Week 11 - Project - A pillar Design with Master Section

DESIGNING A PILLAR USING MASTER SECTION

OBJECTIVES

• To improvise the Class A surface by resolving bad patches and adding flanges to it.
• To create A pillar solid model with the help of improvised class A surface.
• To create B side features for the A Pillar using the master section given to us as an input.
• To create main and side core tooling axis for A pillar and its B side features.
• To do the draft analysis of the overall model of the A pillar i.e including B side features.

INTRODUCTION

MASTER SECTION: Master sections development takes place during feasibility check and concept validation stages of the product life cycle. These are typically the guides for design requirements and which decides the component packaging after the development of the concept design, i.e class A surfaces.

Master section helps us to decide the feasibility of the concept design, the clearances, the packaging and the fixation strategy of a component before converting the concept design into a solid 3D engineering design.

During the period of vehicle concept design the evaluation of the master section performance depends mainly on the reference vehicle data and experience of structure design engineer.

MASTER SECTION: Master sections are the guides for design requirements which decide the component packaging after technical (Styling, Concept or Class-A) surfaces. Creating this master section should need 5 to 6 years of experience. This helps you to decide the feasibility, clearance, the packaging and the fixation strategy before working it on a 3D.

TOOLING AXIS: Tooling axis is the direction in which the core and cavity opens. If we are using proper tooling axis, we can avoid adding side cores thus the cost of manufacturing the component can be reduced.

It is defined as the direction in which the mould/core and cavity open. Selection of the direction of the tooling axis depends on the ease at which components can be easily ejected.

Generally tooling axis is decided from the natural axis of the design, that is, tooling axis is analysed with the x, y and z axis of the system. If the axis doesn’t clear the draft analysis, the next step is to look for the surface in which the drafting axis can be created in such a way that the axis is normal to the surface taken. These are the methods of deciding tooling axis. Bisecting method is the least used method.

BISECTING METHOD: It is a method used to create tooling axis. The sides of the surfaces are chosen in such a way that the edges may affect the tooling axis are taken as the input for the creation of tooling axis. This axis is then created by giving the line type as bisecting line and the inputs as the lines constructed from the edges that affects the tooling axis. This is not frequently used technique for creating tooling axis.

Here, tooling axis is created using the reference from the master section. As there is a doghouse present in the B side, the sides of the doghouse is taken to created the tooling axis. Two lines are drawn from the edges of doghouse and another line is drawn by using the line option as bisecting line, with inputs as these lines. Thus, the line obtained after these inputs is the tooling axis obtained from bisecting method.

Draft analysis in Catia:

Step 1: Ensure that customize view parameter is enabled and material mode is opted in view mode customization.

Step 2: Now go to insert > analysis > feature draft analysis.

Step 3: Drag axis bar to the tooling direction of part.

Step 4: Check for draft.

Surface will be in green if the draft angle is more than 3 degrees, blue if draft angle is between 0 to 3 degree and red if draft angle is less than zero degree.

Three degree is the nominal value for draft, whereas 0.5 degree can also be manufactured at ribs.

DOG HOUSE: It is an engineering feature used in plastic trim design. It is used as a supporting feature. By using dog house, we can support the other engineering features like heat stakes, screw boss and locators to locate them at a certain height where we cannot violate the design rules for the features. By using doghouse, we can avoid sink marks in class A surface.

Doghouse wall thickness at the intersection of the part wall ( C ) should be 40% or less than the main wall stock ( T ).

The height of ( B ) should be between 3.0 – 6.0 mm

OBJECTIVES

• Creation of Tooling axis
• Creation of Class B and Class C surface from provided Class A surface.
• Creation of solid part out of surface modelling.
• Create engineering features from the master section.
• Draft analysis of Class A surface and final part.

PROCEDURE

Creation Of Class A Surface

• Class A surface is obtained as the input.
• Join all the surfaces to obtain Class A surface if different surfaces are given as input and ensure no gap is present between any surfaces. Thus, Class A surface is obtained and publish it. Here, the provided surface is completely joined and can be taken as class A surface.
• Publish class A surface.

Creation Of Tooling Axis

• Tooling axis is created by bisecting method.
• Publish Tooling axis.

Draft Analysis Of Class A surface

• Draft analysis is performed over Class A surface and every surface is obtained as clearing.

Most of the surfaces obtained are green in color, which means that the surfaces are clearing the draft analysis.

Some faces of the surface are not clearing the draft. It is seen that the draft over those surfaces are having draft less than the nominal draft value of 3-degree. So, it is recommended for the class A designer to redesign the class A surface for obtaining all the surfaces cleared.

Creation Of Class B Surface

• Now, Class B surface has to be created. For this surface should be offsetted for 2.5mm.
• Publish class B surface.

From the master section, it is clear that the thickness to be provided for the plastic component is 2.5mm.

So, class B is offsetted for 2.5mm.

Creation Of Class C Surface

• Now class C surface has to be created and it is created from the boundaries obtained from the Class A surface. This boundary is provided as the input curve for sweep command. Using sweep command, class C surface is created.
• Appropriate sweep is the provided considering the flash and considering manufacturing procedures. Surfaces are extrapolated if necessary.
• Publish class C surface.

Creation Of Closed Surface

• Now Class A surface and Class C surface is joined.
• Now Class B surface is also trimmed with the obtained surface to get the closed surface.
• Boundary check is done to check for any open boundaries in the part.

Draft Analysis Of Plastic Component

• The obtained part is draft analysed to check for the correctness of obtained model by following the draft analysis procedure mentioned above.

Side core has to be created for the doghouse to get ejected. So, a side core axis is also created for checking the draft analysis of the component.

Minimum of 0.5-degree draft is provided and the B side engineering features are analysed using the side core axis. Green colour is obtained in the draft analysis, which indicates that the draft provided all are in correct direction.

Minimum of 1.5-degree draft is provided and the B side engineering features are analysed. Green colour is obtained in the draft analysis, which indicates that the draft provided all are in correct direction.

Ribs are made such a way that following the design rules and it is made to clear with the main tooling axis.

B surface: