Design of backdoor

INTRODUCTION:

The distinguishing feature of a hatchback is a rear door that opens upwards and is hinged at roof level (as opposed to the boot/trunk lid of a saloon/sedan, which is hinged below the rear window). Most hatchbacks use a two-box design body style, where the cargo area (trunk/boot) and passenger areas are a single volume. The rear seats can often be folded down to increase the available cargo area.Hatchbacks may have a removable rigid parcel shelf,or flexible roll-up tonneau cover to cover the cargo space behind the rear seats.

When describing the body style, the hatch is often counted as a door, therefore a hatchback with two passenger doors is called a three-door and a hatchback with four passenger doors is called a five-door.

A backdoor of a car also known as tailgate is a commodity which normally serves the purpose of covering the car from the rear end.A door is a hinged part which is used for entry and exit of the vehicles. Back doors are one of the type doors of the vehicle which are located next to the passenger seat which provides access to the luggage compartment. Hatchback or station wagons are sold as 3 door or 5 door models. In this case, the rear hatch is classified as a door because it enters the passenger compartment. The naming is mainly used in European countries. In most of the cars, these back doors are operated with the help of gas stay which in turn reduces the effort required to lift open the door. Some luxury cars have powered backdoors which in turn are driven by an electric motor. This kind of system is also called a powered trunk lid system. In case of safety, the back door designed should meet the safety requirement for the rear collision.

TYPES OF DOOR OPENING:

• Top mounted door
• Side mounted door
• Bottom Door

As we have got the styling or Class A surface of Top mounted door,we are going to design the Back Door Assembly.

DESIGN CONSIDERATION FOR BACKDOOR INNER PANEL:

1. Rear Visibility.
2. Support structures like hinges and gas stays.
3. Mounts for wiper motor, tail lamps, and other wiring loops.
4. Fit and clearances.
5. Boot space

6.Rear crash regulations and requirements.

7.Sealing and its functions.

8.Joining techniques like hemming, spot welding etc.

COMPONENTS OF BACKDOOR:

• Inner panel
• Outter panel upper and Lower
• Hinge reinforcement LH
• Hinge reinforcement RH
• Gas stay reinforcement LH
• Gas stay reinforcement RH
• Wiper motor reinforcement
• Latch reinforcement

OUTTER PANEL UPPER AND LOWER:

The outer panel is the styling surface or Class A surface of the backdoor.Glass for rear visibility is mounted on the outer panel upper.

The number plate is mounted on the outer panel lower.Rear lights are also mounted on the outer panel Lower. Spot welds and Hemming manufacturing process should be done only on the inner panel because the outer panel is the styling surface which should not have any scratches or welds .Because it affects the style of the car which leads to a bad impression on the customers.

HINGE REINFORCEMENT:

Hinges support the weight of the whole backdoor.Hence, the reinforcements must be provided there too.The emboss is designed in such a way that the hinges should operate freely.The hinge is connected to the rear roof of the car.

GAS STAY REINFORCEMENT:

Gas stay is used to lift the backdoor automatically.

There are two types of gas stay

1)semi-automated

2)Fully automated

In semi automated type the back door needs little force to lift after that it lifts the backdoor automatically.In fully automated , it has a power spindle which lifts the backdoor automatically.

WIPER MOTOR REINFORCEMENT:

Wiper is used to to wipeout the rain water which fall on the backdoor window.It is actuated by the motor which is mounted on the inner panel.Due to the vibration and heat created by the motor .the inner panel where the motor is mounted gets deform and the parts attached to the motor starts to vibrate which leads to poor NVH.So we have to provide the reinforcement where the wiper motor is placed.

LATCH REINFORCEMENT:

At bottom of the panel , reinforcement and emboss are given to accommodate the latch and striker assembly. The location of the latch reinforcement is obtained by drawing the trajectory from the hinges . Generally key operated or automatic remotely controllable mechanism is used to keep the door open or closed.The actuators , receivers and other electronic devices are mounted on the inner panel only.

Innert Panel

Outer Panel With Reinforcements

Outer Panel

All Reinforcements

Draft Analysis of Inner Panel

Draft Analysis of Outer Panel

HEMMING:

Hemming is the metalworking process in which a sheet metal edge is rolled into itself.The outer surface of the panel is rolled 2 or 3 times over the inner panel.In first roll the panel is bent slightly,and in the second roll the sheet metal is rolled even more and in the last roll it completely fits or covered the inner panel.There must be a 0.2mm gap between outer and inner panel in both upper and lower side.

Spot Welding:

Spot Welding is a form of resistance welding also known as Resistance Spot Welding (RSW). Spot Welding involves using heat produced by resistance to an electrical current to join materials together. The current heats the materials to a point where they become malleable. The use of strong pressure bonds them together.

Another form of resistance welding is Projection Welding. This process involves fusing a fastener’s embossed or coined projections to the metal base material to form a weld. As the materials never melt, they do not intermix. This means the resulting weld is more like a forging of the materials.

Spot welding is only suitable for a small selection of base materials. Low carbon steel is the most suitable material for spot welding. This is because it is more resistant to electricity and has a lower thermal conductivity than the copper electrodes used to create the required electrical current.

High carbon steels and aluminum alloys can form brittle welds that don’t last with the spot welding process. Pure aluminum can qualify for spot welding but requires higher current levels. This is because it has a lower resistance to electricity than low carbon steel.

Conclusion : with the help of given Class AA surface back dor inner panel and outer panel is designed by using NX CAD