OPSM 301 Operations Management Class 4: Business process flows: Measurement Koç University Zeynep Aksin [email protected].

OPSM 301 Operations Management

Class 4:

Business process flows:

Measurement

Koç University

Zeynep [email protected]

Announcements

New module: business process flows Chapter 3 Study questions and examples

Performance Measurement

External performance strongly depends on output, input, and resource markets, and transformation effectiveness of the process

Internal performance measures: processing cost, flow time, variety, service availability...

The Dynamics of a Process

We examine processes from the perspective of flow To study process flows, we first answer three important

questions:– On average, how many flow units pass through the process

per unit time?

– On average, how much time does a typical flow unit spend within process boundaries?

– On average, how many flow units are within process boundaries at any point in time?

Operational Measures

On average, how many flow units pass through the process per unit time?

THROUGHPUT or FLOW RATE (R)

Throughput or Flow Rate (R)The average output of a production process per unit time. At the firm level, it is defined as the production per unit time that is sold.

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Terminology

Operational Measures

On average, how much time does a typical flow unit spend within process boundaries?

FLOW TIME (T)

Terminology

Flow Time (T)The flow time (also called variously throughput time, cycle time) of a given routing is the average time from release of a job at the beginning of the routing until it reaches an inventory point at the end of the routing.

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Flow time

Operational Measures

On average, how many flow units are within process boundaries at any point in time?

INVENTORY (I)

Work in Process inventory (I)The average inventory between the start and end point of a product is called work in process Inventory

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WIP (9 for this realization)

Terminology

Slope (R), verical distance (I), horizontal distance(T)

Koç University as a process:

How many students are enrolled on average? (within the process)

Need more information? Program length is 4 year. What if program length were 6 years?

Inventory= Throughput x Flow Time12

Question

600 new students admitted on average

600 students graduate on average

X studentsenrolled

LITTLE’S LAW

Relating throughput rate, flow time, and inventory

Throughput RateInventoryFlow Time

Inventory I[units]

Throughput Rate[units/hr]

... ...... ......

Flow Time T [hrs]

...Inventory I

[units]

Throughput Rate[units/hr]

... ...... ...

Flow Time T [hrs]

Time=0

...Inventory I

[units]

Throughput Rate[units/hr]

... ...... ...

Flow Time T [hrs]

Time=t

...Inventory I

[units]

Throughput Rate[units/hr]

... ...... ...

Flow Time T [hrs]

Time=FT

Understanding Little’s Law: Consider a first come first served Queue

An Intuitive Argument for Little's Law

Consider a process with the FCFS queue discipline

An order departs the process: At this moment there are I (Inventory) orders within the process

The orders that are in the process now are the ones that came after our departing order had arrived, in other words, they arrived during the waiting period of the departing order

Since order arrival rate is equal to the throughput rate, we have the following relationship:

Inventory = Throughput Rate x Flow Time

Little’s Law basics

Little’s Law is for a system in steady state: input rate = output rate

Applies to most systems, even those with variability

Uses AVERAGE values

Example: flow unit is material

Fast food restaurant processes an average of 5000kgs, of hamburgers per week. Typical inventory of raw meat in cold storage is 2500kg.

Throughput R=5000kg/week Average Inventory I=2500 kg. Average flow time T=I/R=2500/5000=0.5 weeks

Example: flow unit is customers

A café in Beyoglu serves on average 60 customers per night. A typical night is about 10 hours. At any point there are on average 18 customers in the café.

Throughput R=60 customers/night; 6 customers/hour

Average Inventory I=18 customers Average flow time T= I/R= 3 hours

Example: flow unit is cash

A steel company processes $400 million of iron ore per year. The cost of processing is $200 million per year. The average inventory is $100 million. How long does a typical dollar spend in the process?

R=$600 million/year I=$100 million T=I/R=1/6 year or 2 months

Example: Auto-Moto Financial Services

Auto-moto provides loans to qualified customers. The company receives about 1000 loan applications per 30-day working month and makes accept/reject decisions based on an extensive review of each application

Auto-Moto Financial Services

Currently, Auto-Moto processes each application individually. On average, 20% of all applications received approval. An internal audit showed that, on average, Auto-Moto had about 500 applications in process at various stages of the approval procedure, but on which no decisions had yet been made.

In response to customer complaints about the time taken to process each application, Auto-Moto called in OPSM Consulting Inc.

Current System

1000/month200/month

800/month

review

500

accept

reject

20%

80%

Example: cont’d

OPSM Consulting found out that although most applications could be processed rather quickly, some took a disproportionate amount of time because of insufficient and/or unclear documentation. They suggested the following Process II:

Because, the percentage of approved applications is fairly low, and Initial Review Team should be set up to pre-process all applications according to strict but fairly mechanical guidelines.

Auto-Moto Financial Services

Each application would fall into one of three categories: type A (looks excellent), type B (needs more detailed evaluation), and type C (reject summarily). Type A and B applications would be forwarded to different specialist subgroups

Each subgroup would then evaluate the applications in its domain and make accept/reject decisions

Example: (cont’d)

Process II was implemented on an experimental basis. The company found out that, on average, 25% of all applications were of type A, 25% were of B, and 50% were of C. Typically, about 70% of type A and 10% of B were approved on review.

Example (cont’d)

Internal audit checks showed that, on average, 200 applications were with the Initial Review Team undergoing preprocessing. Only 25 were with the Subgroup A Team undergoing the next stage of processing and approximately 150 were with the Subgroup B Team

Auto-moto would like to determine if the implemented changes have improved service performance.

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Proposed System

initialreview

1000/month

200

Subgroup Areview

Subgroup Breview

accept

reject

200/month

800/month

25%

25%

50%

70%

30%

10%

90%

25

150

C

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Proposed System

initialreview

R=1000/month

I=200

Subgroup Areview

Subgroup Breview

accept

reject

200/month

800/month

25%

25%

50%

70%

30%

10%

90%

I=25

I=150

C

New process

Flow units: applications Initial review: R=1000, I=200 T=0.2 months or 6 days Team A: R=250, I=25, T=3 days Team B: R=250, I=150, T=18days Type A: 9 days Type B: 24 days Type C: 6 days Average: R=1000, I=375, T=11.25 days

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New process: different flow unit definition

Flow units: approved/rejected applications

Approved: 70% of Type A and 10% of Type B= 0.7(250)+0.1(250)=175+25=200 applications/month

Tapproved=175/(175+25)*(TIR+TA)+ 25/(175+25)*(TIR+TB) = (175/200)*9 +(25/200)*24=10.875 days

Rejected: 30% of Type A and 90% of Type B and all C= 75+225+500=800 applications/month

Treject=11.343 days

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Key learnings: Little’s Law

Relates three leading performance measures based on process flows: throughput, inventory, flow time

Applies to processes in steady state Important to

– First determine process boundaries for analysis– Then identify appropriate flow unit for your analysis