design final report

7/31/2019 Design Final Report

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Abstract

The purpose of this project is to design, analyze, build and demonstrate the use of

stretcher for medical purposes. The design of structure of medical stretcher has light weight

but it must be stronger and also carry incapacitated person at most 100kg of load. This

design of this device may used for indoor or outdoor occasions. This report will outline the

design of process as well as the final selected design. Comprises of 3 important of phases,

whereby it called phase 1, phase 2 and phase 3. This report covers almost all design stages

from the concept generation (phase 1) until the preparation of final drawings for manufacture.

It included the useful design tools, an updated and improved product design, detailed budget

or cost as well as a list of calculations done for the project. Consideration on all engineering

aspects should be considered such as ergonomics, functionality, environmental friendly and

sustainability.


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SATU PAGE TUK ACKNOWLEDGEMENT


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TABLE OF CONTENTS

1.0 INTRODUCTION ................................................................................................................ 5

1.1 Background information ................................................................................................ 5

1.2 Problem statement ....................................................................................................... 7

1.3 Project objectives .......................................................................................................... 7

1.4 Scope of project ............................................................................................................ 8

1.5 Significant of project ..................................................................................................... 8

1.6 Methodology of data collection ..................................................................................... 9

2.0 LITERATURE REVIEW ....................................................................................................... 10

3.0 CONCEPT OF GENERATION .............................................................................................. 13

3.1 Functional decomposition ........................................................................................... 13

3.2 MORPHOLOGY CHART ................................................................................................. 15

3.3 BRAINSTORMING ........................................................................................................ 16

4.0 CONCEPT OF EVALUATIONS ............................................................................................. 20

4.1 Pugh concept .............................................................................................................. 20

4.2 Decision matrix ........................................................................................................... 20

4.3 Datum ........................................................................................................................ 20

4.4 Benchmarking ............................................................................................................. 22

4.5 Final decision .............................................................................................................. 24

5.0 PRODUCT ARCHITECTURE ................................................................................................ 25

5.1 Design for Human Factor ............................................................................................. 25

6.0 CONFIGURATION DESIGN ................................................................................................ 37

6.1 Modeling .................................................................................................................... 37

6.1.2 Simulation .............................................................................................................. 43

6.2 Details Analysis of Calculations .................................................................................... 44

6.3 Material Selection ....................................................................................................... 47

6.4 Design for Manufacture ............................................................................................... 51

6.5 Design for Assembly .................................................................................................... 53

7.0 PARAMETRIC DESIGN ...................................................................................................... 61

7.1 Design for Robust by Failure and Effect Analysis (FMEA)............................................... 61

7.1.1 Severity Rating Scale .......................................................................................... 62

7.1.2 Occurrence Rating Scale..................................................................................... 63

7.1.3 Detection Rating Scale ........................................................................................ 63


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7.1.4 Sample calculation for Risk Priority Number (RPN) .......................................... 64

7.2 Final dimension ........................................................................................................... 66

1.0 Introduction................................................................................................................... 74

8.0 DETAILS DRAWING .......................................................................................................... 75

8.1 Bill of Materials ........................................................................................................... 87

8.2 Costing ........................................................................................................................ 89

8.2.1 The Basics Of Costing ............................................................................................... 89

8.2.2 Fixed Costs .......................................................................................................... 89

8.2.4 Direct Costs ......................................................................................................... 91

8.2.5 Indirect Costs ....................................................................................................... 91

8.3 Estimating Total Costs ................................................................................................. 92

8.3.1 Account Analysis .................................................................................................. 92

8.3.2 Engineering Approach .......................................................................................... 92

8.3.3 High-Low Approach .............................................................................................. 93

8.3.4 Standard Costs ........................................................................................................ 93

8.3.5 Direct Materials. .................................................................................................. 93

8.3.6 Direct Labor. ........................................................................................................ 94

8.3.7 Overhead ............................................................................................................. 94

9.0 FINAL SPECIFICATION ...................................................................................................... 97

10.0 REFERENCES ................................................................................................................... 98


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1.0 INTRODUCTION

1.1 Background information

On the middle of the 20th century, stretchers have been used since

antiquity, on battlefields and in emergency situations, where wheeled vehicles

are hindered by rough terrain. In their simplest form, they generally consisted

of a canvas sling with long edges sewn to themselves to form pockets through

with wooden poles could be slid. This form was common with militaries, and

in disaster situations, where rapid triaging and movement of patients based on

severity of injuries is critical, they are still used by emergency responseproviders.

In the modern stretcher, it used in ambulances have wheels that make

transportation over pavement easier, and have a lock inside the ambulance to

secure the victim during transport."Normalized" stretchers, or folding

stretchers, are the simplest type. They are made of two poles and two

transversal hinged bars with a cloth stretched between the poles and four feet.

The bars can be folded for storage. They are now rarely used by modern

emergency services, but are still widely used by organizations for which the

storage space is an important factor such as first aid associations, or French

companies (a stretcher is mandatory). These stretchers are often used as beds.

Disaster stretchers are designed for easy storage and transport. They

consist of a tubular aluminum structure with a washable cloth. They cannot be

folded, but can be piled up. As normalized or disaster stretcher have no

wheels, they are usually carried by three or four people. When they must be

carried by only two people, they tie straps to the poles, so the weight is

supported by the shoulders and not by the hands.
http://en.wikipedia.org/wiki/Sling_%28furniture%29http://en.wikipedia.org/wiki/Triagehttp://en.wikipedia.org/wiki/Ambulancehttp://en.wikipedia.org/wiki/Bedhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Aluminumhttp://en.wikipedia.org/wiki/Bedhttp://en.wikipedia.org/wiki/Ambulancehttp://en.wikipedia.org/wiki/Triagehttp://en.wikipedia.org/wiki/Sling_%28furniture%29


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The basic medical stretcher, it needs the simplest structure to ensure

bring at anywhere places or situation. It also has a bed as place to hold the

body of patient. The bed should be comfortable to make sure the patient will

be felt suitable upon this bed. Nevertheless, an in-depth study will be carried

out to identify all possible problem and its solutions to ensure the success of

this project. In conclusion, by applying all knowledge learned, with careful

study and consideration, a functional and hopefully a new generation of

medical stretcher could be produced, without any compromise on its reliability

and sustainability. The end of result might provide us with not only a

functionality medical stretcher, but also better understanding of design process

which could lead to a vital breakthrough in our future career.


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1.2 Problem statement

Stretcher is widely used in medical field as the best device which gives

benefit to the human. Stretchers ensure the safe transportation of patients to

and from the many different areas that each campus has, may it be from the

emergency room to inpatient surgery to the post-op recovery area, or whatever

the individual case calls for. Stretchers have always served to protect a person

from further injury during transportation as well as to ease the burden on the

people carrying the stretcher itself, as opposed to carrying the injured person

without assistance at all. A wide variety of hospital stretchers that will suit

your facilitys many needs. Nowadays, we need stretchers that are designed to

suit the demands of different patients.

1.3 Project objectives

To gain knowledge about medical stretcher in order to design a newmechanical stretcher for indoor and outdoor occasions. In a mean time,

to perform analysis on improving structure and functionalities.

To fabricate a quality medical stretcher for a massive production inmanufacturing field.

To reduce cost in manufacturing stretcher in order to break the worldmarketing.

To design a better stretcher than existing stretcher with priority usercomfortable, safety and quality.

To produce a long lasting use of product and search for alternative toproperly dispose the stretcher.
http://durable-medical-equipment.medical-supplies-equipment-company.com/product/ppf/id/17334/new_prod_full.asphttp://www.medical-supplies-equipment-company.com/product/ppf/param/2113_0__1_true/product_search.asphttp://www.medical-supplies-equipment-company.com/product/ppf/param/2113_0__1_true/product_search.asphttp://durable-medical-equipment.medical-supplies-equipment-company.com/product/ppf/id/17334/new_prod_full.asp


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1.4 Scope of project

The study of this research focused on the view of hospital attendances,

patients and doctors at hospital. It was concerned only with matters directly

related to the design and function of medical stretcher. The scope covered a

small group of student to make the evaluation be easier. As we all know,

stretcher is the main equipment in hospital. All the consideration to build

medical stretcher must take into account such as strength of framework, light

and easy to store and the function of the stretcher in every situation. In this

research, it must satisfy outdoor and indoor usage and be able to accept 100kg

for the minimum load. One of the main points is portable.

1.5 Significant of project

A stretcher is a medical device used to carry casualties or an

incapacitated person from one place to another. It is a simple type of litter, and

still called by that name in some cases. Stretchers have been used since

antiquity, on battlefields and in emergency situations, where wheeled vehicles

are hindered by rough terrain. In their simplest form, they generally consisted

of a canvas sling with long edges sewn to themselves to form pockets through

with wooden poles could be slid. This form was common with militaries right

through the middle of the 20 thcentury, and in disaster situations, where rapid

triaging and movement of patients based on severity of injuries is critical, they

are still used by emergency response providers.

From research, we got to know and learn about the historical of the

stretcher itself. Not all medical stretcher are multipurpose use, some of the

medical stretcher are made or fabricate just in case of emergency happen, but a

lot we seen are just on standby from the ambulance and in hospital nowadays.


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In making medical stretcher, there are a lot of things that must or

should be improve. We must make sure that the problems that should take

have been identified. It not a possible to make a good medical stretcher for

everyone, but to make the comfortable one for the sake of human is really

hard. We learn how to design the project based on our information that we

have gathered. Conceptual design really helps us in sticking to the one

objective that we must stick on it.

1.6 Methodology of data collection

The study of this research focused on the view of hospital attendances,patients and doctors at hospital. It was concerned only with matters directly

related to the design and function of medical stretcher. The scope covered a

small group of student to make the evaluation be easier. As we all know,

stretcher is the main equipment in hospital especially in the emergency room.

All the consideration to build medical stretcher must take into account such as

strength of framework, light and easy to store and the function of the stretcher

in every situation.


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2.0 LITERATURE REVIEW

With the single push of a button, emergency medical technicians for Pasquotank-

Camden's service can lift a patient who weighs up to 700 pounds. This week, theservice's five ambulances were outfitted with new stretchers that can accommodate

the growing girth of its patients and help lower the incidents of injury among the

emergency medical technicians. Pasquotank-Camden Emergency Medical Service is

the only one in the region to boast the cutting-edge equipment.

(Article: Ambulances get stretchers to handle heavier patients, ELIZABETH

CITY -- By Lauren King)

Wendell See, an EMT-A from the Circleville Emergency Medical Service sits in an

ambulance next to two medical stretchers that are used daily by the EMS, Saturday,

Aug. 16, 2003 in Circleville, Ohio. The "FernoProflexx," right, which was been

designed to carry patients weighing as much as 650 pounds is becoming a top seller

over lighter capacity stretchers like the "Stryker," left, which can handle 450-pound

patients. (AP Photo/Jay LaPrete).The sharply rising number of obese Americans is

leading medical-equipment manufacturers and ambulance crews to supersize their

medical stretcher.

(Article: Manufacturers Supersizing Stretchers, JONATHAN DREW,

Associated Press Writer, Dateline: WILMINGTON, Ohio 10-18-2003)

WILMINGTON, Ohio (AP) - The sharply rising number of obese Americans is

leading medical-equipment manufacturers and ambulance crews to supersize their

stretchers. Manufacturers are adding thicker aluminium frames, bulkier connectors

and extra spine supports to create stretchers with a capacity of 650 pounds, instead of

the standard 350 to 500. Ambulance crews are switching to the heavy-duty models to

avoid injuries to rescue workers and patients alike. "If the stretchers aren't big enough,

a person may fall off. It's a disaster. Or if the stretcher collapses, it can lead to injury

for them or the attendant," said Dr. Richard Atkinson, president of the American

Obesity.


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Accordingly, the emergency stretcher of the present invention includes a support

frame with the handling capability of prior support frames, but with increased

stiffness in the raised position to reduce wobbling or play of the litter surface that may

occur on prior ambulance stretchers. Further, when it its compact, folded

configuration, the patient support is locked relative to the base, which eliminates

base sag.

(Article: Summary of the Emergency Stretcher, By: Ericfu, 5.10pm, 4 August

2010)
http://www.articlesnatch.com/Article/Summary-Of-The-Emergency-Stretcher/1161041http://www.articlesnatch.com/Article/Summary-Of-The-Emergency-Stretcher/1161041


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3.0 CONCEPT OF GENERATION

3.1 Functional decomposition

Medical stretcher

Concept of

design

Framework

Tires

Shape:

i. Single caster.ii. Double caster.iii. Compound caster.

Materials:

i. Rubberii. Plasticiii. Stainless steel.

Shape:

i. Oval shape,ii. Rectangular shapeiii. Combination of

rectangular and

pentagon

Materials:

i. Aluminium alloyii. Stainless steeliii. Aluminium

Joint

i. Weldingii. Bolt and nutiii. Rivet

i. Indoorii. Outdooriii. Emergency


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Control system

Mattress

Medical stretcher

i. Mechanical The structure of device

ii.Vibration Spring

iii.Electrical

i. Latexii. Wooliii. Cotton


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3.2 MORPHOLOGY CHART

FUNCTION OPTION

THEME OUTDOOR INDOOR EMERGENCY

FRAMEWORK(UPPER)

SHAPE

RECTANGULARRECTANGULAR

ANDPENTAGON

OVAL

MATERIAL STAINLESSSTEEL

ALUMINIUMALLOY

ALUMINIUM

HANDLINGPARTS

NO YES YES

TYREPATTERN

SINGLECASTER

DOUBLECASTER

DOUBLECASTER

MATERIAL PLASTIC RUBBER STAINLESS

STEELNUMBER 4 6 2

MATREESS

ABILITY WATER PROFF ANTI-BACTERIA

WASHABLE

MATERIAL COTTON WOOL LATEX

THICKNESS 6mm 8mm 10mm

CONTROLSYSTEM

MECHANICAL MECHANICAL VIBRATION

FRAMEWORK(LOWER)

SHAPE

X-SHAPE SAND CLOCK-SHAPE

C-SHAPE

MATERIAL ALUMINIUM ALUMINIUMALLOY

STAINLESSSTEEL

JOINT WELDING BOLT AND NUT RIVET


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3.3 BRAINSTORMING

The discussion from our group, we had been highlighted and finalized ideas

that come out with three initial concepts. The crucial elements in generating

those three concepts are about the:

3.3.1 Framework

The body or framework of the medical structures materials

should be lighted weight. This is because it will make easier to bring at

anywhere places. The structures materials should be stronger to ensure

it can support the weight of patient at a time. The material that we used

to build up this device is aluminium alloy. Aluminium alloys are alloys

in which aluminium is the predominant metal. Typical alloying

elements are copper, zinc, manganese, silicon, and magnesium.

There are two principal classifications, namely casting alloys

and wrought alloys, both of which are further subdivided into the

categories heat-treatable and non-heat-treatable. About 85% of

aluminium is used for wrought products, for example rolled plate, foils

and extrusions. Cast aluminium alloys yield cost effective products due

to the low melting point, although they generally have lower tensile

strengths than wrought alloys. The most important cast aluminium

alloy system is Al-Si, where the high levels of silicon (4-13%)

contribute to give good casting characteristics. Aluminium alloys are

widely used in engineering structures and components where light

weight or corrosion resistance is required.
http://en.wikipedia.org/wiki/Alloyshttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Castinghttp://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Extrudinghttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Extrudinghttp://en.wikipedia.org/wiki/Heat_treatmenthttp://en.wikipedia.org/wiki/Castinghttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Alloys


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Aluminium alloy surfaces will keep their apparent shine in a

dry environment due to the formation of a clear, protective oxide layer.

In a wet environment, galvanic corrosion can occur when an

aluminium alloy is placed in electrical contact with other metals with a

more negative corrosion potential than aluminium.

Concept 1 - The design we provide in this first concept is we try to

minimize the area of structure of device. It means a simple structure of

frameworks.

Concept 2 - The simple flat stretcher featuring a lightweight aluminum

frame and a heavy-duty, vinyl-coated nylon cover. Exclusive slimline

center hinges enable the stretcher to fold for compact storage.

Concept 3 - The design device with removable stretcher top made of

sheet pressed on epoxy coated tubular frame.

3.3.2 Caster( wheels)

The caster is the one of important part in this device. Where,caster is used to move the device. A caster is an undriven, single,

double, or compound wheel that is designed to be mounted to the

bottom of a larger object so as to enable that object to be easily moved.

They are available in various sizes, and are commonly made of rubber,

plastic or stainless steel. Casters are found in numerous applications,

including shopping carts, office chairs, and material handling

equipment. High capacity, heavy duty casters are used in many

industrial applications, such as platform trucks, carts, assemblies, and

tow lines in plants. Generally, casters operate well on smooth and flat

surfaces.
http://en.wikipedia.org/wiki/Galvanic_corrosionhttp://en.wikipedia.org/wiki/Wheelhttp://en.wikipedia.org/wiki/Shopping_carthttp://en.wikipedia.org/wiki/Office_chairhttp://en.wikipedia.org/wiki/Material_handlinghttp://en.wikipedia.org/wiki/Material_handlinghttp://en.wikipedia.org/wiki/Office_chairhttp://en.wikipedia.org/wiki/Shopping_carthttp://en.wikipedia.org/wiki/Wheelhttp://en.wikipedia.org/wiki/Galvanic_corrosion


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We had two option types of caster that provide to use in this

device such as single caster and double caster wheel. We need to

choose the type of materials to make this caster. We considered the

criteria of the materials such as cheaper, strong and rain groove. We

provide average friction between casters surface and floor. It is

because average friction will reduce movement of device to ensure the

device not easy to slip.

Concept 1 - Used double caster and plastic as material.

Concept 2 - Introduce single caster to put it as wheel in this device.

The material that we used in this caster is rubber synthetic.

Concept 3 - The caster that provides is single wheel. We decide to use

stainless steel as materials.

3.3.3 Control system

We need system to control this device. We provide to use

mechanical system. This system is better compare the other system,where we just use mechanical as system to move this device. We also

use electrical system as alternative ways to move this device.

Concept 1 - Use mechanical system (push the device) to move this

device.

Concept 2 - Introduce mechanical to fold the parts as compact as it can

be.

Concept 3 - Combination of mechanical such vibration and electrical.

We control the height of stretch to comfort users.


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3.3.4 Mattress

A mattress is a mat or pad, usually placed on top of a bed, upon

which to sleep or lie. The mattress we want to use in this device such

as vacuum mattress, mattress anti-bacteria, and foam mattress.

Designed for patient comfort and clinical efficacy such as low friction

for ease of patient transfers, anti-microbial, anti-static, stain resistance,

abrasion resistant and non-allergenic

Concept 1 - Use latex mattress as a place on this device. Latex mattress

will put on the frame of medical stretcher.

Concept 2 - The second concept we use unique secondary fluid barrier

to Protects the foam if the outer cover is compromised.

Concept 3 - Multi-layered, ultra comfort, high resiliency, medical

grade, urethane foam to provide maximum comfort for those long stays

on the stretcher.
http://en.wikipedia.org/wiki/Bedhttp://en.wikipedia.org/wiki/Sleephttp://en.wikipedia.org/wiki/Sleephttp://en.wikipedia.org/wiki/Bed


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4.0 CONCEPT OF EVALUATIONS

4.1 Pugh concept

Pugh concept is a tool for methodically making a choice from

several alternatives concept that we have. The selection can simply do

with aid of any spreadsheet. This method regularly called as Pugh

Concept Selection. Pugh comes from its creator, Stuart Pugh. In

Pugh concept, we compare the criteria of our alternatives concept with

an existing product (datum) by rating it whether it better, equally, or

worst that the datum.

4.2 Decision matrix

Decision matrix is basically an arrangement presenting on a list

of alternatives (i.e concept) that are evaluated regarding to list of

criteria, which are weighted dependently of their level of importance in

the final decision to be taken. By combining these two methods, the listof criteria is weighted while the alternatives concept compared and

rated respectively to the datum.

4.3 Datum

The datum is the references point in evaluate our generated

concept and to compose the final decision. In this case, we decide to

choose the stretcher manufactured by Hospital Furniture & Hospital

Product from series HEHF-0048. In order to rally the design of our

concept, we use the scale model of HEHF-0048 (stretcher on trolley

stretcher). The tubular frame work has size of 2030 mm (length), 560

mm (width), and 820 mm (height). The tubular frame work is made

from strong steel. The trolley is mounted on four 150 mm dia

swivelling castors. It is the removable stretcher top and can carry the


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capacity of load approximate to 150 kg. The stretcher is also supplied

with 35 mm thick mattress.

The specification of the model as state down below:

Specifications Descriptions

Size 2030 mm (L) x 560 mm (W) x 820 mm (H) (Approx.)

Criteria - Carrying Capacity : Approx. 150Kg

-Strong steel tubular frame work of trolley mounted on four 150 mm dia

swiveling castors.

- Removable stretcher top.

- Pre treated and Epoxy powder coated.

Material -Made of aluminium sheet supported on tubular frame.

- Supplied with 35mm thick PU mattress.

Figure 1: STRETCHER ON TROLLEY STRETCHER(HEHF-0048)


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4.4 Benchmarking

The idea to design a new model medical stretcher in hospital user is

from the benchmarking with model produce from Hospital Exports. The

model was we refer it is stretcher on trolley for code HEHF0048 produce by

that company. The model is look very basic and we try to make over to design

then fabricate better medical stretcher based on user and marketing. The size

of that medical stretcher is 2030 mm for their length 560 mm for wide and 820

mm for their height. So, we want to design wider stretcher so that the

stretcher can use for all user included obese person. The frame work of that

model is made by strong steel where that strength ability for this material is

high but the disadvantages of this material are expensive. For record, the price

of steel in world marketing is about US$ 3314 per ton for average lastly

update at May 2010. But the manufacturing cost can be reducing if the product

was produce in large scale. But for our project, we try to use aluminum alloys

to reduce the cost and the strength of material is not bad and the young

modulus for aluminum alloys is about 65Gpa to 75Gpa. Then for stainless

steel about 200Gpa, strong material compare aluminum alloy but very

expensive compare than the last update price for aluminum alloys that is

average US$ 2028 per ton.

Furthermore, the structure of frame work or mounted for datum model

is H shape and the top stretcher is able to remove from the framework. For our

medical stretcher design, we change the structure of mounted to X shape and

can be adjustable. The reason we make the mounted to X shape because easy

to handling and can be adjustable based on the operator height. Not like the

previous model, the H shape structure cause the height is fix and difficult to

stock the stretcher compare the our design. Next, from the model HEHF

0048 the stretcher is just flat only. So we get idea to make the stretcher have

an arm rest to provide comfortable to patient.


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We also observed the shape of mattress on the top medical stretcher

where the shape is rectangular and supplied with 35mm thick PU mattress.

The material use for the mattress is soft foam and covered by black canvas.

For our design, we decide to use more complex shape and more soft foam

covered with waterproof and anti fungus canvas. it is because to make the

mattress more safely and comfortable to patient.

Besides that, the benchmarking model for that stretcher have four

trolley tires on the behind stretcher to support the stretcher and make the

stretcher easy to move. The trolley tires also can fully turn around 360

degrees and the purpose is to make easy for handler. So, from that existing

idea, we have to plan to added 2 more trolley tires to in the middle to make the

movement is smoothly in the mean time not give bad effect for patient. We

also added damper on the trolley system to absorb the vibration occur during

the stretcher was move. Then, we are too responsible to make sure the safety

factor on our product is guaranteed. So, we are going to plan added the three

safety belts on the stretcher. It is because the safety factor for previous model

on that stretcher is weak and simple.


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4.5 Final decision

After finalize the result from the Pugh matrix, we choose the concept 2

as the concept scoring the highest point. In the concept 2 the frame work use is

sand clock shape where it is easy to fold and easy to store this equipment.

Compare than the concept 1 and concept 2 that is X shape, the framework type

is fix and make some difficult to handling and store. Based on the cost, the

material use in concept 2 is cheaper than concept 1. Note that the price if

aluminum alloy is cheaper than stainless steel price. Furthermore, the system

on the medical stretcher for the concept 2 is better than concept 1 and concept

3. The system technology was added in concept design is like arm rest to be

comfortable for patient. Then, the stretcher on concept 2 is more safely

because three strips safety belt was added in the design. So, the most relevant

safety factor is concept 2.


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5.0 PRODUCT ARCHITECTURE

5.1 Design for Human Factor

Ergonomics

Ergonomics is the scientific discipline concerned with the

understanding of interactions among humans and other elements of a

system, and the profession that applies theory, principles, data and

methods to design in order to optimize human well-being and overall

system performance.

Ergonomics is employed to fulfill the two goals of health andproductivity. It is relevant in the design of such things as safe furniture

and easy to use interfaces to machines. Proper ergonomic design is

necessary to prevent repetitive strain injuries, which can develop over

time and can lead to long-term disability.

5.1.1 Ergonomics in making StretcherThe comfort and the ergonomics of the stretcher have been

raised and this allows for a reduction in the effort expended, to an

increase in safety and therefore improved performances of the

operators.

5.1.1.1Criteria of the Stretcher Stretchers is light (to facilitate field portability)- The use of the stainless steel, welded framework

with aluminium and polycarbonate inserts

guarantees this equipments durability

Stretchers is strong (to handle large patient loads)- The use of the stainless steel, welded framework

with aluminium and polycarbonate

A stretcher is compact (to allow movement throughcramped spaces).
http://en.wikipedia.org/wiki/Repetitive_strain_injuryhttp://en.wikipedia.org/wiki/Repetitive_strain_injury


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Adjustable stretcher height. Good surface- A polished finish and easy access to all parts

enables efficient maintenance and cleaning.

5.1.1.2Control

Optimisation of the position of the controls and centre

of gravity enables absolute control and command of the

stretcher.

Its potential uses are many. For example, many X-ray

tables are about a metre high, but no stretcher is produced in

that height. Thus patients have had to be lifted, creating risks

for patient and operator safety

5.1.1.3Stability

The system continuously verifies stability, adapting

itself to a necessary height. The flexible distribution of the two

axles allows the wheels to achieve a maximum traction and to

make the most of the thrust. Therefore, the stretcher always

offers an optimal stability and gear dynamics.

5.1.2 AnthropometricDesigning of human factor for medical stretcher consider the

interaction between human and product. The matters that take into

account in this analysis are the characteristic, abilities and the interfaces

between human and products. Two main categories is divide that is

ergonomic and anthropometric.


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The study of people in order to design products and systems

which are better adapted to human capabilities is known as ergonomics.

Ergonomists are employed to improve efficiency, reliability and safety.

They aim to improve the design of things, such as control panels, to make

them easier for people to use.

(Young Technologies Handbook, YHT Version 1.1)

Anthropometry is the measure of physical human traits that is

applied to determine allowable space and equipment size and shape used

for the work environment. Factors that are considered include agility and

mobility, age, sex, body size, strength, and disabilities. Engineering

anthropometry applies these data to tools, equipment, workplaces, chairs

and other consumer products, including clothing design. The goal is to

provide a workplace that is efficient, safe and comfortable for the

worker.

(L.A. Weaver Co. of Raleigh, N.C. The L.A. Weaver Co.)

An important thing that must take into account in designing

medical stretcher is the shape and size, which is dimension. It plays such

as huge role in consideration to build a product. The human interaction

with the medical stretcher such as power to push with certain amount of

load and how patient interact with it; suitable to climb and come down.

One of the physical activities involved is grasping. It happen

when the stretcher is about to move. Way the object is grasped will

affect the power of moving. Type of grasping that use is prehensile that

is an object is wholly within the palm of the hand. Major types of

prehensile grasp are known as power of grasp. It means the object is held

in the palm of hand with thumb and other finger is meeting gives more

combination power.


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Figure a: Types of power grasp

Hand grasp gives differ power depend on the size and shape of

the object. The main types of power grasp are hook and cylindrical

grasp. In cylindrical grasp, the fingers are wrapped around the cylinder

surface. While hook grasp, the index and thumb fingers hold the object.

As the effect of grasp between cylindrical and hook, the suitable

shape for handle for a person to push and pull the medical stretcher is

cylindrical. It shown as the comfort of the grasp and further gives morepower rather than hook shape.

The thickness of the mattress base must have a proper thickness

so it easy to grasp by users and the mattress base be able to

accommodate load by the patient. User will easy to handle especially to

grasp the side of medical stretcher to easy the user push the stretcher. So,

the side of base mattress should have a suitable grip breadth where the

size or diameter that suitable for human to hold it.


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Figure 1: Size diameter of hand grip

Based on the figure, it represent the often hand grip diameter for

human. Application of hand grip for hold the side of medical stretcher or

their holder is about to 1.62.1 inches equal 3.4-5.2cm. For this design,

the coordinator of medical stretcher or the user may easy to hold the side

of medical stretcher and the grip is more like comfortable to handle

stretcher and easy to push and pull it. The size of side mattress base is

not be too thickness and too bulky. In practically it is not proper and not

suitable for design the simple medical stretcher to bulky because the

criteria of medical stretcher are must simple and easy to handle.

The term of simple and easy to handle is influence design for side

base mattress because should design the suitable thickness. So, in

dimensioning the thickness of medical stretcher and side holder is about

3.4 cm until 5.2 cm.


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In determining the shape of the base medical stretcher, it required

a lot of consideration. It is because the shape, size and weight of the base

will give the big affect toward the medical stretcher handler or operator

and toward the patient too. The medical stretcher designed as simple as it

can be as an easy to handle by operator and must be consider the

environmental where the limit of medical stretcher is use in hospital

especially to transfer patient and emergency case in the hospital.

Table 1: Height and Weight anthropometric data by different ethnic in Malaysia.


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Figure 3: Right way to measure human height

The length, width and height of the medical stretcher is influence

by the human factor such as the height of human, breadth of shoulder

and others factor required. For the length of medical stretcher, data from

the figure was use in decide the dimension. Based on that figure, the

maximum human height is about 167.5 cm and the minimum is about

153.3 cm. the data from the table is represent in average height. For

actually height in Malaysia can reach about 180 cm. Then, for find the

length dimension for medical stretcher, the maximum human height is

consider because to ensure the length of stretcher is able to accommodate

all patient from different ethnic especially the design of medical stretcher

is more focus to Malaysian human user. So in dimensioning the length of

medical stretcher the length must be more than 180 cm that is about 190

cm.


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Table 2: Anthropometric data for the overall Malaysian citizen. All unit in mm.

(Baba Md. Derus, 2009)

Figure 4: Shoulder breadth measurement

The width of medical stretcher is influence by the maximum

body breadth. The figure shows the anthropometric data overall

Malaysian citizen including the shoulder breadth. The 5 th and 95th

percentiles are based on overall where the data is including of men and

women. Each vale is given in millimeters. The average dimension for

shoulder breadth is given 459.54 mm. 5th percentile of people from the

data have 561.06 mm shoulder breadth dimension. According the data,

the width of medical stretcher base is must greater the maximum body

breadth because be able to accommodate all human in different size.


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So, consider the criteria the dimension of width medical stretcher

is about the 60 cm. unfortunately, the width is not satisfy for the obese

person because that width is not enough to accommodate the breadth of

big person. But the priority for this design is simple and easy to handle.

This is reason the stretcher is not too width to achieve the objective in

design medical stretcher.

Table 3: Distribution of anthropometric variables in the children and adults

(Fortaleza,2006)

Figure 5: Hip height

Ergonomic design cases are used to demonstrating the

requirements and dimension in ergonomic design. Is so doing, it

becomes obvious that design process, in line with the complex problems

inherent in humans and medical stretcher. It is dependent on many varied

factors, with technical and physical criteria considerations in addition to

ergonomic design criteria. The hand location to hold the stretcher holder


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of medical stretcher must be appropriate way to give the comfort for the

human.

For the height of medical stretcher, the hip height is considered to

get the suitable dimension. The reason consider the human hip height is

because to ensure operator of medical stretcher is easily handle that

stretcher such as push and pull it. In addition, to make the medical

person easy treat the patient. According from table by Fortaleza the

mean value for hip perimeter is equal to 81.27 cm. Comparison the

datum height of medical stretcher the height is about the 85 cm. The

height of medical stretcher should not be too highly and too lower so that

easy to handle by operator or medical officer. Actually the design of

medical stretcher height is can be adjustable. So in dimensioning, the

maximum high of medical stretcher is about 85 cm but the recommended

height setting for the comfortable with human factor is about 81 cm. For

the minimum height adjustable is about 20 cm.

Furthermore, the medical stretcher must be able to accommodate

the human load. From the figure the maximum load show from the data

is about 65 kg and that is in average. Actually the medical stretcher is

must be able accommodate the greater load about the 150 kg. It is

because to ensure the safety for patient on the medical stretcher to avoid

the unfortunate accident like the frame work of stretcher is broken. This

section is will be argument in the material selection section where the

section is related and influence by material.

In conclusion, anthropometric data and ergonomic data is

influence or interact with the human to give the user or operator will be

more conducive and efficient.


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5.1.3 Physical arrangementPhysical arrangement is the second step for embodiment design

phase. It is also known as configuration design. During this stage, the

shape and general dimension of each our products components of the

medical stretcher is established. We just follow the selection of viable of

conceptual design; the design team must use their analytical and

scientific skills to transform the concept into reality. In this stage also, all

the parts or components and sub-systems of the propose design have to

be given specify sizes, dimensions, power ratings, capacities and etc.

In this section, we can elaborate the physical or configuration

design various phase used in the realization of the medical stretchers

project. These include the modeling, simulation, analysis, material

selection, design for manufacture and design for assembly.


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6.0 CONFIGURATION DESIGN

6.1 Modeling

Modeling can be defined as the process of generating abstract,

conceptual, graphical and/or mathematical models. Science offers a growing

collection of methods, techniques and theory about all kinds of specialized

scientific modeling. Also a way to read elements easily which have been

broken down to the simplest form. It is also will represent the design ideas into

the physical appearance. In this section, the design put into physical form and

all the parameter are decided by our group.

6.1.1 Mattress blocks

Mattress blocks are the part crucial. It is because this part holds

the mattress and links the other parts. The mattress must be design

accordingly to the shape of the mattress blocks. To get the best

dimension of mattress shape we must design the mattress that has fit to

the size of mattress blocks. In our design, we make two parts to hold the

mattress. This can be illustrating as shown figure below:

Figure 6: Structure to hold the body of patients. (Base rod)
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Figure 7: Structure to head base.

Based on figure that illustrated above, it is called head base. It

has function to hold the head of patient. It is linked with the structure on

figured 6. As same concept with structure to hold body of patients, this

structure will be assembled with a plate to hold the mattress.

Figure 8: Assemble of head base with base rod

Figure 8 shows a plate will assemble with base rod (figure 6). We

just insert it into base rod structure. Then, we screw up to give a force tothe structure so that it so strong to hold a patient.


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Figure 9: Body base

Figure above show, it shows a body base. This part is used to

hold the body of patient. This size has dimensioned based on the

maximum size of the Asian people.

Figure 10: Assemble of head and body base with base rod.

Figure above; show how it assembles with base plate. Where, it

will assemble with base rod.


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Figure 11: Caterpillar.

From picture above, it shows a caterpillar where it used as main part tohold the head and body base. It will assemble with a rod to make a structure ofstretcher.

Figure 12: Rubber

The figure above shows a grip. It used to make some frictions when itmoving on floor or while turning the stages. It will inserted or combine withcaterpillar (Figure 11).


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6.1.1 Wheel systemA wheel is a circular device that is capable of rotating on an axle

through its centre, facilitating movement or transportation while

supporting a load (mass), or performing labor in machines. Common

examples are found in transport applications. A wheel, together with an

axle overcomes friction by facilitating motion by rolling. In order for

wheels to rotate, a moment needs to be applied to the wheel about its

axis, either by way of gravity, or by application of another external force.

In our design, we had been decided to choice swivel caster as our wheel

system.

Like the simpler rigid caster, a swivel caster incorporates a wheel

mounted to a fork, but an additional swivel joint above the fork allows

the fork to freely rotate about 360, thus enabling the wheel to roll in any

direction. This makes it possible to easily move the vehicle in any

direction without changing its orientation. Swivel casters are sometimes

attached to handles so that an operator can manually set their orientation.

Figure 13: A swivel caster wheel.
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Figure above shows a swivel caster wheel that our group design.

This is good choice in our design because when in motion along a

straight line, a swivel caster will tend to automatically align to, and

rotate parallel to the direction of travel. This can be seen on a shopping

cart when the front casters align parallel to the rear casters when

travelling down an aisle. A consequence of this is that the vehicle

naturally tends to travel in a straight direction. Precise steering is not

required because the casters tend to maintain straight motion. This is also

true during vehicle turns. The caster rotates parallel to the turning radius

and provides a smooth turn. This can be seen on a shopping cart as the

front wheels rotate at different velocities, with different turning radius

depending on how tight a turn is made. The angle and distance of the

wheel axles and swivel joint can be adjusted for different types of caster

performance.

Figure 14: Holder swivel caster.

Figure above shows, a holder that can hold swivel caster. It will

be attached with swivel caster wheel and bearing. Then, it will be

screwed.


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6.1.2 Simulation

All the movement and function are related to simulation of

mechanical medical stretcher. Simulation is about to see the behavior of

mechanical medical stretcher.

For the main part movement of stretcher is wheel. The function

of wheel caster is it can move easier and give 360 o movement so that the

stretcher difficult to stuck. The smoothes of wheel rotate gives less force

apply to the stretcher movement. The function is to fold and easy to

store.

Braking system involved as a function in this mechanical medical

stretcher. It works when the holder of the carrier is push inside for

certain amount. The system needs to setup with an appropriate amount of

grip to stop the stretcher from move.

According to the vibration characteristics including carriage,

vehicle stretcher system was built up with system dynamic simulation.

Through the simulation analysis and optimization design, the reasonable

absorbing vibration scheme was applied, and the effects of shockabsorbing before and after optimization design were analyzed. A new

kind of vibration isolation scheme is designed using small stiffness

springs added vibration damping device. The vibration isolation

properties of this scheme has been simulated and optimized with system

dynamic simulation. The new scheme can enhance the system

stabilization.


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6.2 Details Analysis of Calculations

Area of the base

[ ]

Stress

Assume that maximum weight applied is W = 150kg


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Forces equilibrium

1471.5

F F


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Ductile test

( )

1471.5

2.155

0.03


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6.3 Material Selection

Material selection is the most important part in the mechanical design

process. The selection of material is must consider the principle of mechanics,

dynamics and so forth are well established and not changing much, whereas

new material are appearing all time, innovation in design is frequently made

possible by the use of the new material. Each class of materials has its own

strengths and limitations which the designer must be fully aware. In designing

a structure or a part, selecting the right material or the combination of

materials is important. This is because; the mistakes can cause the disasters or

failure to the design product. A selection process must be greatly influenced

by the analysis of experience in similar applications, specifically an analysis of

the causes and mechanisms or failure.

So, this process is important in designing our new product of medical

stretcher. There are three parts that are to be considered in selection material.

6.3.1 Frame workThis part is usually most important part in medical stretcher.

The framework have to be strongest compared to others part because it

required to accommodate patient weight. The base parts have to be

high in strength usually has relation with yield strength. The materials

of framework part must not only resist bending, it also resists fracture,

and for instant has yield strength and hardness. The base parts usually

received a lot of forces from weight load of patient. And also from

other part that has been assemble.

The framework part also has maintained their shape when acted

by load. So, the framework part must have a high stiffness where the

stiffness is usually related with the Hookes Law which is relationship

between stress and strain. When a metal is loaded, the stress-strain

curve is linear and the slope is measure of the stiffness of the metal. It

is also important to know how much of total life can be hold by the

framework part. This all criteria that the framework part needed are

suitable for the material is aluminum alloy. Aluminium alloys with a


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wide range of properties are used in engineering structures. Aluminium

alloys are widely used in engineering structures and components where

light weight or corrosion resistance is required. In general, stiffer and

lighter designs can be achieved with aluminium alloys than is feasible

with steels. An important structural limitation of aluminium alloys is

their lower fatigue strength compared to steel.

Actually steel is more strong than aluminium alloy, but

consider the cost of material the aluminium alloy were selected beside

that material is enough to resist the patient load. . For record, the price

of steel in world marketing is about US$ 3314 per ton for average

lastly update at May 2010 compare than the last update price for

aluminum alloys that is average US$ 2028 per ton.

Property Value

Atomic Number 13

Atomic Weight (g/mol) 26.98

Valency 3

Crystal Structure Face centred cubic

Melting Point (C) 660.2

Boiling Point (C) 2480

Mean Specific Heat (0-100C) (cal/g.C) 0.219

Thermal Conductivity (0-100C) (cal/cms. C) 0.57

Co-Efficient of Linear Expansion (0-100C) (x10-6/C) 23.5

Electrical Resistivity at 20C (cm) 2.69

Density (g/cm3) 2.6898

Modulus of Elasticity (GPa) 68.3

Poissons Ratio 0.34

Table 4: Typical Properties for Aluminum
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6.3.2 Caster wheelCaster wheel is a wheel at the bottom to support the body and

to help in body movement. The caster wheel is widely using in design

of stretcher like for the trolley at the supermarket, laboratory lab and

others use. For the design of medical stretcher, the wheel caster is often

using to make the stretcher easy to move anywhere.

In material selection, the designer must consider several criteria

so that the material use in for produce wheel caster is suitable with the

hospital environment and the specialist. The criteria should be like the

wheel surface must have the better surface friction to avoid that wheel

not slippery when the operator push or pull the stretcher especially

when emergency case where the stretcher will move very quickly.

Other criteria are, the wheel caster should be absorbing the vibration to

give patient get comfortable when the medical stretcher is operate.

Then, the criteria required is that material will select must long lasting

and durable to make the easy maintenance for that wheel. So, the

suitable material for this device is synthetic rubber. The synthetic

rubber is better than natural rubber and plastic. Synthetic rubber canproduce the extra soft rubber on these caster wheels helps to absorb

vibration and shock, thus protecting the load or patient while in transit.

Another benefit of these extra soft rubber caster wheels is noise

reduction. These caster wheels are designed for use in Hospitals.

6.3.3 Mattress or PadMattress is a mat or pad usually place on top medical stretcher.

The main purpose is to give comfortable to human body. In design of

medical stretcher, the mattress or pad is more to give patient support

for their body. Moreover, the design of medical stretcher is only short

patient stay use in other word not using for a long time. So, the simple

mattress is required for this design. Besides that, others criteria should

be considered while choose the right material use for mattress. The

criteria is like the mattress is should fluid proof, soft, excellent support,cushioning while transport patient and durable. The mattress must have


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easy maintenance such as while cleaning the mattress surface and to

store it.

From all the criteria previously, the suitable material in design

the medical stretcher pads is using soft foam or polyurethane foam

with polyurethane coated nylon cover material. Polyurethanes are

widely used in high resiliency flexible foam seating, rigid foam

insulation panels, microcellular foam seals and gaskets, durable

elastomeric wheels and tires, automotive suspension bushings,

electrical potting compounds, high performance adhesives and

sealants, Spandex fibers, seals, gaskets, carpet underlay, and hard

plastic parts (such as for electronic instruments).

6.3.4 Thread Rod and NutThread rod and nut always work together in the system. Thread

rod purpose is to connect the parts and nut is to tighten the connection

between the parts. If one of these parts is no exist, the work to connect

the parts cannot be successfully because they are a gap between the

part and the connection not complete.There are many types of fasteners that been used in build

medical stretcher. Screw, nuts, bolts and many more all used to make

tools. The thread rod, nut, screw and bolts are chosen depends the joint

purpose. Otherwise, the welded is use to join the several parts such as

framework. The material selection is for nut, bolt and others is

according the standard hardware like several of steel.
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6.4 Design for Manufacture

Design-for-assembly (DFA) and design-for-manufacture (DFM)

techniques can be applied to products assembled manually or automatically or

manufactured by specific techniques, such as machining, die casting or

injection molding.

The application of DFM must consider the overall design economics.

It must balance the effort and cost associated with development and refinement

of the design to the cost and quality leverage that can be achieved. In other

words, greater effort to optimize a products design can be justified with higher

value or higher volume products.

A number of general design guidelines have been established to

achieve higher quality, lower cost, improved application of automation and

better maintainability. Examples of these DFM guidelines are as follows:

Reduce the number of parts to minimize the opportunity for adefective part or an assembly error, to decrease the total cost

of fabricating and assembling the product, and to improve the

chance to automate the process.

Foolproof the assembly design (poka-yoke) so that theassembly process is unambiguous.

Design verifiability into the product and its components toprovide a natural test or inspection of the item.

Avoid tight tolerances beyond the natural capability of themanufacturing processes and design in the middle of a part's

tolerance range.

In addition to these guidelines, designers need to understand more

about their own company's production system, i.e., its capabilities and

limitations, in order to establish company-specific design rules to further guide

and optimize their product design to the company's production system. For

example, they need to understand the tolerance limitations of certain

manufacturing processes.


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Design for Manufacturability and Integrated Product Development

may require additional effort early in the design process. However, the

integration of product and process design through improved business practices,

management philosophies and technology tools will result in a more producible

product to better meet customer needs, a quicker and smoother transition to

manufacturing, and a lower total program/life cycle cost.

In an increasingly competitive world, product design and customer

service may be the ultimate way to distinguish a company's capabilities.

Because of the growing importance of product design, Design for

Manufacturability and Integrated Product Development concepts will be

critical. It will be the key to achieving and sustaining competitive advantage

through the development of high quality, highly functional products effectively

manufactured through the synergy of integrated product and process design.


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6.5 Design for Assembly

Design-for-assembly (DFA) and design-for-manufacture (DFM)

techniques can be applied to products assembled manually or automatically or

manufactured by specific techniques, such as machining, die casting or

injection molding.

Design-for-assembly analysis will suggest the optimal assembly system

and degree of automation for many applications. The design is analyzed for its

overall efficiency and suitability for the chosen assembly method. For example,

three steps can be used to determine if a product is suitable for automatic

assembly:

6.5.1.1Estimate the cost of handling the part automatically in bulk anddelivering it in the correct orientation for insertion on an

automatic-assembly machine.

6.5.1.2Estimate the cost of inserting the part into the assemblyautomatically, and any extra operations.

6.5.1.3Decide if the part must be separate from all others in theassembly.

The cost of assembling a product is typically proportional to its number

of parts. Such parts as fasteners, clips, and washers may be small in size, but

they often account for the majority of assembly cost. Small parts particularly

influence the cost of automatic assembly, because each part requires a feeding

and orienting device, a work head, at least one extra work carrier, a transfer

device, and an increase in size of the basic machine structure.

Must the part be separate from all other parts already assembled

because necessary assembly or disassembly would otherwise be impossible?

Decisions on the feasibility of a design should take both DFA and DFM

analyses into account. Reducing the number of parts may simplify the total

assembly. However, combining several functions in one component may result

in a complicated part that is prohibitively expensive to manufacture. In

addition, such complicated parts might be too difficult for automated systems

to handle. Balancing the results of DFA and DFM analyses can reduce both the


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total number and total complexity of parts, resulting in efficient product

designs.

On order to successfully apply the concept of design for assembly in

our medical stretcher design, a few approach is taken such as the concept of

simplicity (minimize part number and variety), standardize on material usage,

use the widest possible tolerance (avoid finishing process), choose material that

suit function and ease the production difficulties and minimize non value added

operations.

6.5.2 The components or parts that used in our design:

6.5.2.1Screw

Figure 15: Types of screw


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As shown figure above, we had been decided to use the

suitable screw in our design. The heads of screws can be oval,

flat or round, and each style has a specific purpose for perfect

appearance and seating. Flat heads can be countersunk or rest

flush with the surface. Oval heads allow for countersinking, but

the head protrudes a bit. Round-headed screws sit on top of the

material and are easy to remove. Some screw types include the

wood screw which will make a stronger joining than a nail, or

for when other materials must be fastened to wood. A wood

screw is tapered to draw the wood together as the screw is

inserted. Sheet metal screws can also be used to join metal to

wood, as well as metal to metal, plastic, or other materials.

Most sheet metal screws are threaded the entire length

from the point to the head, and the threads tend to be sharper

than those of wood screws. Use a machine screw for joining

metal parts, such as hinges to metal door jambs. Machine

screws are usually inserted into pre-threaded holes and are

sometimes used with washers and nuts. When choosing screw

length the screw should penetrate two-thirds of the combined

thickness of the materials being joined. To avoid corrosion you

should consider the moisture conditions and the makeup of the

materials being fastened. The use of galvanized or other rust-

resistant screws may be necessary where rust could be a

problem.


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Figure 16: Screw and nut selected

Figure above shows the type of screw that our design

being selected. It will clamp between base rod and half rod. We

select this kind of screw because it has countersunk or flat

head. Where, it has conical, with flat outer face and tapering

inner face allowing it to sink into the material. The angle of the

screw is measured as the full angle of the cone.

Figure 17: Joining screw and bolt nut inserted in the red circle.
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6.5.2.2NutA nut is a type of hardware fastener with a threaded

hole. Nuts are almost always used opposite a mating bolt to

fasten a stack of parts together. The two partners are kept

together by a combination of their threads' friction, a slight

stretch of the bolt, and compression of the parts. In applications

where vibration or rotation may work a nut loose, various

locking mechanisms may be employed: Adhesives, safety pins

or lock wire, nylon inserts, or slightly oval-shaped threads. The

most common shape is hexagonal, for similar reasons as the

bolt head - 6 sides give a good granularity of angles for a tool to

approach from (good in tight spots), but more (and smaller)

corners would be vulnerable to being rounded off. Other

specialized shapes exist for certain needs, such as wing nuts for

finger adjustment and captive nuts for inaccessible areas.

Figure 18: Nut

We had been used bolt nut in our design because it can

clamp conneting thread rod that inserted in hole between base

rod and half rod.
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6.5.2.3T-joint

Figure 19: T-joint

Base on figure above, it shows T-joint. It used as joining

part that will join with the rod. Where the rod is will link

together with caterpillar and body base. This is some of

mechanism of its function.


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6.5.2.4Attachment of screw on plate mattress blocks

Figure 20: The screw inserted.

Figure above shows how screw inserted into rod and

plate mattress blocks. The screw will clamp plate mattress

blocks and rod. It is design to ensure the plate can fix at that

place and no movement occur when applying a force. The red

arrow show the force applied on screw toward rod structure and

plate mattress blocks.

Rod

Base body


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6.5.3 Sub assembly of body base with connected rod.

This shows how we join the caterpillar with other connecting,

rod. We combine the grip into caterpillar and also the holder of wheel.

The holder of wheel with joints it by using welding technique. We have

weld-joint with connecting rod. Then, all this parts are tightening by

the screws, bolts and nuts. We have been show how we assemble it by

illustrating below figured:

Figure 21: Sub assembly for caterpillar with rods.

6.5.4 Sub assembly of wheelThe wheel will assembled as shows on figure below. We

assemble holder of wheel with swivel caster. We just design suitable

size so that it can rotate at certain force or weight when the patients

applied on it.

Figure 22: Sub assembles for wheel.

Holder wheel

Swivel caster

Base rodCaterpillar

Grip

Holder wheel

T-joint


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7.0 PARAMETRIC DESIGN

7.1 Design for Robust by Failure and Effect Analysis (FMEA)


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7.1.1 Severity Rating Scale

Ranking Description Criteria

1 None No discernible effect

2 Very Minor Fit and finish/Squeak and rattle item do not conform.

Detect noticed by discriminating customers (less

than 25%)

3 Minor Fit and finish/Squeak and rattle item do not conform.

Detect noticed by 50% customers.

4 Very low Fit and finish/Squeak and rattle item do not conform.

Detect noticed by most customers (greater than

75%)

5 Low Item operable but Convenience item(s) inoperable.

Customer somewhat dissatisfied.

6 Moderate Item operable but Convenience item(s) inoperable.

Customer dissatisfied.

7 High Item operable but at a reduced level of performance.

Customer very dissatisfied.

8 Very high Item inoperative (loss of primary function)

9 Hazardous with warning Very high severity ranking when a potential failure

mode effects safe operation and/or involves

noncompliance with government regulation with

warning.

10 Hazardous without

warning

Very high severity ranking when a potential failure

mode effects safe operation and/or involves

noncompliance with government regulation without

warning.


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7.1.2 Occurrence Rating Scale


1 Remote: Failure is unlikely

0.01 per thousand items2 Very Low: Relatively few failures 0.1 per thousand items3 Low: Relatively few failures 0.5 per thousand items

4 Moderate 1 per thousand items



7 High: Frequent Failures 10 per thousand items

8 High: Frequent Failures 20 per thousand items9 Very High: Persistent Failures 50 per thousand items

10 Very High: Persistent Failures 100 per thousand items

7.1.3 Detection Rating Scale


1 Almost Certain Design control will almost certainly detect a potential

cause/mechanism and subsequent failure mode.

2 Very High Very high chance the design control will detect a

potential cause/mechanism and subsequent failure

mode.

3 High High chance the design control will detect a potential


4 Moderately High Moderately high chance the design control will detect a


mode.

5 Moderate Moderate chance the design control will detect a


mode.

6 Low Low chance the design control will detect a potential



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7 Very Low Very low chance the design control will detect a


mode.

8 Remote Remote chance the design control will detect a


mode.

9 Very Remote Very remote chance the design control will detect a


mode.

10 Absolute Uncertainty Design control will not and/or cannot detect a potential

cause/mechanism and subsequent failure mode; or there

is no design control.

7.1.4 Sample calculation for Risk Priority Number (RPN)

RPN Calculation Method:

Cause RPN = Severity (SEV) Occurance (OCR) Detect (DET)Based on the Failure Mode Effect Analysis, (FMEA) form:

RPN = Severity (SEV) Occurance (OCR) Detect (DET)

= 7 7 6

= 294

New RPN = New Severity (SEV) New Occurance (OCR) New

Detect (DET)

= 5 3 3= 45


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7.1.5 Description

An overall analysis and study about the stretcher have been

done. Hence, several failures are found at some of the function that

will make the stretcher not functioning well. So, after a lot of

consideration, a solution is creating to overcome all the failure that will

make the stretcher stronger and can last for the long time. So, using

this stretcher can cut the cost.

First the framework was observed. The problem that occurs is

the framework is overload because it is been use for a long time. This

will make framework cannot support the load.

Then the base is observed. The failure that occurs is the base is

crack because it is been use for a long time. This will damage the

stretcher. The stress concentration at the overload part and it will cause

crack. To overcome this problem, we should put another supporter

under the base to support the base.

There will also be a crack at the tread rod due to the vibration

created by the movement of the stretcher. Stress concentration willoccur at the rod that will cause crack. And addition supporter is

inserting to avoid an unexpected accident that is by putting another

stopper.

In the other hand, the mattress of the stretcher is can be tear if it

is etch with the sharp tools or object. A proper storage must be placed

all of the medicine tools to avoid all this thing will tear the mattress.

Lastly, the tyre also has a potential failure due to the hard

movement when handle the stretcher. The tyre are possible can come

out from its position. Add extra thread rod to join the tyre and the part

of the stretcher is the best solution to this problem.

After a properly analyzed about the stretcher and some

precaution action to avoid the failures is taken, a stretcher that is more

efficient to use can be design.


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7.2 Final dimension

By this, the final dimension for medical stretcher as been determined. It is

in meter unit, where each part of the components is review by research start from

part 1, Product architecture until part 3, Design for Robust.

Base rode


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Nut

Main Bar


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Head Base

Body Base 1


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Body Base 2

Middle Beam


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Lower Beam

Upper Beam


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Base plate

Wheel Caster Tire


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Wheel caster frame

Assembly of the leg


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Assembly of the lower part

Rubber


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1.0 Introduction

Proceed after done previous phases, task is continued for the final phase that is

detail design. In this phase, about 85% of overall progress is done and advance to

complete all the analysis titled Mechanical Medical Stretcher.

In this particular phase, all the detail drawing is illustrate including

component, subassembly and assembly. It gives details of product specification in

size and layout. Besides that, all the drawing should be understandable for production

or gives complete information to customer. The next part is proceed to bill of

materials (BOM) is a list that specifies the parts used to build a product. When a

company produces a product, it must keep track of the materials and components used

in its creation. This bill of materials must be included with the product before

shipping it to a merchandiser, client, or buyer. Generally, it is included inside the box

in which the product is shipped.

After all detail design and bill of material is done, the next progression is

about to calculate cost to build a stretcher. Each component is needed to take into

account in this part. Detailed on material used in this product like material cost, labor

cost and vendor is estimated exactly to know the price of stretcher in market.


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8.0 DETAILS DRAWING


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8.1 Bill of Materials

A bill of materials (BOM) is a list that specifies the parts used to build

a product. When a company produces a product, it must keep track of thematerials and components used in its creation. This bill of materials must be

included with the product before shipping it to a merchandiser, client, or

buyer. Generally, it is included inside the box in which the product is shipped.

In a way, a bill of materials is similar to a recipe. Every ingredient used

is listed in the bill of materials. Strict record keeping is the key rule to creating

a bill of materials, because no item can be skipped. This is largely because

the bill of materials can be used later to narrow down issues for repairs of a

product if necessary. In addition, a bill of materials is essential when ordering

replacement parts.


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Part Number Quantity Type of materials Vendor

1 1 Aluminium alloy Kemuning Machinary & HardwareSdn. Bhd.










11 1 Plastics BP Plastic Holding Bhd.




15 1 Plastics BP Plastic Holding Bhd.




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8.2 Costing

Costing are accounting techniques that are used to help understand the

value of inputs and outputs in a production process. By tracking andcategorizing this information according to a rigorous accounting system,

corporate management can determine with a high degree of accuracy the cost

per unit of production and other key performance indicators. Management

needs this information in order to make informed decisions about production

levels, pricing, competitive strategy, future investment, and a host of other

concerns. Such information is primarily necessary for internal use, or

managerial accounting.

All manufacturing companies sell their products to makeprofit. The

profit on each product sold can be defined as the difference between the

selling price of the product and the total cost of making the product. Cost

therefore plays a very important role in the product design process. To be

successful, a product must not only satisfy a set of functions defined in the

product design specification, but it must also be possible to build the product

within the cost criteria set out at the start of the project. Before the

development of any product begins, it is essential to perform some form of

economic analysis on the product to determine if it is worth making. This may

involve some form of market analysis to determine what the customer is

willing to pay for a product.

8.2.1 The Basics Of Costing

8.2.2 Fixed CostsOne of the key issues in conventional costing stretcher design is

distinguishing among types of costs. A basic distinction is made between fixed

and variable costs. Fixed costs are those costs that are invariant with respect to

design final report

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