Week 8 - Challenge 4 - Bumper

LASTIC DESIGN OF A COIN HOLDER USING CATIA V5

OBJECTIVE

To design a coin holder used in automobiles using Catia V5 using a Class-A surface as input and performing draft analysis on the component to ensure manufacturability

INTRODUCTION

Manufacturing process: Injection Molding

Brief about the process

It is a manufacturing process used for the mass production of plastic components. It works by injecting molten material (plastic) into a mold. Under the application of heat and pressure, the material solidifies into the required shape. Once the product cools, it is ejected from the mold with the help of ejector pins.

Terms in the injection molding process associated with this project

Draft

To facilitate easy removal of components from the mold, it is necessary to add a taper all along the surface with reference to the tooling direction. This taper is termed as a draft and its value ranges from 0.5 degrees to 3 degrees, with the latter being the most widely accepted norm.

The Draft analysis command in CATIA enables to detect if the drafted part can be removed in an easy manner. This analysis is performed based on colour ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.

Tooling direction

The direction along which the core pulls apart from the cavity is termed as the Dyeline or the Tooling direction.

Software : CATIA V5

CATIA (an acronym of Computer Aided Three-dimensional Interactive Application) is a multi platform software suite for CAD, CAM, CAE, PLM and 3D , developed by the French company Dassault Systèmes.

The version of CATIA used for this project is V5. For the target model, the features in the part and surface workbench were extensively used.

Target Model: Coin holder used in automobiles

A coin holder is a plastic component usually found in automobile interiors especially as a part of the door arm rest.

Terms in CAD associated with this project

Class-A Surfaces

The aesthetic/free-form surface which constitutes the visible outer layer of a component can be termed as a Class-A Surface. In this project, the Class-A surface of a coin holder which is composed only of curvature continuous surfaces is used as the input for performing the draft analysis.

B and C Surfaces

The B surface forms the inner components and acts as a base for the Class-A surface. C surface connects the A and B surfaces and thereby provides a thickness for the final component

Tools in CATIA associated with this project

• Sketcher workbench: Point, Line, Intersect 3-D elements
• Part workbench: Close surface
• Surface workbench: Boundary, Extract, Multiple extract, Untrim, Extrapolate, Offset, Trim, Join, Edge fillet

Methodology in CATIA associated with this project

Bisecting line method

Since draft is measured with reference to a tooling axis, the first step after importing the model into CATIA was the creation of a tooling axis. To incorporate for tool clearances due to the presence of tapered surfaces in the part, the bisecting line method was used to create the tooling axis.

After converting the surface into a 2D profile using the Intersection command from the surface workbench, two inclined lines were created using the endpoints of the 2D curves which represented the tapered faces. Using a bisecting line type, a third line was created along the centre point which signified the coincidence of the tapered faces. This line was the required tooling axis for this component.

NOTE: This project did not have features which needed a titled tooling axis and hence the tooling axis was created using a bottom face extract and creating a line through the centre point.

Draft Analysis

The draft analysis command in CATIA helps to detect whether the drafts provided in the model will facilitate easy removal of the component during manufacture.

This analysis is performed based on colour ranges identifying zones on the analyzed element where the deviation from the draft at any point, corresponds to specified values.

• When the draft angle value of the surface is equal or smaller than a graduated value, the color below the graduated value is applied
  
  
• When the draft angle value of the surface is greater than the greatest graduated value, the color above this graduated value is applied.

n this project, the required draft for all surfaces were chosen as 3 degrees and hence the quick mode option in draft analysis was chosen which incorporated two different colours for two input values.

B and C surface creation:

The B surface was created by offsetting the Class-A surface and then extrapolating it to accommodate the entire area of the Class-A surface.

The C surface provided the thickness and acted as the joining surface between Class A and B surfaces.

The Class A and C surfaces were made into a single surface using the Join command in the surface workbench. This was then trimmed (Trim tool) using the B surface to create the final component. The model was then converted into a solid using the Close Surface command.