Design of backdoor

Back Door Design

• Objective: -

1. The main objective of this project is to design a back door of a car with an inner panel , outer panel and reinforcements for hinges , gas stay , wiper motor and latch
2. The inner panel is subjected to the draft analysis to ensure whether it is satisfying the deep drawing requirements for the tooling direction that is created in the design.
3. Perform the draft analysis for each component & reinforcement.

• Introduction: -

Product design starts with requirements. The designer will sketch the product based on your requirements. He then uses advanced CAD software to transform the 2D sketch into his 3D model with proper dimensions. Another important aspect of design is that any designed product is manufacturable.

Therefore, the designer's role is to design products that are easy and inexpensive to manufacture.

This is where Design for Manufacturing [DFM] and Design for Assembly [DFA] play an important role in product development.

The design development process continues until the design meets the customer's requirements.

The product to be developed this time is car back door.

CAR DOOR INTRODUCTION:

A vehicle's rear door is also called a tailgate. A vehicle's rear door is the rearmost part of the vehicle that provides access to the vehicle's trunk. The back door is one of BIW's sheet metal engineered locking products. The materials used to manufacture back door will depend on budget and vehicle performance.

Mostly aluminium and steel are used in manufacturing, but steel is used in budget cars and is easy and cheap to manufacture following the stamping process.

Parts of a Back Door:

• Outer Panel
• Outer panel Lower
• Inner panel
• Hinge Reinforcements
• Latch and Striker Reinforcement
• Wiper Motor Reinforcement
• Gas Stay Reinforcements

All these parts are assembled altogether to obtain the back door of a car.

GAS STAY :

Back door opening rod as Gas Stray Type is the ideal and most used tailgate mechanism from low end to luxury vehicles. An ideal tailgate component consists of hinges, doors, gas struts, and a rubber strip to seal the door, as shown in the image below:

Powered/Electrified Back door Opening:

The Powered Trunk Lid System is another sophisticated type of trunk/tailgate opening mechanism that automatically opens and closes the trunk/tailgate and unlatches it at the push of a button. The image below shows the components used in the electric trunk/rear door lift system.

Electric trunk lift system consists of electric lock, anti-pinch switch, PTG assembly and PTG master switch. Pressing a switch inside or outside the compartment will unlatch the electric lock and open the entire back door. The anti-trap switch is positioned to prevent accidental hand insertion during door operation.

Reasons to reinforce:

A back door itself is strong component of car but at mounting locations it has some stresses/forces which has to be addressed 7 resolved with the help of reinforcements.

To increase the strength of the back door, local reinforcements such as Hinge Reinforcements, Latch and striker Reinforcement, Wiper Motor Reinforcement, Gas Stay Reinforcements, are introduced and connected to the back door surface by various joining methods.

Manufacturing Methods & Basics:-

Let’s discuss some of the manufacturing methods & some basics related to manufacturing of back door.

1. Manufacturing Basics-

In recent years, there have been two approaches to reducing the weight of automobiles. The first is to use materials that are lighter than steel and the second is to redesign the steel structure.

The former appears to be very effective but is so expensive that it can only be used in expensive cars. Therefore, the automotive industry Inexpensive and recyclable.

Weight reduction in steel can be achieved by improving the performance of the structure or by introducing new manufacturing techniques.

One of these efforts is the ULSAB (Ultra-Light Steel Body) concept. ULSAB proposes his three main weight saving techniques such as hydroforming and Tailor Welded Blanks (TWB).

1. Foils, Sheet-metals & Plates-

Now that we have covered the main measurement systems, let's look at the classification of foils, sheets, and plates. Here we use millimetre as the unit of measure.

mm, mil, gauge:- Foils, sheets and plates are almost the same, differing only in thickness. Thickness is measured in the three ways: millimetres, mils, and gauges. Millimetres are a simple unit, but mils and gauges are common only in engineering and manufacturing.

Metal foil is especially common with aluminium and is often called tin foil.

Foil thickness is typically up to 0.2 mm.

Next is Sheet metal thicknesses range from 0.5 mm to 6 mm. Above that is a metal plate i.e. thickness more than 6 mm.

Thin sheet metal is easy to form yet has excellent strength. It's relatively inexpensive and excellent for most technical purposes. That's why it's all around us.

1. Standard Sizes-

Knowing the standard plate sizes will help you optimize your part layout. You will often receive parts for production that are slightly larger than the standard size.

This means more rejections and higher overall costs for customers. Also note here that different blade sizes are available.

Also small, medium and large sheets are always in stock in any sheet metal fabricator's warehouse, but extra-large sheets may not be available.

1. Processes for sheet-metal-

Now we will be discussing different methods used with sheet metal is formed or manufactured.

1. Rolling-

Rolling can be performed on sheet metal to reduce the thickness or make it more uniform throughout the sheet metal. Sheet metal is guided through a series of rollers.

In cold rolling, the process takes place at room temperature. The material is pickled, and heat treated to finish.

Depending on the temperature, the process is divided into hot rolling or cold rolling. During hot rolling, the temperature of steel is approximately 1400 degrees Fahrenheit. This helps achieve thicknesses from 1/16 inch to 5/16 inch.

For construction steel, cold rolling is only sufficient up to 3 mm. From there the sheet is hot rolled for cost reasons.

For stainless steel, the hot rolling process starts again at 3 mm, while the cold rolling covers all sheets, i.e., up to 6 mm.

For technical purposes it is important to distinguish between the two. For precision applications, cold rolled steel is preferred as it allows for greater control over the final dimensions. This is because in hot-rolled steel, the steel may shrink slightly after cooling and change its shape somewhat.

2. Cutting:-

In recent years, laser cutting has become an increasingly popular sheet metal forming process. Laser cutting involves exposing sheet metal to a high power laser to punch holes in the metal.

This is a faster and more accurate cutting process that can also be done automatically using a CNC (Computer Numerical Control) laser cutting machine.

3. Punching-

Punching is a common technique for making holes in sheet

metal. The structure consists of a punch and a punching die. There is a very small distance between the two.

When the punch and die come into contact, the material is forced between the two, and as they are pressed, shear forces puncture the sheet metal. This process is relatively inexpensive in high volumes and can drill holes in both strip and sheet metal.

Various sizes of holes can be punched, but it is generally recommended that the diameter of the hole required is larger than the thickness of the material being punched. Especially for stable alloys, the hole diameter and thickness difference should be large.

4. Sheet metal Expanding-

In this forming process, a sheet of metal is run through a punch shear where it is cut and stretched into a pattern. Rhombic meshes are usually preferred as they have structural advantages over other shapes.

This moulding process is commonly used to make fences, sidewalks, platforms, trellises, etc. This process produces a strong, self-draining product capable of supporting the weight for which it is designed.

These products can be used where passage of air or liquid is required, but passage of large particles should be prevented. Retains the original strength of metal.

5. Hydroforming –

Hydroforming is an innovative method of shaping sheet metal into a desired shape. In this process, the metal is placed in a mould, but instead of being punched, a high pressure fluid is used to form the sheet.

This method allows you to create more complex parts in less time. It is also relatively inexpensive and requires less work. Hydroforming is compatible with nearly all materials including stainless steel, aluminium, carbon steel, brass, and precious metals. Unconventional shapes can be hydro formed, as a suitable matrix is ​​usually not required.

6. Sheet metal Bending-

Bending is a forming process that applies bending stress to sheet metal to bend it into a desired shape. Sheet metal is bent in such a way that plastic deformation is achieved. This will prevent the metal from returning to its original shape.

Air bending by V die: Parts such as flanges and beads are formed by bending. The most common bend is the V-bend. There, a V-shaped die, and a punch are pressed together to give the sheet metal the desired shape. Edge bending is another common method of bending flanges using wipe dies and punches.

7. Sheet Metal Curling: It is the process of forming a circular ring on the edge of a can to make handling safer. There is a difference between the frilled hem and the teardrop them.

In curling, the beginning is rounded into a formed circle, but the beginning of the teardrop hem is still exposed.

Curling can also be divided into off-center and center roles. Off-center rolls have their centers above the plane of the sheet metal, while Center rolls have their centres in the same plane as the plane of the metal sheet.

8. Sheet metal Decambering –

Decambering is the process of removing warpage from metal sheets. For sheet metal, especially strip parts, horizontal bending occurs when flattened to the sheet metal.

Decamber removes this horizontal bend by flattening edges and removing curves. Apply force to the deformed edge, not the face, to push it into a straight shape. It is usually performed in sections of limited length.

9. Sheet metal Deep Drawing-

Deep drawing is a sheet metal forming process that involves using a series of punches to change the shape of a metal sheet into a desired shape in multiple stages.

It is deep drawing only if the depth of the formed shape exceeds the original diameter of the sheet. Use stamps and dies to create changes at each stage.

This process transforms sheet metal into various shapes such as fuel tanks, sinks, and auto parts. Deep drawing is mainly used for mass production.

Fig:- sheet Metal Deep Drawing

• Incremental sheet metal forming -

Incremental sheet metal forming is a metalworking process for giving sheet metal a specific shape. It can only be realized in small quantities. Changes to the product can be made quickly and effortlessly.

Products are created in incremental steps. The sheet material is formed using a single-point sphere. This process produces results similar to deep drawing but does not require a separate punch and die set. Therefore, the greatest advantage of this method is its flexibility.

Snap of different process combined:

Reinforcements:-

As mentioned earlier, local strengthening is usually provided by local reinforcements. Preference is given to using thin sheet metal with thicker local reinforcements wherever necessary, rather than manufacturing the entire panel from thick sheet metal.

The thickness of the reinforcements is typically 1-1.5 mm, while the plate itself is 0.55-1 mm thick.

Fig:- Different Reinforcements for Back door

Outer Panel:-

The outer panel has a styling surface hatchback design for back door assy. Other components of the back door are designed in relation to the outer panel face. It acts as the outer shell and handles the car's aesthetics. In this version the outer panel he is split in two.

1. Outer Panel Back Door Upper
2. Outer Panel Back Door Lower

3. Outer Panel Back Door: -

Outer top panel extracted from the provided styling surface. The plate is modified to the desired design using CATIA surfacing tools. The thickness of the outer panel is 0.75mm. There is a corner cut on the hem. Outer bottom plate: The outer top panel extracted from the specified styling surface. The plate is modified to the desired design using NX CAD surfacing tools. The thickness of the outer panel is 0.75mm.

Inner Panel:-

The Back door inner panel consists of all necessary stampings and mounting locations for gas stay mountings, hinges & latches, and striker locations. At impact, all forces are directed to the hinge as shown.

Snaps for references:-

Back Door Assy: -

• Conclusion: -

The Backdoor Design is very critical task for designer as a design & safety POV for passenger. The back door design is completed with the help of CATIA software.