Challenge

Design of backdoor

MMaktumsab Hallikeri26 Feb 2023

DESIGN NX-CAD

AIM:=

Use the provided styling surface to come up with a back door design, use appropriate design methodologies, and provide the necessary reinforcements and embosses.

What is a back door?

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 based on working positions.

The door or opening of a cargo area may be hinged at the top, side, & bottom. If the door hinged in the bottom it is called as a tailgate.

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.

2. 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. These doors are more convenient for the goods handlers for long pipe and lengthy components where one door is kept open.
These doors also save accidental head impacts. It is a lot easier to load and unload items in the side-mounted doors.

3. Bottom / split type:

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 the most convenient type of back door in which the bottom split is used as a support or even as a table for the tour going people.

Types based on working mechanism.

Gas stays type:

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 which is shown in the image below:

2. 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.

Powered trunk lift system consists of a power latch, anti-pinch switch, PTG ass’y, PTG main switch.
When the switch is pressed in the compartment or outside the power latch releases the latch and the entire backdoor is opened.
The anti-pinch switch is located in order to avoid accidental hand insertion during the operation of the door.

MANUFACTURING METHODS:

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.

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.

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:

Conventional die hemming: In conventional die hemming, the flange is folded over the entire length with a hemming tool.
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.

2. 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.

3. 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.

Door Test video link: https://www.youtube.com/watch?v=BcbBpNbziaU

Design of Back door in NX CAD:

BACK DOOR ASSEMBLY:

The back door assembly of a hatchback or SUVs has the following components.

Inner panel
Outer panel
Hinge reinforcement
Gas stay reinforcement
Wiper motor reinforcement
Latch/striker reinforcement

INNER PANEL:

The inner door panel is a component which is used for strengthening the door assembly and it is one of the most important components on which all accessories are mounted like hinges, glass guide channel, moulded 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 other BIW components where it is the aesthetic part of a 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 licence plate mountings. Most of the hatchback cars have the provision for wiper motor.

DRAFT ANGLE IS 7

Door parts thickness is given below,

Outer Panel - 0.75 mm
Inner Panel - 0.75 mm
Reinforcements - 1.5 mm

Given Data,

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. That is 5mm gap for mastic filling

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.

DESIGNING THE REINFORCEMENTS:

The thickness provided for all reinforcements is minimum thicken 0.75mm

HINGE REINFORCEMENT
GAS STAY REINFORCEMENT
WIPER MOTOR REINFORCEMENT
LATCH REINFORCEMENT

All the reinforcements were created using the same method, first, the linked body was created separately for each with the help of extract geometry and then the required portion was trimmed out and then thickened.

REINFORCEMENT:

The reinforcement provided is of 4 numbers which consist of hinge reinforcement, gas stay reinforcement, wiper motor reinforcement and latch/striker reinforcement.

Hinge reinforcement

Hinges enable the opening and closing of the back door. One end of the hinge is fixed on the backdoor and the other end on the Roof, on both sides. Hinges can be placed outside or inside the backdoor.
The hinge reinforcements are added to compensate for the weak region due to the acting load over it.

2. Gas Stay Reinforcement:

Gas Stay is a device used for supporting the back door in its open position. Gas stay requires no manpower and is engaged into support position automatically as the back door opens. One end of the Gas Stay is fixed on the backdoor and the other end on the Body Side or on the Back door stationary area.
Embossing is provided at the Gas Stay mounting area to compensate for weakness and improve strength.

3. Wiper Motor Reinforcement:

Wiper motor reinforcement is created to mount the wiper motor assembly.

4. Latch and Striker Reinforcement:

The Latch & Striker forms the locking mechanism of the backdoor with the car. Due to regular opening, closing, and over slamming of the backdoor, there is stress developed in the Latch and Striker area. To compensate for the same, reinforcements are added in this area.

HEMMING AND RELIEF OPERATION:

Hemming is a mechanical joint 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 relief:

Hemming reliefs are cut-outs 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

Latch/striker rotation angle:

This rotation angle of the line denotes the line of action of backdoor when hinged to the body of the car.
For positioning the Latch & Stricker, we have to create a trajectory passing through a midpoint of line/ axis of two hinge mounting holes,