Design of backdoor

Design of Backdoor

Objective: To design the Back door of the car using the given Class ‘A’ surface.

Introduction:-

It is a hinged board or door at the rear of the vehicle that can be moved up or down during loading and unloading.

Back Door is also referred to as 'Hatch' or 'Tailgate' or 'Trunk-lid' or 'Boot-door'. It's the rearmost part of the vehicle which gives access to the trunk and has mounts for tail lamps, hinges, wiper motor, gas stay etc.

Functions of the Backdoor:

• It protects the occupants and luggage from getting damaged.
• It houses the assembly of tail lamps, wiper motors and other components.
• It serves as an entry and exit point for luggage/passengers.
• It houses windshield glass which helps in rear visibility.
• Parking sensors and rearview cameras are mounted on them.

MANUFACTURING PROCESS

Conventional tailgate assemblies are made from stamped metal panels welded together to form a tailgate. Latches are added on either side of the tailgate to engage a striker on the pickup sides. A handle operates the latches to open and close the tailgate assembly. Steel tailgate assemblies provide a durable and secure closure for the pickup bed.

Another disadvantage of steel tailgate assemblies is the cost of the tooling required and the equipment required to stamp metal tailgate components. Metal tailgate components are generally produced in a large stamping press. The stamping presses generally require finely machined tools made from hardened steel. The cost of tooling a metal tailgate is much more expensive.

3.1 MATERIAL FOR BODY PANELS

Materials for car body panels require certain specific characteristics to meet the industry’s challenges: rationalisation of specifications for leaner inventory, improved formability for reduced rejection rate and better quality. Higher Strength Low Alloy (HSLA) steels of thinner gauges are getting preference for weight reduction and the resulting better fuel economy. Other quality characteristics under demand are higher yield stress (strength), toughness, fatigue strength, improved dent resistance as well as corrosion resistance in materials used for body panels for improved durability and reliability.

To obtain the consistent quality of autobody skin panels without failures during stamping, the formability/ductility specifications of strip steels are the basic requirements. Most of the steels used in automotive applications are aluminium-killed steels of about 0.7 to 0.9 mm thickness.

Intensive research and development are going on for alternate materials, manufacturing processes and stamping tools for sheet-metal components with the main objectives of cutting down the weight and unit cost of the vehicle. Simultaneously, the steel content of the car is falling with the use of aluminium and new materials, such as plastics. Aluminium may provide the most sought-after solution to reduce the weight of vehicles. A reduction of 30% in weight is achievable if the same strength, stiffness, and stability of the component are to be realised by substituting steel with aluminium. The possibility of a significant reduction in die cost will be another advantage of aluminium. However, problems related to strength, serviceability,
manufacturability, and above all cost, require effective solutions before the acceptance of aluminium as a substitute for steel for body panels. Plastics for bumpers,

3.2 STAMPING PROCESS

The stamping processes to be used for a panel depend on its design. However, normally the processes used extensively are blanking, drawing, piercing, forming, notching, trimming, hemming, etc. Blanking prepares the initial approximate form of the part in a flat sheet. Drawing is generally the first operation to attain depth-related form. Piercing, notching, and hemming, are product design-related operations. Trimming generally removes the extra material on the periphery of the panel provided for blank holding during draw operation. Decision on the trim line is very important and becomes deciding factor to obtain a good draw.

1. Blanking

When required, blanking is the first step of the stamping process. Blanking is the process of cutting larger sheets or coils of metal into smaller, more manageable pieces. Blanking is usually performed when a stamped metal piece will be drawn or formed.

2. Piercing

If a part requires slots, holes, or other cutouts, piercing can be employed. Piercing, which can be performed simultaneously with blanking, punches the requisite shapes out of the metal sheet.

3. Drawing

Drawing is the actual stamping in the metal stamping process. A punch forces a section of metal through a die, providing the primary shape of the part. When the depth of the part is less than the primary opening, it is considered shallow drawing; parts with a depth greater than the opening are deeply drawn.

4. Bending

Bending is a fairly self-explanatory process. The part-in-progress is placed on a specially designed die and a ram pushes against the metal, providing the required bend. Bending is performed after drawing, as attempting to punch an already bent piece of metal causes the entire part to deform.

5. Hemming

Hemming is a technology used by the automotive industry to join inner and outer closure panels together (hoods, doors, tailgates, etc.). It is the process of bending/folding the flange of the outer panel over the inner one. The accuracy of the operation affects significantly the appearance of the car’s outer surfaces and is therefore a critical factor in the final quality of a finished vehicle.

Roller hemming:-The robotized hemming systems use a standard industrial robot integrated with a roller hemming head, offering a very flexible solution. This roller hemming head consists of a body, some guides and several rolls that are designed according to the geometry of the part in each case.

BACK DOOR DESIGN

The design consideration of the back door is,

• Visibility Criteria
• Force Dissipation
• Latch and Stricker Positions
• Hinge Position
• Gas Stay Position
• Hemming and Relief Areas

PARTS OF BACKDOOR

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

1. BACK DOOR OUTER PANEL:-

In this design, the back door is created as two different parts back door outer panel upper and lower. This outer panel is designed based on visibility criteria and proper reliefs provided at the corner for hemming operation. The thickness of the outer panel is 0.75 mm.

2. BACK DOOR INNER PANEL

The back door outer panel is designed based on a hinge, gas stay, wiper motor position and reinforcement as well as visibility criteria. A suitable tooling direction is created for a trouble-free manufacturing process. In this design stamping operations are created based on this tooling direction. Embosses is provided in this design for force dissipation. In this design appropriate clearance is given in mastic areas. The inner panel thickness is 0.75 mm.

EMBOSSES:-

It is provided to give extra strength to sheet metal panels and to help dissipate forces/energy towards a specific direction. Here embosses (Y/V emboss) are designed in such a way as to direct them towards the outer end of the backdoor as shown in the image.

Reinforcements:-

Reinforcements are generally placed to increase the strength of the panel in localized areas which is relatively small compared to sheet metal parts for absorbing loads imposed thereon and dissipating such loads throughout the panel assembly to help maintain rigidity of the panel assembly. The reinforcements are usually 1-1.5mm thick as opposed to the 0.75mm thick panels used in this part.

• Hinge reinforcements

The hinge is a pivot mechanism which supports the total weight of the backdoor. So reinforcements are added for strength and rigidity.

• Gas stay reinforcements

Gas stay is used to lift the backdoor automatically and is used to support the backdoor in its open position. It can be of Two types Semi-automated and fully automated.

• Wiper Motor reinforcement

The wiper is used to wipe out the dust particles/water on the windshield glass which affects the rear visibility. It is actuated by the motor which is mounted on the inner panel. Due to the vibration and heat of the motor, the inner panel gets deformed which results in loss of strength & rigidity of the panel thus leading to poor NVH. So reinforcement is provided to avoid these conditions.

• Latch and Striker reinforcement

In the bottom part of the panel emboss is created for placement of the latch and striker assembly. There is over-slamming and abusing while opening and closing the door, thus arising the need for reinforcement to be placed.

Assembly:

In this assembly Top down approach was followed wherein from given styling surface the inner panel was created using various tools/commands in NX. After that others parts were modelled as per the requirements one by one.

Draft Analysis:-

The draft analysis will be performed for the tooling direction created at first and checked that the model is suitable for manufacturing. 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.