Design of Back door of an Automobile | BIW

BACKDOOR DESIGN OF CAR

INTRODUCTION :

Backdoor/tailgate is one of the closure commodities in BIW sheet metal design. The backdoor has a lot of components inside and is designed to incorporate them easily. It affects the rear visibility and luggage area.

Objective

1. From the given styling surface, develop a back door using appropriate design methodologies.
2. Provide the necessary reinforcements and emboss definitions.

components

The backdoor consists of the following basic components:

1. Backdoor inner panel
2. Back door outer panel upper
3. Back door outer panel lower
4. Hinge reinforcements
5. Gas-stay reinforcements
6. Latch and striker reinforcement
7. Wiper motor reinforcement

Major parts

Outer panel

The Outer Panel is the styling surface of the back door. Other components of the backdoor are designed with reference to the outer panel. It acts as the outer cover and deals with the aesthetics of the car.

In this design outer panel is divided into 2 parts

1. outer upper panel
2. outer inner panel

outer upper panel

outer inner panel

Backdoor outer panel

Inner panel

The Inner Panel provides strength to the back door. There are many cases where the Inner panel is subjected to stress due to frequent opening and slamming. These stress and depression factors are compensated by features like embosses and reinforcements.

all other components of the backdoor i.e, reinforcements are accomodated by the backdoor inner panel.

cutouts are made in the inner panel for fixing the lightning systems and the wiring harness.

Reinforcements

Reinforcements are provided in the design to improve the strength in the area where loads are acting

Hinge reinforcement

Hinges enable the opening and closing of the back door. One end of hinge is fixed on the backdoor and the other end on the Roof, on both sides. Hinges can be placed outside or inside the backdoor.

hinge reinforcements are added to compensate the weak region due to acting load over it.

Gas Stay reinforcement

Gas Stay is a device used for supporting the back door in its open position. Gas stay requires no man power and is engaged into support position automatically as the back door opens. One end of the Gas Stay is fixed on the backdoor and the other end on the Body Side or on the Back door stationary area. Embossing is provided at the Gas Stay mounting area to compensate weakness and improve strength.

Latch and Striker reinforcement

The Latch & Striker forms the locking mechanism of the backdoor with the car. Due to regular opening, closing and over slamming of the backdoor, there is stress developed in the Latch and Striker area.To compensate for the same, reinforcements are added in this area.

position of this reinforcement is determined by the midpoint of axis of the Hinges called the Hinge Axis point, which should be aligned with the Latch and Striker through the trajectory of the back door opening and closing.

Wiper Motor reinforcement

Wiper motor reinforcement is created to mount the wiper motor assembly.

reinforcements assembly

Hemming

Hemming is a metalworking process in which a sheet metal edge is rolled over onto itself. The outer and inner panel are joined together using Hemming operation . There is a 0.2 mm gap between the two panels and 1-2 mm clearance at the edge of the inner panel.hemming is preferred over spot welding because of better finish.

reliefs are provided for the hemming in the corners

Mastic sealents

To improve NVH (Noise, Vibration and Harshness) i.e to reduce these levels, Mastic Sealants are used.They are made of hard Rubber and are introduced as a paste thereby joining the inner and outer panel with a thickness of 5mm.

mastics are perferred over welding to join inner and outer panel as welding reduces the aesthetics of the car from the outer surface.

Draft Analysis

Draft Analysis is done to analyze the draft angle. This allows us to verify whether the product will be easily removed from the tool.

Images

Conclusion

Back door was designed and developed from the given styling surface with essential reinforcements and emboss definitions. Draft analysis was also done on the Inner Panel.