Design of backdoor

CAR BACK DOOR DESIGN

Aim: To design back door of car using given outer class 'A' surface.

What is back door of a car?

A door which is located at the rear side of a car which gives access for the boot space to store luggage, spare wheel etc.

These doors can be operated manually or electric powered. In most of the luxury cars door is electrically operated.

 

Types of doors based on working position,

1. Top Mounted Door
2. Side mounted Door
3. Bottom Door

 

Gas Stay Powered:

Electric Operated:

Back Door Assembly:

• Inner panel
• outer panel
• hinge and its reinforcement
• wiper motor reinforcement
• latch & stricker and its reinforcement 

 

 

Another form of resistance welding is Projection Welding. This process involves fusing a fastener’s embossed or coined projections to the metal base material to form a weld. As the materials never melt, they do not intermix. This means the resulting weld is more like a forging of the materials.

Spot welding is only suitable for a small selection of base materials. Low carbon steel is the most suitable material for spot welding. This is because it is more resistant to electricity and has a lower thermal conductivity than the copper electrodes used to create the required electrical current.

High carbon steels and aluminium alloys can form brittle welds that don’t last with the spot welding process. Pure aluminium can qualify for spot welding but requires higher current levels. This is because it has a lower resistance to electricity than low carbon steel.

The outter panel upper and outter panel lower are joined through the spot welding .So there must be no gap between the outter panel upper and outter panel lower.

Design of Back door in NX CAD: 

Door parts thickness is cosidered below,

1. Outer Panel - 0.75 mm
2. Inner Panel - 0.75 mm
3. Reinforcements - 1.5 mm

BACK DOOR DESIGN 

The design consideration of back door are ,

• Visibility Criteria
• Force Dissipation
• Latch and Stricker Positions
• Hinge Position
• Gas Stay Position
• Hemming and Relief Areas

 PARTS OF BACKDOOR 

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

  1. BACK DOOR OUTER PANEL 

In this design back door is created as two different parts back door outer panel upper and lower. This outer panel designed based on visibility criteria and proper reliefs provided at the corner for hemming operation .The thickness of outer panel is 0.75 mm .

Backdoor Outer Panel Front View:

Backdoor Outer Panel Back View:

 

2.BACK DOOR INNER PANEL 

Back door outer panel  designed based  on hinge, gas stay, wiper motor position and reinforcement as well as visibility criteria .Suitable tooling direction is created  for trouble free manufacturing process.In this design stamping operations created based on this tooling direction. Embosses are provided in this design for force dissipation. In this design appropriate clearance given in mastic areas .The inner panel thickness is 0.75 mm 

Backdoor Inner Panel Isometric View:

Backdoor Inner Panel Front View:

Backdoor Inner Panel Side View:

 

• Force dissipation 

This inner panel  design created by considering the force dissipation criteria.The embosses are created in such a manner that force will dissipate in to sides of the back door during a collision and prevent reaching inside the passenger cabin.Y and V embosses provided in the back door for force dissipation and improve the strength of the metal.

                                                                                                     

                                                                                                                                          fig.4.3 Embosses and force distribution

• Mastic Area 

Mastics sealants used for  joining of outer panel and inner panel. It increase the strength of back door and good NVH. So accurate clearance given for mastic sealant.

                                                                                                          

                                                                                                                                                fig.4.4.mastic area 

Reinforcements in inner panel 

• Hinge reinforcement

In this design hinges provided on the top side of the door. Appropriate  reinforcement given for hinge mounting areas to improve the strength.

 

 

• Gas stay reinforcement    

Gas stays support the weight of the back door while they are open. More load act on this region ,So suitable  reinforcement provided  for better strength 

it is spot  welded on the inner panel.

 

 

 

• Wiper motor reinforcement  

Reinforcement provided in this region for fixing the wiper motor.

 

 

• 

 

Latch and striker reinforcement 

The striker is designed to create a tight fit between the door and the seal on the cab. The door open and shut several times in a day.So more force acting on  this area.The reinforcement given in the latch and striker mounting area to increase the strength.it is  spot welded on the inner panel   

                   

 

                                                             

                                                                                                       

All reinforcement parts spot welded on the inner panel for better strength on that area.  

 

 

• trajectory 

The trajectory is created to position the latch and striker .latch system must be able to catch the striker of the door  the while  closing. Circle is drawn from the hinge axis. The striker follow this path.

                                                                                         

                                                                                                                                       fig.4.8 trajectory 

• Hemming 

Hemming is a technology used by the automotive industry to join inner and outer closure panels together (hoods, doors, tailgates, etc.).In addition adhesive bond provide for excellent joining of panels it also reduce vibration .here this design 0.2mm clearance provided for hem glue . At the edges hem relief is given:-

                                               

 

                                                                                                                                                               fig4.9 hemming area and corner relief 

• Proper corner relief provided for trouble-free hemming operation 

5.0 Draft Analysis    

 draft analysis performed to check the designed part  is suitable for stamping operation with respect to the tooling direction.We can find out the  errors by using this feature.The minimum draft angle is 7.The negative draft is  denoted by different colour so we can easily find out the unsuitable areas.

 

 

             

                                                                                                                                                    fig .5.draft analysis 

 

6.0 Final Assembly:-

Final Assembly of the below mwntioned parts:

 

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

Final Assembly Isometric View:

Final Assembly Front View:

Final Assembly Back View:

7.0CONCLUSION 

The backdoor is designed  based on design considerations .Required  reinforcement provided on inner panel. The design is checked by using draft analysis feature .

 Thus the back door was designed and developed from the given styling surfaces with essential reinforcements and emboss. To satisfy the manufacturing requirements draft analysis was also done on the inner panel.