Design of backdoor

Back door design

Objectives

Use the provided styling surface to come up with a back door design, use appropriate design methodologies and provide the necessary reinforcements and embosses.

Introduction

An automobile back door or tailgate is the panel that covers the boot (or trunk) of an automobile. It enables access to the main luggage compartment. A hinge allows the boot lid to be raised, while devices such as springs or gas cylinders hold it up in the open position. The back door is an assembly of many parts such as inner panel, outer panel lower, and reinforcement. Inner panel is attached to the outer panel using mastic sealant.

Components of back door

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

Inner panel design

The inner panel, as the name suggests, is the inner part of the door. It is where most of the reinforcements and components are mounted. It is manufactured either by casting (aluminum) or sheet metal stamping (steel). Thickness of inner panel is 0.75mm.

Outer panel

As the name suggests it is the outer panel 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 panel and outer lower panel prospectively. Outer panel is manufacture by stamping sheet metal. Thickness for outer panel is 0.75mm.

Hinge reinforcements

Reinforcements are provided to provide support and add extra material to the sheet metal part to increase its strength near component installation region and minimize the impact of collisions. We have considered following reinforcements during our design. The reinforcements may be manufactured by stamping. Thickness of all reinforcements is 1.5mm.

Gas stay reinforcements

Gas stay is basically a gas spring that relies on elastic deformation of a compressed gas which is enclosed in a cylinder. It is used to reduce required effort while opening the back door. Although all the cars don’t come with gas stays, it may be required in case of a heavy back door.

Wiper motor reinforcements

As the name suggests wiper is used to wipe of the dust and water from the rear windscreen of the vehicle.

Latch and striker

Design methodology

We start with the styling surface that is provided to us, and consider top-down approach for this assembly modeling. First, we create the assembly and then create the components in the assembly file itself. Inner and outer panel are the largest parts and all other parts depend on them so we start with them. Also, the given styling surface is part of the outer panel so we create it first. Using various commands and features we design the outer panel from the styling surface. We have 2 parts for outer panel, which are separated by a flange, hence we create outer panel upper and lower respectively. They will be spot welded with each other. It is necessary to make sure that all the surfaces are properly joint to their adjacent surface and there are no disjoints at their intersection edges to avoid further errors. Also inner and outer panel are connected by hemming process so we can come back to outer panel and do that after completion of inner panel.

Tooling direction

As we know inner panel is at a particular distance from outer panel, we offset the outer panel surface and design inner panel on the same. Inner panel is important as most the mountings will be done on it. Before starting inner panel design, we need to define the tooling direction as a reference for manufacturing team. Then we design the inner panel.

hemming flange

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. normally hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges.

hemming relief

Relief is provided onto the part or component in order to remove any stresses developed in a particular area i.e sharp corners that takes place during the hemming process is carried out. thus corners are rounded or chamfered.

Assembly of back door

Draft analysis

In order to make sure the drawing of inner panel body is proper, we do draft analysis. We need to define the drawing direction and select the inner panel body. We take limit angle as 5 degrees. The result of the draft analysis is as follows.

Conclusion

Car back door was designed using the given styling surface, and under provided design regulations.