Challenge

Design of backdoor

AAkshay Wagh15 Dec 2022

Aim: Design of backdoor

Objective: Use the provided styling surface to come up with a back door design, use appropriate design methodologies, and provide the necessary reinforcements and embosses

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.

iii) The Inner Panel must be subjected to Draft Analysis for verifying whether it satisfies the Deep Drawing requirements for the tooling direction created in the design.

Introduction :

Design of back door is also called as the Tail gate. A car back door which is consist of Inner panel, Outer panel. Basically the car parts are made of Steel or Aluminium based on the budget of the car.

Using Aluminium improve the Strength where we can avoid the reinforcements. Aluminium parts are casted and we can very the thickness of the part, because of this avoid or reduce the number of parts as compared to Steel. Only drawback is the cost of aluminium, which is high cast As compared to steel.

Steel Parts are stamped, we cannot vary the thickness of the part because of more number of parts are added. which could increase the weight of the part.

So now a days most of the car manufacturers are trying to use Aluminium instead of Steel and they reduce the number of parts and weight of the car drastically.

Types of doors based on working position,

Top Mounted Door
Side mounted Door
Bottom Door

Back door is operated by two types of comodities

1.electrically operated

2.gas stay powered

the main purpose of these mechanisims is to open the back door without heavy efforts, because the backdoor have different parts and the weight of the back door is high, so we are not able to open the back door manually, so we introduced these two types comodities. and these also decides the premium of the car, mostly the electrically operated used in premium cars.

Back Door Assembly:

Inner panel
outer panel
hinge and its reinforcement
wiper motor reinforcement
latch & stricker and its reinforcement
gas stay reinforcement

the major problem in back door is material selection. mostly in past days steel is used, but it makes a very problems the steel parts have heavy weight,so it reduces the fuel economy, insted of steel presently in high end cars aluminium is used, the main objective of aluminium it have less desnser material and its sutaible for complex shapes, and it also gives the thcikness locally because it it done cating, in case of steel we used deep drawing operation. there are some of the advatanges and disadvantages are there

Backdoor Assy

Backdoor Outer Panel

Backdoor Inner Panel

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

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:

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 Upper & Lower Panel:

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.

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 0.5 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.

Force Distribution:

When the car hit at rear end, the force which acted should be react outside. The Y/V emboss which is helps to move the force to the outer end

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 gas stay emboss which was created using the surface of the connecting flange.

The Wiper motor emboss which was created using the surface of the connecting flange.

HINGE EMBOSS:

GAS STAY EMBOSS:

WIPER MOTOR EMBOSS:

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

DESIGNING THE REINFORCEMENTS:

The thickness provided for all reinforcements is 1.5 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

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 color ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.