Design of backdoor
Tail Gate (Back Door)?
The Tailgate or the Back door of a car is the Door at the rear end of the car, which provides access to the luggage compartment. In most of 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 a powered backdoor that is driven by an electric motor. This kind of system is also called a powered trunk lid system. The Back door is also responsible for dissipating the force created while rear collisions, away from coming inside the car.
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 back door is usually made of an inner panel and 2 or 3 separate inner panels joined together by hemming or spot welding wherever necessary.
Types of opening method:
Upward opening
Sideway opening
Downward opening
Materials Used:
Aluminum -Made with Casting Process - Non uniform Thickness can be achieved and no reinforcements required separately and less in weight.
Steel - made with Deep Drawing, stamping or Lancing, uniform thickness so additional reinforcements is necessary.
Design Considerations:
Material selection
Stiffness strength and weight of the part
Rear Visibility Criteria
Boot Spaces and luggage associability
Fits and Clearance
Hinge and Gas stay placement
Mounts for Wiper motor, lamps and number plate placement
Crash Requirements
Sealing criteria to resist vibrations
Drawability (Draft Analysis)
Designing of Back Door components:
Outer Panel surfaces (Upper / Lower)
Inner Panel surface
Hinge Reinforcement (LH / RH)
Gas Stay Reinforcement (LH / RH)
Wiper motor reinforcement
Latch Reinforcement
Thickness Information:
Thickness of outer and inner panel is 0.75mm
Reinforcements is 1.5 mm
DESIGN METHODOLOGY:
Back Door outer panel:
As we have the styling surface as the reference, we need not to work more on the outer panel only need to create the hem flanges after the creation of the inner panel. Here the outer panel of the tailgate consists of two parts which are the Outer panel upper and the Outer panel lower. These two components are joined using the Laser Brazing method
From the Class A surface will create the outer panel with the considerations for hemming process to join the inner and outer panel.
Back Door inner panel design methodology
The inner panel is the part that gives enough strength to the outer panel as well as is the part where the viper, latch, hinge, and gas stays are mounted along with the Reinforcements.
The first thing I have created is the sealing flange of the Tailgate
Sealing Flange
The sealing flange is the part of the tailgate where it touches and presses the rubber gasket on the Body's side outer in order to avoid the entering of water into the luggage area.
The sealing flange is created by offsetting the outer panel to the required distance and also by creating some studio surfaces guided by some bridge curves
Embosses For Hinge. viper mount and Gas stays
I have made one emboss for the Hinge in the appropriate position and another one emboss for the Gas stay mount. Also, I have made a flat surface on the embosses as the hinge and the gas stay need to be mounted on it.
Flanges for the mastic
Apart from the hemming, the outer panel of the tailgate must be supported using some flanges from the inner panel and some mastics on it. So I have created some cutouts and created some flanges from the edge of the cutouts for creating the mastic points as shown in the figure.
The embossed are created in such a way that when there is an impact on the tailgate the force is distributed along the sides tailgate flowing towards the hinge to minimize the impact.
Latch positioning
Latch positioning is one of the critical operations in the designing of the inner panel. For positioning the latch, first, a line is drawn from the axis of one hinge to the axis of the other hinge. After that, a trajectory circle is drawn from the center of that line as it crosses the surface where the latch is placed. And then make the latch axis tangent to the trajectory circle.
Here as i don't have the Hinges as well as the Latch, I am drawing a line from the emboss of the hinge to the other from that line I have drawn a circle and an emboss is created for the Latch where the circle crosses the inner panel.
Draft Analysis
I have created a line for the tooling direction and after draft analysis, There are some embosses with the negative draft. But in this case, it's negligible as all the embossing cannot be deep drawn in a single stretch.
Back Door inner panel design views
Reinforcements
Reinforcements are used in the areas of sheet metal where other components are attached. The reinforcements compensate Reduced strength of the sheet metal while another component is added to it.
Complete Tail Gate design views
FILE LINK:
https://drive.google.com/drive/folders/16WqyrfYm4uRHSiTykcQ7gcMHB4S9XaZM?usp=drive_link
https://drive.google.com/drive/folders/16WqyrfYm4uRHSiTykcQ7gcMHB4S9XaZM?usp=drive_link