Challenge

Design of backdoor

VVeeralekshmanan K11 Apr 2023

BACK DOOR DESIGN

Aim:

To design a Back door of a car from the given styling surface provided by using NX CAD.To develop a back door and its reinforcements,draft analysis for deep drawing satisfaction by sheet metal design.

Back Door:

Back door is one of the BIW component in automotive car which is gives the acces tothe trunk sapce of vehicle.The back door protects the trunk area and hiding the luggages to storing insid the car. In back door has some major reinforcements for access the backdoor to opening and closing purpose.The main purpose of the back door is to storing luggages and rear visibility.It is also called as Tail Gate of the outomotive car.

Components of Backdoor/Tail Gate

Outer Panel Upper
Outer Panel Lower
Inner Panel of the Back Door
Hinge Reinforcement
Gas-Stay Reinforcements
Wiper Motor Reinforcements
Striker Reinforcements

Design Consideration:

Rear Visibility
Mastic Gap 5mm
Spot Weld gab 0mm
Min. Draft angle 7°
Force Dissipation
Latch and Stricker Positions
Hinge Position
Gas Stay Position
Space Availability
Hemming and Corner Reliefs

Design Methodology:

The objective of this design to develop the Body In White of car Back Door with the reinforcements of components such as Inner Panel, Outer Panel, and Reinforcements for the Hinges, Gas stay, Wiper Motor, and Latch by following the engineering standards. The Outer Panel of the back door is the styling surface which is given by the challenge section.The other components of the back door are designed with the reference of outer panel skin data.

Material Selection

The material selection is the major role in BIW design,because of the cost and weight of the BIW depends on the material which is used to manufacture the car BIW. Steel and Aluminium is the most comonly used in BIW design. The Density of Steel is higher than the Aluminium, that means the weight of BIW is more when we using steel. Basically, which material is going to be used is based on the budget of the car.

The cost of the Aluinium is much costlier than the steel,but if we used aluminium instead of steel ther is no many model part creations for each mounting and the overall weight of the BIW are reduced by 6-9 Kg approximately. In back door another factor to using Casted Aluminium instead of Steel components and reinforcements to the space for the luggage trunk area gets little more because of the draft angle for Casted aluminum is much lesser (3 degrees) than the deep drawn Steel in inner panel of the Back door(7-9 degree). But the cost of aluminium is much costlier. The high budget cars like Audi, Porshe, Benz,BMW,GT,etc., which is used aluminium in backdoor BIW resulting to reduce the weight of the car and increase the perfomance of the vehicle.

Finally, in this design we are going to proposr the medium budget car, so we are not to be offere the Aluminium is to be used in backdoor. The steel is budget friendly, so we are going to select the materail is Steel.

Sheet Metal Manufacturing Process

Deep Drawing:

The sheet metal deep-drawing process is one of the effective method to produce the sealing flange, hinge and gas-stay emboss area, Latch and striker emboss are,etc.There are two stages of Deep-drawing process,

First-stage drawing
Redrawing

Outer Panel

The outer panel of the back door is the styling surface and cover the inner panel and its reinforcements.In this steel outer panel is split into two parts, they are

Outer panel Upper
Outer Panel Lower

Outer panel Upper

Upper outer panel is extracted from the styling surface and design the required design consideration and blends the sharp corner.The Thickness of the outer panel is 0.75mm

Outer Panel Lower

The lower panel is also extracted from the given skin data and crate the required flanges, blends and thickening it by 0.75mm.

Back Door Inner Panel:

The inner panel is extracted from the outer panel upper and lower,and design the required flanges, embosses, blends by using NX/CAD tools.

Tooling Direction

Before creating inner panel of the backdoor should be create the tooling direction to perform the deep drawing process.

After creating tooling direction the sealing flanges and the embosses for the reinforcements should be the create in tooling direction only.

Emboss

The embossing is the stamping process for create the diiferent mount and reinforcement of the inner panel. This is the similar process of forming process can be made by means of matched male and female dies are by passing sheet metal between rolls of the desired pattern.In this inner pane hinge, Gas-Stay,Latch areas created by embossing process.

Mastic Area

The Mastic area is fix the inner and outer panels with the help of Mastic Sealants. The gab between the inner and outer panel is should be 5mm for the mastic sealants to melt and gets fixed at the surface of the inner and outer panels.

Mastic Gab - 5 mm

Hinge, Gas-Stay, Wiper Motor & Striker Reinforcements

The other components of the back door is Hinge Rinforcements, Gas-Stay Reinforcements, Wiper motor Reinforcements and Striker Reiforcements are shown in below figures.

Hinge Reinforcement

Hinges are used to the opening and closing of the back door. One end of the hinge is fixed with backdoor and the other end to the Roof, on both sides. Hinges can be placed outside or inside the backdoor its depends upon the styling designs.

Gas-Stay Reinforcements

Gas Stay is the one part used for supporting the back door in its open position. When the back door is open the gas stay is automaticaly engaged to support the back door on its possitions. One end of the Gas Stay is fixed to the backdoor and the other end with the Body Side.

Striker Reinforcement

The Striker reinforcements performs the locking mechanism of the backdoor to the car. Due to regular opening, closing, and over slamming of the backdoor, there is stress acting in the Striker area. So compensate for the stress developed area, the reinforcements are added on that area.

Trajectory

The position of the striker should be perpendicular to the Hinges. The circle is drawn from the center of the hinge axis to find the path of the striker and positioned perpendicular to the path.

Wiper Motor Reinforcement

To placing the wiper motor, the wiper motor reinforcemnets was created.

Hemming:

Hemminh is the process of Sheet metal edge and sharp corner metalworking process in which the sheet metal edges flush rolled over itself by apropriate roller.

The outer panel is to be hemming rolled over the Inner panel by using the roller and smoothening the edges by itself.

Corner Reliefs

In hemming process the curved and embossed edges deformed in rolling process, so that area should be relief the stress and reduce deformation by corner relief method.

Final Back Door Assembly

SideView

Front View

Top View

DRAFT ANALYSIS:

The draft analysis is to analys the model by using the tooling direction.The draft analysis is to perform and analys the model by its drafting angle and check the stressing area is found or not. The minimum drafting angle should be 7°.

Outer Panel