Design of backdoor
Design of backdoor
It is a hinged board or door at the rear of the vehicle that can be moved up or down during loading and unloading.
Back Door is also referred as 'Hatch' or 'Tailgate' or 'Trunk-lid' or 'Boot-door'. Its the rearmost part of the vehicle which gives access to the trunk and has mounts for tail lamps, hinges, wiper motor, gas stayetc
Functions of the Backdoor:
It protects the occupants and luggage from getting damaged.
It houses assembly of tail lamps, wiper motor and other components.
It serves as entry and exit point for luggage/passengers.
It houses windshield glass which helps in rear visibility.
Parking sensors, rear view camera are mounted on it.
Inner Panel
The inner panel is one of the most important components of the backdoor assembly. It provides strength and helps in the dissipation of forces outside the part with the help of embosses made on it. It helps in the mounting of accessories like hinges, wiper motor, gas stay, latch & striker, etc. The inner panel is produced by either casting or through the Deep drawing process Mostly aluminum part is cast, and steel inner panels are manufactured by the deep drawing process. If deep drawn, there must be a tooling direction through which that panel must be deep drawn. Embosses It is provided to give extra strength to sheet metal panels and to help dissipate forces/energy in a specific direction. Here embosses (Y/V emboss) are designed in such a way as to direct them toward the outer end of the backdoor as shown in the image. Sealing Flange It is that section of the inner panel which enables the backdoor to sit over the rear body side of the car. Its design is important as it decides how a backdoor is mounted on the rear body side of the car and also restricts any external matter to enter the vehicle Mastic Sealants As we know the outer panel gives the aesthetic look to the vehicle, so we can’t use bolting or spot welding or any other joining technique which damages the aesthetic looks of the panel. Thus mastic sealants are used for joining the Inner panel elements with the outer panel. A maximum gap of 5mm is to be maintained in between parts where mastics are to be applied.
Latch and Striker reinforcement :
In the bottom part of the panel emboss is created for the placement of the latch and striker assembly. There is over-slamming and abusing while opening and closing the door, thus arising the need for reinforcement to be placed.
Positioning of Latch & striker/ Latch Trajectory:
A backdoor is a swinging part that rotates about the hinge axis. The position and orientation of the latch striker are important for the proper opening and closing of the backdoor. The positioning is done by sketching a circle with the center as the axis of the hinge which passes through the striker at the appropriate position concerning the inner panel.
Design considerations
1)Rear visibility
2)Boot space & accessibility
3)Sealing Flange
4)Support structures like hinges and gas stays.
5)Mounts for wiper motor, tail lamps, and other wiring loops
6)Rear crash regulations
7)Joining techniques such as hemming, spot welding, etc.
8)Gap and flush requirements
Assembly:
In this assembly, the top-down approach was followed wherein from the given styling surface the inner panel was created using various tools/commands in NX. After that others, parts were modeled as per the requirements one by one.
Analysis: Draft analysis
Every part which is manufactured from a press tool or other forming tools requires some positive draft on the faces which are parallel to the tooling direction. If we don’t give a draft (Zero Draft) or give negative drafts on these faces it will stick to the mold surface and when the mold is in motion it will destroy the surface thus reducing its surface finish. Thus Draft Analysis command enables us to detect if the part we have drafted can be easily ejected or not. It also gives insights into the critical zones, so that appropriate changes in the design can be made if needed.
Materials Selection:
The selection of material plays a major role in determining the overall weight of the back door. The common materials used are Steel & Aluminum. The density of Steel is higher than Aluminum thus adding more weight to the door. The material used in the manufacturing of the backdoor depends upon the budget of the car, most low cost vehicles use steel as it is cheaper compared to Aluminium. Another aspect to be noted is that, if casted Aluminum parts are used instead of deep drawn steel parts there is no need of reinforcements and the overall weight of the car is reduced by approximately 5-10kg thus increasing the performance of the vehicle. Also the draft angle for casted parts is around 3 degrees while for deep drawn parts is around 7-10 degrees which helps in increasing the luggage/ cabin space.