SIX BAR SLIDER CRANK POWERHAMMER 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 ram cylinder. Piston 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. one of the links is to be fixed. Degrees of Freedom of a Rigid Body in a Plane The degrees of freedom (DOF) of a rigid body are defined as the number of independent movements it has. In a two dimensional plane such as this computer screen.2 shows a rigid body in a plane. To determine the DOF of this body we must consider how many distinct ways the bar can be moved.INTRODUCTION Concept of degrees of freedom In the design or analysis of a mechanism. Degrees of Freedom of a Rigid Body in Space An unrestrained rigid body in space has six degrees of freedom: three translating motions along the x. Figure 1. In general.3 Kutzbach Criterion Equation Consider a plane mechanism with number of links. The bar can be translated along the x axis. therefore the number of movable links will be ( -1) and thus the total number of degrees of freedom will be 3(n-1) before they are connected to any other link. translated along the y axis. one of the most important concern is the number of degrees of freedom (also called movability) of the mechanism. a mechanism with number of links connected by j number of binary joints or lower pairs (i. Since in a mechanism.e. there are 3 DOF. y and z axes respectively in the as shown in the fig 1. 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. . y and z axes and three rotary motions around the x. and rotated about its centroid. each of them forms a turning pair. l and s. 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. . If there are no two degree of freedom pairs (i. The mechanism in which no link makes a complete revolution will not be useful. In a four bar chain. will make a complete revolution relative to the other three links. According to Grasshof’s law for a four bar mechanism. one of the links. q. A very important consideration in designing a mechanism is to ensure that the input crank makes a complete revolution relative to the other links. Such a link is known as crank or driver. The four links may be of different lengths. then h= 0.single degree of freedom pairs) and h number of higher pairs (i. as shown in below fig.e. we have n=3(-1)-2j Four bar chain mechanism The simplest and the basic kinematic chain is a four bar chain or quadratic cycle chain. substituting h= 0 in equation 1. if it satisfies the Grasshof’s law. in particular the shortest link. then the number of degrees of freedom of a mechanism is given by n = 3(-1)-2j-h This equation is called Kutzbach criterion for the movability of a mechanism having plane motion. two degree of freedom pairs). It consists of four links p. higher pairs). 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.e. According to Grasshof’s law for a four bar mechanism. The crank (link 5) is provided for oscillating the connecting rod at a fixed path. Ram Die and composite bush are connected by a sliding pair G. they are rigid enough to absorb the vibrations and shocks produced during work. . The motion is further transmitted to the connecting rod which is joined with the link 3 at D. Crank (link1) is joined at turning pair F to the column and also crank (link 5) is joined at turning pair A. Composite bush is made up of two materials outer one is of Mild Steel and the liner is made up of Gun Metal to prevent from wear. The connecting rod (link 4) and link 3 are connected by a turning pair D. Base and Vice are made up of Mild Steel. Where a slot is provided for getting a straight line motion of the ram Die. Column. Connecting rod (link 4). Crank (link 5) and Ram die (link 2). The link 1 rotates about a turning pair F. A handle is provided at point E. Column is welded to the base. All the links.WORKING PRINCIPLE The Crank (link 1) rotates at a fixed axis at F it is joined to link 3. Ram Die (link 2) and connecting rod (link 4) are connected by a sliding pair C. The Connecting rod (link 4) and Ram Die (link 2) are connected at C. link 3. the link 3 and link 1 is connected by a turning pair E. Construction As shown in above diagram it consists of 5 links. tear and corrosion resistance. with the help of the handle the crank (link 1) is rotated.Column can be considered as a fixed link. vice (not shown in above fig) is fitted to the column for holding the work piece. Crank (link 5) and connecting rod (link 4) are connected by a turning pair B. The five links are crank (link 1). it is rotated by a pin joint axis. The crank (link 5) is fixed at a turning pair A and oscillates about the pin joint axis. As the link 1 is rotated the motion is transmitted to the link 3 which is connected at point E. Finally the connecting rod transmits the motion to the Ram Die (link 2) which reciprocates at a fixed path G. and one fixed link. Upsetting. Press Press working involves production of final component from sheet metal in cold condition. Fullering. 3. 8. 5. Press. 6. 4.ADVANTAGES Ease of operation. The typical forging operations are: 1. Bending. 7. Cutting. The machine which is used to apply the required pressure of force in a . Welding.Four wheeler vehicles etc. rolls. or by an upsetting machine of some kind. Drawing down. Provide better and comfortable performance APPLICATIONS Forging Forging refers as the process of plastically deforming metals or alloys to a specific shape by a compressive force exerted by some external agency like hammer. A number of operations are used to change the shape of the raw material to the finished form. Setting down. 2. Punching. The press consists of a frame. (i) Mechanical press. (ii) Hydraulic press.short duration is called press. The punch and die block assemble are generally referred to as a die set or simply die. The ram is equipped with special punches and moves towards and into the die block which is attached to a rigid body. Classification of Presses Presses are classified in various ways as listed below. supporting bed and ram. .