Design of backdoor

AIM

Using the provided styling surface to come up with a back door design and  using appropriate design methodologies and make 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 DOOR

This type of back doors is used in a station wagon, pickup truck and some of the sport utility vehicles .

oday’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.

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.

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.

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.                  

SIDE /SLIP TYPE :

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:

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.

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.

     Recently, 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.

ULSAB suggests three main weight reduction techniques such as hydro-forming and the tailor welded blank (TWB).

Tailor welded blank:

     A tailor-welded blank is a blank that is comprised of two separate pieces of sheet metal that have been welded together prior to stamping. Tailor welded blanks allow the welding of the different grades, different thickness or different corrosion coatings together in order to give the properties needed in different areas, without increasing the number of tools needed to form the part and eliminating the fit ability concerns. They also allow a high degree of flexibility in designing parts and large blanks can be formed from much smaller sheets. The use of tailor-welded blanks would reduce the weight of the car. Having the ability to selectively place different thickness of material would result in weight reductions. An example of this used in production is the door inner panel. The only strength requirement on a door inner is in the region where the hinges attach to the panel.

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

OUTER PANEL

INNER PANEL

CLASS A SURFACE

in Automotive Industry There Will Be a Dedicated Team Who Will Perform the Aesthetic Designing of VariousComponents Including The Whole Vehicle. They Will Create Various Concept Sketches After Ideation. AfterThat, They Will also create a Class A Surface Of The Product. This Class A Surface Is Then Passed Over To The NPD CAD Team. They Will Initially Inspect The Class A Surface In Order To Check If The Design IsManufacturable Or If It Is Following The Engineering Principles. If There Are Any Issues About The Design, TheyWill Contact The Product Design Team And Will Ask To Modify The Class A Surface In Order To Solve TheProblem. Here I Received The Class A Surface of Back Door.

OUTER UPPER SURFACE

OUTER LOWER SURFACE

TOOLING AXIS CREATION

      

Later on, edges are Swept along the tooling direction with the draft angle of all the partsdesigned have to be producible

Here The surface of the inner panel is created using the multi-section and then extrapolatingand trimming .At the trimming region of the upper and lower panel 

 

 

 

LANCING

 

Lancing is a press operation in which a single line cut or slit is made on part way across the strip stock, without removing any metal. As a result, the proper lancing engineering method prevents fracturing by improving the sheet metal flow.

 

 

EMBOSSING

 

Creating emboss in the outer panel direction because when collision happens from backside of the car thisimpact initially falls on the embossed faces then force dissipates according to the design of emboss then theremaining force hits the inner panel. For this case I designed my emboss towards outer panel direction.

 

Emboss should be in 7 degrees to 25 degrees inclined in angle and it should not be in 90-degree angle, whybecause when we do stamping in manufacturing the stamping tool fits the sheet metal hence it will not comeout of that sheet metal, So this is the main reason why the emboss face is in angle.

 

 

MOUNTINGS

 

 

HING AND GAS STAY MOUNTINGS

 

Hinge is used to connect the door to the BIW also enables the opening and closing of the hood. So, theembosses are created of the hinge along with reinforcements to provide additional support to the innerpanel.-The Hinges are created at the top of the inner panel using the parallel curves and corner option. Use the split option to cut the elements and perform a sweep with an angle of 7 to 15  degrees. Offset the surfaceto 4mm and trim it with the sweep surface. Give the fillets of 4mm to it

 

 

LATCH MOUNTING

 

For the latch, it is important to keep the latch embossment according to the trajectory the door opening andclosing follows.-Take create a centre point between the two hinge parts and draw a circle marking the sweep of the lower endof the inner panel. Draw a Tangent to the Circle and create the cut on the tangent area and give the cut-outsto it

 

 

WIPER MOUNTING

 

Similarly, the embossment for the wiper motor has been created as shown below

 

 

 

REINFORCEMENT

 

 Reinforcements and embosses are added or designed to compensate for loss of strength in a region or areadue to the load acting there. In back door's case load acts in the form of Hinge, Gas Stay and Latch & Striker.These load cases are determined with the help of various tests and simulations.-Thickened the inner panel and extract the hinge and around surfaces

 

Gas stay Reinforcement

 

Gas Stay is a device used for supporting the back door in its open position. Gas stay requires no man powerand is engaged into support position automatically as the back door opens. One end of the Gas Stay is fixed onthe backdoor and the other end on the Body Side or on the Back door stationary area. Embossing is providedat the Gas Stay mounting area to compensate for the functional holes punched.

Various simulation tests like Bend test, Torsion test, Abuse test performed on the back door , there a veryweak zone developed at the Gas stay region. To compensate that, a reinforcement is added in that region

 

 

 

HING REINFORCEMENT

 

Hinge is a pivot mechanism which supports the total weight of the backdoor. So reinforcements are added for strength and rigidity

 

 

 

 

LATCH 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. Further,during a rear collision this area will be the first point of contact. To compensate for the same, reinforcementsare added in this area.

 

 

 

WIPER MOUNTING REINFORCEMEN

 

Wiper is used to wipeout the dust particles/water on the windshield glass which affects the rear visibility. It is actuated by the motor which is mounted on the inner panel. Due to vibration and heat of the motor, inner panel gets deformed which results in loss of strength & rigidity of the panel thus leading to poor NVH. So reinforcement is provided to avoid these conditions.

 

 

ALL REINFORCEMENTS

 

 

 

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

 

 

 

 

CORNOR 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.

 

 

CORNOR RELIEF ON LOWER PANEL

 

 

CORNOR RELIEF ON UPPER PANEL

 

 

 

DRAFT ANALYSIS

 

Every part which is manufactured from press tool or other forming tools require some positive draft on the faces which are parallel to the tooling direction. If we don’t give draft (Zero Draft) or give negative drafts on these faces it will stick to the mould surface and when the mould is in motion it will destroy surface thus reducing its surface finish. Thus Draft Analysis command enables us to detect if the part we have drafted can be easily ejected or not. It also give insights about the critical zones, so that appropriate changes in the design can be made if needed.

 

DRAFT ANALYSIS OF OUTER UPPER SURFACE

 

 

DRAFT ANALYSIS OF OUTER LOWER SURFACE

 

 

DRAFT ANALYSIS FOR INNER PANEL