six bar slider crank power

7/25/2019 Six Bar Slider Crank Power

1/6

SIX BAR SLIDER CRANK POWER

HAMMER MECHANISM

ABSTRACT

Until now we have confined ourselves to study of hand tools used in smithy work. They certainly

perform very well so far as the hand- forging is concerned, but their use for satisfactory

production is limited to small forging only. It would not be difficult to understand that the

intensity of blows, however great one may try to achieve through hand hammering, will not be

sufficient enough to effect the proper plastic flow in a medium sized or heavy forging. For this, a

power hammer is usually employed. The hammer has two cylinders compressor cylinder and ramcylinder. iston of the compressor cylinder compresses air, and delivers it to the ram cylinder

where it actuates the piston which is integral with ram delivering the blows to the work. The

reciprocation of the compression piston is obtained from a crank drive which is powered from a

motor through a reducing gear. The air distribution device between the two cylinders consists of

rotary valves with ports through which air passes into the ram cylinder, below and above the

piston, alternately. This drives the ram up and down respectively.


2/6

INTRODUCTION

Concept of degrees of freedo

In the design or analysis of a mechanism, one of the most important concern is the number of

degrees of freedom !also called movability" of the mechanism. It is defined as the number of

input parameters !usually pair variables" which must be independently controlled in order to

bring the mechanism into a useful engineering purpose.

Degrees of !reedo of " R#g#d Bod$ #n " P%"ne

The degrees of freedom !#$F" of a rigid body are defined as the number of independent

movements it has. Figure %.& shows a rigid body in a plane. To determine the #$F of this body

we must consider how many distinct ways the bar can be moved. In a two dimensional plane

such as this computer screen, there are ' #$F. The bar can be translated along the ( a(is,

translated along the y a(is, and rotated about its centroid.

Degrees of !reedo of " R#g#d Bod$ #n Sp"ce

)n unrestrained rigid body in space has si( degrees of freedom* three translating motions along

thex, y andz a(es and three rotary motions around thex, y andz a(es respectively in the as

shown in the fig %.'

K&t'("c) Cr#ter#on E*&"t#on+onsider a plane mechanism with number of links. ince in a mechanism, one of the links is

to be fi(ed, therefore the number of movable links will be ! -%" and thus the total number of

degrees of freedom will be '!n-%" before they are connected to any other link. In general, a

mechanism withnumber of links connected by number of binary oints or lower pairs !i.e.


3/6

single degree of freedom pairs" and h number of higher pairs !i.e. two degree of freedom pairs",

then the number of degrees of freedom of a mechanism is given by

n + ,-./0.12.)

This euation is called /utzbach criterion for the movability of a mechanism having plane

motion.

If there are no two degree of freedom pairs !i.e. higher pairs", then h0 1,

substituting h0 1 in euation %, we have

n+,-./0.12

!o&r ("r c)"#n ec)"n#s

The simplest and the basic kinematic chain is a four bar chain or uadratic cycle chain, as shown

in below fig. It consists of four links p, , l and s, each of them forms a turning pair. The four

links may be of different lengths. )ccording to 2rasshof3s law for a four bar mechanism, the sum

of the shortest and longest link lengths should not be greater than the sum of the remaining two

link lengths if there is to be continuous relative motion between the two links.

)ccording to 2rasshof3s law for a four bar mechanism, the sum of the shortest and longest link

lengths should not be greater than the sum of the remaining two link lengths if there is to be

continuous relative motion between the two links. ) very important consideration in designing a

mechanism is to ensure that the input crank makes a complete revolution relative to the other

links. The mechanism in which no link makes a complete revolution will not be useful. In a four

bar chain, one of the links, in particular the shortest link, will make a complete revolution

relative to the other three links, if it satisfies the 2rasshof3s law. uch a link is known as crank or

driver.


4/6

WORKIN3 PRINCIPLE

The +rank !link %" rotates at a fi(ed a(is at F it is oined to link '. )s the link % is rotated the

motion is transmitted to the link ' which is connected at point 4. The motion is further

transmitted to the connecting rod which is oined with the link ' at #. Finally the connecting rod

transmits the motion to the 5am #ie !link &" which reciprocates at a fi(ed path 2. The

+onnecting rod !link 6" and 5am #ie !link &" are connected at +, 7here a slot is provided for

getting a straight line motion of the ram #ie. The crank !link 8" is provided for oscillating the

connecting rod at a fi(ed path.

Constr&ct#on

)s shown in above diagram it consists of 8 links, and one fi(ed link. The five links are crank

!link %", link '. +onnecting rod !link 6", +rank !link 8" and 5am die !link &".+olumn can beconsidered as a fi(ed link. The link % rotates about a turning pair F, it is rotated by a pin oint

a(is, the link ' and link % is connected by a turning pair 4. The connecting rod !link 6" and link '

are connected by a turning pair #. The crank !link 8" is fi(ed at a turning pair ) and oscillates

about the pin oint a(is. +rank !link 8" and connecting rod !link 6" are connected by a turning

pair 9. 5am #ie !link &" and connecting rod !link 6" are connected by a sliding pair +. 5am #ie

and composite bush are connected by a sliding pair 2. +rank !link%" is oined at turning pair F to

the column and also crank !link 8" is oined at turning pair ). +olumn is welded to the base, vice

!not shown in above fig" is fitted to the column for holding the work piece. )ll the links,

+olumn, 9ase and :ice are made up of ;ild teel, they are rigid enough to absorb the vibrations

and shocks produced during work. +omposite bush is made up of two materials outer one is of

;ild teel and the liner is made up of 2un ;etal to prevent from wear, tear and corrosion

resistance. ) handle is provided at point 4, with the help of the handle the crank !link %" is

rotated.


5/6

AD4ANTA3ES

4ase of operation.

rovide better and comfortable performance

APPLICATIONS

!org#ng

Forging refers as the process of plastically deforming metals or alloys to a

specific shape by a compressive force e(erted by some e(ternal agency like hammer,

ress, rolls, or by an upsetting machine of some kind.Four wheeler vehicles etc.

) number of operations are used to change the shape of the raw material to the

finished form. The typical forging operations are*

/5 Upsetting.

15 Fullering.

,5 #rawing down.

65 etting down.

75 unching.

85 9ending.

95 7elding.

:5 +utting.

Press

ress working involves production of final component from sheet metal in

cold condition. The machine which is used to apply the reuired pressure of force in a


6/6

short duration is called press. The press consists of a frame, supporting bed and ram.

The ram is euipped with special punches and moves towards and into the die block

which is attached to a rigid body. The punch and die block assemble are generally

referred to as a die set or simply die.

C%"ss#f#c"t#on of Presses

resses are classified in various ways as listed below.

!i" ;echanical press.

!ii"

six bar slider crank power

Documents