Design of backdoor

BACK DOOR DESIGN CHALLENGE #8

Aim:- Design and development of a SUV's back door (tail gate) assembly using NX by provided styling surface to came up with a back door design, use appropriate design methodologies, and provide the necessary reinforcements and embosses.

Introduction:_ A back door or tail gate simply refers to the back of the car that can open and close. Its basically a covering of the rear of the vehicle. it provide access to a trunk/luggage area. back door is also swinging commodity. we first decide hinge axis points and latch and striker trajectory to find out the motion of the door.

Types of back door based on working positions.

1. Top mounted doors:- fig.

This type of back door is used in a station wagon, pickup truck and some of the sport utility vehicles. now days modern cars use top mounted and also gas stay supported. These top mounted tailgate provide greater rear visibility critaria as compared to side mounted or bar doors which have canter pilled in it.

2. Side mounted doors:- fig.

these types of door are the one which is used in the van , MPVs, SUVs and some sort of pickup trucks. these doors are more convenient for the goods handlers for long pipe and lengthy components where one door is kept open. these type of door also save accidental head impacts. 

3. bottom/ spilt type doors: fig.

 this type of door generally used in pickup trucks and some antique cars. these type of door are more convenient for support as table for the tour going people.

Type back door based on working mechanism.

1. Gas stays types:

gas stay type door an ideal and most commonly uesd tailgate mechanism from lower segment car to luxury car segment. The ideal commonents of tailgate consist of a hinge, door, gas stay and some rubber bendings for sealing of door which is shown as fig

2. Power lifter system:

by their name we can understand that this kind of system used in luxury cars.

Given data:- As we have given with only the styling class A surface. We are going to design with all design requirements and industrial standards.

fig.1 Class A surface of back door.

Different approach on materials for tailgate:-

The selection of material plays a vital role in determining the overall weight of the back door .so for that we commonly used steel or aluminium in sheet metal industries. The density of steel is higher than aluminium thus adding more weight to the door. most low cost vehicles use steel as it is cheaper compared to aluminium. another aspect to be noted is that, if casted aluminium parts are used instead of deep drawn steel parts there is no need of reinforcements and the overall weight of the vehicle is reduced by approximately 5-10 kg thus increasing the performance of the vehicle. also the draft angle for casted parts is 3+ deg while for deep drawn steel parts are around 7-10 degrees which helps in increasing the luggage or cabin are.

Aluminium vs steel 

Aluminum	Steel
1.parts are casted	1. Parts are stamped
2.Reinforcement can be neglected	2. reinforcements are necessary
3.Local thickness can be varied	3. Has only uniform thickness
4.Lighter in weight and less number of components	4. Heavier in weight and more number of components
5.costlly	5. comparatively cheaper

Different sheet metal processes are used in manufacturing of back door such as Deep Drawing, embossing and hemming

i am going to prepare the back door with steel.

Softwere used:- NX 12 CAD

Parameters :- parameter are going to followed in BiW design.

Opening angle = 7° to 30° (depending on region)

Fillet radius = 4 to 5 mm (with minimum hole requirement) 

Thickness = 0.75mm

reinforcement thickness = 1.7mm

flange length = 10 to 40mm (depending on the region)

Clearance distance = 0.2mm btw the sealing flange , 5 to 10mm for holes and 2mm for hemming sealant

Remove all sharp corners and corner relief also provided.

BACK DOOR ASSEMBLY: 

 The back door assembly of a SUV has the following components with image.

• Inner panel
• Outer panel upper
• outer panel lower 
• Hinge reinforcement RH
• Hinge reinforcement LH
• gas stay reinforcement RH 
• Gas stay reinforcement LH
• Wiper Motor reinforcement
• Latch and striker reinforcement

 Design consideration of a back door 

• Functional requirement of hinge and gas stay: Define the distance btw the hinge axis point to gas stay body side region.
• Rear visibility criteria is important factor
• Luggage area : consider factors such as the height ,width and thickness of door.
• Crash analysis
• Load tests 
• Rear crash regulation
• Gap and flushness requirements
• Opening and closing
• Weather resistance 
• Safety features
• Aesthetics
• European/ Regulatory standards
• etc.

these requirements provide a general overview but it is important to note that specific design consideration may vary depending on the vehicle manufacturer, market segment, and customer preferences.

 Note: As we have given with only the styling class A surface. so we have to developed whole components for from the scratch.

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 back door outer panel

in this design outer panel is divided into two parts

1. Outer upper panel: The outer upper panel extracted from the styling surface, the thickness provided for the outer panel is 0.75mm.and last hemming is provided with the corner relief.

2. Outer lower panel:-  The outer lower panel extracted from the styling surface, the thickness provided for the outer panel is 0.75mm. and hemming is provided with the corner relief.

Design of back door inner panel

after creating the tooling direction the design of inner panel will begin where we first develop the sealing flange with certain dimension. after that 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 other components like a hinge, latch, gas stay and wiper motor area also created.

the emboss were created in y or v shape, so that if the vehicle undergoes the crash analysis then the force dissipates over it which reduces the damage transferred to the trunk space. 

mastic region and 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. although hemming is sufficient for joining but we provide more adhesive material to join the inner panel to outer panel. for that we provide 2mm clearance to ooze out the sealant.

Hinge, Gas stay and Wiper Motor Embosses:- 

Gas Stay Embosses: When we have predefine hinge points then we can start the design accordingly

Hinge emboss: Hinge embosses can be define by other commodity positions such as roof end position.

Wiper motor emboss : wiper motor region can be improved according to design requirements 

Latch and striker emboos

latch and striker trajectory:-  the latch and striker trajectory refers to the path following by the latch mechanism of a door as it engages with the striker plate to securely close and latch the door. it is important to design the trajectory in away that allows the latch to smoothly and reliably engage with the striker plate. to illustrate this follow these steps to draw the hinge striker trajectory. 

1. Imagine a rectangular door frame with a door that swings open and closed on hinges,. visualize a straight horizontal line representing the hinge trajectory of the door. at the end of this line , draw a perpendicular line representing the striker plate, which is positioned perpendicular to the hinge trajectory.

2.Now, imagine a curved arc or circle starting from a point near the hinge trajectory and gradually curving away from it. This arc represents the latch trajectory( path ). it should be drawn in a way that it aligns with the striker plate when the door is fully closed. The end point of the arc should meet the perpendicular line representing the striker plate.

Factor such as latch geometry, striker plate design, ergonomics, tolerances and smooth engagement are considered to ensure easy operation.  (thanks to skill lync team for explaining this) 

Draft analysis result:- The kay function of draft analysis is to find out draft angle, moldability, part functionality, manufacturing feasibility and assembly jamming.

CONCLUSION : An automotive Sheetmetal (BiW) designing of a backdoor of compact SUV car is successfully designed with its components with its respectively reinforcements. my backdoor design can be improved in future it is made in such a way that anyone can easily modify it with proper industrial parameters.

Best Regards

Er. Uday Singh Baghel