Design of backdoor

AIM:

Using the provided styling surface to come up with a back door design and using appropriate design methodologies and make the necessary reinforcements and embosses.

BACK DOOR:

A door is a hinged part which is used for entry and exit of the vehicles. Back doors are one of the type doors of the vehicle which are located next to the passenger seat which provides access to the luggage compartment. In most of the cars, these back doors are operated with the help of gas stay which in turn reduces the effort required to lift open the door. Some luxury cars have powered backdoor which in turn is driven by an electric motor. This kind of system is also called a powered trunk lid system. Hatchback or station wagons are sold as 3 door or 5 door models. In this case, the rear hatch is classified as door this is because it enters the passenger compartment. The naming is mainly used in Europe countries. In case of safety, the back door designed should meet the safety requirement for the rear collision.

TYPE OF BACK DOOR:

CLASSIFICATION BASED ON THE MOUNT,

• TOP MOUNTED

This type of back doors is used in a station wagon, pickup trunk and some of the spot utility vehicles. Today's modern cars use top mounted tailgating system which are both powered and also gas stay supported. These top mounted tailgates provide greater rear visibility compared to side mounted or backdoor which have center pillars in it .

• SIDE MOUNDED DOOR

As the name signifies the 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 compare 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 door also save accidental head impacts. It is a lot easier to load and unload items in the side mounted doors.

• BOTTOM TYPE

This bottom type type backdoor system are used in the car type such as car, pickup truck and some luxuary 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.

CLASSIFICATION BASED ON WORKING MECHANISMM,

• GAS STAY TYPE

Gas Stay type backdoor is an ideal and most commonly used tailgate mechanism from 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 SYSTEM

Power trunk lift system is another sophisticated way of trunk or liftgate opening mechanism which is to automatically open and close of the trunk and release of the latch by the touch of a bottom. Powered trunk Lift system consists of a power latch, anti pinch switch, PTG assly, PTG main switch. When the switch is pressed in the compartment or outside the power latch releases the latch and the entire backdoor is opened. The anti pinch switch is located in order to avoid accidental hand insertion during the operation of the door.

DESIGN CONSIDERATION OF BACK DOOR:

• Rear visibility
• Boot space and acceability
• Sealing flange
• support structure like hinge and gas saty
• Mount for tail lamps,wiper motor and other wirings
• Rear crash regulation
• Gap and fllush reguirement

MANIFACTURING METHOD:

Recently, there have been two approaches to reducing automobile weight. One is by using material lighter than steel and the other is by redesigning the steel structure. Although the former seems very effective, it is very expensive so that it may only be used for an expensive automobile. Therefore, the automobile industry is trying to use steel, which is not costly and recyclable. Lightweight steel can be achieved by improving the performance of the structure or adopting new manufacturing techniques. One of the efforts is the ULSAB (ultra-light steel auto body) concept .

ULSAB suggests three main weight reduction techniques such as hydro-forming and the tailor welded blank (TWB).

TAILOR WELD BLANK:

A tailor-welded blank is a blank that is comprised of two separate pieces of sheet metal that have been welded together prior to stamping. Tailor welded blanks allow the welding of the different grades, different thickness or different corrosion coatings together in order to give the properties needed in different areas, without increasing the number of tools needed to form the part and eliminating the fit ability concerns. They also allow a high degree of flexibility in designing parts and large blanks can be formed from much smaller sheets. The use of tailor-welded blanks would reduce the weight of the car. Having the ability to selectively place different thickness of material would result in weight reductions. An example of this used in production is the door inner panel. The only strength requirement on a door inner is in the region where the hinges attach to the panel.

MATERIAL SELECTION:

The selection of material plays a major role in determining the overall weight of the back door. The common materials used are Steel & Aluminum. The density of Steel is higher than Aluminum thus adding more weight to the door. The material used in the manufacturing of the backdoor depends upon the budget of the car, most low cost vehicles use steel as it is cheaper compared to Aluminium. Another aspect to be noted is that, if casted Aluminum parts are used instead of deep drawn steel parts there is no need of reinforcements and the overall weight of the car is reduced by approximately 5-10kg thus increasing the performance of the vehicle. Also the draft angle for casted parts is around 3 degrees while for deep drawn parts is around 7-10 degrees which helps in increasing the luggage/ cabin space.

Possible number of aluminium parts,

Possible number of steel parts,

By using aluminium we ca reduce number of parts casted also reduces the weight,

DIFFERENT TYPE OF OPERATION DONE IN BACK DOOR DESIGN:

• DEEP DRAWING

1.FIRST STAGE DEEP 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.

• 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.

• 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.

• EMBOSS:

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.

DESING PROCEDURE:

• Surface correction and tooling direction

The given skin data of the back door is need to be some corrction, some portion not giving an soomth surface .After the surface correction we create a 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.

• Inner panel

Basically we create the inner panel according to the master section .In this case we do not have a master saction so we designed by asssuming the values.for the design of inner panel we first start with creating an sealing flange.

The sealing flange is offseted at distance from outer panel and and we create connection flange to join the inner panel and sealing flange.

Then for the back door glass we create an flange for that,

After creating smooth inner panel we create embosses on the surface for increase the strength .we also provide embosses and re inforcemet for hinge,gas stay,wiper mount,and striker.

Hinge and gastay embosses with reinforcement,

wiper mout with re inforcement,

striker emboss with re inforcement,

We provide matic region on the inner panel.The mastic points are defined on the backdoor inner panel where the backdoorcan easily deform. They help the backdoor outer panel to come back to its original shape after it gets deformed.Mastic sealants are elastic compound that behaves like the rubber.

The gap between the inner panel and the outer panel over the embosses is filled with mastic sealents at certained specified places, this helps to reducing vibrations and overall NVH ( Noise, Vibration, Harshness).

• Hemming

After creating inner panel the outer and inner panel joint togother by hemming operation,

• Assembly

DRAFT ANALYSIS:

Draft analysis along tooling direction,

CONCLUTION:

The back door outer and inner panel were designed with the help of the styling surface along the tooling direction and draft analysis was performed on the inner panel and All the reinforcements were designed and placed at appropriate positions.