Design of backdoor

AIM:

• To design the back door of the carr and make the inner panel for the back door and also design the necessary re-enforcements.

Objective:

• To design Back door of car using the given Class ‘A’ surface.

62785-60030	Spacer, Back Door Glass; Spacer, Quarter Window Glass; Spacer, Quarter Window Glass Lh; Spacer, Quarter Window Glass, Rh	1.54	2
62786-10010	Spacer, Quarter Window Glass, No.2	1.71	4
64818-10020	Spacer, Back Window Glass, No.1	1.81	1
64819-10010	Spacer, Back Window Glass, No.2	1.81	1
67281-10010	Stopper, Back Door	7.33	1
67293-10010	Cushion, Back Door Lower Stopper	3.31	1
67294-10010	Cushion, Back Door Stopper	3.31	1
67881-10090	Weatherstrip, Back Door	66.27	1
67893-10010	Protector, Back Door Panel, No.1	10.04	1
67894-10010	Protector, Back Door Panel, No.2	10.04	1
68105-10901	Glass, Back Door	459.88	1
75129-40010	Cushion, Rear Licence Plate; Cushion, Rr Licence Plate	1.00	2
75573-10100	Moulding, Back Window, Outside	8.53	1
75574-10030	Moulding, Back Window, Outside Lh	8.53	1
75575-10040	Moulding, Back Window, Lower	11.95	1
90109-08316	-	1.00	-
90119-06782	Bolt	1.00	-
90541-09142	Cushion (For Back Door Panel)	1.00	2
PANEL SUB-ASSY, BACK DOOR
67005-10A00	Panel Sub-Assy, Back Door	443.82	1
67005-10A10	Panel Sub-Assy, Back Door

Functions of the Backdoor:

• It protects the occupants and luggage from getting damaged.
• It houses assembly of tail lamps, wiper motor and other components.
• It serves as entry and exit point for luggage/passengers.
• It houses windshield glass which helps in rear visibility.
• Parking sensors, rear view camera are mounted on it.

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 mounted

Bottom type or split type backdoor system is used in estate type cars, 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.

Materials Selection:

The selection of material plays a major role in determining the overall weight of the back door. The common materials used are Steel & Aluminum. The density of Steel is higher than Aluminum thus adding more weight to the door. The material used in the manufacturing of the backdoor depends upon the budget of the car, most low cost vehicles use steel as it is cheaper compared to Aluminium. Another aspect to be noted is that, if casted Aluminum parts are used instead of deep drawn steel parts there is no need of reinforcements and the overall weight of the car is reduced by approximately 5-10kg thus increasing the performance of the vehicle. Also the draft angle for casted parts is around 3 degrees while for deep drawn parts is around 7-10 degrees which helps in increasing the luggage/ cabin space.

Fig. above shows possible no. of parts in aluminium backdoor

Back Door Assembly:

• Inner panel
• outer panel
• hinge and its reinforcement
• wiper motor reinforcement
• latch & stricker and its reinforcement

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.

Components to be designed:

1) Outer panel

• It is the outer styling skin surface of the back door. It is provided with multistage coatings which has property of scratch resistance, rust prevention etc. It is wrapped around the inner panel through hemming process.

Hemming:

• Hemming is a forming operation in which the edges of the sheet are folded over another part in order to achieve a tight fit. Usually 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.

Design of Back door in NX CAD:

Door parts thickness is given below,

1. Outer Panel - 0.75 mm
2. Inner Panel - 0.75 mm
3. 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.

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,

Assembly:

Draft Analysis:

Inner Panel:

Hinge reinforcement:

Gas Stay reinforcement:

CONCLUSION

• The back door outer and inner panel were designed with the help of the styling surface along the tooling direction.and
• Draft analysis was performed on the inner panel and All the reinforcements were designed and placed at appropriate positions.