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DESIGN OF CAR BACK DOOR Objective: From the given styling surface, develop a back door using appropriate design methodologies. The Design of Back Door of a car consists with an Inner Panel, Outer Panel(Upper & Lower) and Reinforcements for the Hinges, Gas stay, Wiper Motor, and Latch by following the engineering…
Satya Mohan Kurumalla
updated on 30 Sep 2022
DESIGN OF CAR BACK DOOR
Objective:
From the given styling surface, develop a back door using appropriate design methodologies.
Introduction:
The Back Door/Tail gate of a car is the rearmost part of the vehicle which gives access to the trunk space/luggage compartment of the vehicle.
It provides the aesthetic outer appearance to the vehicle as well as wind flow aerodynamic surface. Tailgate is a single stamped or split outer panel. It integrates with the inner reinforcement panel. To avoid air rushing noise as well metal rubbing noise, protected with the sealer application process. Outer edges hemmed by Robot hemming process with 3 pass hemming to ensure sealer fill rate uniformly as well clinch tightness rigidly. in such a way easy to open at the same time, it should not pass external environmental noise inside the passenger compartment and should not lead to any water leak. High closing effort leads to improper locking. Gas Stay is used to easily access opening and closing.
The rear door also supports the reinforcements and added weights of the Wiper Motor, Gas Stay, Tail Lamp, and Latch and Striker. It 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 Aluminium 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 Sheet of metal.
The Main Parts of the Back Door:
Tailgate:
Tailgate is a door at the back of a truck or car, that is hinged at the bottom so that it opens downwards.
Design Intent:
The intent of the project is to design a Body-in-White (BIW) Back Door of the vehicle considering the engineering standards and manufacturing requirements which satisfies the Deep Drawing Process.
STYLING SURFACE:
Back Door Outer Panels Upper & Lower
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:
Outer Upper Panel:
The Outer Upper Panel Extracted from a styling surface.
The panel is altered for the required design with the surface tools of NX CAD
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 is developed from styling surface, the thickness provided for the outer panel is: 0.75 mm. Hemming is provided with corner relief.
Back Door Inner Panel:
While designing the inner panel the consideration for its design are Thickness, the gap between the outer panel, and embossing.
The nominal thickness of the inner panel is 0.75 mm
The clearance gap between the inner and outer panel is 0.2mm
Embosses of the inner should follow the force dissipation criteria.
Hinge Reinforcement Emboss![]() |
Gas stay Reinforcement Emboss |
Latch & Striker Reinforcement Emboss |
Tooling Direction:
Before starting to design the inner panel of the back door the tooling direction for Deep Drawing purpose should be created.
Then the styling surface needs to be checked and analyzed since it might have irregularities, hence it must be fixed first.
Then the back door was designed using the top-down approach.
Hinge Reinforcement![]() |
Gast Stay Reinforcement![]() |
Wiper Motor Reinforcement |
Latch & Striker Reinforcement |
Design Considerations of Backdoor:
Striker Position:
The position of the hinge should be perpendicular to the latch when the latch and striker meets. For that, a circle is drawn from the centre of hinge axis to find the path of the striker. and positioned it perpendicular to the path
Rear visibility criteria: Federal motor vehicle safety standard (FMVSS) No. 111, “Rear Visibility,” currently requires that vehicles be equipped with rear-view mirrors to provide drivers with a view of objects that are to their side or to their side and rear.
Luggage volume
The Outer Panels (Upper & Lower) are joined with Inner panel using Mastic sealant, 0.2mm gap given between Inner panel & outer panels for sealant
Draft Analysis:
Draft Analysis is for checking the stamping feasibility in the tooling direction.
It is a method of checking the draft angle on various faces of a part with a particular direction.
It should be more than 7 deg for aluminum for hard metals, min draft angle is 10 deg.
The draft analysis for the inner panel is shown below.
Conclusion:
Understood Car Back door design concepts & standards and Created Back door design with Outer panels, Inner panel and reinforcements using styling surface.
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