Challenge

Back Door Project

SShivram Hulgunde30 Aug 2022

Designing a BIW Back Door of a Car

OBJECTIVE:

i) From the given styling surface, develop a back door using appropriate design methodologies.

ii) The objective of this project is to design a BIW Back Door of a car with an Inner Panel, Outer Panel, and Reinforcements for the Hinges, Gas stay, Wiper Motor, and Latch by following the engineering standards.

SOFTWARE USED:

Siemens NX CAD (Unigraphics)

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 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 METHODOLOGY:

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.

fig. Outer Upper Panel

Outer Lower 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.

fig. Outer Lower Panel

fig. Backdoor Outer Panel

DESIGN OF BACKDOOR INNER PANEL:

The Inner 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

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 modeling 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 factor and stiffness of the back door.

HINGE, GAS STAY & WIPER MOTOR EMBOSS:

The Orange circle denotes the hinge emboss 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 for assembling the hinges using it.

The violet circle denotes the gas stay emboss which was created using the surface of the connecting flange.

The yellow circle denotes 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.

The outer panel was designed as two separate parts named as outer panel upper and outer panel lower.
After designing the outer panel the Hemming was created by offsetting the surface with the help of face blend and swept surface.
The two separate outer panels will be joined using Blanking

CORNER RELIEF:

During the hemming process, when giving the Corner Relief helps to control sheet metal material behavior 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 mm

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 extract geometry and then the required portion was trimmed out and then thickened.

Hinge reinforcement

Hinges enable the opening and closing of the back door. One end of the hinge is fixed on the backdoor and the other end on the Roof, on both sides. Hinges can be placed outside or inside the backdoor.

The hinge reinforcements are added to compensate for the weak region due to the acting load over it.

Gas Stay Reinforcement:

Gas Stay is a device used for supporting the back door in its open position. Gas stay requires no manpower and is engaged into support position automatically as the back door opens. One end of the Gas Stay is fixed on the backdoor and the other end on the Body Side or on the Back door stationary area.

Embossing is provided at the Gas Stay mounting area to compensate for weakness and improve strength.

Wiper Motor Reinforcement:

Wiper motor reinforcement is created to mount the wiper motor assembly.

Latch and Striker Reinforcement:

The Latch & Striker forms the locking mechanism of the backdoor with the car. Due to regular opening, closing, and over slamming of the backdoor, there is stress developed in the Latch and Striker area. To compensate for the same, reinforcements are added in this area.