DESIGN OF B PILLAR TRIM USING CATIA

DESIGN OF INTERIOR TRIM OF B PILLAR

B-Pillar trim:

The floor of the car is connected to roof with 3 pillars namely A-Pillar, B-Pillar and C-Pillar. The pillar between the front door and the windshield is A-Pillar, B-pillar is the one which is there between the front door and back door, and the pillar between the rear door and the back door is C-Pillar. B-pillar has the seat belt assembly which is covered by multiple trim parts. In this model we will be designing one of the trim parts along with its B side features like locators, doghouse, and the ribs.

Inputs:

To design this model, we had provided with Class A surface and the Master sections of the B side features. When ever we are about to start the modelling, we need to check the input surface for the discontinuities and the surface imperfections. If found anything we need to finalize the surface after discussing with the surface design team.

Flange creation:

In this model the class A surface does not have the flanges, but the master section is shown with flanges. The flanges are created using the sweep command with reference to the surface. These flanges then aligned with the master section using offset option. Then these surfaces were trimmed or joined together to form a complete Class A surface with the flanges.

Flanges:

Flanges trimmed with Class A:

Now we have the complete Class A surface as per the master section.

Tooling Axis Creation:

Tooling axis must be created by which the Class A surface clear the draft analysis. First the tooling axis created along Y direction which is almost normal to the Class A surface and the draft analysis shown this direction is creating some negative draft areas.

Therefore, a line is created at an angle of 2.6 degrees from this normal line created to act as a main tooling direction as this axis makes Class A surface to clear the draft analysis. The blue region has minimum draft of 0.5 degrees near the edge and it increases as to moves along the surface with 2.8 degrees in the blue region.

B Surface creation:

The B surface is created by simply offsetting the class A surface as the styling fillet on the Class A surface cannot be created with the fillets. After offsetting the Class A surface then it must be offset to at least 3 to 5 mm of length as it needs to intersect with the Class C Surface. In  the below image we can see that the edges were extrapolated.

C Surface creation:

In this model, Class C surface must be created such that it is formed along with Class A surface so that the parting line falls on the B surface of the part. Class C surface is modelled using sweep with tooling direction command. The surface should be swept away from the tooling axis and at an angle of 3 degrees. The image below clearly shows the surface is swept away from the tooling direction so that it can be formed with Class A surface in the injection moulding process.

Joining the surfaces:

Joining A and C surface:

Trimming the joined surface with Class B surface:

The solid body of the base surface is created with using Close Surface in the part workbench.

Doghouse creation:

The doghouse dimensions were extracted from the master section provided. The extrudes which are meant to be made along the Y direction were extruded in the tooling direction. If they were extruded along the Y direction it will raise a negative draft in rear face of the doghouse. For this doghouse draft angle of 1 degree is provided. Then the solid body is created using the Close surface option in part workbench.

Side Core axis:

The side core axis is created along the Z direction as the master section shown is along the XY plane. Then to enable ease of ejection of part from the side core axis draft of 0.5 degree is provided on the inner faces of the doghouse.

Four way locator:

Four-way locator is placed over the doghouse, Thickness of the locators were kept 1 mm and it is extruded along the direction of the main tooling axis and the draft of 0.5 degree is provided in the direction of main tooling axis. Then the doghouse and the four-way locator are assembled. Then this complete assembly is added to the B-Pillar solid part.

Doghouse assembly on opposite side:

Doghouse on the other side can be created creating a symmetry with the plane which is created between the doghouses. Else this also can be created in a same way as we created the other one by providing the proper draft.

Ribs:

The B-Pillar has a straight wall on both sides which makes the walls weaker. Therefore, ribs were created along the walls of the B-pillar with minimum distance of 50mm each rib to improve the strength. The thickness of the rib is provided as 1.2mm which is 60% of the base wall thickness and draft angle provided as 0.25 to achieve the 0.75mm thickness at the top of the rib. Top limit of the ribs is where the fillet starts between the side wall and flanges. We know total height of the ribs can be up to 5 times that of wall thickness the faces of the fillet between the side walls and the Base of Class A surface is offset for 10mm and splitting the ribs with the offset surfaces so that the total length of the rib from the base is maintained as 10mm.

B-Pillar with B side features:

The image below shows the main tooling direction and the side core axis along with the B-Pillar and its B side features.

Front View:

Side View:

Top View:

Isometric View:

Draft Analysis:

Draft analysis with main tooling axis:

B side draft analysis:

B surface with green faces have draft angle greater than 3degrees. Blue faces have the draft between 0 to 3 degrees.

A side draft analysis:

Enlarged area 1:

Enlarged area 2:

Side core tooling axis:

CONCLUSION:

Thus, the B-pillar is designed with the design rules and the draft analysis is carried out.