Activity 7.4 Assembly ModelsIntroduction

Have you ever pieced together a jigsaw puzzle? The individual puzzle pieces have to be rotated and sometimes flipped around. A piece that makes up an outside edge of the puzzle must have its flat edge flush with other pieces of that side. Pieces that have exterior protrusions must be mated to their counterpart interior recesses. The process of putting a jigsaw puzzle together is very similar to building an assembly of components in a CAD program.

In this activity you will develop your knowledge of CAD assembly modeling by first practicing on a relatively simple mechanical device called a Jack Lift. This will include performing an interference analysis to determine if any unnecessary overlaps occur between the various components. Next, you will apply your skills to assemble an Automoblox toy vehicle.

Equipment Engineering notebook Pencil Jack Lift CAD files:

Base Wedge Wedge Screw

(Optional) Automoblox CAD files: T9 Axle T9 Bed T9 Connector T9 Front T9 One Block Socket T9 Passenger Base T9 Passenger Section T9 Tire T9 Two Block Socket T9 Windshield T9 Wheel

ProcedurePart I. Use the CAD modeling software to create an assembly of the Jack Lift. You will need access to the five parts of the machine: Base, Wedge, and Wedge Screw.

1. Create a new assembly file titled Jack Lift and save it to your student folder.

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 1

2. Place the Base component into the assembly. This component will be grounded and, therefore, locked in space. Next, place the Wedge and Wedge Screw components into the assembly.

3. Apply a tangent constraint to the neck of the Wedge Screw component (selection shown in blue) and one of the vertical walls of the open slot on the Base component (selection shown in green).

4. Apply a mate constraint to the back face of the Base component (selection shown in blue) and the circular face on the underside of the Wedge Screw’s head.

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 2

5. Apply a mate constraint to the bottom face of the Wedge component (selection shown in blue) and the top angled face on the Base component (selection shown in green).

6. Apply a mate constraint between the center axis of the threaded hole in the Wedge component (selection shown in blue) and the center axis of the Wedge Screw component (selection shown in green).

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 3

7. Apply a flush constraint to the front faces of the Wedge component (selection shown in blue) and the front face of the Base component (selection shown in green).

8. Perform an interference analysis between the Wedge and Wedge Screw components.

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 4

9. Revert to wireframe screen mode and perform a screen grab of the image. Print the image out and affix it to a page in your engineering notebook. Make an entry in your notebook that speculates as to the reason why interference exists between these two components.

10.Save the Jack Lift assembly file.

Part II. Use the CAD modeling software to create an assembly of the Automoblox T9 vehicle (or another Automoblox model). Use subassemblies as detailed below for parts that are to be permanently connected. Use the image of the assembled vehicle and the exploded assembly view below to help you assemble the vehicle correctly. Save your assembly files (for the complete vehicle and for the subassemblies). The following should be assembled separately and used as subassemblies in the final assembly drawing.

Subassembly 1: T9 Bed, (2) T9 Axles, and T9 One Block Socket

Subassembly 2: T9 Front, (2) T9 Axles, and T9 Two Block Socket

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 5

Subassembly 3: T9 Passenger Section, T9 Two Block Socket, T9 One Block Socket, and T9 Passenger Base

Exploded Assembly of T9 Automoblox

Perform a screen grab of each assembled sub assembly and the complete assembly. Print each image and affix it to a page in your engineering notebook. Label each subassembly and the assembly

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 6

Assembly of T9 Automoblox

Conclusion1. What is an offset and how is it used?

2. What is the difference between a mate and flush constraint?

3. What constraint would you use to place a pin inside a hole? Which degrees of freedom does this constraint remove? Use a sketch to define the degrees of freedom.

4. Describe a situation in which you would use a tangent constraint. Which degrees of freedom does a tangent constraint remove? Use a sketch to define the degrees of freedom.

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 7

5. What is a subassembly? How is it useful in the assembly of a complex product that involves multiple parts?

© 2012 Project Lead The Way, Inc.Introduction to Engineering Design Activity 7.4 Assembly Models – Page 8