Transcript Slayt 1
OMSAN LOJİSTİK Top Management Program in Logistics & Supply Chain Management (TMPLSM) Production and Operations Management 2: Process Flow Fundamentals Common Measures in Process Flow • 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 / 3 Capacity How Fast do we make it? Bread-making Cycle Time (CT) = 1 hour/100 loaves WIP Packaging FGI CT = 3/4 hour/100 loaves 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? • Bottleneck? • Capacity? (hint: inverse of the cycle time for the entire process) 4 A Simple Example An Emission Inspection Line Assume this is the situation during most 2 cars in queue Drive In Inspection Station Drive Out Capacity: Average 20 cars/hr What is the “throughput What is the “cycle rate?” [Average number of units p time?” [Average time between completion What is the “throughput time?” [Average time a unit spend What is “Work-in-process?” [Number What is the “capacity 5 utilization?” of units in the syste A Slightly more complicated example An Emission Inspection Line Again assume this is the situation during most of the day 2 cars in queue Set Up & Pay Drive In Capacity: 60 cars/hr. What is the “throughput What is the “cycle Check Exhaust Print Report 40 cars/hr. 20 cars/hr rate?” [Average number of units p time?” [Average time between completion What is the “throughput time?” [Average time a unit spend What is “Work-in-process?” [Number What is the “capacity 6 Drive Out of units in the syste utilization” for each station? Any relationships among these variables? Let’s start with the “obvious” ones • Arrival Rate • Departure Rate • Throughput Rate • Cycle Time 7 Consider A Simple Process Queue Arrivals 8 Sever Departures At Equilibrium Average Arrival Rate = Average Departure Rate (Except for “Black Holes!”) Queue Sever Arrivals Departures l = Departure Rate l = Arrival Rate Same as Throughput Rate 9 Cycle Time (Time between departures) l = Arrival Rate Cycle Time = 1/ Or Cycle Time = 1 / Throughput Rate 10 l = Departure Rate l Throughput Time Total Time in the System m = Average number of jobs serviced per period Time in Queue Wq (hrs/job) W =11Throughput time W = W + 1/m Service time: 1/m (hrs/job) Now the relationship between Arrival Rate 12 Throughput Time Work In Process Little’s Law Looks complicated but it is stating the obvious! L=lW l = Arrival Rate (or Throughput Rate) W= Throughput Time L= Work In Process WIP = Throughput Rate x Throughput Time 13 An Example Assume Georgetown has 6,000 undergrads. Applicants totaled 12000 but only 20% were accepted. Of those accepted, 50% actually enrolled. How many years, on average, does an undergrad spend at Georgetown? 14 Capacity Utilization Arrivals l (jobs/hr) Service Capacity Departures l (jobs/hr) m (jobs/hr) Capacity Utilization: r = l / m 15 So, once again • Throughput Rate: l Average number of units processed per time unit . • Cycle Time: 1 / l 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: r=l/m Throughput Rate / Service Rate Capacity 16 60 cars/hr.* 40 cars/hr.* 20 cars/hr.* Set Up & Pay Check Exhaust Print Report Drive Out LINE 1 Set Up & Pay Check Exhaust Print Report Drive Out LINE 2 Set Up & Pay Check Exhaust Print Report Drive Out LINE 3 6 cars 10 cars 8 cars Cars In Cars Out 5 cars * Capacities for operations in each line. 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 17 the situation is like the above, what is the throughput time for a car in different lines?