Design of backdoor

AIM:

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

INTRODUCTION:

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.

Types of the back door

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.

Functions of the Backdoor:

• It protects the occupants and luggage from getting damaged.
• It houses assembly of tail lamps, wiper motor and other components.
• It serves as entry and exit point for luggage/passengers.
• It houses windshield glass which helps in rear visibility.
• Parking sensors, rear view camera are mounted on it.

Types of mechanisms for Rear Door:

Gas stays:

Gas stay types backdoor/liftgate/tailgate 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 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.

Components to create:

1. Outer Upper Panel.
2. Outer Lower Panel.
3. Inner Panel.
4. Gas Stay Reinforcement LH And RH.
5. Hinge Reinforcement LH and RH.
6. Striker Reinforcement.
7. Wiper Reinforcement.

Materials 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.

Fig. above shows possible no. of parts in aluminium backdoor

Fig. above shows possible no. of parts in Steel backdoor

The below table gives a comparative information about Steel and Aluminium.

	Aluminium	Steel
Parts	Parts are casted	Parts are stamped
Reinforcements	Reinforcements can be neglected	Reinforcements are necessary
Thickness	Thickness can be varied	Thickness should be uniform
Weight	Lighter in weight	heavier in weight
Cost	Costly as compared to Steel	Cheap as compared to Aluminium
No. Of components	Less No. of components	More No. of components

PROCEDURE:

1. Checking the Geometry:

• Once the model is opened, we get a Class A Surface of the back door.

• Try joining the Upper surface of the car, if the surface sews together, we get the outer surface and if the surface didn’t join then we need to create the surface by using studio surface tool
• Create the fillet areas, Tail Lamp areas as those areas will be vulnerable and are unable to join together.

2. Tooling axis creation:

• Draw a line from left and right extremities almost parallel to the path of the surface along the unsymmetrical axis.
• Using the Derived lines tool, create a bsecting line as shown below:

3. Creating Inner panel

• First offset the surface to a distance of 1.7mm, which will give the innerpanel surface position.
• Now the sealing flange for the inner panel has to be created.
• The seaing flange created by cuttng from the surface is shown below:

• In between, the tangent tensioning (Shape control) can be adjusted by modifying the surface using the Bridge curve tool.
• This flange has to be in a depth of 30 mm from the surface
• Now connect the flange with the surface using law extension w.r.t the tooling axis and proper draft given.

• Fillets has to be applied at each steps and check whether the surface is getting thickened or not.
• The next step is to create the other side which has to be connected with the sealing flange. ]

• Similarly connect the lower side of the surface by creating a surface and sew it all together.

• A mastic sealent is used on the surface to connect the inner and outer panel with a gap of 5mm.

• So offset the outer surface 5mm downwards and create a plate from the inner panel.
• Give proper embosses and cut-outs in the surface of the inner panel which is shown below:

• Now, embosses has to be created for the Hinge, Gas stay, Latch & striker as well as the wiper motor areas.

• The above latch emboss can be created with the help of drawing trajectory for opening/closing w.r.t the hinge axis.

4. CREATING REINFORCEMENTS:

• The reinforcements can be directly offseted from the inner panel surface using the Wave geometry linker and trim it accordingly
• All reinforcements are shown below:

5. OUTER PANEL CREATION-UPPER :

• Offset the surface to a distance of 2.65mm so that 0.2mm of clearance can be given in between the surfaces.

• Create the hem using the through curve mesh or swept tool in the surface panel. lso the surface must have tangent continuity.

• Reliefs has to be given in the corner areas for the easy manufacturability.

• The final part after creating the hem is shown below:

6. OUTER PANEL CREATION-LOWER :

• The same steps has to be followed for lower surface as well.

The thickened part after the assembling of all these components is shown below:

FINAL PART:

7. DRAFT ANALYSIS:

Every part which is manufactured from press tool or other forming tools require some positive draft on the faces which are parallel to the tooling direction. If we don’t give draft (Zero Draft) or give negative drafts on these faces it will stick to the mould surface and when the mould is in motion it will destroy surface thus reducing its surface finish. Thus Draft Analysis command enables us to detect if the part we have drafted can be easily ejected or not. It also give insights about the critical zones, so that appropriate changes in the design can be made if needed.

(I) Inner Panel

CONCLUSION

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.