Design of backdoor

CAR BACK DOOR DESIGN

AIM : To design car back door from given styling surface data under given design rules and regulations.

CAR BACK DOOR AND ITS COMPONENTS: The back door is a tail gate at the rear of the vehicle. It may used for loading and unloading utlities or to get passengers in and out . The back door comprises of certain components which from the back door assembly together.

COMPONENTS OF BACK DOOR:

INNER PANEL – The inner panel as the name suggest is the inner part of the door. It is where most of the reinforcements and components are mounted. It is manufactured either by casting or sheet metal stamping .The thickness of inner panel is 0.75mm.

OUTER PANEL- As the name suggest it is the outer part of the door and mostly responsible for asethetics 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 2part outer panel for our design , outer panel upper and outer panel lower respectively. Outer panel is manufactured by stamping steet metal. The thickness of the outer panel is 0.75mm.

REINFORCEMENTS - 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 collasions. The reinforcements are manufactured by stamping and the thickness is 1.5mm.

GAS STAY – Gas 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.

DESIGN METHODOLOGY – We start with the styling surface that is provided to us and considered top-down approach for the assembly. First we create the assembly and the create the components in the assembly it self. Inner and outer panel are the largest parts and all other parts depending on them so we start with them . Also the styling surface is the part of the outer panel so we create it first using various coomands and features we design the outer panel from styling surface. We have 2 parts for outer panel namely outer panel upper and outer panel lower . They will be spot welded with each other . Inner and outer panels are connected by hemming process so we can come back to outer panel and do that after completion of inner panel.

Now as we know that the inner panel is at a particular distance from outer panel , we offset the outer panel surface and design inner panel on the same . Inner panel is imporatant as most the mountings will be done on it. We need to define the tooling direction as a reference for manufacturing team. Then we design the inner panel.

While designing the inner panel we need to considered various factors like the mounting point positions , mastic sealant application positions and the cut outs in sheet to make access to tail light assemble easier. As the lower part of the inner panel is not connected to outer panel we need to create a surface that comes out and connects to outer panel as shown in the figure. This part will be connected to outer panel using mastic sealants. Also the hinge embosses must be taken by considering proper directions.

As the inner and outer panel are connected by hamming process we can completed the hemming after completion of the inner panel. Now as the major parts are designed we can move to reinforcements. It is fairly easy to design reinforcements as shown in the figure and we can use the inner panel surfaces using wave geometry linker into the corresponding reinforcement parts.

IMPORTANT FEATURES USED IN DESIGNING OF BACK DOOR-

• 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 object may be edges or sketch curves.
• Sew- it combines sheet bodies together by sewing their common edges .
• Projected curve – it is used to project an existing curve or curves on a selected plane or surface by selecting a direction for projection.
• Offset surface – it allows 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 a portion of sheet using curves , faces, edges, or planes.
• Through curves – it will allow you to create a body through multiple sections.
• Law extension – it extend a curve or edge to create a sheet body at desired angle and length .
• Trim and extend – it helps 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 to extend the sheet to required distance.
• Emboss – it creats an embossing by modifying a body with faces created by projecting a curve along a direction.
• Wave geometry linker – with this we can create linked copies of any entity of a part into other parts.
• Mirror geometry – we can create an mirror geometries about selected plane or surface.
• Thicken – it used to convert a surface to solid body by providing thickness.

In order to sure that the design of inner panel is proper or not we do draft analysis. We need to define the drawing direction and select the inner panel . We take limit angle as 5 deg . The result of the draft analysis is as follow.

CONCLUSION- Car back door was designed using NX CAD by using given styling surface and the design regulations.