Design of backdoor

Backdoor

Aim

To Design the outer upper and lower panel, inner panel with the necessary reinforcements by following the Master section with the design parameter for the given class A surface.

Introduction of Backdoor

• 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 Back door

1)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.

Design Considerations

• Rear Visibility for safety and functionality
• Support structures (Hinge,Gas stay)
• Rear crash regulation
• Boot Space
• Mounts for wiper motor
• Strength
• Draft Analysis

Mechanisms for Rear Door

1)Gas stays

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.

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.

Components to Create

1. Outer Upper Panel
2. Outer Lower Panel
3. Inner Panel
4. Gas Stay Reinforcement
5. Hinge Reinforcement
6. Striker Reinforcement
7. Wiper Reinforcement

Procedure

1. Checking the Geometry

• Once the model is opened, we get a Class A Surface of the Back door.
• We want to see weather the surface is joined or not . If it is not joined try joining the surface of the backdoor, if the surface sews together, we get the outer surface and if the surface didn’t join then we need to create the surface by using studio surface tool
• Create the fillet areas, Tail Lamp areas as those areas will be vulnerable and are unable to join together.

2. Tooling axis creation

• Draw a line from left and right extremities almost parallel to the path of the surface along the unsymmetrical axis.
• Using the Derived lines tool, create a bsecting line as shown below

3. Creating Inner panel

The inner panel, as the name suggests, is the inner part of the door. It is where most of the reinforcements and components are mounted. It is manufactured either by casting (aluminum) or sheet metal stamping (steel). Thickness of inner panel is 0.75 mm.

• First offset the surface to a distance of 1.7mm, which will give the innerpanel surface position.
• Now create sealing flange for the inner panel and create a upper flange and lower flange.
• By using blend command connect the upper and lower flange.

• Then create a wind shield and saw the two surfaces and create emboss for latch and stricker, gas stay, hinge and wiper motor region.
• A mastic sealent is used on the surface to connect the inner and outer panel with a gap of 5mm.
• So offset the outer surface 5mm downwards and create a plate from the inner panel and give proper embosses and cut-outs in the surface of the inner panel.

• Now, embosses has to be created for the Hinge, Gas stay, Latch & striker as well as the wiper motor areas.

• The above latch emboss can be created with the help of drawing trajectory for opening/closing w.r.t the hinge axis.

4. Creating Reinforcements

• The reinforcements can be directly offseted from the inner panel surface using the Wave geometry linker and trim it accordingly.
• Reinforcements are provided to provide support and add extra material to the sheet metal part to increase its strength near component installation regions and minimize the impact of collisions. We have considered following reinforcements during our design. The reinforcements maybe manufactured by stamping. Thickness of all reinforcements is 1.5 mm.

a) Hinge

Hinges connect the door with the vehicle body and allow the door to rotate around a fixed axis for opening and closing movement. Generally, hinges are a 2-part assembly, where one part is bolted to door and other is bolted to vehicle body.

b)Gas Stay

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. Although all the cars don’t come with gas stays, it may be required in case of a heavy back door.

c) Latch

5. Hemming fur outer Panel

• Offset the surface to a distance of 2.65mm so that 0.2mm of clearance can be given in between the surfaces.
• Create the hem using the through curve mesh or swept tool in the surface panel. lso the surface must have tangent continuity.
• Reliefs has to be given in the corner areas for the easy manufacturability.

6. Outer Panel

As the name suggests, it is the outer part of the rear 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. The outer door handle and in some cases, the number plate may also be installed on the outer panel of the back door. We have considered a 2-part outer panel for our design, outer upper panel and outer lower panel prospectively. Outer panel is manufacture by stamping sheet metal. Thickness for outer panel is 0.75 mm.

Important features used while designing

• Wave Geometry Linker – With this you can create, associative or linked copies of any entity of a part into other parts. It may be a surface, edge, curve, body, sketch etc. The changes made to the original entity will be reflected in the copy of that entity.
• Extract Body – It is used to create an associative body by extracting faces, entire body or region of faces.
• Bridge Curve – It helps to create a tangent blend curve between two objects. The objects may be edges or sketch curves.
• Sew – It combines sheet bodies together by sewing their common edges. There shouldn’t be any gaps larger than specified tolerance.
• Unsew – This command is used to separate the existing sheet body or solid body into multiple bodies.
• Projected Curve – It is used to project an existing curve/curves on a selected plane or surface by selecting a direction for projection.
• Trim Body – It is used to trim one or more bodies using a face or plane. You can also specify the bodies to retain and the bodies to discard.
• Offset Surface – It allows you to offset one or more existing surfaces.
• Offset Curve in Face – This command will allow you to offset particular edges or curves on selected faces.
• Trim Sheet – It is used to trim off a portion of a sheet body using curves, faces, edges or planes.
• Through Curves – It will allow you to create a body Through multiple sections, where it’s shape changes to pass through each section.
• Law Extension – This command extends a curve or edge to create a sheet body at desired angle length by changing the rules under angle law and length law.
• Trim and Extend – It helps you to trim and extend intersecting surfaces and make corner at their intersection.
• Face Blend – It creates fillets between faces.
• Edge Blend – It creates fillets on edges.
• Extend Sheet – It will allow you to extend an existing surface to required distance.
• Emboss – Emboss command creates an embossing by modifying a body with faces created by projecting a curve/section along a direction. You can modify the emboss using options like endcap location and draft angle.
• Mirror Geometry – As name suggests, it allows you to mirror geometries about selected plane or surface.
• Thicken – It is used to convert a surface to solid body by providing thickness.
• Extrude – It helps you to create a feature from a sketch. You are also able to create thin feature using a sketch or curve under this command.

FINAL PART

Draft Analysis

In order to make sure the drawing of inner panel body is proper, we do draft analysis. We need to define the drawing direction and select the inner panel body. We take limit angle as 5 degrees.