OMSAN LOJİSTİK

Production and Operations Management 2: Process Flow Fundamentals Top Management Program in Logistics & Supply Chain Management (TMPLSM)

3 Throughput Rate : Average number of units processed per time unit. (Also called production rate, flow rate, output rate or processing rate. ) Cycle Time : Average time between completion of successive units Throughput Time : Average time a unit spends in the system (including all waiting times). Also called production lead time Work-In-Process : Number of units in the system Capacity Utilization : Throughput Rate / Capacity Common Measures in Process Flow

4 Bread is made in batches of 100 loaves each. Bread-making completes a batch of 100 loaves every hour  one hour is the bread-making cycle time for a batch of 100 loaves. Packaging needs only ¾ of an hour to place the 100 loaves in bags  ¾ of an hour is the packaging cycle time for a batch of 100 loaves. Questions: Cycle time for the entire process? Is the process balanced? Cycle time for the entire process? Is the process balanced? Bottleneck? Bottleneck? Capacity? (hint: inverse of the cycle time for the entire process) Capacity? (hint: inverse of the cycle time for the entire process) Cycle Time (CT) = CT = 1 hour/100 loaves 3/4 hour/100 loaves Bread-making WIPFGIPackaging How Fast do we make it?

5 What is the “capacity utilization?” Average 20 cars/hr Drive Out Drive In Inspection Station Capacity: 2 cars in queue A Simple Example An Emission Inspection Line Assume this is the situation during most of the day What is the “throughput rate?” [ Average number of units processed per time unit] What is the “cycle time?” [Average time between completion of successive units] What is the “throughput time?” [Average time a unit spends in the system] What is “Work-in-process?” [Number of units in the system]

6 60 cars/hr.40 cars/hr.20 cars/hr Drive Out Drive In Set Up & Pay Check Exhaust Print Report Capacity: 2 cars in queue A Slightly more complicated example An Emission Inspection Line Again assume this is the situation during most of the day What is the “capacity utilization” for each station? What is the “throughput rate?” [ Average number of units processed per time unit] What is the “cycle time?” [Average time between completion of successive units] What is the “throughput time?” [Average time a unit spends in the system] What is “Work-in-process?” [Number of units in the system]

7 Arrival Rate Departure Rate Throughput Rate Cycle Time Let’s start with the “obvious” ones Any relationships among these variables?

8 Consider A Simple Process Arrivals QueueSever Departures

9 Arrivals QueueSever Departures At Equilibrium Average Arrival Rate = Average Departure Rate (Except for “Black Holes!”) Same as Throughput Rate = Arrival Rate = Departure Rate

10 Cycle Time Cycle Time (Time between departures) Cycle Time = 1/ Or Cycle Time = 1 / Throughput Rate = Arrival Rate = Departure Rate

11 Throughput Time Throughput Time Total Time in the System W = Throughput time W = W q + 1/  Service time: 1/  (hrs/job) Time in Queue W q (hrs/job)  Average number of jobs serviced per period

12 Now the relationship between Arrival Rate Throughput Time Work In Process

13 Little’s Law Looks complicated but it is stating the obvious! WIP = Throughput Rate x Throughput Time = Arrival Rate (or Throughput Rate) W= Throughput Time L= Work In Process

14 An Example Assume Georgetown has 6,000 undergrads. Applicants totaled but only 20% were accepted. Of those accepted, 50% actually enrolled. How many years, on average, does an undergrad spend at Georgetown?

15 Capacity Utilization Arrivals  (jobs/hr) Service Capacity  (jobs/hr) Departures  (jobs/hr) Capacity Utilization :  =  

16 Throughput Rate : Average number of units processed per time unit. Cycle Time : 1 / Average time between completion of successive units Throughput Time : W Average time a unit spends in the system (including all waiting times). Work-In-Process : L Number of units in the system Capacity Utilization :  =   Throughput Rate / Service Rate Capacity So, once again

17 a) What is the cycle time for this (entire) inspection facility? b) What is the capacity of this inspection facility (how many cars per day can be tested) ? c) When the process is working at capacity, what is capacity utilization rate at each station?: d) If you are the first person in the morning, how long would it take to have your car inspected (i.e., the “throughput time” when you don’t wait)? e) When the situation is like the above, what is the throughput time for a car in different lines? * Capacities for operations in each line. Cars In Set Up & Pay Check Exhaust Print Report Drive Out LINE 1 Set Up & Pay Check Exhaust Print Report Set Up & Pay Check Exhaust Print Report 60 cars/hr.*40 cars/hr.*20 cars/hr.* 6 cars 8 cars 5 cars Drive Out LINE 2 Drive Out LINE 3 10 cars Cars Out