Hood design-Week 2

Title: Design Of Hood Using NX CAD System.

Objective:

The objective of this project  is to design Hood Outer Panel,Inner Panel and assembling all if them along with hinge and striker with showing the trajectory of Hood with reference to hinge axis.

Introduction:

 A car hood also referred to as a bonnet in some other countries is the hinged cover that rests over the engine of a front-engine vehicle. Its purpose is to provide access to the engine for repair and maintenance. Car hoods are typically constructed from steel and sometimes from aluminum.

                                                                                    

The hood release system is common on most vehicles and typically consists of an inner hood latch/lock handle, a hood release cable, and a hood lock assembly. The hood lock handle is usually located under the steering wheel, next to the driver’s seat, or in the door frame.A hood is meant to protect the vehicle’s performance parts like the engine or battery.

Design Methodlogy:

In this design project we are going to see some of predefined standard rules to be followed while designing the hood of a car by considering the outer look of the vehicle along in the perspective of the safety for riders and pedestrains in case of accident.

                                                         

Parts Of Hood :

-Hood Outer Panel

-Hood Inner Panel

-Striker

-Hinges and Reinforcements

HOOD DESIGN CONSEDERATIONS:

BENCH MARKING:

For the design of hood, benchmarking plays a key role. Comparing the products of same class of vehicle in market provides the better information to achieve or identifies the solutions to be the best in market.Resource management and scrap control have a major part in process adaptions after benchmarking.

ERGONOMIC CONSIDERATIONS:

 Automotive ergonomics is the study of human comforts, that’s to be consider in automotive design.

1)Hood opening angle

2) Latch and Striker operation

1 Hood Opening Angle:

Head zone criteria is one of the important factors in designing the hood. The proper head reach should maintain to avoid head injuries. This angle will vary from person to person and country to country. Hood opening angle is design in a way by taking average height of the people in that country into consideration.

                                                       

If average height increases and opening angle should be designed accroding to that. A good opening angle provides better comfort and ease, in performing maintenance and repairs at engine compartment

2.Latch And Striker Operation:

Latch and Striker mechanism take a main role in effective locking operation of hood. As a design engineer one must calculate the hood hinges center axis and striker trajectory.
And then striker and latch should arrange in such a way that their centerline falls on the hood hinges axis center point to have better locking conditions,
A design engineer must check this possibility and should position the latch and striker to have effective locking of hood.

DESIGN OF HOOD:

-Hood Outer Panel :

                                               

 It will be provided as skin and the hemming should be done to it by considering the relief dimensions for glueing and bending operations.Along with hemming we join the panels with mastic sealant, for that 0.2mm gap is maintained between both inner and outer panel for mastic sealant to seat. 

-Hood Inner Panel :

By using the master sketch we should make the inner panel by using appropriate commands in NX.Embossing need to be done in the inner panel to strengthen the hood because any vibrations in the hood will cause large noise while the engine is turned on and while travelling.

Embossing :

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 by passing sheet or a strip of metal between rolls of the desired pattern.

The metal sheet embossing operation is commonly accomplished with a combination of heat and pressure on the sheet metal, depending on what type of embossing is required. Theoretically, with any of these procedures, the metal thickness is changed in its composition.

                                                                     

                                                                                

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. The pressure and a combination of heat actually "irons" while raising the level of the image higher than the substrate to make it smooth. The term "impressing" refers to an image lowered into the surface of a material, in distinction to an image raised out of the surface of a material.

In most of the pressure embossing operation machines, the upper roll blocks are stationary, while the bottom roll blocks are movable. The pressure with which the bottom roll is raised is referred to as the tonnage capacity.

Mastic Points :

Mastic adhesive is a very strong bonding agent used in many commercial and industrial settings, building construction. It is traditionally derived from the resin of the mastic tree, which is where it gets its name, though it is commonly manufactured synthetically as well. Depending on the application it is generally available in thin liquid, thick glue, or paste form. It can quickly and permanently bind many different materials together, though in most cases it works best on hard, non-porous surfaces like metals.

                                                                

In the Inner Panel we will need to provide the mastic points for glueing the outer and inner panel because fasteners cannot be used to screw the Class A sufaces of a vehicle i.e, it will damage the outerlook if we use fasteners.

- Striker :

It is nothing but the mounting which provide locking to the hood with the car body by carrying a hook.It is screwed to the inner panel on a separate emboss to mount the striker.

                                                                              

-Hinges And Reinforcements :

Hinges allow the hood to rotate about the axis of hinge to easily open and close the hood.They are fatened to the inner panel and the other end to the body of car.

                                                 

                                                        

Behind the hinge placement position on the inner panel ectra reinforcement sheet to be added for strengthening purpose.

Draft Analysis :

This analysis is used to know the uneven or excess bends on the surface that we have created.Draft angles more than certain limits is difficult to manufacture.

                                                       

-Latch Trajectory :

 Finally after completing the design and assembly of hood we need to check the trajectory of the hood by taking the axis of rotation from the hinge.

                                                                                

                                                                      

Hood Assembly Views: 

                                                                 

                                                                     

Conclusion:

               Thus the design of Hood is completed by following the different set of rules by considering safety,manufacturability and easy accessability.