Week 8 - Challenge 1 - Base Bracket Design

Aim: To create a Base Bracket Plastic Component through a given Class A Surface and perform Draft Analysis on the final plastic component.

Objectives:

• Creation of Tooling Axis.
• Creation of Class B and Class C surface.
• Creating a solid part out of surface modelling.
• Draft Analysis of Class A surface and final plastic component.

Tool Used: CATIA V5

Introduction: In this project we are designing a base bracket using given class A surface. The approach includes creation of Class B surface keeping 3 mm thickness in mind for the complete component. The design also included Class C creation from the given parent surface.

Constraints:

• NO CHANGES IN CLASS A ARE ALLOWED.
• PART THICKNESS CANT DEVIATE BY MORE THAN ±±30%
• ALL DESIGN RULES SHOULD BE STRICTLY FOLLOWED.
• ALL SURFACES SHOULD BE CLOSED BEFORE CONVERTING TO SOLID.
• ALL FACES SHOULD MEET THE ALLOWED DRAFT REQUIREMENTS.

What is the class-A surface?
Class ‘A’ surfaces are primarily used in the automotive environment and refer to those surfaces which are visible in a product. In other words: A - class surfaces are those aesthetic/free-form surfaces, which are visible to us (interior/exterior), and have an optimal aesthetic shape and high surface quality.

Here, one should understand the difference between the internal or external and visible or hidden surface. The surfaces or regions which are visible nowadays are considered for Class-A modelling. It is one of the reasons why the importance of Class-A modelling is increasing day by day. Majority of the time this term is used in Plastic Part designs.

Class A: The Class A finish is the highest quality finish Microform Precision can provide. It is often specified for high visibility surfaces such as control panels, front covers, etc. in which the Customer demands the highest quality appearance. This Class is for surfaces that are of such prominence that imperfections will tend to degrade the public image of the product.

Class B: The Class B finish is a quality finish with only minimal imperfections. A Class B finish is the most common finish for exterior surfaces. It is normally specified on surfaces such as external covers, panels, and parts that are fairly prominent.

Class C: The Class C finish allows more imperfections than Class A or B. Class C is often specified for interior surfaces not readily visible, surfaces that will be covered by another part when assembled, or surfaces which the Customer feels do not need to meet a high cosmetic finish. This Class is generally used for parts or surfaces which are not viewed after installation or viewed only for service.

Class D: The Class D finish might be used when cosmetic appearance is not important. With a Class D finish, all imperfections are permissible provided they do not impair the function, safety, structural strength, environmental, electrical or dimensional requirements of the part; part is usually never viewed.

CLASS A: Following surface is given as the input for the component creation.

To continue with the design process first we need to find out the tooling axis for the surface and check for all the drafts using Draft Analysis tool of CATIA.

Draft Analysis for Surface A:

The analysis is done for 3degree draft. So as can be seen all the surfaces are more than 3deg.

Creating of Tooling Axis:

• Create an intersection of CLASS A surface with ZX plane and from the intersection create the tooling axis as shown below.

Creation of Class B:

• Now for Class B creation, we have extracted surface from Class A and untrimmed them to obtain the original parent surface.
• These surfaces are then offset to the required thickness.
• After offsetting, all the surfaces are trimmed into the required shape.
• Required fillets are given to the surfaces.

Creation of Class C:

• For creating this surface we have extracted the boundry of Class A using multi-extract and then converted to smooth curve.
• Now this smooth curve is swept along the draft direction with a 3deg draft.

Final Trims:

Class A + Class C:

To make sure that there is not any open boundry between class A and class C, we have used join option to created the single body. This is done to make sure that the parting line doesn't lie between the these two surfaces.

Class A + Class B + Class C:

For this we have trimmed the above shown surface with the Class B surface using trim feature.

All the main features are published as can be seen in the image shown above.

Draft Analysis on the Final Component:

For this analysis, main tooling axis is taken draft reference.

Following results were obtained:

part body:

hence the surface is converted into solid :

tree structure:

conclusion:

the Base Bracket 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 is done