Design of backdoor

BACK-DOOR DESIGN

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.

Software Used:
NX CAD

Backdoor Introduction:

An automobile back door or Tailgate is the panel that covers the boot (or trunk) of an automobile. It enables access to the main luggage compartment. A hinge allows the boot lid to be raised, while devices such as springs or gas cylinders hold it up in the open position The Backdoor is an assembly of many parts such as inner panel, outer panel upper, outer panel lower and Reinforcement. Inner panel is attached to the outer panel using mastic sealant.

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

Total no. of parts in Backdoor are:

• Back door outer panel (upper)
• Back door outer panel (lower)
• Back door inner panel
• Hinge reinforcements
• Gas stay reinforcements
• Latch and striker reinforcements
• Wiper motor reinforcements

BACK DOOR 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.

INNER PANEL DESIGN:

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.

OUTER PANEL DESIGN:

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.
• 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
• 

WIPER MOTOR REINFORCEMENT:

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

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.

LATCH AND STRIKER REINFORCEMENT:

• 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.
• 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 AND RELIEF:

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

RELIEF:

Relief is done to decrease the stress concentration along the corners and also to decrease the clumping of metal along the corners, this is done by trimming the corner by a minimum radius for the rollers to pass along smoothly.

MASTIC SEALANTS:

DRAFT ANALYSIS:

Draft analysis is done to show that the Part can be easily drawn out from the mould.

• 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.

ASSEMBLY IMAGES :

CONCLUSION:

Thus the back door was designed from the given styling surface and Draft analysis is also done on the inner panel to check the manufacturing conditions. In this challenge i learned to design the Inner panel, the Outer panel, Wiper Motor reinforcement, Hinge reinforcement, Gas Gtay reinforcements, Latch and Striker reinforcement and its position.