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.

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.

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.

Mastic Region:

The mastic points are defined on the back door inner panel where the back door can 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 believe like the rubber.

The gap between the inner panel and the outer panel over the embosses is filled with mastic sealants at curtained specified places, this helps to reducing vibrations and overall NVH (Noise, Vibrations and Harness)

Then, the sheet will bend with the helped of another die to make the flanges in “L” Shape.

 

Inner Panel:

The inner panel is a component which is used for strengthen the door assembly and it is one of the most important components on which all accessories are mounted like hinges, glass guide channel, molded trim, latch etc. the possible method is the integration method. In the integration method, the part is stamped out of a single blank. This reduces the number of tools needed, the assembly cost and eliminates any fit ability problem.

Outer Panel:

 

The outer panel of the back door is similar to the other BIW components where it is the aesthetic part of vehicle. The coating provided is of multi stage which has the property of scratch resistance, rust prevention and smooth and attractive finishes. The outer panel also has the provisions for the tail. Lamp, rear fog lamp and also has the provision for license plate mountings. Most of the hatchback cars have the provision for wiper motor.

Embosses & Reinforcement:

With the distinctive cross section, embosses are created. The embossed are used to increase the strength of the backdoor. While designing we should keep in mind that it should not be over strength. So we prefer to design big embosses rather than small embosses. These embosses are used to despite the forces sideways.

                                                                                                  Indoor Embosses:                                                                       

                                                                                                          Gas Stay Reinforcement:                                                                                                                                                                                                                                     

Hinge Embosses:

The backdoor is a swinging commodity, which swings with the help of hinges. This can be done by tentatively positioning the hinges and on the hinge axis, we take a center point. Again we take another center point on the latch hole. Taking these two points as a reference we draw a circle. This circle is the striker trajectory and it has to be perpendicular. This can be achieved by moving the hinge axis back and forth or by rotating the latch area.

 

Latch and striker trajectory:

To define the opening and closing trajectory, the hinge and latch are positioned based on the hinge axis and trajectory. The circle drawn should be perpendicular to the latch striker to satisfy the condition. Based on the rotation trajectory the hinge axis, latch striker and predefined Gas stay are correlated for smooth kinematics of the door opening and closing.

                                                                                                  5 Wiper Mechanism Reinforcement:                                                                                                                                                                                                                  

Hemming Operation:

                                                               

Hemming is a mechanical joints design which is used for joining inner and outer closure panels as found indoors, hoods, bonnets and lift gates. To increase crash resistance the gap between the hemmed panels is filled with a high strength adhesive which also prevents from corrosion.

                                                               

Hemming Corner Relief:

Hemming relief are cut out which are provided on the hemmed corner of the panel assembly which in turn to avoid some of the hemming defects such as wave – like or wrinkle formed surface as shown below,

The back door design requires two locations where the roller type of hemming relief is required which are shown belief.

 

DRAFT ANALYSIS:

(I) Inner Panel