Design of backdoor

BACK DOOR / TAIL GATE

Aim:

To design a Backdoor of the car on sheet metal using he appropriate design and provided skin data by considering design rules.

Objective: To design the backdoor with design methodologies and and provide the emboses,reinforcements in the inner panel and side relief in outer panel to increase the strength.

Theory:

Backdoor:

The Back door of a car is a component which hinges at the back of the car to cover the boot space or luggage area, But there are more functions that come with it which has to be considered while making a design of the same like rear visibility criteria and boot space.

This part is usually designed keeping the master section of the rear roof rail because of the sealant flange and also various other considerations, as it is also in contact with the side body of the car.

It has back lights/ Tail lamps and Braking lights which is termed as "Third brake light" mounts on it, rear windshield fixes between inner and outer panel, in some back door spare wheel can be mounted on it, sometimes car registration number plate mounts on it and it gives a complete closed design to the car.

Backdoor images:

Design Considerations:

• Rear Visibility for safety and functionality
• Support Structures like Hinge and Gasstay/ Power lifter
• Rear Crash regulations
• Boot Space
• Mounts for wiper motor and lights
• Strength criteria
• Draft Analysis

BACK DOOR ASSEMBLY:

The back door assembly of a hatchback or SUVs has the following components.

• Inner panel
• Outer panel
• Hinge reinforcement
• Gas stay reinforcement
• Wiper motor reinforcement
• Latch/striker reinforcemment

Gas stays

Gas stay types backdoor/liftgate/tailgate is an ideal and most commonly used tailgate mechanism from lower segment car to luxury car segment. The ideal components of tailgate consist of a hinge, door, gas stay and some rubber beadings for sealing of door

Procedure:

Firstly we have to check if there are any surface irregularities in the skin data, If irregularies are there, then repair if by using a bridge curve curve and Through curve mesh and sew it.

Then we create a sealing flange. Generally with the help of master sketch, we will design the panel with appropriate dimensions. But here there is no master sketch,we designed by assumption.

Here the sealing flange is created by maintaining a gap between inner panel to the sealing flange.

Tooling Direction-

The back door is going to be manufactured by deep drawing process. In Deep Drawing process have a tool which is core and Die. The core part follows the single Straight path the inclination angle of the core is known as a tooling direction. The tooling direction/axis is created so, that the Manufacturing team take the reference of this tooling axis and manufacture the part accordingly.

Inner Panel:

The inner door panel is a component which is used for strengthening the door assembly and it is one of the most important components on which all accessories are mounted like hinges, glass guide channel, moulded trim, latch etc. The possible method is the integration method. In the integration method, the part is stamped out of a single blank. This reduces the number of tools needed; the assembly cost and eliminates any fit ability problem.

Mastic region:

• The mastic points are defined on the backdoor inner panel where the backdoorcan easily deform. They help the backdoor outer panel to come back to its original shape after it gets deformed.Mastic sealants are elastic compound that behaves like the rubber.
• The gap between the inner panel and the outer panel over the embosses is filled with mastic sealents at certained specified places, this helps to reducing vibrations and overall NVH ( Noise, Vibration, Harshness).
• Then, the sheet will bend with the help of another die to make the flange in "L" shape.
• Thus, the flange will have somehow same design and the length will completely depend on the Cut-out, if we need more length of flange, then we need to cut more sheet.

Emboses:

With the distinctive cross-section, embosses are created. The embosses are used to increase the strength of the backdoor. While designing we should keep in mind that it should not be over strength. So we prefer to design big embosses rather than small embosses. These embosses are used to disipate the forces sideways.

Hinge Emboses

The backdoor is a swinging commodity, which swings with the help of hinges. This can be done by tentatively positioning the hinges and on the hinge axis, we take a center point. again we take another center point(approx) on the latch hole. Taking these two points as a reference we draw a circle. This circle is the striker trajectory and it has to be perpendicular. This can be achieved by moving the hinge axis back and forth or by rotating the latch area.

Gas stays

Gas stay types backdoor/liftgate/tailgate is an ideal and most commonly used tailgate mechanism ,similarly like as hinge it done here

Wiper Embose:

Latch and Striker Trajectory:

Outer Panel:

The outer panel of the back door is similar to other BIW components where it is the aesthetic part of a vehicle. The coating provided is of multi-stage which has the property of scratch resistance, rust prevention and smooth and attractive finishes. The outer panel also has the provisions for the tail lamp, rear fog lamp and also has the provision for licence plate mountings. Most of the hatchback cars have the provision for wiper motor.

outer panel upper

outer panel lower

Heming

Hems are folds to the edge of a part to create a rounded, safe edge. Hems may be open, flat, or tear-dropped, and tolerances depend on the hem’s radius, material thickness, and features near the hem. The process of creating hems is called hemming.

Hems are created by bending a flange of your part back on itself. This increases the strength of the hemmed edge and also gets id of any sharp edges.

Side Reliefs:

• Here we added a relief at the curvatures. Because these reliefs will avoid sharpness and it is easy to manufactural.

REINFORCEMENTS

HINGE REINFORCEMENT

GAS STAY

WIPER MOTOR

LATCH AND STRIKER

DRAFT ANALYSIS

ITS CLEARS 7 DEGREE OF DRAFT

FINAL ASSEMBLY