Week 9 - Challenge 3 - Bumper
AIM: To Design the bumper of a car using class A surface using CATIA sotfware.
INTRODUCTION:
A bumper is a structure attached to or integrated with the front and rear ends of a motor vehicle, to absorb impact in a minor collision, ideally minimizing repair costs.
They are designed to absorb impact to the front and rear of vehicles and minimize low-speed collision damage. Today, standard passenger vehicle bumpers have a rigid reinforcing bar under the outer cover, with sections of compressible foam or plastic underneath.
A bumper is made up of four parts:
- Bumper cover.
- The bumper absorber.
- The bumper reinforcement bar.
- The bumper mounting system
Modern bumpers are made with a combination of materials. The first element is an impact absorbing spring device, usually gas-filled cartridges which mount the front bumper to the chassis. This allows the bumper system to absorb minor impacts without any damage.
Actually, bumpers in cars are meant for absorbing shock or impact at low velocity like accidentally hitting while reversing the car.
Now coming to the selection of material for making bumper, the material should have the capability to absorb the impact (i.e.) either nullify the effect or reduce the effect of the strike.
Lets consider metals as bumpers, metals transfer the load applied at one end to the other with negligible loss, so metals are not optimum material for bumpers. Lets consider plastics as bumpers, they have tendency to absorb load and reduce the effect of the impact also rubbers have the tendency to absorb and almost nullify the effect.
Looking into design and processing aspect, bumpers are big in size so they are processed by techniques like injection molding, blow molding and roto-molding. Considering the above processing techniques plastics are suitable material of choice.
Considering the above said processing methods, most commonly ABS, PC/ABS is injection molded and blow molded ABS are used in cars like Hyundai, Ford. When processed by roto-molding pulverized HDPE is processed easily and is used in making bumpers.
Acrylonitrile Butadiene Styrene(ABS):
Acrylonitrile Butadiene Styrene is a copolymer made by polymerizing styrene and acrylonitrile in the presence of polybutadiene. The styrene gives the plastic a shiny, impervious surface. The butadiene, a rubbery substance, provides resilience even at low temperatures. A variety of modifications can be made to improve impact resistance, toughness, and heat resistance.
STEPS INVOLVED in Designing Bumper:
- TOOLING AXIS CREATION
- DRAFT ANALYSIS.
- CLASS B CREATION
- CLASS C CREATION
- FINAL TRIM
- SOLID BODY
CLASS A SURFACE: Styling or A class surface are the terms used in plastic product design which means the surface of a component which is smooth( aesthetic) or visible side to human eye after the part is assembled. Generally this surface needs to be more asthetic and smooth for the customer attention.
CLASS B SURFACE:
class B is basically referred as an engineering surface where lot of components like heat stakes, screw bosses,doghouses are designed It is the surface that lies beneath the class A to a thickness range of upto 3mm
CLASS C SURFACE:
Basically class C is the intermediate surface lies between class A and class B surface . It is the surface generated with the aid of class A surface.
TOOLING AXIS CREATION:
First of all check the boundary continuity of the class A surface using boundary feature or the join feature , then come to conclude the best view for the creation of the tooling aaxis so that all the components need to clear the draft in thet specified tooling direction
DRAFT ANALYSIS:
DRAFT ANALYSIS:
- Draft Analysis is a tool in CATIA which identifies the zones which deviates from the specified values of angles along a defined draft direction using colour codes.
- -It highlights the regions of draft using colours.
- -Draft analysis is the first step performed after receiving the Class A of the component.
- -Draft analysis should be passed in order to make the plastic component manufacturable.
- -Acceptable draft angles are used as range for draft analysis that is 0 to 3 degree.
Final draft analysis screenshot given below:
- Four Views ISO, FRONT, SIDE, TOP
Step file and CATPRT is attached below.