Topics: Circle, Boolean logic, Sweep line algorithm Pages: 16 (4098 words) Published: March 31, 2013
Ch740713

Project Goals
The goal of this project was to help students become familiar with a program created by the company Siemens called NX, specifically versions 8.0 and 8.5. Somewhat similar to the program SolidWORKS, NX allows the user to create sketches of simple and complex objects, and then create a 3-D model of the object. Also, an assembly of these models can be made by assigning constraints to create an overall 3-D assembly model. This project was made to utilize NX in order to create an assembly model of a skateboard, made of 6 different parts: The Bearing, The Board, The Bushing, The Connection, The Shaft, and The Wheel. Some parts were easier than others, such as the Shaft, which just required a sketch of a circle to be extruded to a certain length. Others required much more commands, such as the Connection and the Bearing, which required a sweep and many other constraints. Before the project was assigned, students were given many homework assignments that required them to create a part using NX, which didn’t require many commands. Over time, these assignments became more and more challenging, requiring more and more commands. After these parts were modeled, students were taught how to create an assembly using the parts modeled, which use constraints to keep them together such as Concentric, Touch Align, and Center. In order to model the 6 parts of the Skateboard Assembly, students were given IGS files as a reference. These files allowed students to open them in NX and use the Drafting environment to infer dimensions to recreate the part on their own. Dimensions in the sketches were the most important, especially when putting the board together, as dimensions that were not proportional to one another could cause an error in the assembly environment when assigning constraints.

Background
The following parts were used in the overall skateboard assembly: The Bearing, The Board, The Bushing, The Connection, The Shaft, and The Wheel. The Board is the main part of the assembly, which the rest of the parts are built top down. On the bottom of the board, the connections are placed in line with the holes and attached to the skateboard. The connection allows the Bearing and the Bushing to be placed into the assembly. After the connection is in place, the bushing is placed into the appropriate space, where it keeps the bearing at a horizontal angle. The Bearing is then placed into the opposite space of the connection, where it is inserted until the bottom of the bearing is touching the bushing. The Bearing allows for the Shaft to be put into place. When the bearing is put into place, the shaft is inserted making the opposite ends equidistant from the center of the bearing. By making the centers of the Bearing and the Shaft aligned with each other, the wheels are placed at an equal distance, which allows for motion of the Board, completing the assembly of the Skateboard.

The Board

Figure 1a
To start off the skateboard, the top half of the sketch (above the XC axis) was created, and then mirrored across the XC axis, shown in Figure 1a. The Concentric tool was used to make sure the circles shown were of equal radius, and a rectangle (not shown) was drawn to ensure the distances were correct.

Figure 1b
After the sketch is created, it is then extruded to a depth of 0.5 inches. No Boolean operation is necessary since the board is being extruded out of the sketch. It is important that there is no protruding lines or open areas in your sketch, as it will make the sketch unable to extrude.

The Bushing

Figure 2a
To start off the bushing part, a carefully constrained sketch was made in the X-Y plane as shown in Figure 1a.

Figure 2b
After making the sketch, the revolve too was used to revolve the sketch using the Y-Plane as the Centerline axis, and it was revolved 360 degrees as shown above in Figure 1b....