DESIGN AND DEVELOPMENT OF THE B-PILLAR THROUGH MASTER SECTION DEVELOPMENT (INTERIOR TRIM)

Full report

(https://drive.google.com/file/d/1sRDYwSJ4FB_G0q4EO7YMPZ9tY0-B_ecz/view?usp=sharing)

DESIGN AND DEVELOPMENT OF THE B-PILLAR THROUGH MASTER SECTION DEVELOPMENT (INTERIOR TRIM)

AIM:

To design and develop B-Pillar from given Class’A’ surface and master section into a functional product design following the OEM design standards using CATIA V5 Surface workbench and Part Workbench following the injection moulding principles.

ABSTRACT:

Pillars are the vertical or near-vertical supports of a car's window area or greenhouse, designated respectively as the A, B, C, or (in larger cars) D-pillar, moving from front to rear, in profile view.

B Pillar is the central pillar of the car. It is the most complex component or structure of the vehicle body. This is because the front door attaches to the B pillar and the rear door hinges to the B pillar. The B Pillar is welded to the top panel of the car and the floor panel of the car. Hence B-Pillar provides structural support to the roof.

The report explains the steps followed in creating the tooling axis followed by detailed methods in creating Class ‘B’ Surface, Class ‘C’ Surface, and to closed body. The overview of the approach followed is mentioned below:

1. Check for any defects or irregularities in the class-A surface.
2. Make a tooling axis.
3. Run the draft analysis beforehand in case if there are any faces that do not have drafts, those can be corrected by the class-A designer.
4. Understand the master-section.
5. Make the flange on both sides to make the aesthetic model complete.
6. Make class-B and class-C surfaces.
7. Make a surface model by trimming surface A, B, and C together.
8. Close the model.
9. Make a B-side feature.
10. Run draft analysis on the final model and make a report

A surface:

A surface is the styling surface that is visible to the consumer and gives an aesthetic look for the model designed. Surfaces which is having curvature continuity is also called Class A Surface. Engineering features are not added to this surface.

B Surface:

Class B surfaces are the secondary surfaces that you can see sometimes includes all the engineering features such as dog house, locators, ribs, flanges, etc. This surface is the direct offset of the Class A surface which gives thickness to the component.

C Surface:

This surface is the combination of the Class A and Class B surfaces also they are the backside surfaces that can have tool marks, flash, and other imperfections without hurting appearance, function, etc...

Tooling Axis:

It is the direction in which the component is removed from the mold cavity.

Automotive trims(interior and exterior):

Trims are the plastic parts installed on the inside and outside of a car. The interior trims are usually used for giving the aesthetic look to the interior of the car. There are various types of trims used in automobiles.

GIVEN:

1.A-surface

2.Master sections

3.Distance between ribs should be 50mm.

Clean A surface

Draft Analysis for A surface:

Tooling axis:

The given Class A input is analyzed to envision the part to manufacture and the Tooling axis or Tooling Direction or Die line is the direction that molds pull apart in injection molding. There are two mold pieces names core and cavity. Thus tooling direction determines Mold separation and also becomes vital in developing the plastic product which is drafted to desired nominal angle for feasible clearance and ejection of the final part from the mold.

The Steps Followed in creating Tooling Axis:

1. A Reference Point is created along the Surface zero and a new Axis system is created.
2. The X-direction and Y direction along the Class A were used to create the Tooling direction.
3. Finally, the Tooling axis is created by bisecting the two lines and it is published. Class A Surface as input using surface operation commands Class B is developed.
4. The tooling Axis determines the direction of Class C boundary swept with draft direction.
5. When viewing from tooling direction normal all the parts that are drafted should be visible so it gives a rough idea to determine product manufacturing in Injection molding.

In B Pillar Model there are Two Tooling Directions one on the Main tooling and the other on Lifter Side that is used to eject the parts during injection molding.

Lifter Axis is used because the Attachment feature is bounded by close walls.

B-Surface creation:

According to the master section, the offset value for the B-surface is 2mm. But while making an offset, we faced the below problem due to which a patch of surface was missing from the offset.

This problem was rectified by following the mentioned method:

1. Taking extracts of all the edges.
2. Making the curves smooth if necessary.
3. Using a multi-section surface tool to fill the surface in the gap.
4. Joining all the sub-elements together to get one single surface.

The resulting surface is our class-B surface.

CREATING FLANGE:

The creation of the flanges was the next procedure. For that purpose, master sections are provided. I created two flanges using the master section on the class B surface.

COMPLETE B SURFACE

Now Offset the flanges so we can trim with class A also.

The offset created a patch after working on the patch and trimming it with A surface gives

Complete Class ’A’ Surface.

CLASS A SURFACE

C Surface Creation:

The Next step is to from the Class C surface with a nominal draft direction of 3 degrees with the tooling direction. so that flash occurs along the boundary of B surface. At some edges, we extrapolated so they intersect each other.

Once this is done, we have to trim all of them with each other to get the class-C surface. We have extrapolated class-B with flange too, so that it intersects with class-B and we get the required class-C surface after trimming.

Combined CLASS B and CLASS C

FINAL BODY CREATION:

Both B and C surfaces were joined together and trimmed with the A surface for final closed surface creation. The closed surface was inspected for openings using the ‘Boundary’ tool. There were no openings and the surface was perfect.

CHECKING FOR BOUNDARIES

As it displays an error saying this command is applicable for open boundaries, it can be confirmed that the created model using the surface workbench is closed.

Draft Analysis for Plastic Component:

This patch need to work on for draft angle purpose we should no make any changes. But, need to informed to Class ‘A’ surfacing team.

PARTING LINE

ATTACHMENT FEATURES

The Attachment features are the Fixation and Location features that Fixes the components The Common Attachment features used in B Pillar Are

1. Doghouse with 4 Way Locator
2. Ribs

The dimensions of the dog house and the four-way locator are taken from the

MASTER SECTION.

DESCRIPTION:

MASTER SECTION: These are the guidelines provided to a design engineer which describe how a component would/must look like once it is modeled into a solid component from the class-A surface. For example, in this model, we have received a master-section as an input which tells us about the thickness of the component and dimensions & type of the engineering features on the component.

DOG HOUSE &FOURWAY LOCATOR: Dog house is an engineering feature used in plastic trim design. The primary function of a dog house is to avoid sink marks on the class A surface which may occur due to features such as a thick screw boss or rib on the backside of Class A. So the best possible solution is to increase the height and decrease the cross-sectional thickness of the ‘legs’ by using a dog house. We can also use them for solving the necessity of large length features such as a screw boss which may require a large length sometimes. We can use a dog house and make a screw boss above it in such situations. We can also use them for making features that are perpendicular to the main tooling direction.

Ribs: Ribs provide a means to economical stiffness and strength in moulded parts without increasing overall wall thickness. They also facilitate:

1) Locating & arresting components of an assembly.

2) Providing alignment in mating parts.

3) Acting as stops or guides for mechanisms.

DESIGN RULES FOR DOG HOUSE:

1. Minimum height: Less than 6mm causes steel condition.
2. 3:1 ratio of steel width to height. But 2:1 is preferred.
3. Minimum width: 3:1 ratio of steel width to height. But 2:1 is preferred.
4. Draft: minimum 1.5deg.
5. Sink saver: height (C) = 40% of nominal thickness. Width (B) = 3.0mm-6.0mm.
6. Optimal radius:25mm

DESIGN RULES FOR RIBS:

1. Draft: 0.5 deg per side (minimum), but this value should not be high enough that it will cause

failure for other considerations. For example, more draft will result in less thickness at the top surface.

2. Thickness of ribs: 40% of wall thickness or 0.4*t where t is the wall thickness.
3. Height: ≤ 5 times the wall thickness i.e. 5*t.
4. Spacing (for more than 1 rib): 3:1- steel height/width ratio (maximum). h/w =3or2(preferred)

where h is the height of the rib and ‘W’ is the space between two ribs.

5. Minimum thickness at the tip: 0.75
6. Radius: 0.25mm max.
7. Ribs on the opposite side of the wall should be offset.
8. Ribs should be connected to other structural features where possible.
9. Rib root thickness should not be more than 30% of the wall thickness.

Dog house with Fourway locator

Dog house following Master Section

Draft Analysis for Dog house with Fourway locator:

Tooling Axis:

Sliding Axis:

Ribs:

Draft Analysis for Ribs:

Draft Analysis for Final Component with Attachment Features:

Tree Structure:

Conclusion:

1. The B Pillar trim is created using a generative shape design workbench.
2. The model is designed with the nominal draft angle of 3 degrees for the component and 0.5 degrees for the engineering features.
3. The Closed body of the model is created using close body command in part design workbench.
4. The engineering features in the model are designed following the design rules.

B-Pillar