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Suez Canal UniversityFaculty of EngineeringProduction and design dept.4 th year

eport about:Presses used in forming process and their design

consideration

Prepared by:

Ahmed Mohammed Mahmud

Amr Tarek Hegazy

Ayah Ahmed Kenawy

Manar El- Islam Yahiya

Manar Shaban Abd El-Fatah

Moemen Abdu Barkat

Norhan Mohammed El-Sharawy

Supervised by:D / Mohammad Saber

Data:

https://www.facebook.com/eng.m.barkathttps://www.facebook.com/eng.m.barkathttps://www.facebook.com/eng.m.barkat

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15/5/2012

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contents pages

Types of press 3

Presses controlled by work 3

Presses controlled by the ram path 3

Presses controlled by force 4

Types of hammer 5

Fields of application for hammers 6

Screw presses 6

Forms of structural design 6

Advantages of screw presses 8

Eccentric and crank presses and its

types

8-9

Application of eccentric and crank

presses

9

Knuckle-joint presses 9

Hydraulic presses 11

Advantages of hydraulic presses 11

Reference 12

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Types of press

According to their characteristics, presses can be classified into those controlled mainly by

work (energy), the ram path or force.

Presses controlled by work

Hammers and screw presses are machines whose main characteristic is their work capacity

(Energy). A hammers work capacity is determined from the ram mass and drop height. With A

screw press, the work capacity is stored in the rotating masses (mainly in the flywheel),

Therefore it depends upon the angular velocity and the mass moment of inertia. The two kinds

of machine are similar in that the work capacity can be influenced or adjusted. The force, on theother hand, cannot be directly adjusted, but depends upon the kind of work piece and the

deformation distance.

Fig (1)

The principle of presses controlled by work, a) drop hammer, b) screw press

Presses controlled by the ram path

These include crank presses and knuckle-joint presses. With these presses, the deformation is

complete when the ram has reached its lowest position (bottom dead centre BDC). This

means their characteristic value is the ram path limit, which comes from the crank radius r in

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crank presses and from the leverage with knuckle-joint presses fig (2) With crank presses the

nominal force of the press is available at a crank angle of 30 before BDC up to BDC, whereas

with a knuckle-joint press, the nominal press force (depending on the leverage) is only available

within a range of 3 to 4 mm before BDC.

Fig (2)

Drive layout of presses controlled by the ram path, a) crank press,

b) knuckle-joint press

Presses controlled by force

The operation of hydraulic presses depends upon force, as the only thing which can be

adjusted about them is the force (via the operating pressure).As the deformation forces fluctuate within certain limits (differences in material strength, blank

tolerances, lubrication and condition of the tooling), a dimensionally accurate part can only be

produced on a hydraulic press if the deformation distance is limited. This can be carried out in

the press itself using positive stops, or in the die. This kind of ram path limit is also needed for

presses controlled by work.

Hammers

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Types of hammer

Hammers are classified according to the drive design into:

Drop hammers

Double-acting hammers

Counterblow hammers.

With drop hammers, the ram drops freely. The impact energy comes from the mass of the ram

and the drop height. Belts, chains or with hydraulic drives the piston rod are used to lift the ram.

The hydraulic drop hammer has a three-part frame. The materials used are: e.. Anvil and side columns: grey cast iron with added steel.

This special cast iron is a better damper and has a more homo generous structure than cast steel.

b) Ram: high-alloy, hardened and tempered cast electric steel or quenched and tempered steel.

c) Guides: hardened, ground steel prism guides.

Fig (3)

Mechanically powered hammer

Fields of application for hammers

Uses for hammer types:

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Hammer type Application

Drop hammers

Double-acting hammers

Counterblow hammers

Small to medium-sized impression-

die forgings,

e.g. wrenches, levers, coupling

components

medium to large-sized impression-

die forgings,

camshafts, flanges

difficult and extremely difficult

impression-die forgings,e.g. large crankshafts, levers which

are hard to form,

large coupling components

Screw presses

Forms of structural designFlywheel construction is categorized:

1. According to the way the flywheel is accelerated:Friction wheel with disc drive.

Hydraulic drive.

Direct electric motor drive.

wedge drive.

2. According to the way the ram is moved vertically:

ram moves up and down with spindle and flywheel.

Spindle fixed in place with flywheel. Only the ram, shaped like a nut, moves vertically.

This construction is called a Vincent press.

A screw press is a type ofmachine press in which the ram is driven up and down by a screw.

The screw shaft can be driven by a handle, or a wheel. It works by using a coarse screw to

convert the rotation of the handle or drive-wheel into a small downward movement of greater

force. The overhead handle usually incorporates balls as a flyweight. This weight helps to

maintain the momentum and thrust of the tool to make it easier to operate.

http://en.wikipedia.org/wiki/Machine_presshttp://en.wikipedia.org/wiki/Screw_%28simple_machine%29http://en.wikipedia.org/wiki/Screw_%28simple_machine%29http://en.wikipedia.org/wiki/Machine_press

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The screw press was first invented and used by the Romans in the first century C.E. It was

used primarily in wine and olive oil production. The screw press was also used in Gutenberg's

printing press in the mid-15th century.

A press is a metalworking machine tool used to shape or cut metal by deforming it with a die. It

is frequently used to punch holes in sheet metal in one operation, rather than by cutting the hole

or drilling.

If used as a punch, the tool itself consists of a punch and a matching die, into which it very

closely fits. Both are usually precision machined and then hardened. The material is introduced

between the punch and die, and the machine operated. The punch will cut through the material

in one movement by shearing it. The punch and die may be of any desired shape, so odd shaped

holes and cutouts may be created.

If used as a forging tool the dies can be many different shapes varying from flat to various

shapes that will mold the metal to the desired configuration.

Fig (4) Ball-drive screw press

http://en.wikipedia.org/wiki/Metalworkinghttp://en.wikipedia.org/wiki/Machine_toolhttp://en.wikipedia.org/wiki/Sheet_metalhttp://en.wikipedia.org/wiki/Die_%28manufacturing%29http://en.wikipedia.org/wiki/Guillotine_%28metalwork%29http://en.wikipedia.org/wiki/File:GoldsmithPress.jpghttp://en.wikipedia.org/wiki/File:GoldsmithPress.jpghttp://en.wikipedia.org/wiki/Guillotine_%28metalwork%29http://en.wikipedia.org/wiki/Die_%28manufacturing%29http://en.wikipedia.org/wiki/Sheet_metalhttp://en.wikipedia.org/wiki/Machine_toolhttp://en.wikipedia.org/wiki/Metalworking

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Fig (5)

PR 800 fully-automatic screw press (Photograph from LASCO Umformtechnikworks, Coburg, Germany)

Advantages of screw presses

(Compared to hammers and crank presses)

1. Screw presses require only a small base.

2. The noise level is far lower than with hammers.

3. Screw presses are high-energy machines. For this reason, work pieces which require a lot of

energy can be formed with them.

4. The dwell periods (the time during which the work piece is being forged) are short. This

means that tool life is improved.

5. The spindle thread is not self-locking. This means that a screw press cannot block under

stress.

6. Like hammers, screw presses have no kinetically-fixed bottom dead centre. It is no longer

necessary to adjust the height of the tooling. Forging can also take place in a closed die, as the

excess material can be balanced out in the height of the work piece.

Eccentric and crank presses

Eccentric and crank presses are controlled by the ram path.

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Types of these presses

These presses are categorized according to the design of the press frame (Figure 6) into:

a) gap-frame presses.

b) open-back presses.

c) straight-side presses.

Application of eccentric and crank presses

Eccentric pressesare mainly used for blanking, embossing and bending, as long as only small

displacements arerequired, as the eccentric demands. Crank presses are used for all chip less

forming methods where the deformation force does not have to beconstant over a long distance

i.e. for the forward extrusion of short components, deep drawing, bending and impression-die

forging on heavy forging presses.

Knuckle-joint presses

Knuckle-joint presses are a special kind of crank press where the crank force is produced via a

(knuckle joint) joint system. In principle, the rules which govern a crank press apply here, both

as concerns the construction design and the way it works.

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Fig (7) Knuckle joint press

Fig (8)

Force-displacement diagram for a knuckle-joint press

Hydraulic presses

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A hydraulic is a machine using a hydraulic cylinder to generate a compressive force. It

uses the hydraulic equivalent of a mechanical lever, and was also known as a Bramah

press after the inventor, Joseph Bramah, of England. He invented and was issued a

patent on this press in 1795. As Bramah (who is also known for his development of the

flush toilet) installed toilets, he studied the existing literature on the motion of fluids and

put this knowledge into the development of the press.

Fig (9)

Hydraulic press in a machine shop.

This press is commonly used for

hydro forming.

Advantages of hydraulic presses

The advantages of hydraulic presses are:

a) Constant power all through the stroke,

b) Force can be finely regulated (so no extra load-limiting safety device required),

c) Work capacity unlimited until Wmax = Fmaxsmax.

One disadvantage is the lower operating speed compared with crank presses, which results in

lower output (parts per time unit).

Reference

http://en.wikipedia.org/wiki/Hydraulic_cylinderhttp://en.wikipedia.org/wiki/Leverhttp://en.wikipedia.org/wiki/Joseph_Bramahhttp://en.wikipedia.org/wiki/Hydroforminghttp://en.wikipedia.org/wiki/Hydroforminghttp://en.wikipedia.org/wiki/File:Hydraulic_Press.pnghttp://en.wikipedia.org/wiki/Hydroforminghttp://en.wikipedia.org/wiki/Joseph_Bramahhttp://en.wikipedia.org/wiki/Leverhttp://en.wikipedia.org/wiki/Hydraulic_cylinder

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Metal Forming Practice

Translated by Anne Koth

www.wikipedia.org

http://www.wikipedia.org/http://www.wikipedia.org/http://www.wikipedia.org/http://www.wikipedia.org/http://www.wikipedia.org/