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TABLE OF CONTENTS

ABSTRACT

This project Life Cycle assessment aims at learning about how to conduct a life cycle assessment of a given product ( in this project computer mouse is the product) using Cambridge Engineering Selector (CES) software. In this document History of the mouse as of when it was invented and what are the developments that took place in years, composition of mouse, raw materials used in the mouse, the manufacturing process and the by products and waste during the manufacturing and extraction of the computer mouse will be discussed. Later on with the help of Cambridge Engineering selector we use the application of Eco audit tool and provide it necessary input into it to achieve the necessary output. The output is the outcome or the result of the project. In addition to that each and every component of the computer mouse will be discussed in detail and the environmental hazards related to the production of each of them will be discussed.

ACKNOWLEDGEMENTS

I would like to express my deep appreciation to my supervisor Mr. N.HART, for his guidance, review, suggestions, kindness, valuable time, criticisms and comments throughout my M.sc Project.

I am most grateful and thankful to university technical staff Michael Britton for his encouragement from the very beginning of the study and guiding me throughout my M.sc course.

I remain indebted and my love goes to my family for helping me accomplish this thesis. My parents have been a constant source of support-emotional, moral and financial during my post graduate years and this thesis would certainly not have existed without them.

1.INTRODUCTION

History of computer mouse:

Dr. Douglas Engelbart has invented the first device that came out as mouse in the year1964.During this time the only way the cursor scrolling position in the computer screen was by using the arrow keys on the keyboard and it was really inefficient and awkward to use. It incorporates mechanism which is in the form of small brick with one button on top and underneath two wheels and was made by Douglas. The purpose of these wheels is to detect horizontal and vertical movement and on the whole the unit was little bit difficult to use. For viewing the cursor on the monitor The connection to the computer was established by means of a cable so that the motion signals could be sent out electrically. A long cable tail featured like device like a mouse so the name “mouse” came into picture.NASA team tried different methods which enables the cursor to move on the computer screen like the devices Light pens, knee switches and steering wheels, albeit, in testing of these devices Engel arts mouse gained popularity. Engineers thought that the mouse was ideal for drafting and illustration purposes And could build up computer aided designs on the same desk. Slowly mouse began to be called as input/output device. To make the scrolling easier the mouse began to multiply rapidly. The wire coming out from the mouse reminded a tail which is one end and the other end is used for connecting to the central processing unit.

2. BODY AND COMPOSITION OF THE MOUSE:

Body of the mouse:

  • The outer surface of the mouse is Hard plastic body which the user guides across a flat surface
  • The tail of a mouse is an electrical cable that leads out from one end and finishes at the connection at the Central Processing Unit
  • It posses one to three buttons at the extremity which are external contacts to tiny electrical switches
  • With a click on the button the electrical circuit is forced to close and the computer receives a command
  • Below the mouse there's an plastic hatch that fits over a rubberized ball which exposes a small part of the ball
  • A support wheel and two shafts hold the ball in place inside the Mouse
  • Rotation of the spokes causes IR light signals from light emitting diode to flick through the spoke which are then captured by a light detector
  • Phototransistors help to translate these light signals into electrical pulses which reach the integrated circuit interface in the mouse
  • These pulses then confirms the IC whether the ball has followed an up down or left right movement
  • The IC commands the cursor to scroll on to the screen consequently.
  • The interface IC is then ascended onto a printed circuit board. This forms the skeleton to which each and every Internal mechanism in the mouse are joined
  • The information from the signals and switches coming out from the phototransistors is collected by a computer chip or IC
  • These are then sent to the computer by means of a data stream

The Brain of the Mouse:

  • Every mouse design consists of an individual software known as driver
  • These driver are The external brain which enables the PC to comprehend the mouse signals.
  • The driver commands the PC how to understand the mouse's IC data stream including speed, direction, and clicked commands
  • The mouse's IC data stream which includes clicked commands, direction and speed. Few mouse drivers permit the user to specify performance to the buttons and vary the mouse's resolution ( distance relative to cursor and mouse travel).
  • The Mouse which are purchased as a part of computer packages have built in drivers or is programmed initially in the computers

RAW MATERIALS IN THE MOUSE

The outer shell of the mouse and the majority of its internal parts, which includes spoked wheels and shafts are usually made up of Acrylonitrile Butadiene Styrene (ABS) plastic which is usually injection moulded. The ball is basically made of metal which is rubber coated and is usually supplied by a speciality supplier

The electrical micro switches which is produced from metal and plastic are of shelf items which are supplied by subcontractors even though the designers of the mouse can specify force requirements for switches to make it easier of harder to click. The chips or IC could be standard items even though individual manufacturer might have proprietary chips which can be utilised in its complete products line. The outside source also supplies electrical cables and over moulds To suit the design of mouse the printed circuit board (PCB) over Which the mechanical and electrical components are accumulated is tradition made Oscillators, integrated circuits, capacitors, electrical resistors and various other components are made of different types of plastic, metal and silicon

The raw materials which are used in manufacturing of a computer mouse are as follows:

Component name

Material

Mouse ball

Low alloy steel

Housing

Acrylonitrile butadiene styrene(ABS)

Insulation wire

Polyvinylchloride(PVC)

Rubber material

Polyurethane(tpPUR)

USB inside part

Stainless steel

Plastic part inside USB

Phenolics

USB jack(casing)

Acrylonitrile butadiene styrene(ABS)

Internal wires

Copper

Mouse Design:

The basic design of a computer mouse was conceived and prototyped in early 1960s and steriolithography concept is employed efficiently within the concurrent engineering. The concurrent engineering development takes place in two design teams , the electrical team emphasizing on control circuitry and the mechanical team working on casing layout and button geometry. For operating the mouse, the user's posture, finger extension needed to reach the buttons, use by both right and left handed individuals, no prolonged static electricity and lastly the requirements safety and comfort They alter widely depending on whether the use of mouse is in home or office computers The brief design of mouse for the proposed mouse is written to explain Which the mechanical and electrical components are accumulated is tradition made an appearance is also proposed in staying along with the probable market. The design team comes back to the table along with foam models; for a single mouse design scores of various shapes are made and the user testing on the models are performed whereas the preliminary tests are performed by engineers or the focus may be turned onto groups as typical users or observes one to one testing with user samples.

When a suitable selection is chosen, wooden models which are more refined and painted are produced from the winning design. The input of the model is acquired based on the feel, shape and looks and then ergonomist reviews the probable designs and confirms the goal of human factors guidelines to be achieved. After an optimal design is chosen the engineering team starts modelling the internal components. A 3D performance is generated by the computer and same information is used to machine-cut the postures of the exterior shell with every details. Inside the structure the mechanical and electronic engineers fit the printed circuit board and the encoder mechanism.

The phenomena of fitting the workings on to the shell are iterative, the changes are then made and then the design and fit process are conducted so long as the mouse achieves the design objectives and the design team is happy. The custom chips are then designed and produced on a trial basis and then tested; for the design to meet the performance objectives and provide it unique, competitive and marketable characteristics the help of custom electronics is required. The fully completed design figures are handed over to the project tooled who then starts the process of modifying machines to manufacture the mouse. To generate the injection moulding of the shell tooling diagrams are made into use.

The factors like shape and size, volume of the cavity, the number of gates through which the plastic will be injected into the mould, and the plastic flow in the mould are all diagrammed and studied after analyzing the final plans of tooling the tools are fabricated using computer aided data. Prototype plastic shells are made as try shots to find out the actual flow lines and to make sure that voids are not included. the process is precise. Texture is applied to the external outlook of the shell by sand blasting or by acid etching.

The Manufacturing Process:

To manufacture a computer mouse several processes are used to make different pieces of the unit. The processes that are used in manufacturing are as follows.

First the Printed Circuit board (PCB) is prepared in the journey of manufacturing and assembling steps. This board is a flat, resin coated sheet that can be of surface-mount design or through hole design. The assembly of surface mount version is entirely done by the machine. The other electrical components are placed on to the board in prescribed pattern by a computer controlled automatic sequencer. The connecting wires of the electronic components are induced in the holes of the PCB assembly. Then all the components are placed on the board, the bottom surface is passed through molten lead solder in a soldering machine. This machine removes contaminants by passing the board with flux. The board is gently heated by the machine and the component it induces with infrared heat is to lessen the possibility of thermal shock. The solder raises each line by hair-like activity, seals the perforations and repairs the components in the correct placeAfter this process is done the PCB is cooled and is visually inspected before the mechanism is attached.

A separate unit is assembled for the encoder mechanism. Injection moulding process is used to manufacture the plastic parts (computer mouse case housing) with proper specifications and the left over scrap plastic material is trimmed off. The whole unit is fastened to the PC Board using screws keeping in view after the encoder mechanism is completely assembled. With set of wires, rubber and shielding cover the mouse's tail and its electrical cable attached are manufactured. Overmolds are the additional pieces of the cable to obstruct the cable from separating away from the mouse. We can make our own shapes of design for overmolds, the near mouse overmold is hooked to the At the other end of the tail the connector is then soldered to the wires and the connector over mold is exploded into place.

  1. The outer shell pieces are then examined visually after moulding, Trimming and surface finish treatment and before the assembly. The external housing is assembled in four steps. To the bottom of the shell the completed PCB and encoder assembly are inserted. Onto the housing top part, the cable is joined; the bottom and top are joined together using automated screwdrivers.
  2. The last electronics and the achievement quality inspection are accomplished, if assembly is complete in the substantial one. Rubber or neoprene feet with the adhesive covering in front-turned at a side is added the lower surface of the mouse.
  3. A programming team has been developing; testing, reproducing the mouse driver firm ware, while the tooling designs and physical assembly are in progress. As above said “firmware” is the combination of software and hardware codes which has the unity of integrated circuit, translated mouse directional movements and micro switch signals which are understood when the mouse is attached.

By-products and waste:

Computer mice makers do not generate by-products from the manufacturers of mouse, albeit most of them suggest a variety of alike devices for altered applications. In order to avoid the design, tooling, assembly modification costs the new and multiple designs are in corporate when possible.

Waste is minimal. The mouse's ABS plastic skin is highly recyclable and can be ground, moulded, and reground many times. Small quantities can be recycled using metal scrap and other plastics.

3. LIFE CYCLE ASSESSMENT:

LCA is a holistic tool used to identify the environmental consequences of a product, process or activity through its entire life cycle and to identify opportunities for achieving environmental improvements. Life cycle stages include:

  1. Raw materials acquisition,
  2. Manufacturing,
  3. Use/reuse.
  4. Maintenance.
  5. And recycling/waste management.

For epitome, in the case of computer mouse an LCA involves making detailed measurements during the manufacture of the device. In the design stage of new products LCA information is very useful

LCA gives the whole assessment of the point of origin to the end of a product or process, i.e from processing of natural resources to shipping, mining, and also how the material be recycled or reused and till it is disposed permanently. As a system, LCA identifies the whole process and possible environmental effects throughout a products life cycle.

The term life cycle refers to the holistic assessment which assess all the operations in the supply chain ,i.e raw material production , production, fabricating, distribution, modes of transport, end product, use and disposal of all the materials or products involved .

.LCA method is one of the executive methods for evaluating the environment. It identifies that each and every product has certain influence on the environment during its life cycle, where each product is standardized and is temporarily assigned an environmental annex.

For in this regard life cycle assessment is a central tool.

The LCA method can be classified into three steps :-

Inventory analysis

  • Goal and scope definition
  • Impact assessment

The technique which allows the comparison of the environmental impacts of materials and products is Life Cycle Assessment. This assessment allows us to modify the quantitative data and to identify the potential environmental impacts of the material or product on the environment. LCA is common for assessments to be made of more limited periods eg. Cradle-to-gate and cover the entire life cycle life cycle of a material.

The entire analysis is referred to as cradle-to-cradle which refers to production from extraction of raw materials, production and delivery and is often broken down into phases of lesser ambition.

Goal and scope definition :-

Scoping is the most critical component of LCA because it provides a frame of reference for the entire study and helps define interrelationships among the other three LCA components; inventory analysis, impact assessment, and improvement assessment. The goal definition identifies the overall purpose for the LCA and its intended applications. Goal definition and scoping initiates the LCA and then drives the scope, boundary settings, data categories and data needs. This process is continuously revisited during an LCA. Scoping defines the boundaries, assumptions and limitations and should be done before an LCA is conducted to ensure that the breadth and depth of analysis are consistent with the defined goal of the LCA.

Inventory Analysis:

It is the well-developed component of LCA. A completed inventory analysis provides an overview of the life-cycle inputs and outputs associated with a particular system. The results of an inventory analysis may be used to identify areas to achieve improvement, as baseline information for conducting an impact assessment or some combination of the two. This analysis gives the boundaries of the system to be studied and develop a data questionnaire to collect the appropriate data. Develops, stand alone subsystem data and conducts a peer review to validate the results. This analysis may be used to identify areas to achieve improvement as baseline information for conducting an impact assessment.

Impact Assessment:

In this phase of LCA, the inputs and outputs of the system identified in the inventory analysis are translated into quantitative and or qualitative descriptions of environmental impacts by using models. A very few LCA's have attempted to include impacts because of the inherent complexities and data requirements of impact assessment. We do impact assessment because it provides the LCA user information that is more useful for decision making.

Some of the LCA impact categories:

  • Impacts of land use
  • Climate change
  • Stratospheric ozone depletion
  • Human toxicity
  • Ecotoxicity
  • Photo-oxidant formation
  • Impacts of ionizing radiation
  • Acidification
  • Eutrophication
  • Depletion of abiotic resources
  • Depletion of biotic resources

Improvement Assessment:

It is the least developed component of LCA. The main purpose of improvement assessment is to identify and evaluate specific actions that target priority impacts within the life-cycle frame work. Identification and estimation of opportunities to achieve improvements in processes that result in reduced environmental impacts, is based on the results of an inventory study or impact assessment.

LCA may be utilised for several purposes

To develop the environmental aspects of a product and to find out the frail systems in the product chain.

  • For product improvement for environmentally enhanced products.
  • For making executive decisions in governmental organisations.
  • Helps to select and compare among the available products.
  • For mixture of relevant indicator of environmental presentation.

4. ECO AUDIT TOOL

Eco audit tool enables the product designers to quickly evaluate the environmental impact of a product, and it helps to reduce the environmental measures. By making use of CES software, this can be achieved by focussing on two environmental stressors

To minimize the environmental footprint of a product, identification of the dominant phase is very important and it enables a designer to establish which aspect of the design to target The result of the eco audit forms the objective for the product design. This objective is dependent on both the dominant phase and the product application.

Life Cycle Analysis:

The Life cycle analysis of the product life cycle is split into three main sections in the eco audit tool:

  1. Material, manufacture, and end of life
  2. Transport
  3. Use

1. Material, manufacture, and end of life

This the first section of the product definition which allows us to enter the 'Bill of Materials'(BOM) for the product, with each line representing an individual component. There is no limit on the number of components that can be added.

Reading across the input dialog box, the entries are as follows

Quantity

This column tells us about the different number of individual components that are used in making of the product. This quantity column enables the specification of duplicate components in a hierarchal order. . The default value is one because there is no product with zero quantity.

Component name

It is the dialogue box for entering the name of each individual component of the product.

Material

The material drop-down menu displays the full Material Universe tree of the active database. Materials are selected by browsing the tree and clicking on the record for the material of our interest. Once we have done this, the eco audit tool extracts data from the material record to determine what options to display in the 'Primary process' and 'End of life' menus.

Certain products include 'components' that do not contribute to all life phases. For example, the water in a drinks bottle contributes to the transportation phase but not the material and manufacturing phases. This contribution is handled by creating a 'dummy' component with no material, or process, assigned to it.

Recycle content

We have three recycle contents which can be specified as 0%, 100%, and 'typical %'.

As the names suggest, 0% represents the use of virgin material, where all the feedstock is produced from raw materials. 100% represents the other intense, where the material is manufactured entirely from feedstock reclaimed from end of life components. Typical %, lies between these two extremes and accounts for the level of recycled material incorporated back into the supply chain as standard practice. This applies to materials, such as metals and glasses, where end of life recycling has become integrated into the supply chain. This practice leads to standard grades containing significant levels of recycled material. For example, lead alloys generally contain 50-60% recycled material.

Although many materials can be recycled, and have 'recycle fraction in current supply' values quoted in the Material universe database, they are not routinely reintroduced into the standard supply. As a result, the 'typical' recycle content option is only displayed for grades of metal and glass that are flagged as recyclable.

Primary process

The primary process dropdown menu displays the processes that are applicable to the material selected from the tree. This information, and associated data, is extracted from the material's datasheet. The available primary processes in the database are shown in the below table.

Table: Available primary processes (Level 1 and 2 database)

Material

Process

Metals

Casting

Forging

Metal powder forming

Vaporization

Polymers & elastomers

Polymer molding

Polymer extrusion

Technical ceramics

Ceramic powder forming

Non-technical ceramics

Assembly and construction

Glasses

Glass molding

Composites

Casting

Simple composites forming

Advanced composite forming

Natural materials

Assembly and construction

Electrical components

-

As electrical components are finished sub-assemblies, the material and process energies (and CO2) have been incorporated into one value [Embodied energy, primary production]. As a consequence, no processing options are available for these components.

Mass (kg)

Numeric field for specifying the mass of the component. This value is multiplied by the quantity (Qty) field value to determine the total mass for the component.

End of Life

This drop-down menu displays all possible ends of life options for the selected material. There are seven ends of life options and their applicable materials. Out of these seven, the first four are directly displayed on the datasheet depending on the type of material. The remaining life options are not specified and are added as other possible options for all materials.

The end of life option generally defaults to 'Landfill'. The main exception is for toxic materials, which default to the next viable option (usually in down cycle order').

Table: describes the possible end life options and their Summaryrelated to the materials

End of life option

Applicable materials

Landfill

All non-toxic materials

Combust (for energy recovery)

All organic-based materials with a heat of combustion value >5 MJ/kg

Downcycle

All

Recycle

All unfilled: metals / glasses / thermoplastics /TPEs
Particulate filled thermoplastics
Particulate & whisker reinforced metals
(All ceramics / thermosets / elastomers / natural organic / natural inorganic materials and all fiber reinforced materials are marked as non-recyclable)

Re-engineer

All

Reuse

All

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All

2. Transport

Transportation phase is the second part of the product definition. This phase relates to the transport of the finished product from the source of manufacture to the customer

Each line in the table relates to one stage of the process journey. There is no limit on the number of stages that can be added. For each stage, three parameters are defined: stage name, transport efficiency (transport type), and distance.

The transport efficiency is specified through the 'transport type' dropdown menu, which lists the main methods for transporting goods.

Table: transport options and associated environmental burden

Transport energy
(MJ/tonne/km)

Carbon footprint,
source (kg/MJ)

Sea freight

0.16

0.071

River / canal freight

0.27

0.071

Rail freight

0.31

0.071

32 tonne truck

0.46

0.071

14 tonne truck

0.85

0.071

Light goods vehicle

1.4

0.071

Air freight - long haul

8.3

0.067

Air freight - short haul

15

0.067

Helicopter - Euro copter AS 350

50

0.067

To determine the environmental impact of each stage the energy usage and the carbon foot print values are combined with the product mass and distance.

i.e. Energy usage is given by

Transport Energy =Transport energy per unit mass * distance * product mass.

And carbon foot print by

Transport co2=Transport energy per unit mass*Distance*product mass*carbon foot print.

3. Use

The final stage of the product definition is the use phase.

Product life

Numeric field for specifying the product life, in years. The value for the year is considered to be default (1).

Country electricity mix

The Country electricity mix drop-down menu enables the particular mix of fossil and non-fossil fuel of the country of use to be specified. This is split into three main groups: global regions, individual countries, and fossil fuel percentage. The default option is 'World'.

Compared to the other sources, such as nuclear, hydroelectric and wind power, the environmental burden of electricity generated from fossil fuels is significantly higher. So this specification of country of use is very important phase of the eco audit tool.

This is due to the relatively low efficiency in converting fossil fuels to electricity (1MJ of electricity requires about 3MJ of fossil fuel). The impact of a country's energy mix on the energy equivalence and carbon footprint of its electricity supply is summarized in Figure.

The final grouping in the 'country electricity mix' menu specifies the electricity mix based on the proportion derived from fossil fuels (0% to 100% at 5% intervals). The environmental impact of these has been calculated using the following assumptions:

  • The carbon footprint of electricity is dominated by the contribution from fossil fuels, with the proportion derived from other sources having no, or negligible, contribution.
  • And the conversion process for generating electricity from fossil fuels is taken to be 33% efficient.

In this use phase we have two modes namely static mode and mobile mode which describes the product energy usage. In static mode the available options are energy input and output which describes the conversion of one form of energy into another, power rating and usage. In the mobile mode, we have fuel and mobility type and its usage.

Modes of use

The use phase is divided into two modes of operation static & mobile.

Static relates to products that are (normally) stationary but require energy to function. For example: electrically powered products like electric kettles, refrigerators, and power tools.

Mobile relates to transportation systems, where mass has a large influence on energy consumption.

To define these modes of use, 'check' the 'static mode' and 'mobile mode' boxes. For products that operate in both modes, check both boxes.

Static mode:

Three parameters define the static use mode: Product efficiency, power rating, and the duty cycle.

The product efficiency is specified through the 'Energy input and output' dropdown menu. This specifies the energy conversion efficiency of the product and the environmental burden associated with its energy source. For electric products, the energy equivalence and carbon footprint values depend on the country of use

Table: Available energy conversion options and associated environmental data

Input and output type

Product efficiency

Energy equivalence,
source (MJ/MJ)

Carbon footprint,
source (kg/MJ)

Electric to thermal

1

Country specific

Country specific

Electric to mechanical (electric motors)

0.89

Country specific

Country specific

Electric to chemical (lead acid battery)

0.83

Country specific

Country specific

Electric to chemical (advanced battery)

0.89

Country specific

Country specific

Electric to em radiation (incandescent lamp)

0.17

Country specific

Country specific

Electric to em radiation (LED)

0.86

Country specific

Country specific

Fossil fuel to thermal, enclosed system

1

1

0.071

Fossil fuel to thermal, vented system

0.70

1

0.071

Fossil fuel to electric

0.35

1

0.071

Fossil fuel to mechanical, internal combustion

0.30

1

0.071

Fossil fuel to mechanical, steam turbine

0.40

1

0.071

Fossil fuel to mechanical, gas turbine

0.48

1

0.071

Light to electric (solar cell)

1*

1

0

The product power rating and duty cycle are specified by the 'Power rating' and 'Usage' inputs. These parameters are combined with the product efficiency values to determine the static mode contribution:

Static energy (J) =power rating (W)*duty cycle*(energy equivalence /production efficiency)

Static use CO2 (kg) = ((power rating (W)*duty cycle)/1*10^6)) *(carbon footprint/production efficiency)

Where: Duty cycle(S) =production life (years)*days per year*(house per day*3600)

Mobile mode:

The mobile use mode is defined by three parameters: The transport type, efficiency, and the distance travelled over the product's life.

The transportation type and efficiency is specified through the 'Fuel and mobility type' drop-down menu. This determines the environmental burden associated with the transportation and fuel type . For electric transportation modes, the energy equivalence and carbon footprint values depend on the country of use.

Table 5: Available fuel and mobility types and associated environmental data

Fuel and vehicle type

Energy
(MJ/tonne.km)

Energy equivalence,
source (MJ/MJ)

Carbon footprint,
source (kg/MJ)

Diesel - ocean shipping

0.16

1

0.071

Diesel - coastal shipping

0.27

1

0.071

Diesel - rail

0.31

1

0.071

Diesel - heavy goods vehicle

0.90

1

0.071

Diesel - light goods vehicle

1.4

1

0.071

Diesel - family car

1.6

1

0.071

Electric - family car

0.17

Country specific

Country specific

Electric - rail

0.11

Country specific

Country specific

Gasoline - hybrid family car

1.1

1

0.071

Gasoline - family car

2.1

1

0.071

Gasoline - super sports and SUV

4.8

1

0.071

Kerosene - long haul aircraft

8.3

1

0.067

Kerosene - short haul aircraft

15

1

0.067

Kerosene - helicopter (Eurocopter AS 350)

50

1

0.067

LPG - family car

3.9

1

0.58

These values are combined with the product usage and distance parameters to determine the contribution of the mobile mode:

Source :( Granta Design,Cambridge,UK ,2009)

Report:

The final section in the product definition allows an image and notes to be added to the eco audit report. This is compiled by 'clicking' on the View Report button. These can be categorised into three sections:

  1. Summary page - provides an overview of the eco audit, with headline values for each life phase. This enables rapid identification of the dominant life phase.
  2. Detailed breakdown of energy usage (accessed via 'Energy Details…' link on summary page) - provides a component-by-component breakdown of each life phase, enabling the main contributors to the dominant phase to be identified. This page lists all data and calculation factors used by the eco audit tool.
  3. Detailed breakdown of carbon footprint (accessed via 'CO2 Details…' link on summary page) - similar to above, except for carbon footprint.
  4. The summary table quotes two totals for energy and CO2. The first value, 'Total', and sums the environmental burden associated with the life of the existing product - this is similar to the approach used by life cycle assessment (LCA) techniques. The second value, 'Total (including end of life saving/burden)', includes end of life benefits that are realized in future life cycles. This value is useful for designers, looking to design for the environment, as it enables them to maximize the benefits that could be realized in future life cycles.

COMPUTER BALL MOUSE:

Figure below shows a typical computer ball mouse. The bill of materials (BOM) of the product is listed in table. The computer mouse is manufactured in south East Asia and transported to Europe by air freight, a distance of 11,000 km then distributed by 24 tonne truck over a further 275 km. The power rating is 15 W and the mass is 68.5 gms .The computer ball mouse is a pointing device used to generate movement commands for controlling a cursor position displayed on a computer monitor or a laptop.

Step 1: Materials and manufacture: 100 units

Material:

Breakdown by component

Component

Material

Recycle content

Material Embodied Energy * (MJ/kg)

Total Mass (kg)

Energy (MJ)

%

mouse ball

Low alloy steel

Typical %

24.338

0.015

0.365

3.38

Housing

Acrylonitrile butadiene styrene (ABS)

100%

40.423

0.062

2.506

23.23

insulation wire

Polyvinylchloride (tpPVC)

100%

33.757

0.030

1.013

9.39

rubber material

Polyurethane (tpPUR)

100%

49.916

0.012

0.599

5.55

USB inside part

Stainless steel

Typical %

59.288

0.005

0.296

2.75

plasticpart inside USB

Phenolics

0% (virgin)

90.335

0.006

0.542

5.02

USB jack(casing)

Acrylonitrile butadiene styrene (ABS)

100%

40.423

0.021

0.849

7.87

internal wires

Copper

Typical %

48.115

0.096

4.619

42.81

Total

0.247

10.789

100

Mass and energy data for material phase

Component

Qty.

Part mass (kg)

Embodied Energy, primary production (MJ/kg)

Recycle fraction in current supply (%)

Embodied Energy, recycling (MJ/kg)

mouse ball

1

0.015

34.871

41.952

9.764

Housing

2

0.031

96.343

0.707

40.423

insulation wire

3

0.010

80.374

0.707

33.757

rubber material

4

0.003

118.849

0.707

49.916

USB inside part

5

0.001

81.149

37.417

22.722

plastic part inside USB

6

0.001

90.335

0.707

0.000

USB jack(casing)

7

0.003

96.343

0.707

40.423

internal wires

8

0.012

70.937

42.895

17.734

The bar chart in the below figure shows the energy breakdown delivered by the eco audit tool. Table show the energy and co2 summary

Manufacture:

Breakdown by component

Component

Process

Processing Energy (MJ/kg)

Total Mass (kg)

Energy (MJ)

%

mouse ball

Casting

4.173

0.015

0.063

4.21

housing

Polymer molding

10.958

0.062

0.679

45.67

insulation wire

Polymer extrusion

3.575

0.030

0.107

7.21

rubber material

Polymer molding

10.129

0.012

0.122

8.17

USB inside part

Casting

4.140

0.005

0.021

1.39

plasticpart inside USB

Polymer molding

12.755

0.006

0.077

5.14

USB jack(casing)

Polymer molding

10.958

0.021

0.230

15.47

internal wires

Forging, rolling

1.975

0.096

0.190

12.74

Total

0.247

1.488

100

Transport:

Breakdown by transport stage

Total product mass = 0.25 kg

Stage Name

Transport Type

Transport Energy (MJ/tonne.km)

Distance (km)

Energy (MJ)

%

East Europe

Rail freight

0.310

2500.000

0.191

26.00

Rotherham

14 tonne truck

0.850

126.000

0.026

3.59

Hampshire

Light goods vehicle

1.400

308.000

0.107

14.47

Birmingham

14 tonne truck

0.850

75.000

0.016

2.14

East Europe

Rail freight

0.310

2500.000

0.191

26.00

Stortford

14 tonne truck

0.850

351.000

0.074

10.01

Rothernham

14 tonne truck

0.850

126.200

0.026

3.60

Sussex

Light goods vehicle

1.400

302.000

0.104

14.19

Total

6288.200

0.736

100

Total transport distance = 6.3e+03 km

Component

Total Mass (kg)

Energy (MJ)

%

mouse ball

0.015

0.045

6.07

Housing

0.062

0.185

25.10

insulation wire

0.030

0.089

12.15

rubber material

0.012

0.036

4.86

USB inside part

0.005

0.015

2.02

plasticpart inside USB

0.006

0.018

2.43

USB jack(casing)

0.021

0.063

8.50

internal wires

0.096

0.286

38.87

Total

0.247

0.736

100

Step 2: Transport

For step 2 it retrieved the energy and CO2 profile of the selected transport mode from a look-up table.

It then multiplies these by the total weight of the product and the distance travelled. If more than one Transport stage is entered; the tool sums them, storing the sum. For step 3 the tool retrieves an efficiency factor for the chosen energy conversion mode (here electric to mechanical) finding in its look-up table.

STEP 3: USE PHASE: STATIC MODE

Use:

Mode

Energy (MJ)

%

Static

0.000

Mobile

0.000

Total

0.000

100

The tool uses this and the user-entered values for power and usage to calculate the energy and CO2 profile of the use phase. For the final step 4 the tool retrieved the recycle energy and recycle fraction in current supply for each material and replaced the energy and CO2 profiles for virgin materials with values for materials made with this fraction of recycled content.

Finally it created a bar chart and summary of energy or CO2 according to user-choice and a report detailing the results of each step of the calculation. An overall reassessment of the eco impact of the computer mouse should, of course, explore ways of reducing energy and carbon in all four phases of life, seeking the most efficient methods.

Housing

Materials selected are:

  • Acrylonitrile butadiene styrene (ABS) Plastic
  • Polymethyl methacrylate (acrylic,PMMA)
  • Polystyrene (PS)

ABS:

Acrylonitrile -butadiene-styrene is an amorphous polymer consisting of the three monomers (A,B,S) offer flexibility in which acrylonitrile provides chemical resistance, ageing resistance, hardness, rigidity, gloss and melt strength .Butadiene provides low temperature ductitlity,flexibility and melt strength. Styrene provides processing ease, gloss and hardness. The impact strength of ABS is very good at low temperatures and has an average stiffness and dimensional stability, which makes it easy to machine.

The manufacture of ABS is carried out by a number of methods on a commercial basis. The most common polymerisation methods are those of emulsion, mass and suspension with variations on these processes constituting further possibilities. Emulsion polymerisation is a complex process since it take place in a heterogeneous system, consisting of discrete monomer/polymer particles stabilised by surfactant and dispersed in an aqueous medium. Despite its complexity the emulsion polymerisation process for the manufacture of ABS has been practised for more than years. The physical properties of ABS are intermediate between those of the glass and the rubber while the mechanical properties with the notable exception of impact toughness are much closer to those of the glass than to those of the rubber.

The main disadvantages of ABS are its poor solvent and fatigue resistance poor UV resistance, unless protected and maximum continuous use temperature is only around 70 degree centigrade.

Injection Molding:

The injection Process:

Plasticises the material by reciprocating screw

Injects the molten material to a closed mould via a channel system of gates and runners

  • Cools the mould
  • Refills the material for the next cycle
  • Ejects the product easily
  • Closes the mould for further cycle

Advantages of injection moulding:

  • Parts can be produced at high production rates.
  • Large volume production is possible.
  • Relatively low labour cost per unit is obtainable.
  • Process is highly susceptible to automation.
  • Parts require little or no finishing.
  • Many different surfaces, colours, and finishes are available.
  • Good decoration is possible.
  • For many shapes this process is the most economical way to fabricate.
  • Process permits the manufacture of very small parts which are almost impossible to fabricate in quantities by other methods.
  • Minimal scrap loss result as runners, gates, and rejects can be reground and reused.
  • Same items can be moulded in different materials, without changing the machine or mould in some cases.
  • Close dimensional tolerances can be maintained.
  • Parts can be moulded with metallic and non-metallic inserts.
  • Parts can be moulded in a combination of plastic and such fillers as glass, asbestos, talc and carbon.
  • The inherent properties of the material give many advantages such as high strength-weight rates, corrosion resistance, strength and clarity.

Materials used in computer mouse

Copper

Copper is used in the wiring for tail of the mouse. Copper is an excellent electrical conductor which is extremely used in wiring for power lighting, heating and several daily purposes, but copper are not used directly ,they are bounded with insulation wire .The copper metal is available in many forms, in general cadmium free copper is known with the name “electrolyte copper” which is 100 % pure.

Year by year the usage of copper is increasing, at present every year 15 million tonnes of copper is used .copper has several properties which are combidely remarkable .It is a good electrical and thermal conductor it is ductile and can prevent bacterial growth .recycling of copper is important as it is limited .And recycling of copper is well suited as it can be re melted without losing the properties.

Extraction of copper

In nature the metal are found in compounds which are usually combined with oxygen. The compounds are mixed up in rocks or minerals which are called as ores. An ore is a rock that has enough metal in it to make it worth extracting the metal. The main ore of copper are

  • Chalcopyrite
  • Bornite
  • Malachite

The three main stages of extracting copper are

  • Mining
  • Extraction
  • Purification

Mining process: In this process the copper ore will be exhumed from the ground. The ore contains some mineral and lot of waste rock. For every 1000 tones 6 tonnes of copper can be extracted.

Extraction process: In this process the ore has to be changed in to metal, this process is called reduction.

The table explains us the extraction of copper and process used.

Metal

Ore

Reactivity

Primary process

Copper

Various ore

Low

Roasting in air

Purification: In this process many metal are impure when they are extracted from there ores, impurities have to be removed copper is purified by electrolysis process as mentioned above in the figure; the copper is transformed from an impure anode to cathode of an electrolytic cell. The copper produced by this process is 99.99% pure.

Recycling of copper is very important: This process of recycling has several advantages like price, limited resources, energy efficiency, landfills costs, and the last important thing is environment.

Manufacturing process of copper used in mouse cable: There are two process used in manufacturing they are rolling and forging. The process of plastically deforming metal by passing it between rolls is called as rolling and is the most widely used forming process, which provides high production and close control of final product. The metal is subjected to high compressive stresses as result of the friction between the rolls and the metal surface.

USB INSIDE PART (METAL)

  1. Stainless steel
  2. Medium carbon steel
  3. High carbon steel
  4. Low carbon steel

Stain less steel:

The inside part of the USB connector of the computer mouse is made of a variety of stainless steel. Stainless less belongs to the family of iron based alloys that must contain at least 10.5 % chromium and creates an invisible surface film which resists oxidation making the material passive or corrosion resistant due to the presence of chromium. In addition to chromium, stainless steel may contain several other materials like iron, carbon, nickel, titanium, molybdenum etc... It is the addition of a minimum of 12% chromium to the steel that makes it resist rust, or stain 'less' than other types of steel. The invisible layer chrome-containing oxide named passive film can be formed by the mixture of oxygen in the atmosphere and chromium in the steel. Iron has the tendency to rust faster because atomic iron is very much smaller compared to its oxide, and the oxide scraps off. In the low- oxygen and poor circulation of air environments, stainless steels exhibit less oxidising nature. Whereas in seawater the salt water has chlorides which will react with the passive film

Manufacturing process:

The manufacture of stain less steel involves a number of processes, stainless steel is first melted and then it is casted in to a solid form. After the heat treatment is done then it is cleaned and the metal is polished when the desired shape is achieved.

The stages of extracting stain less steel are

  1. Melting and casting
  2. Forming
  3. Heat treatment
  4. De scaling
  5. Cutting
  6. finishing

Melting and casting: In this process the raw materials are melted together in an electric furnace. The whole process takes approximately half a day of intense heat. After the melting is done, the molten steel will be casted into different forms which include blooms (rectangular shapes), billets which are round or square in shape.

Forming: The semi finished steel goes through the forming operations starting with hot rolling in which steel is heated to high temperatures passing through massive rolls, where the stain less steel is formed.

Heat treatment: When the stainless steel is formed, annealing process is done for most types of stainless steel. Annealing is a heat treatment where steel is simultaneously heated and cooled under controlled conditions to relieve internal stresses and to soften the metal.

De - Scaling :

Heat treatment process causes a scale or layer form on the steel. This scale is removed by using several processes, out of which pickling is the common method, using a nitric hydrofluoric acid bath to remove the scale on the steel. Electro cleaning is other method in which electric current is applied to the surface using a cathode and phosphoric acid for removing the scale. So it all depends on the type of steel that being worked, we use the above mentioned annealing and descaling steps. For certain shapes like drawing into bars and wires we go through further forming steps like hot rolling, forging and extruding prior to annealing and descaling steps. For further reducing the thickness cold rolling is done which prepares steel for final.

Cutting :

To obtain the desired shape or size of the metal , cutting operation is done in order to trim the part to final size. The types of cutting operations which we make use are mechanical cutting, circle shearing, nibbling (suited for irregular shapes), flame cutting, plasma jet cutting. In all these cutting processes, extremely high temperatures are produced by the gas to melt the metal.

Finishing:

For stainless steel products surface finish is an important requisite which is critical in applications, where the appearance is taken into consideration. A few surface finishes make stainless steel easy to clean which is apparently important for sanitary applications. Polishing is done after the surface finish, in order to provide a better corrosion resistance to the metal. On, the other hand for lubrication applications, rough finishing is often required so as to carry out further manufacturing steps. Various other finishing processes used are mirror finishing, tumbling, reflective finishing, and bright finishing (using hot rolling), buffing.

Stainless steel has high market value when it is scrapped and is also 100% recyclable. Stainless steel has a less maintenance cost and is robust. It eliminates requirements such as paint, fire protective coatings, and solvents which are hazardous materials. As it is easily recyclable, in general new stainless steel comprises of at least 50% recycled stainless steel product.

Depending on the quality of the stainless steel, grades are assigned to stainless steel and they are classified into the following:

  1. martensitic
  2. duplex
  3. austenitic
  4. ferritic
  5. precipitation hardening

Alloy steel and stainless steel are almost same because both of them has same percentage of chromium but an alloy steel has additional elements like iron, carbon other than chromium which acts as a protective oxide on the surface .

General process used for the manufacture of stainless steel:

Insulation for cables:

Materials used are:

  • Polyvinyl chloride (PVC)
  • Polyoxymethylene (POM)
  • Polyethylene Terephthalate (PET)
  • Polyetherethreketone (PEEK)

Polyvinyl chloride: copper wire is circulated by insulating wire which is made up of poly vinyl chloride It is a thermo plastic layer and also vinyl polymer constructed of repeating vinyl groups, poly vinyl is the most common produced plastic, it is noted that nearly 40 millions of tonnes is manufactured every year.

Manufacturing process:

Poly vinyl is manufactured by polymerization process. Most of the common mass is chlorine which creates a given mass of PVC; due to this it requires fewer polymers than any other polymer. PVC has a higher density than hydrocarbon polymers, and production of chlorine has its own energy requirements. Suspension polymerization is the widely used for production. VCM and water are added into the reactor of polymerization and initiator of polymerization, along with other chemical additives, which starts the chain reaction of polymerization ,the reaction vessel which are contented are mixed in an order to continue the uniformly continuous particle size of the resin.. The reaction comes out to be exothermic, which requires a cooling mechanism this is because it has to ensure that the contents and components of the reactor are at established temperatures. During the course of reaction, the gas and the excess VCM from the PVC slurry is removed and is recycled into the next stage, then passed though a centrifuge to remove the surplus amounts of water. Then the slurry is passed through a hot air bed and is hence forth dried and the resulted powder is examined and sorted before storage. In normal operations, It has a very less percent of monomers as less than 1 part in a million. Whereas the other various manufacturing processes, for example micro-suspension polymerization, cross-linked polymerization and emulsion polymerization, helps us to manufacture PVC with more minimal particle sizes up to 10 μm vs. 120-150 μm for suspension type manufacturing, this types of production processes have different properties and therefore their applications are also limited to them. The PVC obtained from the polymerization process is rather in a crude form and it has to undergo conversion process by the amalgamation of additives such as plasticizers, fillers, flame retardants, heat stabilizers, UV stabilizers, lubricants, blowing agents and smoke suppressors, and thermal and impact modifiers to form the compound.

Low alloy steel: In the research it was found that the properties were similar to stain less steel and the low alloy steel used in the mouse was with same properties as used in the mouse ball.

Rubber material (Coating over metal Ball)

Materials used are:

  1. Polyurethane
  2. ABS
  3. Polyester
  4. Cellulose polymers(CA)
  5. Polystyrene

Polyurethane:

Polyurethane is rubber based material which is bounded on low alloy steel of the mouse, the mouse is in circle shape and that is ripped off with polyurethane. Polyurethanes are most commonly known as polycarbamates.Polyurethane is a polymer consisting of a chain of organic units joined by urethane links. This polymer is formed through step-growth polymerisation by reacting with two monomers groups in the presence of a catalyst and belongs to a class of compounds called reaction polymers. Polyurethanes are used in rigid foam insulation panels, gaskets, microcellular foam seals, high resilience flexible foam setting. The products made from Polyurethane are often called as “urethanes”. Polyurethane foam (foam rubber) is made by adding blowing agents which are volatile materials. The most important component of all is the isocyanate in a polyurethane polymer and the next vital component is the polyol which is formed by polyesterification. The credibility of polyurethanes is that their capability to be turned into foam .For manufacture of polyuerethane polymers, compounds of isocyanate groups react with the compounds of active hydrogen atoms. The main manufacturing method of polyurethane is the reaction between a diisocyanate and a polyol, the presence of catalyst is essentially required in this type of chemical reaction.

Phenolics:

Phenolic resins are obtained by polymerization and in the preparation of phenolic resins; the mode of catalysis of the resulting resin indicates the overall property characteristics.

The phenolic resins have the following features:

  1. These resins have excellent thermal behaviour
  2. High strength level
  3. Mechanical stability
  4. Thermal stability
  5. Low toxicity
  6. Electrical and thermal insulating capabilities
  7. Good cost performance characteristics
  8. Low heat transfer
  9. Excellent flammability performance

As these properties are unique and valuable, they are among the most important thermo sets. For many years Phenolics have been used as general non reinforced thermo set plastics in applications such as electrical switches , computer peripherals etc.. These phenolic resins have high crosslink densities so they are quite brittle and have high shrinkage. The lasting problem of phenolic brittleness and methods to alleviate or improve resin ductility, which suggest some improvement in ductility or reduced brittleness.

5. ENVIRONMENTAL HAZARDS

Global Warming:

It is the measure of increase in the average temperature of earth's atmosphere. Green house gases are the main reason for global warming. The green house gases are produced by combustion of fossil fuels, emission from the industries, large scale deforestation and agriculture. During the production of plastics, huge amount of green house gases are released into the atmosphere. During the combustion process carbon dioxide is emitted along with hydro fluorocarbons. Even during the time of transportation huge amount of CO2 and other gases are released.

Increase in temperature of earth's atmosphere could result in increase in sea levels which will result in destroying the island countries. Other consequences include floods, heat waves, droughts, lower agricultural yields and extinction of species etc.

Acidification:

It's a process of air pollution caused by the air pollutant gases like oxides of ammonia, sulphur and nitrogen which converts into acid substances. It is called acid rain. It has an impact on lakes, vegetation, ecosystem, groundwater and historical monuments. The burning of fossil fuels results in release of sulphur and nitrogen gases. These gases combine with water vapour present in the atmosphere to form sulphuric acid and nitric acid. When it rains the acid destroys the entire soil, water resources and agriculture.

The acidification potential is expressed in sulphur dioxide equivalents (SO2-Eq). It is described as the ability of substances to combine and emit H+- ions. Sulphur dioxide is considered as reference substance.

Photochemical Ozone Formation:

Although ozone is considered as a protective layer when present when present in the stratosphere, but when the production of photochemical ozone in the troposphere which is also termed as summer smog is considered harmful. It has adverse affects on vegetation and poses health risk to humans.

Nitrogen oxides and Hydrocarbons when combine with radiations from the sun results in complex chemical reactions producing highly reactive products. Ozone is one amongst them. The conditions which favour high concentration of ozone are high temperature, low humidity, high concentration of hydrocarbons and static air. High ozone concentration arises in places where there is less carbon monoxide like forests.

Ozone Depletion:

It is a term used to describe two observations: a slow and steady decline of ozone layer in Earth's stratosphere: and the diminishing of stratospheric ozone in the Earth's Polar regions.Depletion of ozone layer in stratosphere is caused due to the photo dissociation of Chlorofluorocarbon (CFC) compounds, basically known as freons, and of bromofluorocarbon compounds called as Halons. Halons CFC's are commonly known as ozone-depleting substances (ODS). The ozone layer present in stratosphere of Earth's atmosphere absorbs the harmful ultraviolet radiations, which are released by sun. If ultraviolet radiation reaches the Earth's surface it will result in skin cancer, damage to plants and decrease in number of plankton populations in the ocean.

For this reason the Montreal Protocol was introduced which aimed for complete ban on the use of CFC's.

Eutrophication:

It is caused by the decrease of an ecosystem with chemical nutrients. These include compounds consisting of nitrogen or phosphorus. Eutrophication is a result of nutrient pollution. Eutrophication causes excessive plant growth and decay, favours weeds over agriculture plants.

It favours growth of aquatic vegetation or phytoplankton that interrupts basic functioning of ecosystem posing a lot of problems. It decreases the resource value of rivers and lakes this posing a health risk to human beings. A slight increase of nitrate content in soil leads to undesirable changes in vegetation composition. E.g. species-rich fens are overtaken by reed or reed grass species.

The main cause of eutrophication is Oil Spill. Oil spill or Oil slick is the term used to describe the formation of thick layer of oil over the water surface as a result of human activity. The best way to avoid oil slick is to effectively treat spilled oil and by installing the systems made for Fast Oil Recovery (FOR) of oil from wrecked ships.

Abiotic Resource Depletion:

Abiotic resources are produced from non-living materials like fossil fuels and ore. These resources are found in large amounts in earth's crust. It acts as a measure of assessment of environmental impact a product causes during the extraction of material from natural resources to manufacture the product.

These resources are no longer available for future and therefore have an impact on how sustainable our development is. These abiotic resources are used in ships, trains and vehicles for the transportation of the product. Thereby it causes depletion of natural resources.

Human Toxicity:

Human toxicity potential (HTP) is a calculated index that emphasizes on the potential harm of a unit of chemical released into the atmosphere. It is based on potential dose and inherent toxicity of the compound. It is used to measure emissions that arise as part of a life cycle assessment (LCA) or in the toxics release inventory (TRI). It is used to aggregate emissions in terms of a reference compound. The total emissions can be evaluated in terms of benzene equivalence and toluene equivalents. The potential dose is calculated using a generic fate and exposure model that helps in determining the distribution of chemical in an environment. Toxicity is represented by safe dose (RfD, RfC) for non-carcinogens and cancer potency q1* for carcinogens.

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