An introduction into CAD

8/13/2019 An introduction into CAD

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B.Eng. Year 1 CAD

B.Eng. Year 1 CADAssignment 1

11/11/2013

Tutor: Yujie Zeng

Student: Christopher Henderson


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B.Eng. Year 1 CAD

Christopher Henderson Page 1

Contents

1 Introduction

2 Creating Shapes

3 Creating A Pulley Guide

4 Creating A Submarine Camera Frame

5 Creating A Technical Drawing

6 Stress Analysis

7 Research and reports into :6.1 Second and Fourth Angle Projection

6.2 Axonometric

6.3 Isometric

6.4 Di-metric

6.5 Trimetric

8 References


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1 Introduction1.1Solid modelling is one of the important methods of creating an object inside a computerthat can be analysed by an engineer to give information about form and function.

Traditional methods of model making as a tool for the refinement of the appearance of an

object are both costly and time consuming. The ability to see and manipulate a virtual

object on a computer screen has allowed both time and money to be saved in the initial

design process. Autodesk software lets you design, visualize, and document your ideas

clearly and efficiently. Using Autodesk to create a solid model allows the user to identify

transformations such as rotate and translate.

1.2Using the methods detailed above. A number of components will be produced,transferred to Third angle orthographic drawings and assembled together demonstrating

the different design tools available for this software package The following assignment is to

demonstrate a basic ability in solid modelling using the AutoCAD inventor software package.

The assignment will show how solid modelled components are produced by sketching and

developing shapes from these sketches.


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2 Creating Shapes2.1 Selecting a work plane

When creating a part on Inventor it usually begins with the creation of a sketch which setsthe basic shapes of the part. The first step when creating a sketch is to select a plane along

which to draw it, this helps later on in the design with keeping track of the part through

rotating it and also when assembling it with other parts.

Figure 2.1 Selecting the plane that the sketch

is to be drawn in.

2.2 Creating a sketchBegin drawing the basic outline by selecting rectangle from the tool bar and drawing the shape on

the work plane.

Add dimensions to this rectangle to give the correct shape and size as required.

Select finish sketch and the work plane will return to a 3 dimensional view with your sketch shown

on the axis previously selected.

Fig 2.2 Creating a sketch


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2.3 Extruding a sketch

Once a sketch has been completed it can then be extruded to become a solid three

dimensional shape, this gives a better visual representation of the part being designed and

the proportions of the other parts that will be assembled with it.

Fig 2.3 Extruding the basic shape to

create a three dimensional part.

2.4 Revolving a sketch

Often the easiest way to produce a required shape is to draw an outline of the profile of the

part to be created and extrude the shape using the revolve feature. This is particularlyuseful when the profile of the shape is very complicated and would otherwise need a lot of

extrusion commands to be performed upon it. Here in the next 2 diagrams we can see a

very simple pen top created by using this method.

Fig 2.4.1 The basic circular part in

sketch form.


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3 Creating a Pulley Guide3.1I have chosen to start the model by creating a sketch using the centreline tool, this is a

cylindrical part so creating it from a centreline will be quicker and simpler way of creating

the part. I start off by drawing the part using the line tool and roughly sketching the shapeof the part. The drawing has only 2 dimensions and 1 of them can be applied in this sketch,

for the other dimensions I will use my judgment to scale it to the drawing.

Fig 3.1 creating the

basic sketch

3.2While I was roughly sketching the part some radiuses did not constrain to tangent, so I

used the show all constraints to identify the radius point that did not constrain and used the

tangent tool to constrain it. I also used the vertical constraint on the End View B line and

constrained it to the centre point, this keeps the sketch referenced to a point and also will

help identify all fully constrained points.


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Fig 3.2 Showing the sketch

constraints

3.3I continue to dimension the sketch till it is fully constrained. I also constrained

horizontally the 2 outer diameter lines, as I have chosen them to be the same dimension,

this helps when editing drawings at a later date, because changing one will change the

other.

Fig 3.3 The completed sketch


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3.4Using the revolve feature I have now revolved the basic sketch 360 degrees to create the

basic shape of the part.

Fig 3.4 The pulley after

being revolved into its shape

3.5The next step I have chosen is to create an extruded part on End View A, this is

because I want to create all parts before extruding the part. To do this I have to create a

second sketch on the part. I have fully constrained and dimensioned the sketch but I have

only sketched 1/3rd of the extrusion because I am going to pattern it on the centre axis.

Fig 3.5 Creating part of the

extrusion.


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3.6Now the sketch is done I extrude it the remaining 10,00mm (to create the 215,00mm

dimension) and revolve it 3 times on 360 degrees, I use the browser to select the circular

pattern feature and the model origin X axis. I can also revolve the sketch inside the sketch

profile before extruding, this will result with the same profile.

Fig 3.6.1 Creating 1/3rd of

the extrusion

Fig 3.6.2 Creating the full

pattern of the extrusion to 360


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3.7Using the same principal as previously, I can now create the extrusion cut on the

opposite face making sure I sketch 180 degrees from the End View A feature. This process

allows me to create a cut into the selected face rather than extrude away from the selected

face.

Fig 3.7.1 Creating1/3rd of

the extruded cut into the selected face.

Fig 3.7.2 Creating the full

extruded cut to 360

3.8To create the last part I create a sketch on the End View A as this will allow me to

extrude in 1 direction To selected face, I also use the project cut edge tool to help me

sketch to the geometry of the internal gear. After extruding the sketch I was able to use the

pattern tool to repeat the process around the part 18 times.


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Fig 3.8.1 Creating a

reference sketch on end view A

Fig 3.8.2 Creating the

completed sketch of the single internal gear.

3.9 The pulley is now finished, To make the pulley look more realistic, we can alter the

material of the pulley. This feature is especially useful when we do a stress analysis later in

this assignment. To change the material we simply click on the drop down box next to the

appearance tab on the tool ribbon and select the material that we require, we then select


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the part of the component that we wish to add this to.

Fig 3.9.1 The finished Pulley

Fig 3.9.2 Changing the

material of the Pulley.

Fig 3.9.3 The

completed Pulley.


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4 Creating a Submarine Camera Frame4.1For the assignment we were asked to 2 design engineering components. The first one

that I shall be attempting is a Submarine Camera Frame as it is a component that construct

where I work

4.2The first part of the frame that I started to construct was one of the two side rails. I

started off by sketching the outer edge and then dimensioning it and then used the offset

tool for the inside edge and dimensioned the offset. I then drew and dimensioned the cross

members.

Fig 4.2 Creating a basic sketch of

the 1st

side rail.

4.3 After sketch one is completed I extruded the sketch 19.0mm, this is the thickness of

each tube used. Now that extrusion 1 is complete I can fillet each edge to create a

cylindrical tube,

Fig 4.3 Using the fillet and the extrusion feature to create the round bar


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4.4 Now that we have completed one side of the frame we can decide what step to take

next, I have chosen to mirror the current model, this keeps it simple and easy to follow, the

part is completely symmetrical and could be completed with a single mirror but this may

cause confusion and errors. To complete this mirror I need to create a work plane at a

certain distance from the origin XY plane.

Fig 4.5 Creating a mirror image

of the side rail

4.6The framework now has two sides, so the next step is to create the tubes that join the

two sides. To create the tubes I need to create a plane in the centre of the first side, this is

because it is cylindrical and creating it on an edge will not join the two sides, there will be a

gap. When in sketch mode I press F7 to cut the part on the sketch plane so I can see the

centre of the first side, I then press project all cut edges to create the reference points I

need. I then extrude the circles to the other side (60019 = 581).

Fig 4.6 Creating a plane in the 1st

side


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Fig 4.6.2 Extruding the crossmembers of the frame.

4.7The main base of the frame is now complete and all to do now is to create the lifting eye

for the framework. First I need to create the side supports of the lifting eye, to do this I

create a plane on the outer edge of the side of the frame, I then create a sketch and project

cut edges, I also project the top middle tube, this creates the centre point of the tube, which

is the centre of the bar for the side support.

Fig 4.7 Sketching the side

supports of the lifting eye.


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4.8After creating a sketch for the lifting eye, I then extrude the part 3.0mm and mirror

using the centre plane that was created for Mirror 1

Fig 4.8 Using the

mirror feature to create a second support arm.

4.9The side supports are now complete so I need to now create a plane in the centre of the

top middle tube so I can create the sketch, to do this I select create plane then select the

origin YZ plane and offset it 75.0mm to match the centre of the tube. I then select create

sketch, project cut edges and roughly draw the lifting eye, then constrain and dimension it.

Fig 4.9 Sketching theshape of the lifting eye.


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4.10The frame now needs the lifting eye cut-out. I started the sketch on the lifting eye base

face and selected project edges. I roughly sketch out the shape of the cut-out then constrain

and dimension it to the projected geometry. I then extrude cut all to create the cut out.

Fig 4.10.1 Sketching the

hole of the lifting eye.

Fig 4.10.2 Extrude

cutting the hole of the lifting eye


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Fig 4.11The final assembly of the framework.


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5 Creating a Technical Drawing5.1 Autodesk Inventor has a feature which allows you to import your final model into a

technical drawing which can then be used to fabricate or construct the component which

has been designed.

5.2 First of all with our finished component still open we select new and then ANSI mm.idw

from the menu which appears as shown in Fig 4.2 and then create.

Fig 5.2 Selecting the

drawing file to be used.

5.3To insert a component onto the blank drawing page we:

Right-click Sheet:1 again, and press Base View Find the component you want to make a drawing of. Pick a scale that will allow the entire part to fit on the page Then, press OK

Fig 5.3 The pop up box

that opens up.


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As we can see in the pop up box that appears on the screen when we want to place a

component it allows us alter the view of the component that we are putting on the drawing

and also it allows us to change the scale of the component onto the drawing.

Fig 5.3.1 Placing

the component on to our blank page.

Once we have chosen our first view we the right click the component and create the

drawing where we want it to be on the page. We then drag the component to the next

position where we would like an alternate view and then press create again as shown in Fig

5.3.2

Fig 5.3.2

Creating a second view of the component.

We repeat the process for a third view of the component. We can also show a master view

of the component to be fabricated to show the producer how it should look.


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Fig 5.3.3 The third

view of the component placed on the page.

Fig 5.3.4 A master view

of the component.

5.4To dimension a drawing we;

Click the annotate tab Select the dimension box Select the part of the drawing that you wish to dimension Drag the pointer to the position that you wish to place the dimension Right click to finish.

It is noticeable that when we hover over the part of the drawing that we wish to dimension

that it is coloured red, when the part is selected it then turns blue.


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Fig 5.4.1 Applying

dimensions to the drawing.

Fig 5.4.2 As the cursor

hovers over the selected dimension it is Red.

Fig 5.4.3 Once the

dimension has been selected it then turns Blue.


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6 Stress Analysis6.1To start a stress analysis, go over to ENVIRONMENTS tab on the tool ribbon, click on it

and on the left side of your screen you will see the stress analysis feature (rainbow coloured

cube). Click on the icon and then click on create simulation. That will bring up a screen ofinitial settings. You can choose a static analysis or modal analysis.

Fig 6.1 Selecting the

Environments tab

The simple definition of static would be your main input force which is not affected by

time/temp/atmospheric pressure. Modal is dynamic forces (vibration) that will have

secondary effects on the part to be tested. For this trial we are going to use a static stress

analysis. Select it and click OK.

6.2Defining what type of material your part is determines the amount and types of forces it

can handle before it fails. This should be the first step before you continue on with your

test. Under your ribbon you will have a materials section with an icon that says ASSIGN, click

on this. It will bring up a pop up window displaying your part material. If you already defined

what the material was when you made your part, that material will be displayed. If you

haven't yet defined it, click on materials and select the desired one. When you select a

material you can also double click on it to see the preset settings for that type if you need to

verify or change them. Once you are happy with your material and settings click OK and

then we will be ready to define our constraints and input forces.


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Fig 6.2 Defining the

material type to be used for each part of the component

6.3Defining constraints for the part is important in order for the analysis to perform

correctly. If I have input forces pushing up on my part, but nothing constrained or held in

place to hold the part down, there would be no stress to display. In this trial I am going to

used a fixed constraint on the top inside face of the part. This means that this area of mypart will remain in place while the input forces are affecting my part

Fig 6.3 Selecting the face

to be constrained.


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6.4The input forces are what are going to actually be exerted on the part. These are defined

using the LOADS tools on the ribbon. The load to be added is a point load on the inside face

opposite to the face which was constrained, this is to simulate the load being applied by the

tightening screw.

Fig 6.4 Defining the load

direction

6.5Once I have defined where the load will be exerted the next step is to define the amount

of force (magnitude) in Newtons. For this I am going to use 1000 Newtons.

Fig 6.5 Applying the force to

be exerted (1000N)


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6.6Now that our constraints and input loads are set, we can run our simulation.

Click on the simulate tab in the tool ribbon (rainbow coloured cube) and the simulation

window will pop up. If you have any errors they will be displayed here. If there are no errors,

click on RUN.

Fig 6.6 The stress analysis toolbar

6.7Inventor will run the simulation and show you the different stress types and amounts

using the colour coded visualization chart. Anything in RED is bad and changed to your

design should be implemented.

Fig 6.7 After running

the stress analysis we can see where the strain runs through the part
http://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=p7uk3QjJ9OH-TM&tbnid=lW1nudkZIF4KkM:&ved=0CAUQjRw&url=http://wikihelp.autodesk.com/Inventor/enu/Community/Transition_to_the_Ribbon_UI/Stress_Analysis&ei=YUR6UqrDJseP0AX7xYDIAw&bvm=bv.55980276,d.d2k&psig=AFQjCNEY9LBFkS75RCYNyqr2SeeU9nO3MQ&ust=1383830997633680http://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=p7uk3QjJ9OH-TM&tbnid=lW1nudkZIF4KkM:&ved=0CAUQjRw&url=http://wikihelp.autodesk.com/Inventor/enu/Community/Transition_to_the_Ribbon_UI/Stress_Analysis&ei=YUR6UqrDJseP0AX7xYDIAw&bvm=bv.55980276,d.d2k&psig=AFQjCNEY9LBFkS75RCYNyqr2SeeU9nO3MQ&ust=1383830997633680


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6.8 By clicking on the results tab on the left of the screen, this brings up a displacement

section, if we select this feature this shows how the part deforms after it has had the load

applied to it. The coloured chart at the side of the part gives the exact deformation

dimensions and shows that those parts in Red are the areas which are deformed the most.

Fig 6.8 Showingthe actual displacement after the test.


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7 Research7.1 Second and fourth Angle Projection

In second and fourth angle projection the object as usual is to be placed in the second andfourth quadrant repectively and the corresponding front and top views are projected on the

vertical and horizontal planes.

Following drawing convention the two views in both cases are to be brought in the vertical

plane. It may be noticed that the two views overlap with each other resulting in confusion.

Therefore these two methods of projection are not recommended in practice.

Fig 7.1 Showing the positions of the

second and fourth quadrant.

7.2 Axonometric Projection7.2.1Axonometric projection is the Three-dimensional drawing of an object, such as a

building, in which the floor plan provides the basis for the visible elevations, thus creating a

diagram that is true to scale but incorrect in terms of perspective. Vertical lines are

projected up from the plan at the same scale; the usual angle of projection is 45. An

isometric projection is a slightly flattened variation.Axonometric projections are classifiedaccording to how the principle axes are oriented relative to the projected surface.

7.2.2There are three main types of axonometric projection: isometric, dimetric, and

trimetric projection.

7.2.3"Axonometric" means "to measure along axes". Axonometric projection shows an

image of an object as viewed from a skew direction in order to reveal more than one side in

the same picture. Whereas the term orthographicis sometimes reserved specifically for

depictions of objects where the axis or plane of the object isparallel with the projection

plane in axonometric projection the plane or axis of the object is always drawn notparallel

to the projection plane.


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7.2.4 With axonometric projections the scale of distant features is the same as for near

features, so such pictures will look distorted, as it is not how our eyes or photography work.

This distortion is especially evident if the object to view is mostly composed of rectangular

features. Despite this limitation, axonometric projection can be useful for purposes of

illustration.

Fig 7.2 The three types

of Axonometric Projection

7.3 Isometric Projection

7.3.1In an isometric projection, the x-, y- and z-axes have the same metric: a unit (say, a

centimetre) along the x-axis is equally long along the y- and z-axes. In other words, if yourender a wire frame cube, all edges in the 2-dimensional picture are equally long. Another

property of the isometric projection is that the projected wire frame cube is also symmetric.

All sides of the projected cube are rhombuses.

7.3.2NEN 2536 describes an isometric projection that is symmetric with regards to the

vertical axis; the angle between the x- and y-axes, and between the z- and y-axes, is 60

degrees. The projection shows three sides of a cube, and the surfaces of each side are equal.

The 30 angle between the x- and z-axes and the "horizon" is convenient for technical

drawings, because the sine of 30 is . This projection is attributed to William Farish who

published a treatise about it in 1822. NEN 2536 has been revised and republished as the

international standard ISO 5456-3.

7.3.3The diagram below shows a cube in the isometric projection as defined by ISO 5456-

3.The first object from the left in the figure is the cube unadorned; the second object is the

same cube with angles and measures annotated around it. The third and fourth graphics are

the top and side views of the perspective scene and they give the camera position that fits

the perspective view. The camera position is what you would feed into a 3D renderer (or ray

tracer) to create the sprites or tiles for the isometric projection.
http://www.google.co.uk/url?sa=i&rct=j&q=axonometric+projection&source=images&cd=&docid=Mf2TJ3s_ly1PyM&tbnid=QAxZMG1KWfYsgM:&ved=&url=http://imeulia.blogspot.com/2011/07/axonometric-projection.html&ei=VOKhUtflKsjJhAem_4GABQ&psig=AFQjCNHS1HI4NaPdhZ8Pc-2mgEWmEDxnMw&ust=1386427348933716


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Fig 7.3 An Isometric

Projection

7.4 Di Metric Projection

7.4.1In Di-Metric Projection one of the 3 axis is at different angle to the other two. Di-

Metric Projections are more flexible than the isometric projections.

7.4.2The asymmetry in Di-Metric Projection provides an additional angle to play with,

which, from an artistic viewpoint, Di-Metric Projections are better than Isometric

Projections because of the asymmetry. Symmetry of an Isometric projection makes the

scene look artificial.

7.4.3 In Di-Metric Projections the picture plane is adjusted so that the foreshortening effect

of any two adjacent is equal.

Fig 7.4 A Di-

Metric projection.
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7.5 Trimetric Projection7.5A trimetric projection is an axonometric projection where no two axes form equal angles

with the plane of projection. Each of the three axes and the lines parallel to them have

different ratios for foreshortening. The object is projected so that no axis forms an angle

less than 90 and three different trimetric scales must be used to lay out measurements

along the axes.

Fig 7.5 A

Trimetric Projection.


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8 References8.1

http://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-

bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle

%20projection&f=false

Fig 8.1http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-

third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-

angle-method-is-not-used/

8.2http://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0039682.html

8.3http://www.compuphase.com/axometr.htm

8.4

http://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection

&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimet

ric%20projection&f=false

Fig 8.2 Fig 8.3 Fig 8.4

http://www.significant-bits.com/a-laymans-guide-to-projection-in-videogames
http://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0039682.htmlhttp://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0039682.htmlhttp://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0039682.htmlhttp://www.compuphase.com/axometr.htmhttp://www.compuphase.com/axometr.htmhttp://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimetric%20projection&f=falsehttp://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimetric%20projection&f=falsehttp://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimetric%20projection&f=falsehttp://www.significant-bits.com/a-laymans-guide-to-projection-in-videogameshttp://www.significant-bits.com/a-laymans-guide-to-projection-in-videogameshttp://www.significant-bits.com/a-laymans-guide-to-projection-in-videogameshttp://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimetric%20projection&f=falsehttp://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimetric%20projection&f=falsehttp://books.google.co.uk/books?id=t6W0ib33kWMC&pg=PA179&dq=dimetric+projection&hl=en&sa=X&ei=8ESfUpuFEYaM0AWrzYGQDg&ved=0CDgQ6AEwAQ#v=onepage&q=dimetric%20projection&f=falsehttp://www.compuphase.com/axometr.htmhttp://www.talktalk.co.uk/reference/encyclopaedia/hutchinson/m0039682.htmlhttp://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://mechanical-engineering.in/forum/blog/112/entry-400-why-first-angle-and-third-angle-projection-method-is-used-in-machine-design-and-why-second-and-fourth-angle-method-is-not-used/http://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=falsehttp://books.google.co.uk/books?id=jRLjQsfjSfAC&pg=PT36&dq=second+and+fourth+angle+projection&hl=en&sa=X&ei=Vj-fUqn6G-bW0QWZmoCIBQ&ved=0CD8Q6AEwAg#v=onepage&q=second%20and%20fourth%20angle%20projection&f=false

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An introduction into CAD