Introduction to production systems
Rossella Pozzi
School of Industrial Engineering
Operations management
Operations management (OM) is defined as the design,
operation, and improvement of the systems that create and
deliver the firm’s primary products and services through:
• strategic decisions
• tactical decisions
• operational
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Production Process Definition
A production process is the TRANSFORMATION of materials into
products (economic goods), which takes place in an industrial plant...
…the TRANSFORMATION occurs thanks to energy exchanges that
imply changes in the physical and chemical features of materials.
3
Production System Definition
The PRODUCTION SYSTEM can be considered as the production
process together with all management subsystems that lead to the
achievement of the transformations
Production Management Information System
Capitals
Organisation Management
Control
Materials
Labour Production process Finished
Tools Products
4
Definition of production process
From a more general point of view a production process is a
transformation process by which a set of resources (process inputs) is
converted into goods and/or services (process outputs).
The transformation process
may be of different types:
§ physical (e.g. machining)
§ chemical (e.g. pharmaceutics)
§ location (e.g. transport)
§ exchange (e.g. retail)
§ storage (e.g. warehousing)
§ physiological (e.g. health care)
§ informational (e.g. telecom.)
Source: Reid & Sanders
5
Production system classification
Classification by market interaction
(standardisation of product)
Prod. to stock
Repeat
Prod. to order
Single / Batch /
Single Unitary
Intermittent Continuous
Classification by production
Fabrication method (way of volume creation)
Discrete
Assembly
Process Fabrication
Classification by nature of process
(type of production technology)
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Bill of material (BOM)
Bill of Material: hierarchical and structural representation of all the
objects (sub-assemblies, components and raw materials) that
compone a product
Cheeseburger
Bread Cooked meat Salad Mayonnaise
Moulded meat
Chopped meat
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Bill of material (BOM)
§ Bill of material (BOM):
a listing of all of the raw materials, parts, subassemblies, and
assemblies needed to produce one unit of a product.
§ BOM (product structure tree):
visual depiction of the requirements in a bill of materials, where
all components are listed by levels.
§ Provides product structure:
• Items above given level are called: parents
• Items below given level are called: children
Bill of Material (BOM)
Product structure tree
Level
0 Chair
1 Leg Back
Assembly Seat Assembly
Cross Side Cross Back
2 Legs (2)
bar Rails (2) bar Supports (3)
(Stevenson)
Structural and indented BOM
A
A B
X
H
B C D
W
Z
X H X Y X K C
X
Y
W Z W X
D
X
K
W
10 X
Classification by nature of process
Classification by sales
Ø Process production
To stock
§ Often concerned with liquids, powders,
gases Repeat
To order
§ Often very high levels of automation Single Batch /
Single Intermittent Continuous
§ Examples of products: Classification
Fabrication by production
• Cement Discrete method
Assembly
• Sugar Process Fabrication
• Coffee
Classification by nature of process
Ø Discrete production (manufacturing)
§ Individual items are produced and can be tracked
§ Volumes can be high
§ Levels of automation are lower
§ Can be the fabrication of individual products and / or the
assembly of several components
§ Examples of products: cars, machine tools, electronic
goods
§ See examples at this link:
§ Auto parts
§ Stapler
Process production features
Technology
§ Not-reversible chemical-physical transformation of raw materials
§ Fixed technological route and mainly flow type
§ Relevance and sensitivity of process technological parameters
§ High level of automation
Management
§ Relative (slight) relevance of management parameters (as WIP,
lead time, phase synch, …)
Cost Structure
§ High investments for infrastructure, machinery and automation
§ Low labour cost
§ High energy and maintenance costs
Discrete production (manufacturing) – overview
Discrete production (manufacturing) typically has a closer relationship to end
customers; often process industries act as suppliers
Characteristics
§ Products are made of discrete parts that are produced in great number
of variants
§ Fabrication (processing) – use of (largely automated) mills, lathes,
presses, grinding (machines), heat treatment (furnaces), etc.
§ Assembly – use of manual or automated systems to create sub-
assemblies and then final assemblies
§ Significant use of human resources
§ Significant inventory levels at all levels of production
§ Lead time is not as predictable as in process production
§ Typically flexible technological route (options)
Discrete production (manufacturing) – fabrication
and assembly
Fabrication (processing) of parts / components
§ Can range from simple packaging of process production output
(e.g. foodstuffs) to the complex machining of parts (e.g. aircraft
wing segments, engine crankshafts)
§ Often combined with assembly
Assembly of products
§ Components produced in-house or bought from suppliers are
assembled into products for either industrial customers or final
consumers
§ Examples: iPods, microwave ovens, gear boxes, turbines, car
engines, cars, washing machines, airplanes, etc.
Discrete Production – Fabrication
Technology
§ Not reversible physical/shape transformations of raw materials and
components
§ Not fixed technology route, with options and variants, with variable level of
flexibility
§ Not particular relevance of process technology parameters, relevance of
product technology parameters
Management
§ Relevance of management parameters (WIP, lead time, delays,
synchronizations, ...)
§ Multiple resources with flexible utilization (operators, machines, tools,
programs, ...).
Cost structure
§ Relevance of fixed assets
§ Labour intensity depending from automation and characteristics of
machinery
Discrete Production - Assembly
Technology
§ Components assembly to make groups, sub-groups and finished products.
Operation can be reversible (and also irreversible, e.g., welding)
§ Free technology route, with degrees of freedom
§ Low relevance of process technology parameters
§ Process flow is synthetic
Management
§ (High) relevance of management parameters (WIP, synchronization, lead time,
delay, ...)
Cost structure
§ Low relevance of fixed assets, depending on utilization and customization of
machinery
§ A lot of manual operations cause relevance of workforce utilization
Classification of Production Systems
Manufacturing
Fabrication
(Discrete Production)
Assembly
(Processing)
Fixed Position
Job Shop
Assembly Shop
Manufacturing Cell
Assembly Cell
Transfer Line
Assembly Line
Linear (Manual)
Rotary Paced
Intermittent
Continuous
Unpaced
Asynchronous
Synchronous
Classification by production method (volume)
Continuous production Classification by sales
§ Mass production To stock
§ Stable demand for commodity type products Repeat
à producer normally does not have to store products To order
in a planned way Single Batch /
Single Intermittent Continuous
§ Product examples: Manufacture
Classification
by production
• Process production products Discrete
Assembly
method
• low-cost mechanical parts (screws, nuts and bolts, …) Process
Manufacture
Batch / Intermittent production Classification by nature of process
§ Volume of production ranges from high to medium to low
§ Trade-off between production and storage costs and demand for different types of
products require production in batches (and thus set-up costs)
§ Product examples:
• Mechanical components of cars or machine tools, electrical components, cars, furniture, …
Single / Unitary production (one of a kind production (OKP) or project)
§ Borderline case: batch production with a batch of one unit of product (set-up issues).
Variability of the range of products manufactured is very high. Production performed unit
by unit and the production cycle is changed from one product to the following one.
Flexibility, no efficiency.
§ Project: (particular case): product produced only once according to special design specs.
Demand for a single item only. Product examples: facilities for process industry or power
station, ship, custom-built car, …
Manufacturing Systems vs. variety, flexibility and volume
Few High
Low Multiple Major Volume,
Volume, Products, Products, High
One of a Low Higher Standard-
Kind Volume Volume ization
I. Commercial Flexibility (High)
Unit Cost (High)
Job Printer
Shop Italian Restaurant These are
the major
II. Heavy stages of
Batch Equipment product
III. and
Automobile process
Assembly
Line Assembly life cycles
Burger King
IV.
Sugar
Continuous Flexibility (Low)
Refinery Unit Cost (Low)
Flow
Classification by market interaction
Classification by sales
Stocked product (production to stock) To stock
§ Often produced in advance of demand Repeat
(on the basis of forecasts)
To order
Single Batch /
Single Intermittent Continuous
§ Standard specifications Manufacture
Classification
by production
method
§ Response time lower then lead time
Discrete
Assembly
§ Production starts in advance of order
Process Manufacture
Classification by nature of process
§ Relatively small range of products, standard
products
§ Ease of purchase for buyer
§ Steady demand
§ Customer demand is fulfilled by stock
availability
E.g. integrated circuits, resistors, standard
valves, consumer goods, PCs, automotive
components, cement, paper, etc.
Classification by market interaction
Classification by sales
To order production: To stock
Customised product (repeated production to
Repeat
To order
order) Single Batch /
Single Intermittent Continuous
§ Flexible specifications, wide range of options Manufacture
Classification
by production
method
Discrete
§ Response time higher then lead time Assembly
§ Fabricated or assembled on repetitive demand Process Manufacture
§ Catalogue production Classification by nature of process
E.g. cars, equipment, PCs, machine tools, etc.
Engineered product (single production to
order)
§ Designed and defined only on order
§ Produced exactly to customer requirements, no
repetition
§ High lead times, but less then response time
E.g. power station equipment, tailored clothes,
special part, assembly equipment, etc.
Wortmann classification (CODP Concept)
Engineering Purchasing Manufacturing Assembly Distribution
ETO er
ord
o
cet
du
o
PTO Pr
CUSTOMERS
SUPPLIERS
MTO
ast
orec ATO
tof
uce
d
Pro
MTS
MTS - Make to stock ATO - Assemble to order
Customer Order Decoupling Point
MTO - Make to order PTO - Purchase to order
ETO - Engineer to order (/ Project)
Production systems classification
Correlations
How these products production systems can be classified in the three axes?
• Single
• Single
• To order
• To order
(single)
(repeat)
• Assembly
• Discrete
fabrication
• Continuous • Batch
• To stock • To stock
• Process • Assembly
Production systems classification
Correlations
Single Batch Continuous
Commercial Water bottles
To stock replenishment
clothing
Repeat Pizzeria Machine tool
Tailored
Single clothing
Production systems classification
Correlations
Single Batch Continuous
Process Semiconductors Cement, paper,
manufacture glass
Discrete Customized Glasses frames Steel plastic
mechanical parts shaping
manufacture
Electronical Car assembly
Assembly Shipbuilding
commodities
Production systems classification
Correlations
Process Discrete
Assembly
manufacture manufacture
To stock Plastic Pharmaceutical Staples
Repeat Pizzeria Machine tools
Single Shipbuilding
Production systems classification
How McDonald’s production system is organized?
McDonald’s production process - classification
How would you classify this production process?
Classification by market interaction
(standardisation of product)
Prod. to stock
Repeat
Prod. to order
Single / Batch /
Single Unitary Intermittent Continuous
Classification by production
Fabrication method (way of volume creation)
Discrete
Assembly
Process
Classification by nature of process
(type of production technology)
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