Design of backdoor

BACK DOOR DESIGN

Aim:

To design Back door of car and reinforcements and emboses by using the given styling surface.

Back door:

• 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 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.

• A car back door is a type of door opening, typically hinged on its front edge, but sometimes attached by other mechanisms such as tracks, for entering and exiting a vehicle. Doors most often integrate side windows for visibility from inside the car and can be locked to secure the vehicle.

Design considerations

• Rear visibility
• Boot space & accessibility
• Sealing Flange
• Support structures like hinges and gas stays.
• Mounts for wiper motor, tail lamps and other wiring loops
• Rear crash regulations
• Joining techniques such as hemming, spot welding etc.
• Gap and flush requirements

Assemblies and components

• Outer panel upper
• Outer panel lower
• Inner panel
• Hinges
• Latch and Stricker
• Gas-stay
• Wiper motor
• Hinge reinforcements
• Latch and Stricker reinforcements
• Gas-stay reinforcements
• Wiper motor reinforcements

Outer panel

• As the name suggests, it is the outer part of the rear door and is mostly responsible for aesthetics of the vehicle. Outer and inner panels are connected by mastic sealants in center and by hemming process at edges. The outer door handle and in some cases, the number plate may also be installed on the outer panel of the back door. We have considered a 2-part outer panel for our design, outer upper panel and outer lower panel prospectively. Outer panel is manufacture by stamping sheet metal

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

 

• Corner Relief: During hemming process multiple rollers are used which causes vibrations and stress concentrations at some locations due to which design intent of the panel shouldn’t be changed (The panel should spring back to original formation after roller is removed). But most of the time that is not the case at corners so to avoid that situation reliefs are provided at corners.

 

Inner panel:

• The inner panel is one of the most important components of backdoor assembly. It provides strength and helps in dissipation of forces outside the part with the help of embosses made on it.It helps in mounting of accessories like hinges, wiper motor, gas stay, latch & striker etc.
• The inner panel is produced by either casting or through Deep drawing process.
• Mostly aluminum part is casted, steel inner panel are manufactured by deep drawing process. If deep drawn, there must be a tooling direction through which that panel must be deep drawn.

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

 

Sealing Flange: It is that section of the inner panel which enables the backdoor to sit over the rear body side of the car. Its design is important as it decides how a backdoor is mounted on the rear body side of the car and also restricts any external matter to enter inside the vehicle.

 

Mastic Sealants:  As we know the outer panel gives the aesthetic look to the vehicle, so we can’t use bolting or spot welding or any other joining technique which damages the aesthetic looks of the panel. This mastic sealants are used for joining the Inner panel elements with outer panel. A maximum gap of 5mm is to be maintained in between parts where mastics are to be applied.

 

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 0.75mm thick panel used in this part.

 

• Hinge reinforcements

Hinge is a pivot mechanism which supports the total weight of the backdoor. So,the 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

Wiper is used to wipeout 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 vibration and heat of the motor, inner panel gets deformed which results in loss of strength & rigidity of the panel thus leading to poor NVH. So, the reinforcement is provided to avoid these conditions.

• Latch and Striker reinforcement

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

Positioning of Latch & striker/ Latch Trajectory:

Backdoor is the swinging part which rotates about hinge axis.  The position and orientation of latch striker is important for proper opening and closing of the backdoor. The positioning is done by sketching a circle with center as the axis of the hinge which passes through the striker at appropriate position with respect to inner panel. 

 

MANUFACTURING PROCESS

• Mostly BIW components are manufacturer by steel material as they can be easily modified and manufactured. the tools to produce steel can be used for different processes so industries prefer steel as they can available as sheet metal.
• the shape of the sheet metal can be changed by mostly stamping process and die forging process
• the drafting angel for stamping process must be always maintained above 7degree to maintain the tool for to produce more jobs
  

 

Analysis: Draft analysis

Every part which is manufactured from press tool or other forming tools require some positive draft on the faces which are parallel to the tooling direction. If we don’t give draft (Zero Draft) or give negative drafts on these faces it will stick to the mould surface and when the mould is in motion it will destroy surface thus reducing its surface finish. This Draft Analysis command enables us to detect if the part we have drafted can be easily ejected or not. It also give insights about the critical zones, so that appropriate changes in the design can be made if needed.

Conclusion

The Backdoor of car and its necessary reinforecements and embosses designed by using NX 12.