Design of backdoor

AIM:

Creating a back door design using the provided styling surface and appropriate design methodologies, as well as making the necessary reinforcements and embosses.

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 rear of 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 electrically 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 uopn the design of the trunk and material used, flenges, embosses, type of joining of inner panel and outer panel etc.

DIFFERENT TYPES OF BACK DOOR

The door or opening of a cargo area may be hinged at the top, side, & bottom. If the door hinged in the bottom it is called as a tailgate.

TOP-MOUNTED:

This type of back doors is used in a station wagon, 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 visibility compared to side-mounted or bar doors which have canter 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. These doors are more convenient for the goods handlers for long pipe and lengthy components where one door is kept open. These doors also save accidental head impacts. It is a lot easier to load and unload items in the side-mounted doors.

BOTTOM/SPLIT TYPE:

This bottom type or split type backdoor system are used in the car type such as estate type car, pickup trucks and some luxury SUVs.

These are the most convenient type of back door in which the bottom split is used as a support or even as a table for the tour going people.

DIFFERENT SHEETMETAL PROCESSES USED FOR MANUFACTURING 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 contact with the punch. When the metal specimen is flat piece of sheet metal used in forming and finish the product. Initially the punch moves in downward direction. The outer rim of blank is subjected to pure radial drawing (drawing toward in vertical axes) between die and blank metal. The metal become a bend and sliding over die and also stretched between die and punch. The metal in vicinity of punch head and contact with it bend and slide over radii 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 punch. 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 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.

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

There are various types of hemming operations:

1. Conventional 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 similar 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.

SPOT WELDING:

Spot Welding is a form of resistance welding also known as Resistance Spot Welding (RSW). Spot Welding involves using heat produced by resistance to an electrical current to join materials together. The current heats the materials to a point where they become malleable. The use of strong pressure bonds them together.

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 given below,

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

Parts Of the BackDoor

• Outer panel upper
• Outer panel lower
• Inner panel
• Hinge reinforcement (LH & RH)
• Gas Stay reinforcement (LH & RH)
• Wiper Motor reinforcement
• Latch reinforcement

Given Data,

CLASS A SURFACE:

The smoothness of the backdoor outer upper and lower class surface must be repaired. After the surfaces have been repaired, the door is divided into two parts: Door Outer Upper Panel and Door Lower Panel.

First, we must define the Tooling direction for the Deep drawing operation. It demonstrates that all operations, such as embossing, are performed with this vector direction in mind, which will aid in the manufacturing of the part.

INNER PANEL:

Inner door panel is a component used to strengthen the door assembly and is one of the most important components on which all accessories such as hinges, mountings, and gas stays are mounted. The back door inner panel is attached to the roof. The inner panel is hemmed to the outer panel.

The material which is used for manufactring the back door inner panel are steels and aluminium. Increasing the strength of the inner panel extra reinforcements added.

We'll make the back door inner panel flange by offsetting the outer surface at a distance that takes into account the sheet thickness and thickening direction. The connecting flange was then created to connect the inner panel and sealing flange. After that windscreen panel is then created and joined with the sealing flange for mounting.

Then, to strengthen the inner panel and reduce weight, a emboss and other cut-outs are created. A cut-out is also made for Latch and Stricker mounting. This cut-out is also done on the other side of the inner panel to keep the Back door's centre of gravity.

OUTER PANEL:

The back door's outer panel is comparable to other BIW parts in that it is an aesthetic component of a vehicle. The given multi-stage coating has the ability to resist scratches, prevent corrosion, and have a smooth and appealing appearance. The outer panel also contains mounting holes for the licence plate and accommodations for the rear fog lamp and tail lamp. The majority of hatchback automobiles are equipped with wiper motors.

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.

HINGE REINFORCEMENT:

Hinges are simple mechanical bearing devices that are used to connect two parts and allow them to rotate relative to each other about a fixed axis. Depending on the type employed, the components can move (most commonly) within a limited arc or with 360° freedom.

Hinge rotates in the rotational axis in that it will loose some strength there,It means huge Back door opens with the help of small hinges only in this case hinge needs extra strength,For this we providing extra strength in the form of Reinforcement

Hinge Reinforcement thickness be 1.2mm to 1.5mm.

GAS STAY REINFORCEMENT:

Gas springs, or gas struts, are rods that provide support for doors, hatches, lids and covers that are horizontally hinged. They act as support in a variety of ways including, lifting, positioning and lowering; because of this versatility they are used in a wide range of applications.

WIPER MOTOR REINFORCEMENT:

Windshield wipers are powered by a small electric motor, usually mounted on the firewall or under the cowl (the area under the windshield's base). The motor activates linkage that moves the wiper arms back and forth. On vehicles with a rear window wiper, a separate motor powers the one in the rear.

LATCH AND STRIKER REINFORCEMENT:

Position of latch and striker is perpendicular to the hinge then only the latch and striker mechanism works properly when the door closing and opening position.

For the proper opening and closing of the Door, the striker should be perpendicular to the trajectory of the Door. For this, hinge is assembled at its position. Once it is placed, hinge axis is drawn.

• To check the hinge axis as the center I draw a big circle to the position the latch in such a way that it is perpendicular to the hood trajectory.
• In between the two hinges the striker is perpendicular to the midpoint of two hinges, why because while closing and opening of latch and striker the opening position be similar actions.

DRAFT ANALYSIS OF BACK DOOR INNER PANEL:

BACK DOOR ASSEMBLY IMAGES:

FRONT VIEW:

RIGHT SIDE VIEW:

LEFT SIDE VIEW:

BACK VIEW:

ISOMETRIC VIEW:

CONCLUSION:

The outer and inner panels of the back door were designed using the styling surface along the tooling direction, and draft analysis was performed on the inner panel. All reinforcements were designed and placed in appropriate positions.