Hood design-Week 2

DETAILED EXPLANATION ABOUT HOOD

HOOD:- A car hood, also referred to as a “bonnet” in some countries, is the hinged cover that rests over the engine bay of a front-engine vehicle. The car hood protects the engine and connected parts from the elements while providing easy access for repairs and maintenance.

LATCH TRAJECTRY :- The latch trajectory is the path which the striker will follow when the hood is open/closed while pivoting on the hinge axis. The latch trajectory is taken as a circle with the hinge axis as the center of the circle.

MASTIC DATA:- MAstic is the sealant applied between hood's outer panel (which is styling surface) and hood's inner panel

the yellow cirlces in the figure above are the regions where mastic sealants are appiled

EMBOSS :-

Embossing is a metal forming process for producing raised or sunken designs or relief in sheet material by means of matched male and female roller dies, theoretically with no change in metal thickness, or by passing sheet or a strip of metal between rolls of the desired pattern.

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.

Characteristics of the metal embossing process include:

Its ability to form ductile metals,

Its use in medium to high production runs,

The ability to maintain the same metal thickness before and after embossing,

The ability to produce unlimited patterns, depending on the roll dies, and

The ability to reproduce product with no variation

Embossed metals are used in industry for two reasons: (1) aesthetic, and (2) functional. Aesthetic applications also include appliance panels, building products, elevator panels, garage door panels, automotive trim, metal office furniture, and others.

The embossing process can produce a variety of patterns. Some of the most common patterns include stucco, leather grain, wood grain, weather grain, and rough sawn cedar. Most embossers will tool to form any needed pattern, depending on the cost parameters involved.

Materials commonly used in the metal embossing process include:

* Aluminum (All Alloys)

* Aluminum (T1/T2)

* Brass

* Cold rolled steel

* Copper

* Galvanized steel

* High strength, low alloy, steel

* Hot rolled steel

* Steel (All Alloys)

* Zinc

Green line shows the emboss direction

DETAILED EXPLATION AABOUT MANUFACTURING PROCESS OF CAR HOOD

1.DEEP DRAWING:-

Deep drawing is a sheet forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter. This is achieved by redrawing the part through a series of dies. The flange region (sheet metal in the die shoulder area) experiences radial drawing stress and tangential compressive stress due to the material retention property. These compressive stresses result in flange wrinkles (wrinkles of the first order). Wrinkles can be prevented by using a blank holder, the function of which is to facilitate controlled material flow into the die radius.

Deep drawing processes are divided into three types:

1.Deep drawing with tools

2.Deep drawing with active means

3.Deep drawing with active energy

In the automotive industry, deep drawing is usually carried out using rigid tools.

Illustration of the deep drawing process

The figure illustrates the deep drawing process. The rigid tools consist of a punch, die and binder. In deep drawing, the plate holder closes after the metal sheet blank has been inserted.

Next, the sheet is clamped between the die and the binder. This process slows down the flow of the sheet while it is being drawn and thereby prevents wrinkles from forming under the binder. The punch stretches the sheet over the die radius and forms it in the die. The amount of punch force necessary for forming is thereby continually increased up to the lower dead center of the punch.

Whereas in pure deep drawing there is no reduction of sheet metal thickness, forming is achieved in stretch forming purely as a result of a decrease in sheet metal thickness. Stretch forming is extensively used for the forming of only slightly curved parts with low depth of draw (e.g. roofs, doors).

When drawing complex car body parts in practice, there is usually a combination of stretch and deep drawing involved. It is necessary that the sheet metal is stretched as well as possible without reaching the material’s limits (e.g. splits, wrinkles).

There are approximately 300 to 400 sheet metal parts that fit together to form the body of a car. In order to manufacture high-quality sheet metal parts optimally for their particular use, specialized software simulates the complete deep drawing process.

2.HEMMING :-

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. Normally hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges.

In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming and flanging operations to join two sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, doors, trunk lids and fenders.

The accuracy of the hemming operation is very important since it affects the appearance of the surface and surface quality. Material deformations, which occur during the hemming process, can lead to dimensional variations and other defects in parts. Typical hemming defects are splits or wrinkles in the flange, material overlaps in the corner areas or material roll-in. This is why it is important to use simulation tools in order to, on the one hand, better understand the hemming process and, on the other hand, significantly reduce the number of “trial and error” loops during tryout and production.

There are two types of hemming process use:

a) Conventional die Hemming

b) Roll Hemming

a)Conventional die hemming :-

Conventional die hemming is suitable for mass production. In die hemming, the flange is folded over the entire length with a hemming tool. Normally the actual hemming is a result of a forming operation in which the flange is formed with a hemming tool after the drawing and trimming operations have been completed. Production plants for conventional die hemming are very expensive, but the cycle times are very low.

B)Roll Hemming :-

Roll hemming is carried out incrementally with a hemming roller. An industrial robot guides the hemming roller and forms the flange. Roll hemming operation can also be divided into several pre-hemming and final hemming process steps. Roll hemming is very flexible to use and tool costs are significantly lower as compared to those of conventional die hemming. However, the cycle times are much higher since the hemming is realized using a hemming roller that follows a defined path.

DESIGN CONSIDERATION THAT I FOLLOWED

1.Every emboss have greater than 7 degree draft angle

2.Giving hemming relief on rear section and front relief

3.Giving clearance of 0.2 mm for hemming glue

4.Giving latch trajectry at an angle of 80 degree for hood opening and closing

5.Give mastic data radius of 7 mm

REAR RELIEF :-

FRONT RELIEF :-

This is the picture that is showing all of the parameters that I followed to do the drawing