Design of backdoor

Objective:

To design car back door from given styling surface data under given design rules and regulations.

To Provide the necessary reinforcements and emboss definitions.

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 Molds.

Major Parts and Reinforcements:

The backdoor consists of the following basic components:

1. Backdoor Outer Panel
2. Backdoor Inner Panel
3. Hinge Reinforcements (LH & RH)
4. Gas-Stay Reinforcements (LH & RH)
5. Latch and Striker Reinforcement
6. Wiper motor Reinforcement

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

Back Door Inner Panel:

• 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.

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.

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.

The position of this reinforcement is determined by the midpoint of axis of the Hinges called the Hinge Axis point, which should be aligned with the Latch and Striker through the trajectory of the back door opening and closing.

Wiper Motor Reinforcement:

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

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.

Designing:

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.

Important features used while designing:

• Wave Geometry Linker – With this you can create, associative or linked copies of any entity of a part into other parts. It may be a surface, edge, curve, body, sketch etc. The changes made to the original entity will be reflected in the copy of that entity.
• Extract Body – It is used to create an associative body by extracting faces, entire body or region of faces.
• Bridge Curve – It helps to create a tangent blend curve between two objects. The objects may be edges or sketch curves.
• Sew – It combines sheet bodies together by sewing their common edges. There shouldn’t be any gaps larger than specified tolerance.
• Unsew – This command is used to separate the existing sheet body or solid body into multiple bodies.
• Projected Curve – It is used to project an existing curves on a selected plane or surface by selecting a direction for projection.
• Trim Body – It is used to trim one or more bodies using a face or plane. You can also specify the bodies to retain and the bodies to discard.
• Offset Surface – It allows you to offset one or more existing surfaces.
• Offset Curve in Face – This command will allow you to offset particular edges or curves on selected faces.
• Trim Sheet – It is used to trim off a portion of a sheet body using curves, faces, edges or planes.
• Through Curves – It will allow you to create a body Through multiple sections, where it’s shape changes to pass through each section.
• Law Extension – This command extends a curve or edge to create a sheet body at desired angle length by changing the rules under angle law and length law.
• Trim and Extend – It helps you to trim and extend intersecting surfaces and make corner at their intersection.
• Face Blend – It creates fillets between faces.
• Edge Blend – It creates fillets on edges.
• Extend Sheet – It will allow you to extend an existing surface to required distance.
• Emboss – Emboss command creates an embossing by modifying a body with faces created by projecting a curve/section along a direction. You can modify the emboss using options like endcap location and draft angle.
• Mirror Geometry – As name suggests, it allows you to mirror geometries about selected plane or surface.
• Thicken – It is used to convert a surface to solid body by providing thickness.
• Extrude – It helps you to create a feature from a sketch. You are also able to create thin feature using a sketch or curve under this command.

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.

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.

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.

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