L09-MechanicalModeling1

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L09-MechanicalModeling1
GET130 Intro to Engineering Technology
Lab 9: Introduction to Mechanical Modeling
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. This lab introduces the basics of using AutoDesk
Inventor as a 3D modeling tool.
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.
Procedure:
Carefully read and follow each of the following steps to create the detail drawing of a 2x4 Lego block as
shown in the following diagram.
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Lab 9: Mechanical Modeling I
Part 1: Building a Lego Block in Inventor
1. Launch AutoDesk Inventor. Note that this is a large program and may take a bit to load.
2. 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. 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.
3. 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.
4.
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.
5. 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.
6. 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.
7. 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.
8. 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.
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Lab 9: Mechanical Modeling I
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, and 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 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:
9. 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 natural orientation of the part.
10. 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:
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Lab 9: Mechanical Modeling I
11. At this point, click the OK button to confirm the change.
12. 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 as follows 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.
13. 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:
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Lab 9: Mechanical Modeling I
14. 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 tool button. Click on the circumference of the circle then drag inside the circle.
Click and specify the diameter to be 5mm. Then use the Dimension tool to place a measurement
from the center of the circle to the each edge of the rectangle. Do this by clicking on the center of
the circle, then click an edge of the rectangle, then drag off to where you want the dimension line
located. Change this distance to 3.9mm. You should arrive at the following:
15. 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
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on the Rectangular Pattern tool. In the dialog menu select Geometry, then select the circle. Next
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, click
Finish Sketch.
16. 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.
Click OK to complete the Extrude dialog.
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Lab 9: Mechanical Modeling I
17. 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.
18. To use the “offset” tool, we first need a perimeter reference. Add a bounding rectangle at the edges
of bottom surface. In the Modify menu, use the Offset tool to make an offset into the block, i.e.
inward after clicking on the block perimeter. Add a Dimension line and set the offset distance to
1.49mm. Note that this will form an interference fit with the bumps on the top of the block.
19. 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 do this for at least the left 2
adjacent knobs. This will create projection lines to show where hidden edges lie on the part. This is a
very handy tool when drawing parts and checking for interferences. You can also project geometry
but set the line settings to be normal lines from the Format pane.
20. 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 centers of the 2
circles you just projected. Hit escape to complete the line. Then draw another construction line from
the center of the previous one to the horizontal axis, to form a T. 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. Your construction lines should look like this:
21. Un-highlight Format “Construction”. 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.
22. Use the Pattern tool you used previously to create the other 2 circles. The spacing is 8mm. Then,
Finish the sketch.
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23. 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.
24. 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 Create 2D Sketch.
25. 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 drawing circles on the faces of all three of the cylinders on the bottom of
the block. Then click Finish.
26. Extrude these circles inward to remove the material, the same depth of 8.1mm.
27. 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.
28. Repeat this process for all 8 nubs. You can shift-click to select multiple edges before you chamfer.
29. Now click on one of the vertical edges of the block and select the Fillet tool. Fillet each of these
edges to a dimension of 0.5mm.
30. 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.
CONGRATULATIONS! You have a created a Lego block.
31. Now, gray Lego blocks are boring, so let’s make lots of colors! On Inventor’s Quick Access Toolbar
(“QAT”, at very top of window), locate the icon for the Appearance tool
. Immediately to its left is
the Material drop-down menu while to its right is the Appearance drop-down menu. Scrolling
through these lists reveals that we can easily make our block look to be made of a lot of materials
and colors (try some!). You can even create your own textures and appearances, but we won’t need
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to do that today. Scroll down the Appearance drop-down and select “Red”. You will see that the
block is now red. Perform a “Save As…” operation from the “I”nventor menu 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 create a 2x2 Lego block on your own from the dimensions given in the following drawing.
Follow the same steps outlined above.
34. Demonstrate completion of this part to the instructor.
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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, rightclick on “ANSI - Large”, then select “Delete” to remove it. This results in a blank sheet as shown.
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Lab 9: Mechanical Modeling I
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.
8. Demonstrate completion of this part to the instructor.
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.
References:
1. AutoDesk Inventor: http://students.autodesk.com
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