Design of backdoor

CAR BACK DOOR DESIGN

AIM: To design back door of car using given outer class 'A' surface.

INTRODUCTION:

A door which is located at the rear side of a car which gives access for the boot space to store luggage, spare wheel etc.These doors can be operated manually or electric powered. In most of the luxury cars door is electrically operated.

• BACKDOOR:

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. It provide access to a cargo area (trunk/boot ).A tailgate hinged at the roof is a predominant characteristic of hatchbacks, estates/station wagons and liftbacks .The door or opening of a cargo area may be hinged at the top, side, or bottom.

            

Requirment of Backdoor,

• It serves as entry and exit point for luggage/passengers.
• It houses assembly of tail lamps, wiper motor and other components.
• It houses windshield glass which helps in rear visibility.

Types of Backdoor:

• Top mounted

These type of back doors are used in a station wagon, pickup truck and some other sports utility vehicles. Today’s modern cars use top mounted tailgating systems which are both powered and also gas stay supported. These tailgates provide greater rear visibility compared to other types.

          

• Side mounted

It is generally used in van type MPVs, SUVs, pickup truck vehicles. These side mounted door/barn doors are a lot easier compared to top mounted ones. These doors are generally small in size and can be easily accessed. These doors are more convenient for the goods handlers carrying lengthy objects, long pipes where one door is kept open. It also saves accidental head impacts. It is a lot easier to load /unload things in vehicles having side-mounted doors.

         

• Bottom/split mounted

This bottom type or split type backdoor system are used in the car type such as estate type car, pickup trucks and some luxury SUVs.These are most convenient type of backdoor in which the bottom split is used as a support or even as a table for the touring people.

          

Working Mechanism,

• 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 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. The following image shows the component as used in the powered trunk/back door lift system.

         

MANUFACTURING PROCESS:

Now a days, 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.

Conventional tailgate assemblies are made from stamped metal panels welded together to form a tailgate. Latches are added on either side of the tailgate to engage a striker on the pickup sides. A handle operates the latches to open and close the tailgate assembly. Steel tailgate assemblies provide a durable and secure closure for the pickup bed.Another disadvantage of steel tailgate assemblies is the cost of the tooling required and equipment required to stamp metal tailgate components. Metal tailgate components are generally produced in a large stamping press. The stamping presses generally require finely machined tools made from hardened steel. The cost of tooling a metal tailgate is much more expensive.

STAMPING PROCESS:

Stamping processes to be used for a panel depend on its design. However, normally the processes used extensively are blanking, drawing, piercing, forming, notching, trimming,hemming, etc. Blanking prepares the initial approximate form of the part in flat sheet. Drawing is generally the first operation to attain depth related form. Piercing, notching, hemming, are product design related operations. Trimming generally removes the extra material on the periphery of the panel provided for blankholding during draw operation. Decision on trim line is very important and becomes deciding factor to obtain good draw.

step by step process,

• Blanking

When required, blanking is the first step of the stamping process. Blanking is the process of cutting larger sheet or coils of metal into smaller, more manageable pieces. Blanking is usually performed when a stamped metal piece will be drawn or formed.

• piercing

If a part requires slots, holes, or other cutouts, piercing can be employed. Piercing, which can be performed simultaneously with blanking, punches the requisite shapes out of the metal sheet.

• Drawing

Drawing is the actual stamping in the metal stamping process. A punch forces a section of metal through a die, providing the primary shape of the part. When the depth of the part is less than the primary opening, it is considered shallow drawing; parts with a depth greater than the opening are deep drawn.

• Bending

Bending is a fairly self-explanatory process. The part-in-progress is placed on a specially designed die and a ram pushes against the metal, providing the required bend. Bending is performed after drawing, as attempting to punch an already bent piece of metal causes the entire part to deform.

• Hemming

Hemming is a technology used by the automotive industry to join inner and outer closure panels together (hoods, doors, tailgates, etc.). It is the process of bending/folding the flange of the outer panel over the inner one. The accuracy of the operation affects significantly the appearance of the car’s outer surfaces and is therefore a critical factor in the final quality of a finished vehicle.

          

BACK DOOR DESIGN:

Backdoor assembly consist of,

• Back door outer panel (upper and lower)
• Back door inner panel
• Hinge reinforcements
• Gas stay reinforcements
• Latch and striker reinforcements
• Wiper motor reinforcements

BACK DOOR OUTER PANEL:

In this design back door is created as two different parts back door outer panel upper and lower. This outer panel designed based on visibility criteria and proper reliefs provided at the corner for hemming operation .The thickness of outer panel is 0.75 mm 

          

Hemming

Hemming is a technology used by the automotive industry to join inner and outer closure panels together (hoods, doors, tailgates, etc.).In addition adhesive bond provide for excellent joining of panels it also reduce vibration .here this design 0.2mm clearance provided for hem glue.

          

Corner Relief

During hemming process multiple rollers are used which causes vibrations and stress concentrations at the some locations due to which design intent of the panel shouldn’t be changed (i.e the panel should spring back to original formation after roller is removed). But most of the time that is not the case at corners so to avoid that situtaion reliefs are provided at corners.

         

BACK DOOR INNER PANEL:

Back door outer panel  designed based  on hinge, gas stay, wiper motor position and reinforcement as well as visibility criteria .Suitable tooling direction is created  for trouble free manufacturing process.In this design stamping operations created based on this tooling direction. Embosses are provided in this design for force dissipation. In this design appropriate clearance given in mastic areas .The inner panel thickness is 0.75 mm.

          

Inner panel with Tooling direction.

          

Tooling Direction

The back door is going to be manufactured by deep drawing process. In Deep Drawing process have a tool which is core and Die. The core part follows the single Straight path the inclination angle of the core is known as a tooling direction. The tooling direction/axis is created so, that the Manufacturing team take the reference of this tooling axis and manufacture the part accordingly

Mastic Area

Mastics sealants used for  joining of outer panel and inner panel. It increase the strength of back door and good NVH. So accurate clearance given for mastic sealant.

          

• Reinforcements in inner panel 

All reinforcement parts spot welded on the inner panel for better strength on that area.  

 Hinge reinforcement

In this design hinges provided on the top side of the door. Appropriate  reinforcement given for hinge mounting areas to improve the strength.

          

Gas stay reinforcement   

Gas stays support the weight of the back door while they are open. More load act on this region ,So suitable  reinforcement provided  for better strength.it is spot  welded on the inner panel.

         

Wiper motor reinforcement  

Reinforcement provided in this region for fixing the wiper motor.

         

Latch and striker reinforcement 

The striker is designed to create a tight fit between the door and the seal on the cab. The door open and shut several times in a day.So more force acting on  this area.The reinforcement given in the latch and striker mounting area to increase the strength.it is  spot welded on the inner panel.

         

Trajectory

The trajectory is created to position the latch and striker .latch system must be able to catch the striker of the door  the while  closing. Circle is drawn from the hinge axis. The striker follow this path.

          

Draft Analysis 

Draft analysis performed to check the designed part  is suitable for stamping operation with respect to the tooling direction.We can find out the  errors by using this feature.The minimum draft angle is 7.The negative draft is  denoted by different colour so we can easily find out the unsuitable areas.

          

FINAL ASSEMBLY:

Backdoor assembly in differend view.

Backside View

          

Front view

         

Side View

          

Isometric View

          

CONCLUSION:

Thus the backdoor is designed  based on design considerations .Required  reinforcement provided on inner panel. The design is checked by using draft analysis feature.