Hood design-Week 2

HOOD DESIGN

Hood and Its components:

Hood is generally used to access the parts easily such as radiator,engine and many other parts.Its is used to decorate the car and add luxurious look.Hood is fundamentally a reinforced skin panel with many safety and quality requirements.The shape of the bannet is made aerodynamic in order to minimize the air effect.The hood systems maincomponents are hood inner panel,hood outer panel,striker plate and hinges.

HOOD DESIGN IN NX CAD SOFTWARE

The design of hood and its parts was done using Siemens NX CADsoftware program using its features surface modeling and sheet metal modeling.It was performed behind it based on the shape of the external surface of the model.Parameters followed in design are overall width of hood outer panel is 962.20mm,Cross height of hood outerpanel is 470.72mm,Outerpanel thickness is 0.75mm,Innerpanel thickness is 0.75mm,Reinforcement thickness is 1.5mm Hemming of outer panel length is 6mm,Hemming glue space height is 0.2mm,master section maximum thickness is 25mm and some filled radius are 6mm,10mm and 15mm.Hood hinges both sides thickness is 1.7mm.NX Assembly features used to assemblies the modeling components in workbench.Some important steps followed in hood design are latch trajectory, Mastic data and Emboss definitions.

In Computer Aided Designing models are first created in two dimensional sketching in sketch environment the converted into three dimensional models.Two dimensional sketching includes sketch environment, sketch curve toolbar and constraints toolbar.Three dimensional modeling NX CAD features are primitives,reference features, swept features,remove features,extract features and user defined features.Its features surface modeling and sheet metal modeling are used in hood and its components design.It was performed behind it based on the shape of the external surface of the model.

LATCH TRAJECTORY

Hood latch is the type of mechanical component that keeps the hood closed shut.the latch keeps the hood connected to the automobile and Its prevents the accidental opening.The latch trajectory is the path which the striker will flow when the hood is open and closed while pivoting on the hinge axis.The striker is placed 90 degree such that it is tangent to the circle.The latch trajectory is taken as a circle with the hinge axis as the center of the circle.

Latch Design Requirements:

• Spring must have enough stiffness to hold the hood.
• Less wear producing material is selected.
• Applied force to the hood latch should not be too large.
• Industry safety standards must be met.

MASTIC DATA

Mastic data should be provided in between hood outer panel and inner panel to achieve better NVH Range,to avoid the spot weld,to maintain the upper hood surface regularity.Generally mastic diameter should be about 80mm which called strengthen diameter of the mastic rubber.Mastic sealants applied must be between inner panel and outer panel.The following figure shows mastic position indicated as dotted circle.

EMBOSS DEFINITIONS

Sheet metal embossing is a stamping process for producing raised or sunken designs or relief in sheet metal.This process can be made by means of matched male and female roller dies or a strip of metal between rolls of the desired pattern.The metal embossing manufacturing process important characteristics are the ability to form ductile metals,use in medium to high production runs,ability to maintain the same metal thickness before and after embossing,ability to produce unlimited patterns depending on the roll dies and ability to reproduce the product with no variation.suitable materials for embossing process are,

• Aluminium(All alloys)
• Aluminium(T1/T2)
• Brass
• Cold & hot rolled steel
• Copper
• Galvanized steel
• High strength,low alloy steel
• Steel(All alloys)
• Zinc

MANUFACTURING PROCESS

Deep drawing and Hemming processes are the widely used method for car hood manufacturing. The deep process is a forming process which occurs under a combination of tensile and compressive conditions.A flat sheet metal blank is formed into a hollow body open on one side or a hollow body is formed into a hollow body with a smaller cross-section.The sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by mechanical action of a punch.The main defects of deep drawn parts are wrinkling or necking.

Hemming is a technology used by the automotive industry to join inner and outer closure panels together.It is the process of bending/folding the flange of the outer panel over the inner one.In this process the rolling wheel rollers is perform the hemming on work part.this process followed in three steps are pre-hemming,hemming and final hemming.before the hemming processes high-strength adhesive is filled on hemmed panels to increase crash resistance and prevents corrosion.To achieve a better final geometry in vehicles part the hemming is performed.