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Life Cycle Assessment of a Computer Mouse

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Any opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of UK Essays.

Published: Wed, 21 Feb 2018

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 year 1964. 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

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, refrig


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