Week 9 - Challenge 3 - Bumper

OBJECTIVE

Create the Bumper Plastic component through the given Class-A surface. To begin with, the tooling axis for the given Class-A Surface should be created meeting the requirements of the draft angle and at the end perform the Draft analysis on the model.

INTRODUCTION

A bumper is a structure that is incorporated or attached to the front and back ends of a car in order to minimize damage in the event of a minor collision. According to current design standards, the bumper structure of modern automobiles are made out of a reinforcement bar covered in plastic that is either composed of steel, aluminum, fiberglass composite, or plastic. The majority of modern cars have bumpers composed of PC/ABS, a material blend of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS).

DESIGN METHODOLOGY

Given input Class A Surface is provided by styling team to create the complete plastic component. Here for the bumper the given input class A surface is:

Tooling Axis or Direction

The Tooling Axis is the direction in which the mold pulls apart from the casting. As the mold is constructed in two independent sections; Core and Cavity. The Tooling Axis is formed when the Core separates from the Cavity. Also the ejection of the part from the mold is determined by the draft angle. A zero draft might cause shrinking, which could lead to difficult or no ejection. Hence for all plastic component manufacturability, the draft angle is given 3 degrees.

In most cases tooling direction could be along the surface, or by creating bisecting line from the surface profile. Here for Bumper, the tooling direction along X-direction itsefl clears the draft and thus the component can be manufactured.

Tooling axis for Bumper:

Draft Analysis

Choosing the class A surface perform Feature Draft Analysis with respect to Tooling Axis. Green colour indicates the surface can be manufactured using core and cavity method. Given draft angle of 2.9 degrees for bumper Class A Surface:

Commands Used to create Class A Surface, Class B Surface, Class C Surface and Final Surface in Generative shape design, CATIA are:

• Join
• Intersect
• Point
• Line
• Extract
• Surface Untrim
• Offset
• Extrapolate
• Boundary
• Split
• Trim
• Curve Smooth
• Sweep
• Edge Fillet

Class A Surface

Class A surface is the aesthetic part of the model, which is already created by design engineer as input Class A Surface. Class B Surface is then created by offseting the Class A Surface according to the thickness of the part.

Class B Surface

Class B Surface is created by offseting the Class A Surface according to the thickness of the part. Here in this model 3mm thickness is taken.

Class C Surface

Class C Surface is the joining surface between Class A Surface and Class B Surface to obtain the solid plastic model.

Final Surface

Final Surface is obtained bt joining Class A Surface and Class C Surface, then using Trim command with joined surface and Class B Surface to obtain the closed surface model.

In part workbench, use Close surface command to obtain the final Bumper plastic model.

Draft Analysis

Draft analysis for Class A Surface, Final Surface model and Bumper part body is done with respect to the Tooling Axis. For any plastic component manufactured using Core-Cavity method needs to follow draft angle which enables the models manufacturability, and the draft angle should be less than 3 degrees. Here in Bumper Class A Surface, clears drafting analysis with 2.9 degrees with respect to the Tooling Axis. Draft angle of 2.5 degrees clears the drafting analysis for Final Surface and Part body of Bumper. In feature draft analysis green colour indicates a positive draft, blue colour indicates negative draft and red colour shows area with zero draft angle. Manufacturability of the component is based upon getting resultant green colour over the component from feature draft analysis.

CONCLUSION

From the given input Class A Surface, created Class A Surface, Class B Surface and Class C Surface using CATIA. Bumper solid model was successfully created using CATIA and performed draft analysis on both Class A Surface and final Surface clearing the required draft angle. Publications for Class A Surface, Tooling Axis, Class B Surface, Class C Surface and Final surface of Bumper was also created using Publication Tool.