Design of backdoor
INTRODUCTION:
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 Backdoor/tailgate 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 carbon Fiber, 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 of Moulds.
Major Parts and Reinforcements:
The backdoor consists of the following basic components:
- Backdoor Outer Panel (Upper)
- Backdoor Outer Panel (Lower)
- Backdoor Inner Panel
- Hinge Reinforcements (LH & RH)
- Gas-Stay Reinforcements (LH & RH)
- Latch and Striker Reinforcement
- Wiper motor Reinforcement
TAILGATE:
Tailgate is a door at the back of a truck or car, that is hinged at the bottom so that it open downwards.
DESIGN INTENT
The intent of the project is to design a Body In White Back Door of the vehicle considering the engineering standards and manufacturing requirements which satisfies the Deep Drawing Process.
DESIGN CONSIDERATION OF A BACKDOOR:
- Functional Requirement of Hinge and gas stay
- Rear visibility criteria
- Luggage volume
- Crash Analysis
- Bend Test, Dent Test, Torsion Test & Endurance Test
- Rear Crash Regulation
- Gap and flushness Requirements
DESIGN OF BACKDOOR OUTER PANEL:
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
- Outer Lower Panel
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:
Given The outer lower panel styling surface taken as input and do corrections if any defects. Offset the given styling surface with 2.65(0.75+0.75+0.75+0.2+0.2). To make the flange of hemming offset the edge of the offset surface using offset in surface and trim the unwanted surface. After trimming the bottom offset surface, the styling surface and bottom flange connected using swept command. The final surface is provided with thickness of 0.75mm.
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 analysed since it might have irregularities, hence it must be fixed first.
Then the back door was designed using the top-down approach.
DESIGN OF BACKDOOR INNER PANEL:
The Inner Panel Extracted from a styling surface. The panel is altered for the required design with Hing location, Wiper motor location, gas stay location and Latch and stricker positions embosses created and to maintain the strength and also to reduce the weight of the panel some cutouts are provided. Some supports also provided between the outer and inner panels at edges of cutouts with 4 to 5mm gap, this gap is created to attach the inner panel to the outer panel with mastics. The thickness provided for the panel is 0.75 mm
After creating the tooling direction, the design of the inner panel will begin where we will first develop an effective sealing flange by checking all the boundaries and by following the shape of the inner panel design. By creating multiple flanges and by using surface modelling techniques the concept design of the inner panel was created.
After the concept of the inner panel is developed, then the child components like a hinge, latch, gas-stay locations, and their reinforcements must be designed. Which completes the overall design of the tailgate.
The embosses were created in ‘V-Shape or Y-Shape’ so that if the vehicle undergoes the crash, then the force dissipates over it which reduces the damage transferred to the trunk space.
MASTIC SEALANT:
The mastic sealant is used to fix the inner panel with the outer panel which increases the NVH( Noise, Vibration, Harshness) factor and stiffness of the back door.
HINGE, GAS STAY & WIPER MOTOR EMBOSS:
The hinge embosses which was created using the datum plane and emboss feature in NX. It was also designed in a way that the emboss should have a flat surface (Local radius of surface should show infinity) for assembling the hinges using it.
The gas stay embosses which was created using the surface of the connecting flange.
The Wiper motor emboss which was created using the surface of the connecting flange.
LATCH AND STRIKER EMBOSS:
The Latch and Striker emboss were designed by creating a trajectory that follows the opening and closing of the back door with respect to the hinge axis.
STRIKER POSITION:
The position of the hinge should be perpendicular to the latch when the latch and striker meets. The circle is drawn from the center of the hinge axis to find the path of the striker and positioned perpendicular to the path.
HEMMING:
Hemming and seaming are two similar metalworking processes in which a sheet metal edge is rolled over onto itself. Hemming is the process in which the edge is rolled flush to itself.
CORNER RELIEF:
During the hemming process, when giving the Corner Relief helps to control sheet metal material behaviour and to prevent unwanted deformation during unbend operations and also helps to reduce the number of passes in hemming.
DESIGNING THE REINFORCEMENTS:
The thickness provided for all reinforcements is 1.5mm
- HINGE REINFORCEMENT
- GAS STAY REINFORCEMENT
- WIPER MOTOR REINFORCEMENT
- LATCH REINFORCEMENT
All the reinforcements were created using the same method, first, the linked body was created separately for each with the help of wave geometry linker, extract geometry and then the required portion was trimmed out and then thickened.
The reinforcements are provided to strengthen the assembly and improve load carrying capacity.
DRAFT ANALYSIS:
- The draft analysis will be performed for the tooling direction created at first and checked that the model is suitable for manufacturing.
- Then to get a complete green portion the necessary changes to the draft angle of the embosses were carried out by optimizing the model.
- The Draft Analysis command enables us to detect that the part drafted will be easily removed or not.
- This type of analysis is performed based on colour ranges identifying zones on the analysed element where the deviation from the draft direction at any point, corresponds to specified values.
From above figure we can observe the back door inner part is completely clearing for the draft angle 7degrees.
The assembly of Backdoor:
The backdoor inner panel with reinforcements:
Back Side view:
Front View:
Isometric View:
Conclusion:
The backdoor of the car (tailgate) is developed from the provided styling surface and followed the engineering standards also provided draft angle.