Design of backdoor

Objective:

To Develop Back door of the Car by using given styling surface & provide necessary embosses and reinforcement to the back door

Software Used:

NX Cad

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:

1. Backdoor Outer Panel (Upper)

2. Backdoor Outer Panel (Lower)

3. Backdoor Inner Panel

4. Hinge Reinforcements (LH & RH)

5. Gas-Stay Reinforcements (LH & RH)

6. Latch and Striker Reinforcement

7. 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.

Different types of Sheetmetal operations are done in the Back Door

1.Deep Drawing:

The metal deep drawing process is an effective method of manufacturing of cups, cans and other similar deep drawing products. The deep drawings having two main categories.

First- stage drawing: The blank shape of metal is placed on the die and contact with the punch. When the metal specimen is flat piece of sheet metal

used in forming and finish the product. Initially the punch moves in downward direction. The outer rim of blank is subjected to pure radial drawing

(drawing toward in vertical axes) between die and blank metal. The metal become a bend and sliding over die and also stretched between die and

punch. The metal in vicinity of punch head and contact with it bend and slide over radii and stretch over punch head.Redrawing: The components

drawn from first stage again it is redrawn convert into more depth to form a cup shape in the die and punch. The second stage of drawing is called as redrawing.

2.Embossing:

Embossing is a metal forming process for producing raised or sunken designs or relief in sheet materials by means of matched male and female roller

dies, theoretically with no change in metal thickness or by-passing sheet or a strip of metal between rolls of the desired pattern. Metal sheet is drawn

through the male and female roller dies producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet.

Materials commonly used in the metal embossing process include:

Aluminum alloys
Steel alloys
Zinc
Copper
Galvanized steel
Brass
Cold rolled steel

3.Hemming:

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. Normally

hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges.

In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join two

sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, doors, trunk lids and fenders.

There are various types of hemming operations:

Conventional die hemming: In conventional die hemming, the flange is folded over the entire length with a hemming tool.
Roll hemming: In roll hemming, the hemming roller is guided by an industrial robot to form the flange.


Open Hem: A Hem has a full round feature and a return flange. In open hem bend angle is equal to 180 degrees.

Tear drop Hem: In tear drop hem the bend angle is greater than 180 degrees.

Closed Hem: Hems without any inside radius are called as closed hem. Closed hems are not recommended if the hem geometry is to be painted or if the material used is SST or Aluminium.



4.Blanking:

Blanking is a cutting operation of a flat metal sheet and the article punched out is known as blank. Blank is the required product of the operation and the metal left behind is considered as a waste.

5.Punching:

It is similar to blanking only the main difference is that, the hole is the required product and the material punched out from the hole is considered as a waste.


inputs for designing of backdoor:

Outer Panel - 0.75 mm
Inner Panel - 0.75 mm
Reinforcements - 1.5 mm

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

1. Outer Upper Panel

2. 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 0.75 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.

1. HINGE REINFORCEMENT

2. GAS STAY REINFORCEMENT

3. WIPER MOTOR REINFORCEMENT

4. 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.

In this we can find some red portion at mastic sealant area but it is not manufactured simultaneously it's done separately then added to there

Views of the designed Back Door:

Front view:

Side view:

Top view:

Bottom view:

Isometric View:

CONCLUSION:

Thus the Body In White Back Door of a car was designed following the engineering standards and also the deep drawing requirements were satisfied.