Explaining CAM And Its Followers

Explaining CAM And Its FollowersBASIC DEFINITION OF CAMA cam is a mechanical factor of a machine that is occasiond to transmit crusade to another dower, called the companion, through a prescribed app atomic number 18nt movement program by direct contact.INTRODUCTION TO CAM AND FOLLOWERSA cam abetter _or_ abettor, also cognize as a track confederate,1 is a specialized type of roller or needle pusher physiqueed to follow cams. Cam companions come in a vast array of different configurations, thus far the most defining characteristic is how the cam ally mounts to its mating part stud style cam attendants use a stud while the yoke style has a hole through the middle.2The first cam follower was invented and patented in 1937 by Thomas L. Robinson of the McGill Manufacturing Comp whatsoever.3 It replaced using just a standard bearing and bolt. The brand-new cam followers were easier to use because the stud was already included and they could also handle higher loads.CAM AND apparatusSA cam instrument consists of triad elements the cam, the follower (or follower system), and the frame. The follower is in direct contact with the cam. The cam may be of variant shapes. The follower system includes all of the elements to which interrogative sentence is imparted by the cam. This may be connected directly to the follower, or connected through linkages and gearing. The frame of the machine supports the bearing surfaces for the cam and for the follower.A CAM changes the input motion, which is usually rotary motion (a rotating motion), to a reciprocating motion of the follower. They ar found in many machines and toysWHAT IS THE CONCEPT BEHIND CAM?A CAM is a rotating machine element which gives reciprocating or oscillating motion to another element known as follower. The cam and follower has a point or overseas telegram contact constitute a higher pair or you can say that it is the mechanicl comp adeptnt of a machine that is utilise to transmit the motio n to the another component of the machine called the follower, through a prescribed program by direct contact.The contact between them is principal(prenominal)tained by an external force which is generally provided by the spring or sometimes by the angle of the follower itself ,when it is sufficient. Cam is the driver member and the follower is the driven member. The follower is in direct contact with the cam.CAM MECHANISM CONSIST OF THREE MECHANISMSCAMIt may be of many shapesFOLLOWER It includes all the elements to which motion is imparted by the cam.This may be connected directly by the cam.This may be connected directly to the follower, or connected through linkages and gearing.FRAME The frame of the machine supports the bearing surfaces for the cam and for the follower.APPLICATIONS OF CAM AND FOLLOWERSCam and follower are widely use for operating inlet and exhaust valve of I C engine.These are used in wall clock.These are used in feed mechanism of automatic lathe Machine.Thes e are used in paper peeled machine.Used in weaving textile machineries.The cam mechanism is a versatile one. It can be designed to produce almost unlimited types of motioning the follower.It is used to transform a rotary motion into a translating or oscillating motion.On certain occasions, it is also used to transform one translating or oscillating motion into a different translating or oscillating motion.Cams are used in a wide transition of automatic machines and instruments.The certain usuages of cam and followers that includes textile machineries, computers, printing presses, food processing machines, internal combustion engines, and multitudinous other automatic machines, control systems and devices. The cam mechanism is indeed a very essential component in modern mechanization.CLASSIFICATION OF CAMS seatd on the physical shapeDisk or plate cams operative of the disc cam with reciprocating follower.Working of the disc cam with oscillating follower.Cylindrical camTranslating camCLASSIFICATION OF FOLLOWES(i) Based on surface in contact(a) Knife edge follower(b) Roller follower(c) Flat faced follower(d) orbicular follower(ii) Based on type of motionOscillating followeTranslating follower(iii) Based on agate line of actionRadial (in line) follower(b) Off-set followerCams can be conveniently classified into two main groupsGroup aCams that impart motion to the follower in a plane in line with the axis of rotation of the cam (as does a cylindrical cam).Group bCams that impart motion to the follower in a plane at 90 degrees to the axis of rotation, as with face or edge cams.Most cams retort into this category.TYPES OF CAMSEccentric camA circular cam is oft called an eccentric cam becausethe axis of rotation of the cam is offset from thegeometric focalize of the circular disc.Concentric discA concentric disc attached to a rotating shaft would guard its axis of rotation coinciding with its geometric centre.PROFILE SHAPES OF SOME CAMSPEAR-SHAPED CAMSThese type cams are lots used for controlling valves. For example, they are used on motor car camshafts to operate the engine valves. Afollower controlled by a pear-shaped cam remains motionless for round half a innovation of the cam. During the time that the follower isstationary, the cam is in a dwell period. During the other half revolution of the cam, the follower rises and wherefore falls. As the pearshaped cam is symmetrical, the rise motion is the same as the fall motion.Edge camsIt essential be apprehended that this type of cam, where the follower is in contact with the edge of the cam disc, is only capable of imparting positive motion to its follower in one direction, that is, during the rise portion of the cam movement. During the fall portion of the cam movement the follower must be maintained in contact with the cam either by the mass of the follower and itsmechanism or, more than usually, by a spring. Both methods have their advantages.Box camsA groove can be dressed in the face of cam discs. As the cam rotates, a follower set(p) in the groove has its motion point by the groove. This type of cam is called a box cam.Cylindrical camsCylindrical cams are used when motion has to be transmitted parallel to the axis of rotation of the cam. The cylindrical or barrel cam consists of a rotating cylinder with a helical (screw shaped) groove in its curvedsurface. A follower with a tapered roller end is located in the groove. As the cylinder turns, the follower moves in a straight line parallel to the axis of the rotation barrel cam.This type of cam is often used to guide thread on sewing machines, looms and stuff making machines.CIRCULAR CAMSThese cams are sometimes called eccentric cams. The cam profile is a circle. The warmheartedness of rotation of the cam is often from the geometric center of the circle. The circular cam produces a smooth form of motion called a simple agreeable motion. These cams are often used to produce motion in pumps. Circular cams are often used to operate steam engine valves. As the cam is symmetrical, the rise and fall motions are the same.HEART SHAPED CAMSThis cam causes the follower to move with a uniform f number. Heart-shaped cams are essential when the follower motion needs to be uniform or steady as, for example, in the mechanism that winds thread evenly on the bobbin of a sewing machine. A heart-shaped cam can be used for winding wire evenly on the former of a solenoid.UNIFORM ACCELERATION AND RETARDATION CAMSA cam shaped as shown controls the motion of the follower so that it moves with uniform acceleration and retardation. The follower gains and looses velocity at a constant rate. Uniform acceleration and retardation cams are used to controls the motion of linkages in complex machinery.Types of Cam FollowersThere are three types of cam followers, and since the type of follower influences the profile of the cam it is worthwhile considering the advantages and disadvantages of each type. The t hree types are the cutting edge, the roller follower and the pes planus or mushroom follower.The Knife Edge FollowerThis is the simplest type, is not often used due to the rapid rate of wear. When it is adopted, it is usually for reciprocating motion, running in slides and there is considerable side thrust, this being a component of the thrust from the cam.The Roller FollowerThis eliminates the problem of rapid wear since the sliding effect is largely replaced by a roller action. Some sliding will still take place due to the alter peripheral speed of the cam profile, due to the changing radius of the point of contact. Note also that the radial mental attitude of the contact between the cam and the roller, relative to the follower center, will change according to whether arise or fall motion is taken place this fact has to be considered when constructing the cam profile. Again,with the roller follower, considerable side thrusts are wassail, a disadvantage when dealing with recip rocating motions. This side thrust will be increased when using low-down rollers.The Flat Foot or Mushroom FollowerThis has the advantage that the only side thrust present is that due to the friction between the follower and the cam. The problem of wear is not so great as with the cutting edge follower, since the point of contact between the cam and follower will move across the face of the follower according to the change of shape of the cam. A trick to lessen further the effect of wear is to design thefollower to be capable of axial rotation and arrange the axis of the follower to lie to one side of the cam. Thus the contact with the cam will tend to cause rotation of the follower. The cam profile, to work with a flatfoot follower, must be convex at all parts, in order to prevent the corners of the follower shaft into the cam profile. The minimum cam radius should be as small as possible to minimize sliding velocity and friction.All three types of cam followers can be mountedi n the following ways1) In-line with the cam center line,2) Offset from the cam center line, or3) Mounted on a swinging radial arm.CAM-VALVECAM TERMINOLOGY proposition pointA theoretical point on the follower,corresponding to the point of a fictitious knife-edge follower.It is used to generate the pitch curve.In the case of a roller follower, the tracepoint is at the center of the roller.2.Pitch curveThe path generated by the trace point at the follower isrotated about a stationary cam.3. Working curveThe working surface of a cam in contact with the follower. Forthe knife-edge follower of the plate cam, the pitch curve and the working curvescoincide. In a close or well-grooved cam there is an inner profile and an outerworking curve.4. Pitch circleA circle from the cam center through the pitch point. Thepitch circle radius is used to calculate a cam of minimum size for a givenpressure angle.5. Prime circle (reference circle)The smallest circle from the cam centerthrough the pitch cu rve.6. Base circleThe smallest circle from the cam center through the cam profilecurve.7. Stroke or throwThe greatest infinite or angle through which the followermoves or rotates.8. Follower displacementThe position of the follower from a specific zeroor rest position (usually its the position when the follower contacts with thebase circle of the cam) in relation to time or the rotary angle of the cam.9. Pressure angleThe angle at any point between the normal to the pitchcurve and the instantaneous direction of the follower motion. This angle isimportant in cam design because it represents the steepness of the camprofile.Some question arises regarding cam and followersWhen is a flat faced follower favored as compared to roller followers andwhy?Flat faced followers are pet to roller followers where space is limitedfor eg cams with flat followers are used to operate valves of an cable car engine but in case of stationary and oil engines, roller followers are preferred because more space is available.What data is plotted on displacement diagram of cam and follower motion?autonomic nervous systemPlot of linear displacement i.e. lift or stroke (s) of follower (on Y axisdirection) versus angular displacement () of the cam for one rotation (on Xaxis direction)REFERENCESWIKIPEDIA.McGILL CAMROLL bearings.Robinson, Thomas L., Bearing, US