LABORATORY 3 (PART I): TO CONSTRUCT CAD 3-D TRANSFORMATION ...portal.unimap.edu.my/portal/page/portal30/Lecturer Notes... · TO CONSTRUCT CAD 3-D TRANSFORMATION AND PROJECTION I AND

Laboratory Manual for Engineering Graphics Sem I, 2013/2014 Session

University Malaysia Perlis Page 35

LABORATORY 3 (PART I):

TO CONSTRUCT CAD 3-D TRANSFORMATION AND

PROJECTION I AND II

OBJECTIVES:

After completing this session, you should be able to:

1. Define, reorient, and utilize the User Coordinate System;

2. Create a simple solid model from primitives and combine them using Boolean

Operations;

3. Use the ROTATE and MOVE commands to reposition parts for a model;

4. Use the HIDE command to remove hidden features in a solid model;

5. Use the RENDER command to add shading to a solid model;

6. Insert a model into the titleblock, scale it, and print it.

METHODS:

STEP 1

How to start?

Select 3D Modeling from the Workspaces dialog box that you can see when you start

AutoCAD 2007 (see Figure 3.1).

Figure 3.1



Select 3D Modeling from the Workspaces dialog box when you start AutoCAD. If

you start AutoCAD in the AutoCAD Classic workspace, you can do the following to get to

the 3D Modeling workspace.

1. Start AutoCAD, and then choose Tools<Workspaces>3D Modeling. You’ll see a

new palette to the right of the AutoCAD window.

2. To start a new 3D model, choose File<New> to open the Select Template dialog box.

Select the acad3D.dwt template file and click Open. Your screen will look similar to

Figure 3.2.

Figure 3.2: The AutoCAD 3D Modeling Workspace

To work effectively with CAD programs, such as AutoCAD, you must be able

to create three-dimensional models of an object and convert them to two -

dimensional drawings. In AutoCAD, variations of the Cartesian System are referred to as

the User Coordinate System (UCS). The User Coordinate System allows you to

reposition the location of the origin point (0,0,0) and the X, Y, and Z axes during a model's

construction.



Look at Figure 3.3, which displays the World Coordinate System (WCS) icon you have been seeing in the AutoCAD drawing area.

Figure 3.3

Type ucsicon at a Command: prompt.

The prompt will read: Enter an

option[ON/OFF/All/Noorigin/ORi

gin/Properties] <OFF>: type the

letter p, for Properties, Enter.

The UCSICON Properties

dialogue box will appear.

Click on 2D (See Figure 3.4) to

change the icon to a 2-

dimensional version of the icon.

The 2D makes it easier to tell when

you are in AutoCAD’s default

orientation or World Coordinate

System (WCS).

Figure 3.4

The letter W on the icon in Figure 3.5

indicates that you are in AutoCAD's WORLD Coordinate System (WCS).

The Z-axis, which is not labeled on the 2D icon, lies perpendicular to the other two axes. In a default file, the POSITIVE (+) Z-AXIS is perpendicular to the computer screen and points towards you.

Figure 3.5

Look at Figure 3.6 which again shows the

WORLD Coordinate System icon.

X-axis is aligned at the 0 degree mark on a flat 360° XY plane. Your position in this flat XY plane is at the 270 ° mark, but you are also at a 90° from the XY plane or looking straight down the Z-axis.

Figure 3.6



In reality, you would be looking at a top view of a model or drawing in AutoCAD when your point of view matches the default WORLD Coordinate orientation. See Figure 3.7.

Figure 3.7

To see a solid model as a three-dimensional object, you must adjust your viewpoint (using AutoCAD's Vpoint command) to the model. In Figure 3.8 (a) the eye is looking straight down at the model. The image seen from this vantage point would look like the one in Figure 3.8 (b), which appears to be a 2D drawing of the object's top.

Look again at both Figure 3.8 Notice the

WCS icon and its orientation to the

model.

Figure 3.8 (a)

Figure 3.8 (b)

One of the best ways to remember

the relationship of the X, Y, and Z axes

is the RIGHT HAND RULE. This rule

uses three fingers on the RIGHT hand, each

finger representing an axis.

Figure 3.9



Try placing your fingers in the position

shown in Figure 3.9 and then rotate your

hand so that you change the axes to the

position illustrated in Figure 3.10. Figure

3.9 would be the correct position for the X

and Y axes to be oriented to the FRONT of

an object. This orientation would have to

be defined by the user, and, therefore,

would be a User Coordinate System.

Figure 3.10 would be the World

Coordinate System, which is the same as a

coordinate system with the X and Y axes

oriented with the TOP of the object.

Finally, try to position you hand for a

RIGHT SIDE orientation.

Figure 3.10

STEP 2

1. To begin your model, locate and open the class template (Laboratory 1).

2. Use Save As... To rename it Laboratory 3.

3. Click on the Model tab, to move to MODEL Space. Your model must be created in

Model Space, since it is 3-dimensional space.

4. To access the View Point command you can select 3D Views and then

VPOINTunder the View Menu or type VP at command prompt ( a screen as in

Figure 3.11 appeared) OR you can follow these steps :

i. Command : VPOINT

Current view direction: VIEWDIR=0.0000,0.0000,1.0000

ii. Specify a view point or [Rotate] <display compass and tripod>: <Type r to

select the rotate option and press Enter >.

iii. Enter angle in XY plane from X axis <270>: 300 <Type the desired angle in

the XY plane>

iv. Enter angle from XY plane <90>: 35 <Type desired angle from the XY plane>

Note: Notice that the UCS Icon changed.



Figure 3.11

The left side of the dialog box determines the angle from the X axis in the XY

plane. These angles work as follows:

Table 3.1

Angle (in Degrees) View

270˚ Front view

0˚ Right view

90˚ Back view

180˚ Left view

STEP 3

USING TOOLBARS

Toolbars provide a quick way to execute a command with one click of the mouse.

Normally it has the Standard, Styles, Layers, Properties, Draw, and Modify toolbars

showing. You can open other toolbars as you need them.



To display a toolbar, right-click any toolbar and choose the toolbar you want

to display. Displayed toolbars have a checkmark next to their name. To hide a

toolbar, follow the same procedure-choose the toolbar to deselect it.

USING PALETTES

A palette is a window, or panel that you can dock or float (like a toolbar).Palettes

combine related functions in one place. To see palettes only when you need them, you can

auto-hide them. Right-click the pallette’s titlebar and choose Auto-hide from the shortcut

menu. To dock a palette, choose Allow Docking from the same shortcut menu.

TOOL PALETTES

The Tool Palettes window is a tabbed palette that can contain drawings, blocks, hatches,

images, drawing objects, xrefs, tables and command. Each tab is considered a separate tool

palette within the main Tool Palette window. Figure 3.12 shows the default Tool Palettes

window with the Draw tab on the top.

To open the Tool Palette window, choose Tool Palettes Window on the Standard

toolbar, choose Tools <Palettes>Tool Palettes or press Ctrl +3.

Figure 3.12: The standard Tool Palette window



THE DASHBOARD

The Dashboard is a new palette that contains commands and settings. By default, the

dashboard is specific to 3D drawing, but an optional top section contains a number of 2D

commands, matching the Draw and Modify toolbars. To display the 2D commands, right-

click any blank area of the Dashboard and choose Control Panels<2D Draw Control>

Panel.

To open the dashboard, choose Tools<Palettes>Dashboard or type dashboard on the

command line. The full dashboard is shown in Figure 3.13.

Figure 3.13: Dashboard and its components

Figure 3.14: Tools for Model or Layouts Space

Additional Layouts

Layout 1 Model



STEP 4

Creating a 3D Box

Command: BOX or Click the Box tool in the 3D Make control panel (Figure 3.15).

Figure 3.15

Click a point near the origin of the drawing shown in Figure 3.16. You can use the

coordinate readout to select a point near 0,0. Once you’ve clicked, you see a rectangle follow

the cursor.

Figure 3.6

Specify corner of box or [Center] <0,0,0>:

Use a coordinate or an Osnap to locate the first corner of the box on the

XY plane.

Specify corner or [Cube /Length]: type 60,40 and enter.

Specify height: Type a height value (positive or negative). Type 40

The Box should appear as in Figure 3.17.



Figure 3.17

Use the box command again, but instead of drawing the box from the corner to corner, you

will add it about a center point.

To do so, you must add 3 construction lines inside the first box same as Figure 3.18.

Figure 3.18



Command: Box

Specify corner of box or [Center]<0,0,0>:type ce

Specify center of box<0,0,0>: Use the midpoint symbol to locate the center of

this box at the midpoint of the vertical construction line you just added.

Specify corner or [Cube/Length]: type @-20,-10,20.

Erase the construction lines you used to locate the center for the second box.

Command: SUBTRACT

You will use the second box you added to cut a rectangular hole through the first. The

command you will use for this operation is called the Subtract command.

Use the Subtract command to remove the smaller box from the bigger one.

Look at the Figure 3.19 to see how the figure should now look.

To access this command you can: type subtract or su at Command:prompt OR select

button, OR go to Modify Menu, select Solid Editing then Subtract.

AutoCAD will ask you to select the items you wish to subtract a shape FROM.

Click on the big box, Enter.

Next, AutoCAD will ask you to select the items you wish to subtract. Click on the

small box.

When you press Enter they will removed.

Figure 3.19



STEP 5

To add the next feature,

You must change the UCS (User Coordinate System) so the XY Plane is

oriented to the Front face. There are two ways to do this. One way is to type ucs at a

Command: prompt, select the OrthoGraphic option and then Front.

The second way is to type dducs at a Command: prompt, which will bring up the

UCS dialogue box. See Figure 3.20. Now, select the Front UCS orientation in the

UCS dialogue box. Then Set Current Button. Then click OK.

Look at the UCSICON on the AutoCAD screen to be sure the UCS changed.

Figure 3.20

STEP 6

With the UCS oriented to Front, you can add a cylinder, with the CYLINDER command

, through this side of the model.

Note: The UCS change was needed before you could add this cylinder because the

circular base of a cylinder is always oriented with the XY plane of the current UCS.



To locate the cylinder,

Add a construction line diagonally across the front surface of the box (as

seen in Figure 3.21). The cylinder will be located at the midpoint of this

construction line.

Figure 3.21

Now, add a cylinder at the Midpoint of the diagonal construction line that

has a radius of 10 and a height of -50.

* Notice the use of the negative number for height. The cylinder height, which is along

the Z-axis, must be negative so it will be projected into the model. A positive height

value would project the cylinder forward so that it sat on the front of the box's face.

After adding the cylinder, erase the diagonal construction line.

Use the Subtract command to remove the cylinder from the rest of the

model. See Figure 3.22.

Figure 3.22

Construction Line



STEP 7

To carry out the next step, use the UCS command to change back to the World

Coordinate System.

You can make this change by typing ucs at a Command: prompt, and selecting the

World option.

The last primitive you will add to the model is a small Wedge on its RIGHT

FRONT CORNER as in Figure 3.23.

Figure 3.23

The Wedge command will prompt you for the two diagonal corners of the base of the

wedge.

The next prompt will ask for the wedge's height. Wedges tend to be oriented in one

direction. Therefore, you will create the wedge, rotate it into a new position and then

move it to its final location.

With this information, activate the WEDGE command; . Locate the first corner

of the wedge at the Right Front corner of the existing model. When prompted

for the next corner, use a relative coordinate to place this corner at 30,30 and

20 for the height. See Figure 3.24.



Figure 3.24

The Wedge you just added is not in the orientation that is needed, so you need to

ROTATE it and then MOVE it into the correct position.

Use the Rotate; command to turn the wedge -90 degrees.

A prompt will instruct you to select a Base point. The Base point is the position on

the wedge that you will rotate the object around. You should use the Endpoint

Osnap and the front left corner of the wedge as its Base point. See Figure

3.24 and Figure 3.25 as your references.

Finally, the prompt will ask you for the degrees of rotation. Use -90 so that

the figure will rotate into the correct position. Note: You could also have used

270 degrees to rotate the object to the same position.

Your figure should look like Figure 3.25 when you are finished.

Figure 3.25



To change its position, you use the MOVE command

Select object you want to move (the wedge).

Specify base point: select the Front LEFT corner of the wedge. See Figure 3.26.

Figure 3.26

Finally, select the Front LEFT corner of the box as the point to align the wedge with. See

Figure 3.27.

Figure 3.27

The final figure should look like the one in Figure 3.28.



Figure 3.28

STEP 8

To finish the model, you will add a cylinder to the middle of the sloped surface of the wedge.

Because the base of a cylinder is always aligned with the XY plane, and we want to have the

cylinder parallel with the top of the wedge, you must reorient the UCS to the face of

the wedge.

Activate the UCS command; select the New option and then 3point.

Look at Figure 3.29. When the prompts ask for a new origin point, use an Osnap to

select the point labeled as 1. When asked for a positive on the new X-axis, select the

point labeled 2, and when ask for a positive position on the Y-axis, select the

point labeled 3. When you are finished, the UCS will be oriented to the figure as it is

in Figure 3.30.

Figure 3.29



Figure 3.30

With the UCS aligned with the slope of the wedge, construct a line from one corner of the

sloped surface of the wedge diagonally to the opposite corner of the same surface.

See Figure 3.31. Use the Midpoint of this construction line to place a cylinder that has a

radius of 5 and a height of -20.

Figure 3.31

Once the cylinder is placed, Subtract the cylinder from the wedge (Figure 3.32). Erase the

construction line used to place the cylinder.

Construction Line



Figure 3.32

To finish the figure (see Figure 3.33), you will use the UNION command to connect the

wedge to the rest of the model.

To access the Union command you can: type union or uni at a Command:

prompt, OR select the Union button on the MODIFY 2 Toolbar (IF

DISPLAYED), OR select the Solids Editing, and then Union, under the Modify

Menu.

Select object and then press enter.

Figure 3.33



STEP 9

With the model complete, you are ready to insert it into your titleblock.

Move to Layout1 by selecting the Layout1 tab. If the model appears in the layout,

click on the viewport edge and erase it.

Next, use the VPORTS command to create a Single Viewport that fills the

drawing area of the titleblock.

In Layout1, click on the edge of the viewport to select it. HINT: Remember you can

click on the upper edge of the titeblock to select this viewport because it

overlaps the edges of the titleblock image area.

Now, locate the Viewport Toolbar and select a scale of 2:1 in the Scale window to

scale the model size. Finally, if the model needs moving, use the PAN command to

adjust its position in the window.

Once the model is centered in the titleblock, you must Explode it before you can edit

the text if it is not already exploded. Use ddedit to edit the text in the block as

needed. Remember, you need to change the size in the SCALE: section to

match the size of the figure inside the titleblock or 2:1. See Figure 3.34.

Figure 3.34



You are now ready to Plot your drawing, but first we will make two additional settings.

The first setting you need to make will remove the hidden edges in the model

when it is printed.

To remove these edges, you will use the Properties command. To make this

change, again select the edge of the viewport containing the model if it is not

already selected.

Now, type properties or at a Command: prompt or select Properties on the

Modify menu. The Properties dialogue box will appear. See Figure 3.35. In this

dialogue box, locate the listing.

Click in the block to the Right of Hide plot heading and a Drop-down menu will

appear. Click on the drop-down menu arrow and select Yes. Close this dialogue box.

Now, select the Plot command and make the selections that are listed in the

Plot information.

Figure 3.35



The second setting you need to make will remove the contour or mesh lines that are added

to solids in AutoCAD when a solid is printed with the Hide plot setting is selected. Normally

your print with Hide plot selected would look like the model in Figure 3.36.

To remove these so that the model will print, as the one in Figure 3.37, you will use a

command called DISPSILH (Display Show silhouettes).

To access this command you can either type dispsilh at a Command: prompt or

select Options... and then Display Show silhouettes in wireframe under the Tools

menu. The prompts will read: Enter new value for DISPSILH <0>: Type 1 and

press Enter.

Figure 3.36

Figure 3.37

Use the Plot command and make the appropriate settings to print the model.

Check the look of the drawing by selecting Full Preview and then click on OK to

send the drawing to the printer.

Documents

LABORATORY 3 (PART I): TO CONSTRUCT CAD 3-D TRANSFORMATION ...portal.unimap.edu.my/portal/page/portal30/Lecturer Notes... · TO CONSTRUCT CAD 3-D TRANSFORMATION AND PROJECTION I AND