Design of backdoor                                 

     Design of Backdoor using NX CAD :-

INTRODUCTION:-

 Backdoor are one of the type of door of the vehicle, which are located next to the passenger seat, which provides access to the luggage compartment. In the most of the cars, these back doors are operated with the help of gas stay, which in turn reduces the effort required to lift the door. A back door is a type of door opening, typically hinged on its edge, but sometimes attached by other mechanisms such as tracks, for entering , exiting to an automobile .

In case of safety, the back door designed should meet the safety requirement for the rear collision.

Design Considerations for Back door:

• Rear Visibility for functional and safety.
• Boot space and accessibility.
• Type of Backdoor opening.
• Fixing and support Structures like hinge and gas stays.
• Mounts for Wiper motor, Back lights and other wiring loops.
• Fit and clearance
• Strength of Backdoor(Require in collision)

Type of back door

The back door of a car can be hinged at the top, side and bottom .It is also called as Tailgate.

1. Based on mounting :

• Top Mounted Back door :

                              

In this type of door , the hinges are  mounted on the rear roof section of an automobile .This tailgate are both powered and also gas stay supported. These top mounted tailgates provide more strength and greater rear visibility compared to side-mounted or bar doors which have canter pillars in it.

• Side Mounted Back door :

            Single side Mounted door                                              Double Side Mounted door

In this type of door , the hinges will be mounted to the bodyside outer of an automobile .These doors are smaller in size and can be easily accessed. These doors are more convenient for the goods handlers for long pipe and lengthy components where one door is kept open.

Its lot easier to load and inload items in the side mounted doors.

• Bottom Mounted/ Split Type Back door :

                                       

In this type of door , the hinges will be mounted on the floors of an automobile .In this the bottom split is used as a support or even as a table for the trip going people.

These are used in luxury SUVs.

(ii) Based on type of mechanism used :

• Gas Stay Mechanism :

                                  

 This is commonly used mechanism to lift the backdoor . This mechanism can be found in all types of backdoors(based on mountings) . Here little human effort will be required to lift the door .

Gas Stay type backdoor is an ideal and most commonly used tailgate mechanism from lower segment car to luxury car segment.

• Power lifted Mechanism :

                            

 This system or mechanism can be found in top mounted back door. This mechanism requires sensors to automatically open and close the door .

It consists of a power latch, anti-pinch switch, PTG main switch. When the switch is pressed in compartment or outside, the power latch releases switch is located in order to avoid accidental hand insertion during the operation of the door.

Different components of Backdoor Design assembly:-

 (i) Backdoor Outer Panel - Upper :

       This is the upper covering panel of the Backdoor . This is the part, where the windshield and the tail lamp of the automobile lies .The coating provided is of multi stage which has the property of scratch and crack resistance. It has a smooth and attractive finishes. Its thickness is of 0.75mm. It covers the inner panel of the back door. 

                                                                           

(ii) Backdoor Outer Panel – Lower :

       This is the lower covering panel of the backdoor. This is the part ,where generally a number plate is punched .

Outer Panel is manufacture by stamping sheet metal.

                

(iii) Backdoor Inner Panel :

  This is the inner panel of the backdoor . This is also the strengthening structure of the backdoor . This is Used for creating the embosses and mount the reinforcements in it . Some special emboss section is designed to distribute the load impacted from the back of an automobile .

In some cases the inner panel subject to stress due to frequent opening and slamming. Features like embossing and reinforcements compensate these stress factors.

 

(iv) Reinforcements:

 There is four different Reinforcements used while designing the backdoor of an automobile.

Reinforcements are provided to support and add extra material to sheet metal part to increase its strength near component installation regions and minimize the impact of collisions.

(a) Hinge Reinforcements: This Reinforcements are added for placing the hinges on the backdoor inner panel.

                          

 (b) Gas Stay Reinforcements :  This Reinforcements are added to place the gas stay on the backdoor inner panel , which results in the opening and closing of the backdoor.

                                        

(c) Latch and Striker Reinforcements : This Reinforcements is added to place the latch and striker component on the backdoor inner panel , which helps in locking and antilocking of the backdoor .

                                                              

(d) Wiper Motor Reinforcements : This is added to place the wiper motor on the backdoor inner panel , which helps in wiper movement .

 Force Distribution:

When the car hits at the rear end, the impact force should dissipate outside for safety. For that we give Y/V emboss which helps to directs the force to the outer end.

Significance of Y/V Emboss:

As an evident from the test simulations the design and direction of the emboss should guide the dissipating forces away from the passengers to the outside if the vehicle and thereby reducing the impact force drastically in case of a collision. Embosses also create strength on that region.

Mastic Flange

It is a connecting flange between outer panel and inner panel. The manufacturing process called “Lancing ” produces this type of flange.

                                                 

Thickness of Different Components :-

 (i) Backdoor Outer Panel - Upper : 0.75mm

(ii) Backdoor Outer Panel – Lower : 0.75mm

(iii) Backdoor Inner Panel : 0.75mm

(iv) Reinforcements : 

                  (a) Hinge Reinforcements : 1.5mm .

                  (b) Gas Stay Reinforcements :  1.5mm .

                  (c) Latch and Striker Reinforcements :  1.5mm .

                  (d) Wiper Motor Reinforcements :  1.5mm .

Operations Used for the Backdoor Manufacturing :

• Deep Drawing / Stamping : The basic operation used on a sheet metal component for giving it the desired structure . Important parameter to be considered while deep drawing or stamping is the tooling direction. The line in the below figure represents the tooling direction . The process is considered "deep" drawing when the depth of the
  drawn part exceeds its diameter.

                                                                                     

• Spot Welding : This operation is performed to join the outer panel upper and lower components with the help of flanges provided . This welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area. 

 

• Casting : This operation can be used when sheet metal component of variable thickness is to be produced .

• Punching : This operation is done where Deep Drawing / Stamping is not possible or too difficult to be done . This operation is performed only in very small areas. Here the material is removed from a piece of sheer metal by applying a great shearing force.

• Hemming: This is done to combine the inner panel and the outer panel. The outer panel is hemmed to fix the inner panel within it. The important parameter to be considered while hemming is Corner Relief, so as to avoid stress concentrations at the corners.

 

• Lancing:

The lancing is the operation of cutting a sheet metal through part of its length and then bending the cut portion. As a result, the proper lancing engineering method prevents fracturing by improving the sheet metal flow.

 

Final Result of Backdoor Design :