Design of backdoor

AUTOMOTIVE DESIGN OF CAR BACK DOOR USING NX CAD

OBJECTIVE:

• From the given styling surface, develop a back door using appropriate design methodologies.
  
  
• The objective of this project is to design a BIW Back Door of a car with an Inner Panel, Outer Panel, and Reinforcements for the Hinges, Gas stay, Wiper Motor, and Latch by following the engineering standards.
  
  
• The Inner Panel must be subjected to Draft Analysis for verifying whether it satisfies the Deep Drawing requirements for the tooling direction created in the design.
  

SOFTWARE USED:

• Siemens NX CAD (Unigraphics)

INTRODUCTION:

• The Back Door of a car is the rearmost part of the vehicle which gives access to the trunk space of the vehicle. The rear door also supports the reinforcements and added weights of the Wiper Motor, Gas Stay, Tail Lamp, and Latch and Striker.
  
  
• The Backdoor/tailgate is one of the closure commodities in BIW sheet metal design. The backdoor has a lot of components inside and is designed to incorporate them easily. It affects the rear visibility and luggage area.
  
  
• The material used for door manufacturing depends on the budget and performance of the vehicle. Mostly Aluminium and Steel will be used whereas low-budget vehicles use Steel which makes the manufacturing process easy and cost-efficient since it follows the Stamping of Moulds.

TAILGATE:

             Tailgate is a door at the back of a truck or car, that is hinged at the bottom so that it open downwards.

              

                    

Different Sheetmetal processes used for manufacturing the Back Door

Deep Drawing:

The metal deep drawing process is an effective method of manufacturing of cups, cans and other similar deep drawing products. The deep drawings having two main categories.

1. First- stage drawing: The blank shape of metal is placed on the die and contact with the punch. When the metal specimen is flat piece of sheet metal used in forming and finish the product. Initially the punch moves in downward direction. The outer rim of blank is subjected to pure radial drawing (drawing toward in vertical axes) between die and blank metal. The metal become a bend and sliding over die and also stretched between die and punch. The metal in vicinity of punch head and contact with it bend and slide over radii and stretch over punch head.
   
   
2. Redrawing: The components drawn from first stage again it is redrawn convert into more depth to form a cup shape in the die and punch. The second stage of drawing is called as redrawing.
   
   
   

Embossing:

Embossing is a metal forming process for producing raised or sunken designs or relief in sheet materials by means of matched male and female roller dies, theoretically with no change in metal thickness or by-passing sheet or a strip of metal between rolls of the desired pattern. Metal sheet is drawn through the male and female roller dies producing a pattern or design on the metal sheet. Depending on the roller dies used, different patterns can be produced on the metal sheet.

Materials commonly used in the metal embossing process include:

• Aluminum alloys
• Steel alloys
• Zinc
• Copper
• Galvanized steel
• Brass
• Cold rolled steel

Hemming:

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. Normally hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges.

In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join two sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, doors, trunk lids and fenders.

There are various types of hemming operations:

1. Conventional die hemming: In conventional die hemming, the flange is folded over the entire length with a hemming tool.
   
   
2. Roll hemming: In roll hemming, the hemming roller is guided by an industrial robot to form the flange.

                    

Open Hem: A Hem has a full round feature and a return flange. In open hem bend angle is equal to 180 degrees.

Tear drop Hem: In tear drop hem the bend angle is greater than 180 degrees.

Closed Hem: Hems without any inside radius are called as closed hem. Closed hems are not recommended if the hem geometry is to be painted or if the material used is SST or Aluminium.

Blanking:

Blanking is a cutting operation of a flat metal sheet and the article punched out is known as blank. Blank is the required product of the operation and the metal left behind is considered as a waste.

Punching:

It is similar to blanking only the main difference is that, the hole is the required product and the material punched out from the hole is considered as a waste.

Major Parts and Reinforcements:

    The backdoor consists of the following basic components:

1. Backdoor Outer Panel (Upper)

2. Backdoor Outer Panel (Lower)

3. Backdoor Inner Panel

4. Hinge Reinforcements (LH & RH)

5. Gas-Stay Reinforcements (LH & RH)

6. Latch and Striker Reinforcement

7. Wiper motor Reinforcement

Design of Back door in NX CAD: 

Given surfaces has to be repaired according to the smoothness. After repairing the surfaces, the door is divided into two parts as Door Outer Upper and Doo Lower Panel.

First, we need to create the Tooling direction for the Deep drawing operation. It shows that all the operations like embossing is done by considering this vector direction and it will help in manufacturing the part,

After that we have to create Sealing Flange by offsetting the outer panel to the specific distance.

Then we will be creating the Back door inner panel flange by offsetting the outer surface at a distance considering the sheet thickness and thickening direction.

Then created the connecting flange to join the inner panel and sealing flange.

Then for the windshield panel mounting, windshield panel is created and joined with sealing flange.

Then to improve the strength of the inner panel and to reduce the weight 'Y' type emboss and other cut-outs are created. Also, for Latch and Stricker mounting cut-out is created. This cut-out is also done on other side of the inner panel to maintain the centre of gravity of the Back door.

Another Emboss is created for Wiper motor mounting.

Another flange is created to reduce the vibration of door by joining the inner and outer panel with the help of Mastic sealant.

Now to assemble the back door with the vehicle Hinges are used to open and close the door. For that to increase the local area strength we have to design the emboss and provide the appropriate reinforcements to withstand the load acting upon it.

Hinge Reinforcement

For positioning the Latch & Stricker, we have to create a trajectory passing through a midpoint of line/ axis of two hinge mounting holes,

Latch & Stricker Emboss

Gas Stay Emboss and Reinforcement

Wiper Motor Reinforcement

Hemming and Hem Relief:

Hemming and seaming are two similar metalworking processes in which a sheet metal edge is rolled over onto itself. Hemming is the process in which the edge is rolled flush to itself.

Assembly:

Draft Analysis:

• The draft analysis will be performed for the tooling direction created at first and checked that the model is suitable for manufacturing.

• Then to get a complete green portion the necessary changes to the draft angle of the embosses were carried out by optimizing the model.

• The Draft Analysis command enables us to detect that the part drafted will be easily removed or not.

• This type of analysis is performed based on color ranges identifying zones on the analyzed element where the deviation from the draft direction at any point, corresponds to specified values.

Inner Panel:

Hinge reinforcement:

Gas Stay reinforcement:

Views of the designed Back Door:

Front view:

Side views:

 

 

Top view:

 

Bottom view:

 

Back view:

 

Isometric View:

 

CONCLUSION:

Thus the Body In White Back Door of a car was designed following the engineering standards and also the deep drawing requirements were satisfied.