Design of backdoor

DESIGN A BACK DOOR USING NX CAD.

                                                                    OBJECTIVE

To design a back door by with its given styling class A surface. The inner panel is assembled with hinge reinforcement,gas stay reinforcement, wiper motor reinforcement and the latch and striker reinforcement.

                                                                 INTRODUCTION 

• In this project we are going to design back door and the required reinforcements. the back door is a very critical component because we have to keep in mind of passenger safety and the space for luggage. the back door is open and closure commodity.
• The back door has to designed in a way such that we have enough space for luggage and the hinge,striker,gas stay and the wiper motor.
• The back door is made up two components usually the either the steel or the aluminium.
• If the back door is made up of aluminium then the weight of the back door is also reduced and the need of reinforcements is also not needed.
• But if the back door is made up of the steel then the weight of the component is more than the component which is made by aluminium and the need of the reinforcements is necessary also.
• Comparing to both the materials the aluminium is best but the cosrt of the aluminium is too high so the OEMs are manufacturing the back with the steel itself.
• 

DESINGNING OF BACK DOOR AND THE REINFORCEMENTS:

Outer Panel:

• The outer panel is the styling surface and it is the source for designing the inner panel and all the required reinforcements. The outer panel is the aesthetic surface so it has to be very smooth and a good surface finish so it should be attractive to the customers as well  as the visitors and moreover As the name suggests, it is the outer part of the back door and is mostly responsible for aesthetics of the vehicle. Outer and inner panels are connected by mastic sealants in center and by hemming process at edges.
• usually the thickness of the outer panel is 0.65mm to 0.75mm.
• The Outer panel also has the provisions for the tail lamp, rear fog lamp and also has the provision for license plate mountings.
• 

Innner panel:

• The inner Panel is a component which is used for strengthening the door. It's thickness is in the range of 0.65-0.75 millimetres. It is one of the most important components on which all accessories are mounted like Hinges, Gas Stay, Wiper Moter , Latch and Striker etc.
• the possible way for back door inner panel is stamping where the whole sheet is stamped in a single tool and it will reduce many tool to involve.
• when there is a openening and the closing of back door there is a lots of stress in the mounting regions so to make them work correct we will create emboses and the reinforcements.

REINFORCEMENTS:

The reienforcements are provided for the purpose of the reducing stress from the reinforced regions.

The inner panel of the  back door consists of 6 major reinforcements

• Latch and striker reinforcement
• hinge reinforecement RH
• hinge reinforecement LH
• gas stay reinforcement RH
• gas stay reinforcement LH
• wiper motor reinforcement

HINGE REINFORCEMENTS:

The hinge is the part which helps to open and close the door.

The onepart of the hinge is placed in the roof and the other part of the hinge is placed on the back door. when there is a opening and closing of the back door the hinge region will get some stress because it has holes to fix the hinge so the material will be less so there will be some stress to reduce and compensate that stress we are providing reinforcements.

GAS STAY REINFORCEMENT:

Gas stay is basically a gas spring that relies on elastic deformation of a compressed gas which is enclosed in a cylinder. It is used to reduce required effort while opening the back door.

one part of the gas stay is conneted on the back door and the other part is connected to the car so whenever the gas stay opens there is a stress on the gas stay region to compensate that we need to provide reinforcement.

WIPER MOTOR REINFORCEMENT:

Wiper Motor Reinforcement is create to mount the Wiper Motor Assembly.

LATCH AND STRIKER REINFORCEMENT:

The Latch & Striker forms the locking mechanism of the backdoor with the car. Due to regular opening and closing  of the backdoor, there is stress craeted in the Latch and Striker area. Further, during a rear collision this area will be the first point of contact. To compensate for the same, reinforcements are added in that area.

ASSEMBLY OF ALL REINFORCEMENTS WITH THE BACK DOOR INNER PANEL:

for the joining of outer panel upper and the lower and the reinforcements to the required area we use spot welding and for the ineer panel and the outer panel we use mastic sealents and the hemming.

HEMMING :

Hemming is the process of wrapping the flange of the outer panel to the flange of the inner panel so that they are fitting perfectly the below image will show a clear explanation of hemming.

here we have used 0.2 mm of clearence between each surface and the 2 mm of side clearence so that it wont have get frictioned.The reliefs were provided at the corners of the hemming flange to avoid the stress forming in the corner of the hemming.

MASTIC SEALENTS:

Mastic sealant is ideal for closing gaps in areas that need to withstand some movement yet require a durable seal  like shower walls, ductwork, and automobiles.

To improve NVH mastic Sealants are used. They also improves the strength. They are made of hard Rubber and are introduced as a paste thereby joining the inner and outer panel with a thickness of 5mm. Mastic Sealants are preferred over Spot Welding to join the inner and outer panel due to the fact that the latter reduces the aesthetics of the car, especially on the outer panel which is the styling surface. 

DRAFT ANALYSIS:

While designing a component a design engineer must make sure that the component can produced by any means of manufacturing methods with least amount of time material and manpower. So that we can reduce the overall cost of car. When the Back Door is considered it is manufactured by deep drawing at most of the time Deep drawing is the process where the single sheet of metal is place over a die which has the desired shape of the final output and the sheet is pressed against it with a tool. For the tool to come out from the part usually pressing relief of 5° to 9° will be provided during modelling itself. In NX draft analysis can be done after modelling so that we can verify whether the product is manufactured by pressing or not. One side of the surface is highlighted by green and other side by Red colour means that the model can be manufactured. Result of the draft analysis is shown in the below image.

CONCLUSION:

Hence the back door design is completed and all the design requirements of the back door afre satisfying.