Exercise Making Canned Tomatoes BOOK, PAGE 349 EXCEL WORKSHEET AVAILABLE IN ZONECOURS Q&A
