Design of backdoor

INTERODUCTION OF BACK DOOR:-

The Back Door of a car is the rearmost part of the vehicle which gives access to the trunk space of the vehicle. The rear door also supports the reinforcements and added weights of the Wiper Motor, Gas Stay, Tail Lamp, and Latch and Striker.

The 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. The material used for door manufacturing depends on the budget and performance of the vehicle. Mostly Aluminum and Steel will be used whereas low-budget vehicles use Steel which makes the manufacturing process easy and cost-efficient since it follows the Stamping of Molds.

DESIGN CONSIDERATION OF A BACKDOOR:

• Functional Requirement of Hinge and gas stay
• Rear visibility criteria - Regulations
• Luggage volume
• Sealing & Its analysis
• Joining techniques followed like Hemming, Spot Welding etc.
• Rear Crash Regulation & Requirement
• Gap and flushness Requirements
• Manufacturing Techniques followed like Aluminum Casting, Steel Stamping

Major Parts and Reinforcements:-

The backdoor consists of the following basic components:

1.Backdoor Outer Panel (Upper)

2.Backdoor Outer Panel (Lower)

3.Backdoor Inner Panel

4.Hinge Reinforcements (LH & RH)

5.Gas-Stay Reinforcements (LH & RH)

6.Latch and Striker Reinforcement

Wiper motor Reinforcement

Testing:

• Bend Test, Dent Test, Torsion Test & Endurance Test

COMPONENET OF BACK DOOR:-

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 two parts

1.Outer Upper Panel

2. Outer Lower Panel

Outer Upper Panel:

The Outer Upper Panel Extracted from a styling surface. The thickness provided for the outer panel is 0.75 mm

Hemming is provided with the corner relief.

Outer Lower Panel:

The Outer Lower Panel Extracted from a styling surface. The thickness provided for the outer panel is 0.75 mm

Hemming is provided with the corner relief.

The styling surface needs to be checked and analyzed since it might have irregularities, Hence it must be fixed first.

Inner Panel:-

• The Inner Panel Extracted from a styling surface.
• Before starting to design the inner panel of the back door the tooling direction for Deep Drawing purpose should be created.
• After creating the tooling direction the design of the inner panel will begin where we will first develop an effective sealing flangeby checking all the boundaries and by following the shape of the inner panel design.By creating multiple flanges and by using surface modeling techniques the concept design of the inner panel was created.
• After the concept of the inner panel is developed, then the child components like a hinge, latch, gas-stay locations, and their reinforcements must be designed. Which completes the overall design of the tailgate.
• The embosses were created in ‘V-Shape or Y-Shape’ so that if the vehicle undergoes the crash then the force dissipates over it which reduces the damage transferred to the trunk space.
• The thickness provided for the outer panel is 0.75 mm

Hinge, Gas stay, Wiper Motor & Latch Striker Mounting Area:-

• The Blue circle denotes the hinge mounting area LH/RH which is created using the datum plane and Law Extension feature in NX. It was also designed in a way that the mounting area should have a flat surface for assembling the hinges.
• The Green circle denotes the gas stay mounting area which is created using the datum plane and Law Extension feature in NX. It was also designed in a way that the mounting area should have a flat surface for assembling the hinges.
• The yellow circle denotes the Wiper motor mounting area which is created using the datum plane and Law Extension feature in NX. It was also designed in a way that the mounting area should have a flat surface for assembling the hinges.
• The Latch and Striker mounting area were designed by creating a trajectory that follows the opening and closing of the back door with respect to the hinge axis.
• STRIKER POSITION: The position of the hinge should be perpendicular to the latch when the latch and striker meets. The circle is drawn from the center of the hinge axis

DESIGNING THE REINFORCEMENTS:-

All the reinforcements were created using the same method, first, the linked body was created separately for each with the help of extract geometry and then the required portion was trimmed out and then thickened. Thickness is 1~1.5 mm

Hinge Reinforcement:-

Hinges enable the opening and closing of the back door. One end of the 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. The hinge reinforcements are added to compensate for the weak region due to the 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 manpower 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. Reinforcement is provided at the Gas Stay mounting area to compensate for weakness and improve strength.

Wiper Motor Reinforcement:

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

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.

Back Door Assembly Views:-

Draft Analysis:-

Before we give the part for manufacturing we have to some analysis ourself to check all the constraints and to check if we have any negative draft on a part .

We have a tool called draft analysis in NX Cad to check the following.

When the color is green it means it has a positive draft it means area which are more than 7 degree is shown as green. If it is shown in yellow that means it has less then 7 degrees and if in blue or red then it means it has negative draft.

Conclusion:

The design of the Back door BIW was completed with the engineering standard and all the reinforcements.