Design of backdoor

Objective:

• Using the given styling surface of Back door develop the design of Back door Inner panel.
• Develop the necessary embosses to strengthen the inner panel.
• Check and validate the draft analysis of the developed design of Inner panel.
• Develop the design of outer panel with the necessary hemming definition and the required gap for mastic application between the Inner and outer panel.
• Develop the required Reinforcements in the areas of Gas stay mount, Hinge Mount, Latch and striker mount and Wiper mount areas.

Theory:

Car Back door or Tail gate is the rear closing door of the car which will be used for the Luggage storage compartment access. It is also a swinging commodity of the car like Hood and Side doors. The materials can be used for the Back door is Aluminium or Steel. In most of the premium branded cars like Benz, Audi, Porsche, etc. uses Aluminium material for this back door. In this project we designed by considering the steel material as it is most commonly used in all companies cars.

The back door consists of the following parts.

1. Outer Panel Upper of Back door.
2. Outer Panel Lower of Back door
3. Back door Inner panel.
4. Latch and striker Reinforcement.
5. Hinge Reinforcements.
6. Gas stays mount Reinforcements.
7. Wiper motor Mounting Reinforcements.

See Below picture for the above mentioned parts in Back door.

Design considerations:
Thickness and manufacturing requirements:

• Thickness of Roof panel: 0.75mm
• Reinforcement Thickness = 1.5mm
• Minimum draft angle to be maintained 7 degree
• Minimum filet radius should be more than the 3mm+thicknes, i.e., above 3.75mm
• No sharp corners inside the component.

Functional requirements:

• Provide adequate clearance between Outer panels and Inner panel for the mastic inclusion.
• Rear visibility criteria regulations.
• Rear crash requirements and Regulations
• Joining techniques like Hemming and spot welding.
• Latch and striker placement with respect to the opening and closing trajectory of Door.
• Reinforcements for Hinge, Gas stay mountings and Wiper Mountings to strengthen locally for the backdoor inner panel.

Procedure:
First developed the Inner panel of the Backdoor by taking the offset surfaces from the given styling, then developed the outer panels then created the reinforcements.
Inner Panel:
Started with the creation of sealing flange area in inner panel which is required for the sealing purpose to the outer panel then after developed the windscreen area using the styling surface then created the surface below the windscreen to accommodate latch and striker and its motor after that developed embosses to strengthen the inner panel and then created the embosses for mounting the Reinforcement parts of Hinges mount, Wiper mount, gas stay mounting and Latch and striker mountings.

After developing the Inner panel checked for the Draft analysis to check and validate the part in terms of manufacturing feasibility.

Please see the below picture of Draft analysis carried out for 7degree, in this analaysis the inner panel is green so it is satisfied the draft checking.

Outer panel Upper and Lower:
Repaired the given styling surfaces to remove the gaps also created the new surfaces wherever required then joined all the surfaces. Prepared necessary hemming in the outer panels to join with the Inner panel and developed the corner relieves which are required at the corners to avoid the tearing of the material.

See the below pictures of complete outer panel:

In the below picture you can see the coprner reliefs added to avoid the tearing of material at the rounded corners.

Reinforcements:
Developed the reinforcement parts for the Hinge Mount, Gas stay Mount, Wiper mount and Latch and striker mounts.

See below pictures of Reinforcements:

Conclusion:
Thus completed the Car Back door design development which satisfies all the functional and manufacturing requirements.

Please find the below link for the 3d model for review and let me know your valuable feedback.
https://drive.google.com/file/d/1ov17Tav5-uLvQfOQnqIfMwT3BMICLoua/view?usp=sharing

Thanks & Regards,
Gowtham Kumar P.