Design of backdoor

AIM:

To Design the outer upper and lower panel, inner panel with the necessary reinforcements with the design parameter for the given class A surface.

INTRODUCTION:

The trunk (North American English) or boot (British English) of a car is the vehicle's main storage or cargo compartment, often a hatch at the vehicle. It is also called a tailgate. These doors can be operated manually or electric powered. In most of the luxury cars door is electically operated. It involves a very major role during rear crash cases. So our design must be obey crash requirements. the institute of highway saftey analyse the diffrent accidents and they set a test to rate our car. So these rating depends upon the design of the trunk and Material used, flenges, embosses, type of joining of inner panel and outer panel etc.

Types of the back door

Top-Mounted:

This type of back doors is used in a station wagan, pickup truck and some of the sport utility vehicles. Today's modern cars use top-mounted tailgating systems which are both powered and also gas stay supported. These top mounted tailgates provide greater rear vsibility compared to side-mounted or bar doors which have center pillars in it.

Side Mounted Doors:

As the name signifies side-mounted doors are the one which is used in the van type MPVs, SUVs, pickup truck vehicles. These side-mounted doors or barn doors are a lot easier compared to top-mounted doors. These doors are generally smaller in size and can be easily accessed.

Types of mechanisms for Rear Door:

Gas stays:

Gas stay types backdoor/liftgate/tailgate is an ideal and most commonly used tailgate mechanism fron lower segment car to luxury car segment. The ideal components of tailgate consist of a hinge, door, gas stay and some rubber beadings for sealing of door.

Powered lift sysytem:

Power trunk lid system is another sophisticated way of trunk/liftgate opening mechanism which is to automatically open and close of the trunk/liftgate and release of the latch by the touch of a button.

Different types of Sheetmetal operations are done in the Back Door

Deep Drawing:

The metal deep drawing process is an effective method of manufacturing of cups, cans and other similar deep drawing products. The deep drawings having two main categories.

1. First-stage drawing: The blank shape of metal is placed on the die and  contant with the punch. When the metal specimen is flat piece of sheet metal used in forming and finish the product. Initially the puch moves in downwards direction. The outer rim of blank is subjected to pure radial drawing (drawing toward in vertical axis ) between die and blank metal. The become a bend and sliding over die and also stretched between die and punch. The metal in vicinity of puch head and contact with it bend and slide over radil and stretch over punch head.

2. Redrawing: The components drawn from first stage again it is redrawn convert into more depth to form a cup shape in the die and puch. The second stage of drawing is called as redrawing.

Embossing:

Embossing is a metal forming process for producing raised or sunken designs or relief in sheet materials by means of matched male and female roller dies, theoretically with no change in metal thickness or by-passing sheet or a strip of metal between rolls of the desired pattern. Metal sheet is drawn through the male and female roller dies producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet.

Materials commonly used in the metal embossing process include:

• Aluminum alloys
• Steel alloys
• Zinc
• Copper 
• Galvanized steel
• Brass 
• Cold rolled steel

Hemming:

Hemming is a foriming 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.

In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join tow sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, trunk lids and fenders. 

These are various types of hemming operations:

1. Convertional die hemming: In conventional die hemming, the flange is folded over the entire length with a hemming tool.

2. Roll hemming: In roll hemming, the hemming roller is guided by an industrial robot to form the flange.

Open Hem: A Hem has a full round feature and a return flange. In open hem bend angle is equal to 180 degrees.

Tear drop Hem: In tear drop hem the bend angle is greater than 180 degrees.

Closed Hem: Hems without any inside radius are called as closed hem. Closed hems are not recommended if the hem geometry is to be painted or if the material used is SST or Aluminium.

Blanking:

Blanking is a cutting operation of a flat metal sheet and the article punched out is known as blank. Blank is the required product of the operation and the metal left behind is considered as a waste.

Punching:

It is simillar to blanking only the main difference is that, the hole is the required product and the material punched out from the hole is considered as a waste.

Components to create:

1. Outer Upper Panel
2. Outer Lower Panel
3. Inner Panel
4. Gas Stay Reinforcement
5. Hinge Reinforcement
6. Wiper Reinforcement

Procedure:

  Class A Surface:

backdoor outer upper and lower class a surface has to be repaired according to the smoothness. After repairing the surfaces, the door is divided into two parts as Door Outer Upper and Door Lower Panel.

Outer Upper Panel:

Outter panel is the styling surface of the backdoor.Glass for rear visibility is mounted on the outter panel upper.Rear lights are also  mounted on the outter panel upper.

Number plate is mounted on the outter panel lower.Spot welds and other manufacturing process should done only on the inner panel because the outter panel is the styling surface which should not have any scratches or welds .Because it affects the style of the car which leads to bad impression on the customers.

Outer Lower Panel:

Now, we need to create the Tooling direction for the Deep drawing operation. It shows that all the operations like embossing is done by considering this vector direction and it will help in manufacturing the part.

After that we have to create Sealing Flange by offsetting the outer panel to the specific distance.

Then we will be creating the Back door inner panel flange by offsetting the outer surface at a distance considering the sheet thickness and thickening direction.

Then created the connecting flange to join the inner panel and sealing flange.

Then for the windshield panel mounting, windshield panel is created and joined with sealing flange.

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 direct the force to the outer end. 

Inner Panel with Embosses for Force Distribution

Hinge Reinforcement-

Hinges support the weight of the whole backdoor.Hence, the reinforcements must be provided there too.The emboss is designed in such a way that the hinges should operate freely.The hinge is connected to the rear roof of the car.

Gas Stay Emboss and Reinforcement

Gas stay is used to lift the backdoor automatically.There are two types of gas stay one is semi-automated and another one is fully automated.In semi automated type the back boor needs little force to lift after that it lift the backdoor automatically.In fully automated , it has  power spindle which lift the backdoor automatically.

Wiper emboss & reinforcement

Wiper is used to to wipeout the rain water falls on the backdoor window.It is actuated by the motor which is mounted on the inner panel.Due to the vibration and heat created by the motor .the inner panel where the motor is mounted gets deform and the parts attached to the motor starts to vibrate which leads to poor NVH.So we have to provide the reinforcement where the wiper motor is placed.

Assembly

Draft Analysis

Tooling Axis

Conclusion

The back door is designed for the given outer panel using the design rules studied earlier & draft analysis is performed as per the tooling direction. Assembly is done with attaching all the reinforcements.

As my files are exceding 20mb, I am unable to upload the files in the below given space.

 I have uploaded the file in my Drive.

Please find the link of my Assembly .stp file link below

https://drive.google.com/file/d/1rXwXqq7dPmax6seVvJIvTOS4JRzwPZES/view?usp=sharing

Please find the below link for the for the compressed file for the back door assembly.

https://drive.google.com/file/d/1H3qh03geRWcRt_rEt9TDACmYT8h6PSiH/view?usp=sharing