Design of backdoor

OBJECTIVE:

To develop the car backdoor by using given surface method by automotive sheet metal design.

A backdoor is located at the rear end of the car which gives access for the boot space to store luggage.,spare whhel etc.These doors can be operated mannualy or eclectric powered.In most of the luxuary car is electric powered.

Back Door also called as 'Hatch', or 'Tailgate', 'Trunk-lid', 'Boot-door' is basically the 5 door in a 4-door car. It's the rearmost part of the vehicle which gives access to the trunk and has mounts for wiper motor, tail lamps, hinges for supporting its weight in opened position, gas stays which help with its opening and keeping it open, radars and cameras etc.

A backdoor is usually made up of 1 inner panel and 2 or 3 outer panels joined together by hemming and spot welding wherever necessary.

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.

TYPES OF DOOR OPENING:

• Top mounted door
• Side mounted door
• Bottom Door

COMPONENTS OF BACKDOOR:

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

INNER PANEL:

Car backdoor inner panel is made of either steel or alumminium.Most of the luxuary car's inner panel are made of aluminium because of is properties.But the cost of aluminium is high.

Cost of aluminium is more as compared to steel .TO easiy understand , the cost of aluminium for inner panel is higher than the cost of  all parts of backdoor together.

                                             steel                                                               aluminium

Parts                                      parts are stamped                                           parts are casted

Reinforcement                        Necessary                                                       Can be neglected

Thickness                               Constant                                                         Can be varied

Components                           More                                                                lesser no

Weignt                                   More                                                                lighter

Cost                                      less in cost                                                       More as compared to steel

Bechmark between companies who are using steel and aluminum inner panel

Wiper motor , latch reinforcements,hinge reinforcements and gas stay reinforcements are mounted on the inner panel of the backdoor only.

The embosses in the inner panel helps stiffening the inner panel and act as a local reinforcement.Another purpose of giving emboss is to distribute impact forces towards hinges.

Image of inner panel:

OUTTER PANEL UPPER AND LOWER:

Outter panel is the styling surface of the backdoor.Glass for rear visibility is mounted on the outter panel upper.Rear lights are also  mounted on the outter panel upper.

Number plate is mounted on the outter panel lower.Spot welds and other manufacturing process should done only on the inner panel because the outter panel is the styling surface which should not have any scratches or welds .Because it affects the style of the car which leads to 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 one is semi-automated and another one is fully automated.In semi automated type the back boor needs little force to lift after that it lift the backdoor automatically.In fully automated , it has  power spindle which lift the backdoor automatically.

WIPER MOTOR REINFORCEMENT:

Wiper is used to to wipeout the rain water falls 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.

HEMMING:

Hemming is the metelworking process in which a sheet metal edge is rolled into itself.The outter surface of the panel is rolled  2 or 3 times over the inner panel.In first roll the panel is bent slinghtly,and in the second roll the shhet matel 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 outter and inner pannel 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.

DRAFT ANALYSIS:Draft analysis of inner panel is carried out through the tooling direction only.only the green areas are acceptable and i wrost cass yellow regions are acceptable and but the blue and red regions are never accepted .

Backdoor assembly images: