Design of backdoor

Objective

Developing a back-door design based on the styling surface with given information and to position the latch reinforcement striker, hinge and wiper mountings. The report constitutes about positioning of Latch and Stricker, Wiper motor. Tail light mounting, Gas stay Reinforcements with suitable emboss definitions and Hemming flanges.

Software used

NX-Cad

Introduction

A back door or a tailgate is the rearmost part of the vehicle that can be opened and closed for loading and unloading luggage’s. The back door/Tail Gate of a car is very intricate when it comes to its requirements. It act as door for storage compartment of vehicle which secure the carry the spare tyre and luggage’s safely during the traveling. It also protects the passengers seated at the back from any accidents during the rear collision.

Tailgate are open either vertically or sideways depending upon the design of the car model. In vertically opening the tailgate are supported by two gas stay support mechanism and actuated at the hinge axis fixed on the rear rail ditch area.

 A backdoor is an assembly of sheetmetal, trim bodies, locking system, taillight, licence plate mounting with lighting provision. It could be made up of 1 inner layer and two more outer layers. The inner and outer layers are spot welded or hemmed wherever necessary. The embosses on the inner layer are made such that the impact is restricted to affect the passengers at the back seat. The embosses are also designed to make sure all the parts are being mounted (tail lamps, wiper motor, latch and striker, and gas stay).

The inner layer and the outer layer of the tailgate is usually made of steel and are deep-drawn. The thickness of the sheets is between 0.6-0.8mm. Different types of material are used based on various factors such as the cost of the vehicle, customer base etc.

Flow of Design

Outer panel

The outer panel is a styling surface of the Back door that covers the inner panel and all mountings of accessories. The outer panel should provide aesthetic look to the back door and cover the inner panel neatly. Outer panel is divided in two parts as upper and lower part. These parts are attached to inner panel by hemming at around the edges and mastic sealants. Then lower and upper part is joined using spot welding technique. Thickness of these panels is also considered as 0.75mm.

Inner Panel:

The inner panel is single Sheetmetal piece deep drawn to complex shape which ensure to withstand the impact force exerted transferase from outer panel during rear collision of car. It is provided with embosses to add extra strength and it is designed in such a way to distribute the forces equally to all regions away from the centre of inner panner toward the gas stay and hinges support area. On the periphery flanges are kept to apply mastic sealant for doing hemming process. Thickness of inner panel consider 0.75mm

Emboss on the inner panel are faced toward tooling direction so that, during rear collision projected emboss take the impact force  before damaging the inner panel and divert the peak impact force toward the hinge and gas stay support areas routing outside faces.

Reinforcement pad

These are used to increase the local strength of emboss structure and provide strong base for the mounting components like hinges, gas stay, motor mounting and latch Stricker on inner panel. Thickness of all reinforcement pad are 1.25mm.

Door trajectory

This method is done to understand the back door’s trajectory for the latch and striker positioning during the opening and closing of backdoor. This method helps to located the latch assembly parts properly with respect to Stricker.

Draft Analysis

Draft analysis is done to ensure that all deep drawn section of parts satisfy the minimum draft angle criteria along the tooling direction for ease of manufacturing. Minimum draft angle of 7 degree is set for analysis. All green highlighted area signifies positive draft along tooling direction.

Clash analysis

This tool is used to check whether the two part are clashing/ interfering with each other during the assembly module and no such clash are found.

Conclusion

The modelling of all BIW components of backdoor is designed and will be forward to CAE team to do the FEA analysis to check the other parameters.