Challenge

Design of backdoor

PPrakash Manan23 Sept 2022

Design of backdoor

OBJECTIVE:

To develop the car backdoor by using the given Class A surface method by automotive sheet metal Design.

BACKDOOR DESIGN

The backdoor or tailgate is the rearmost part of the automobile which opens upwards, downwards, or sideways to give access to the luggage space or seating area. In most of the cars, the backdoor opens upwards. It is hinged to the roof and a gas stay support is fixed at the body side outer for keeping the backdoor in the open position.

The material used for the backdoor varies as per the price range of the vehicle. Most of the low-cost vehicles use steel as it is cheaper and uses parts that are stamped using moulds. These parts are usually of uniform thickness and reinforcements are added to improve local strength where needed. The premium vehicles use aluminium parts which are usually die-cast and hence can have a variable thickness. This removes the need of reinforcements hence keeping the weight even lower as aluminium parts are lighter in comparison. On the contrary, aluminium is more expensive than steel hence its applications are limited to cheaper vehicles. Currently due to the extensive use of plastic trims and plastic parts the cost of aluminium is affordable for the manufacturers in all price brackets. The use of aluminium reduces the overall weight of the component and hence the vehicle improves its fuel efficiency.

Outer Panel
Inner Panel
Hinge Reinforcement
Gas Stay Reinforcement
Wiper Motor Reinforcement
Latch and Striker Reinforcement

TYPES OF DOOR OPENING:

Top mounted door
Side mounted door
Bottom Door

DESIGN CONSIDERATION FOR BACKDOOR INNER PANEL:

Rear Visibility.
Support structures like hinges and gas stay.
Mounts for wiper motor, tail lamps, and other wiring loops.
Fit and clearances.
Boot space
Rear crash regulations and requirements.
Sealing and its functions.
Joining techniques like hemming, spot welding etc.

COMPONENTS OF BACKDOOR:

Inner panel
Outer panel upper
Outer panel lower
Hinge reinforcement LH
Hinge reinforcement RH
Gas stay reinforcement LH
Gas stays reinforcement RH
Wiper motor reinforcement
Latch reinforcement

Different Sheetmetal processes are used for manufacturing the Back Door:

Deep Drawing:

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

First-stage drawing: The blank shape of metal is placed on the die and in contact with the punch. When the metal specimen is a flat piece of sheet metal is used in forming and finishing the product. Initially, the punch moves in a downward direction. The outer rim of the blank is subjected to pure radial drawing (drawing toward vertical axes) between the die and blank metal. The metal becomes a bend and slides over the die and also stretched between the die and punch. The metal in the vicinity of the punch head and contact with it bends and slides over radii and stretches over the punch head.
Redrawing: The components drawn from the first stage again it is redrawn and converted into more depth to form a cup shape in the die and punch. The second stage of drawing is called 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. The 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:

Aluminium 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, improve the appearance of a part and 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:

Conventional die hemming: In conventional die hemming, the flange is folded over the entire length with a hemming tool.
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 an open hem, the 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 closed hems. 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.