GET130 Intro to Engineering Technology
Lab 9: Introduction to Mechanical Modeling
References:
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AutoDesk Inventor: http://students.autodesk.com
Introduction:
Mechanical modeling serves a number of purposes in the engineering design process. It allows designers
to create and test their designs before materials are purchased or parts are machined to verify that the
finished product will meet the expectations of the customer, thereby saving time and money
throughout the design process. It also allows designers to formulate their ideas into a tangible and
presentable format to present to customers, investors, or team members. Finally, it allows designers to
rapidly and cheaply test and change their designs.
Objectives:
• To understand basic use of AutoDesk Inventor as a modeling tool.
• To apply dimensioning and multiple views in the creation of a detail (part) drawing.
Part 1: Building a Lego Block in Inventor:
1. Since there are many, many different Lego blocks, we may wish to make more than one shape
with which to build our creations. Thus, let’s make a new project to store all of our part and
assembly files. Click on Projects, then select New to make a new project. We now have the
choice whether to create the project for a single user or as a vault project, which can be shared.
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Since you will not be sharing this project, select New Single User Project, and click Next to
continue. Name the project “Legos”, and click Finish. The directory selected will not yet exist, so
confirm that it should be created.
The project “Legos” should now appear on the list of projects and it should be selected. Click
Done.
We want to make a new part. We’ll start with the standard 2x4 Lego brick. Click on New. Select
“Metric” from the Templates list on the left, then select the template “Standard (mm).ipt”, and
click Create.
Now that we have a blank part template, we can begin creating our part. First, let’s get
acquainted with the environment. On the left of the screen is a panel labeled “Model”. This is
the part tree, or model tree. You will see that as we perform operations to this part, a list of
these operations will appear in this panel. This becomes very handy when we want to change
something we did early in the part, especially for complex parts and assemblies (we’ll talk about
assemblies later).
At the top menu is a series of tabs. These contain the tools and functions you will be using. Most
notably, “3D Model” shows functions used to create a part, and “Inspect” contains the tools
needed to measure, or inspect, the part you are creating.
Select the “3D Model” tab. On this tab, we have variety of tools for adding and modifying the
material which makes up a part. To create our lego block, start by clicking the button marked
“Create 2D Sketch”. We add material to a part by creating a sketch in 2D, then converting that
sketch to 3D by either extruding or revolving that drawing.
Before we draw anything, let’s learn to navigate the part. If we use the scroll wheel on the
mouse, we can zoom in and out on the part. Clicking the middle wheel and dragging allows us to
translate the part. Holding down the “Shift” key and the middle wheel while dragging allows us
to rotate the part. Notice as you rotate the part that the Cartesian axes in the lower left corner
rotate with the part to indicate the orientation of the part with respect to the axes. These
manipulations are crucial to building a part, as you will quickly see, so make sure you can control
to the zoom, position, and orientation of the part before moving on.
We want to start by making the bulk of the block, so click on the X-Z plane (the one that lies flat
like the ground). Notice that the program flattens out to show just this plane as a new drawing
surface. Here we want to create a rectangle, which will eventually be the outline of the block.
Although we could just draw lines, there is a “Rectangle” tool. Click the drop-down arrow on this
tool. We have several options to choose from, depending on how we wish to specify our
rectangle. For our purposes, select the “Two Point Center” option. This lets us set the center of
the rectangle and one corner, which determines both side lengths. We want to align the center
of the rectangle with the origin of the axes. Move the mouse toward the center. Notice that the
yellow dot turns green when you get very close; this means that the cursor is “snapped” to this
point. This snapping feature is highly useful to getting your shapes accurate, as you will discover.
Click on the center (with the cursor showing green) to select the origin of the axes as the center
of the rectangle. Notice, now, that as you move the mouse two dimensions appear and change
as the mouse moves. We could move the mouse until these numbers show the desired
dimensions, but that is unnecessary. Simple click anywhere. We can change the dimensions in a
second. On the “Sketch” tab is a button marked dimension. This lets us modify a dimension.
Click this button, then click one side of the rectangle. Drag the dimension marker to a
convenient place and click again. Type the desired number in the edit box and hit Enter. Make
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the length in the Z-direction 15.8mm and the length in the X-direction 31.8mm. You should have
a sketch which looks like this:
8. Click the green check mark in the upper right corner of the screen to finish the sketch. The
sketch will then reorient itself in the Earth reference frame, to show the nature orientation of
the part.
9. Now, click on the sketch, then click the button marked Extrude. This will let us specify a height
and add material to the sketch. Later, we can also use this tool with some different options to
subtract material rather than add it, but in this case we are adding material. Extrude the sketch
upward to a height of 9.6mm. Your screen should look like this:
10. At this point, click the OK button to confirm the change. The part should now look like this:
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11. It is a good idea to save often. Let’s save the file now. Click the Save icon at the very top of the
screen, and you will see a dialog box pop up. Verify that the file is being saved in the workspace
folder “Legos”, then name the file “4x2” and click save. It is a good idea to always name your
parts descriptively, especially when working on a complex project.
12. Now we need to make the bumps on the top that allow the blocks to snap together. Click on the
top of the block. This surface is where we want to create the next sketch. With this surface
selected, click on the Create 2D Sketch button to begin drawing. Your sketch surface should look
like this:
13. Since the bumps are circular, click the draw circle button. Draw a circle inside one quadrant of
the rectangle. It doesn’t matter if the size and location are off; we’ll fix them now. With the
circle drawn, click the dimension button. Select the center of the circle, and specify the diameter
to be 5mm. Then use the Dimension tool to place a measurement from the center of the circle
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to the each edge of the rectangle. Change this distance to 3.9mm. You should arrive at the
following circle.
14. Now, it is possible to simply draw the other circles, but it is more efficient to use the array tool.
Plus, this makes later editing easier, since you can change a dimension and all the circles will
update. Click on the Rectangular Pattern tool. In the dialog menu select Geometry, then select
the circle. Then click Direction 1 and choose the vertical side of the rectangle. Place 2 objects in
the array this direction, at a distance of 8mm. If these are going the “wrong way”, click the
“Switch direction” button (the one with the black and red arrows). Repeat this for the other
direction, except that we want 4 copies this direction. Click OK when the circles appear to be
correct.
When you are finished making the array, you make click Finish on the sketch.
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15. Now, click on the Extrude button. Then click inside each of the circles. They should rise as they
are selected. Extrude these upward 1.7mm. You should now have the top of the Lego block
completed.
16. Now we need to make the recess at the bottom of the Lego block. Here we will be removing
material. Holding Shift and your center mouse button, rotate the block until the bottom is
visible. Select the bottom surface and create a new sketch on it.
17. In the Modify box, use the offset tool to make an offset 1.49mm into the block (Note that this
will form an interference fit with the bumps on the top of the block.
18. Now, we need to draw the centerline circles (the three on the bottom). Since we want these
blocks to interlock, we need to know where the top of the block should mesh with the bottom.
Use the Project Geometry tool to show the circles from the top. Click the tool, then mouse over
the locations of the top knobs. Click on them when they highlight. You should at least do this for
the left 2 adjacent knobs. This will create construction lines to show where hidden edges lie on
the part. This is a very handy tool when drawing parts and checking for interferences. Note that
construction lines are not really part of the sketch as they cannot be used to add or subtract
material or otherwise modify the part. You can also project geometry but set the line settings to
be normal lines from the Format pane.
19. Now we need to create 2 construction lines. Click on the Line tool, then make sure the Format
“Construction” is highlighted. Using the snap feature, draw a line to connect the 2 circles you
just projected. Hit escape to disconnect the line. Then draw another construction line from the
center of the previous one to the horizontal axis, to form a T. Your construction lines should look
like this:
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20. Now, draw a circle in the center of the 4 knobs, just touching these circles, using the center
point you just defined. Notice that you can snap to construction lines the same as normal lines,
which is quite the point.
21. Use the Pattern tool you used previously to create the other 2 circles. The spacing is 8mm. Then,
Finish the sketch.
22. Click on the Extrude tool and click the area between the offset and the circles on the Sketch you
just created. For this Extrude, you will be subtracting material. Thus, reverse the direction so
that the extrusion is going into the material. Use the Extrusion depth of 8.1mm. The part should
now look like this on the underside.
23. Finally, we need to remove the material from the center of the cylindrical parts on the bottom
of the block. Click the face of one of these circles, then click Sketch.
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24. Create a circle with the same center point as the sketch face circle, of diameter 5.314mm. To
snap to this center you will need to use the Project Geometry tool, then highlight the three
circles from the previous steps. Repeat this to draw circles on the faces of all three of the
cylinders on the bottom of the block. Then click Finish.
25. Extrude these circles inward to remove the material, the same depth of 8.1mm.
26. Now we are going to remove some of the sharp edges. Click on the top edge of one of the 8
nubs on the top of the block. You will see 2 options appear, “Create Fillet” and Create Chamfer.”
Choose the “Create Chamfer” tool and chamfer this edge uniformly with a dimension of 0.2mm.
27. Repeat this process for all 8 nubs.
28. Now click on one of the vertical edges and select the Fillet tool. Fillet each of these edges to a
dimension of 0.5mm.
29. Repeat this process for the edges around the top of the block. Note that now you must select all
four edges and all four corners.
30. CONGRATULATIONS! You have a created a Lego block.
31. Now, gray Lego blocks are boring, so let’s make lots of colors! Go to the “Tools” menu tab and
select the Appearance tool. Scrolling through the list reveals that we can easily make our block
look to be made of a lot of materials. You can even create your own textures and appearances,
but we won’t need to do that today. Scroll down and select “Red”. You will see that the block is
now red. Perform a “Save As…” operation to save a red block. Name it “4x2 Red”. The block will
appear as below.
32. Now, repeat this process and save a blue and green block separately. Note that since we can
change the material properties and modify the dimensions of the part, we can save copies of a
basic part and modify as needed if we need variations on the same part. For example, creating
different size bushings, or sprockets with varying diameter or material.
33. Now you will create a 2x2 Lego block on your own from the given dimensions. You will follow
the same steps outlined above. Have your work verified by the instructor.
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Signature:______________________________________________________________________
Part 2: Creating 2D Engineering Drawings
1. One of the most common ways of representing a mechanical design is with a 2D engineering
drawing. These generally contain top, side, front, and isometric views of the part (though there
are others), labeled with the dimensions needed to fully define the design. One convenient
feature of AutoDesk Inventor is the ability to create a 2D engineering drawing from a 3D part.
2. Begin by clicking the Inventor icon at the top of the window and select “New…” Hover over the
arrow to show the menu options, then select Drawing. This will open a blank sheet with the
default ANSI border and title block. The border is used similarly to a map to denote sections of
the drawing. The title block records the name of the drawing, the author, version number, and
approvals as needed.
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3. First, we need to set our paper to the correct size. Since we will be using a printer and not a
plotter, we are limited to paper 8.5”x11”. Thus, right-click on “Sheet:1” in the part tree on the
left. Select “Edit sheet…”, then choose paper size A in landscape orientation. Click OK.
4. Now we see that the title block and border are far too large for this paper size. We could
redefine this title block, but instead we will remove it since we are not using it here. In the part
tree, right-click on “ANSI - Large”, then select “Delete” to remove it. This results in a blank sheet
as shown.
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5. Now we can place the views. We begin by defining the master view. On the tab marked “Place
Views”, click on the button marked “Base”. Leave the base view set to “Front”, but change the
scale to “3:1” because part is small and we want to make the most of the available space on the
drawing. Also, go to the tab marked display options in the Drawing View window and check the
box labeled “All Model Dimensions”. Do not close this window yet, but move it out of the way of
the sheet. Click in the bottom left quadrant of the sheet and place the front view of the block.
Then move the mouse up and click to place the top. Place the isometric view in the top right and
the side view in the bottom right. These initially show up as rectangles. Right click on one of the
projected view, then select “Create” and the Inventor will create the details for this drawing.
6. Now we can use the Dimension tool (on the Annotate tab) to add all necessary dimension
information to the sheet. When dimensioning a drawing, it is best to label a measurement only
once, rather than on all the views. However, when in doubt, redundant information is
preferable to not enough. Use the dimension tool to add dimensions to the areas labeling in the
Figure at the beginning of this document. Make sure to change your dimension units to mm.
7. Repeat this process to create a drawing for the 2x2 Lego block you constructed. When you are
finished, have the instructor verify your work.
Signature:______________________________________________________________________
Part 3: Continued Practice
AutoDesk Inventor is available to students with a valid .edu email address (i.e. all of you). Go
home and install Inventor on your own machine, then explore the program. Create a new part of
your choice. Consider where to start and what processes can be used to define the model.
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