Cam And Follower Mechanism

[Lotte Donohoe]

Inthe intricate domain of mechanical engineering, where the demand for precision and efficiency is paramount, the cam and follower mechanism emerge as a dynamic and indispensable duo, serving a pivotal role in the conversion of rotary motion into reciprocating or oscillating motion. This ingenious pairing extends its influence across a spectrum of industries, ranging from automotive engineering to various manufacturing processes. In the ensuing exploration within this blog, we shall unravel the captivating intricacies of cam and follower mechanism, navigating through their fundamental principles, diverse types, and myriad applications.

Circular in shape, these cams are commonly used for simple applications where the follower's motion is linear. They are easy to manufacture and find applications in devices like printers and simple automation systems.

Cylindrical cams are shaped like a cylinder and are ideal for applications requiring more complex motion, such as oscillation. They offer versatility and are often found in internal combustion engines and machinery with intricate movement requirements.

These cams feature an inclined surface, providing a combination of linear and oscillating motion to the follower. Translating cams are widely used in packaging machinery and other systems requiring precise and controlled linear motion.

Camshaft systems in internal combustion engines use cams and followers to control the opening and closing of valves, optimizing engine performance. The application of cam and follower knowledge in automotive engineering encompasses critical aspects of engine operation, fuel delivery, transmission, suspension, and braking systems. Understanding and optimizing these mechanisms are essential for enhancing vehicle performance, efficiency, and overall driving experience. Explore our Automotive engineering courses to master these skills.

As we continue to push the boundaries of mechanical engineering, cam and follower systems remain at the forefront of innovation, inspiring the next generation of engineers to drive progress and shape the future. For those intrigued by the complexities of cam and follower mechanisms, delving deeper into core mechanical engineering courses can unlock a wealth of knowledge and opportunities. Aspiring engineers can gain the expertise and skills needed to tackle real-world engineering challenges, from optimizing cam profiles for efficiency to designing innovative follower mechanisms for cutting-edge applications.ourney to upskill today!

Hello, I am using CREO 7 and currently doing the cam follower mechanism for a cam rod and tappet and was following the tutorial provided PTCU. The tappet is having a flat surface. The mechanism works well for curved follower but not for the flat surface. I gave the necessary parameters that are required to define the mechanism but I am not getting the usual motion that is expected from this mechanism. The tappet sticks to the cam surface and rotates along with the cam rotation, which I don't want (I need the reciprocating motion). What should I do? Are there other parameters need to get the required cam motion?

Check Constraint Types: Ensure that the constraints defined between the cam and the tappet are appropriate. For a flat surface follower, the constraint should allow for linear motion without rotation.

I implemented this, I creating an array called followers, containing the userIDs of all users following a particular user. To get the news feed, I simply forEach in every user's followers array, to find which of them contains logged in user's id. If it is found, all the posts of those users should be retrieved in JSON format. This works for now, but I believe as many more users sign up, fetching the feed will become a more cumbersome task, slowing down the feed page's loading.

Have you observed the movement of the needle in the sewing machine? The. periodic to and fro or up and down motion of the needle is called reciprocating. It is a unique mechanism that can be seen in controlling the opening and closing of valves in IC(Internal Combustion) engines.

The cam and follower is a mechanical device used to achieve the desired reciprocating motion. The cam is the rotating member, and the follower is the reciprocating member. The cam is a profiled disc, cylinder or sphere that rotates. The shape or profile of the cam influences the motion of the follower. The follower is a rod that is in contact with the cam. The contact between the cam and follower is achieved using spring or the follower's weight.

As the cam rotates, its varying cross-section makes the follower in contact with it to reciprocate. The frame or guide guides the follower while reciprocating and acts as a support for the cam and follower.

In Automatic Lathe Machines: The motion of tools in an automatic lathe machine is controlled by this mechanism. Also, the feed mechanism in lathe machines is done by the cam and follower mechanism.

Many types of research are still underway to promote the performance of the cam and follower mechanism. A student of Skill-Lync designed a simple cam and follower model in Hyper Works using 3D contact in 2019. He had achieved a curve-to-curve joint and successfully reduced the damping by implementing a phenomenon called lift-off.

Yi Zhang

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Susan Finger

Stephannie BehrensTable of Contents 6 Cams6.1 Introduction6.1.1 A Simple Experiment: What is a Cam?Figure 6-1 Simple Cam experimentTake a pencil and a book to do an experiment as shown above. Make thebook an inclined plane and use the pencil as a slider (use your handas a guide). When you move the book smoothly upward, what happens tothe pencil? It will be pushed up along the guide. By this method, youhave transformed one motion into another motion by a very simpledevice. This is the basic idea of a cam. By rotating the cams in thefigure below, the bars will have either translational or oscillatorymotion. 6.1.2 Cam Mechanisms The transformation of one of the simple motions, such as rotation,into any other motions is often conveniently accomplished by means ofa cam mechanism A cam mechanism usually consists of two movingelements, the cam and the follower, mounted on a fixed frame. Camdevices are versatile, and almost any arbitrarily-specified motion canbe obtained. In some instances, they offer the simplest and mostcompact way to transform motions. A cam may be defined as a machine element having a curvedoutline or a curved groove, which, by its oscillation or rotationmotion, gives a predetermined specified motion to another elementcalled the follower . The cam has a very important functioninthe operation of many classes of machines, especially those of theautomatic type, such as printing presses, shoe machinery, textilemachinery, gear-cutting machines, and screw machines. In any class ofmachinery in which automatic control and accurate timing areparamount, the cam is an indispensable part of mechanism. The possibleapplications of cams are unlimited, and their shapes occur in greatvariety. Some of the most common forms will be considered in thischapter.

6.2 Classification of Cam Mechanisms We can classify cam mechanisms by the modes of input/output motion,the configuration and arrangement of the follower, and the shape ofthe cam. We can also classify cams by the different types of motionevents of the follower and by means of a great variety of the motioncharacteristics of the cam profile. (Chen 82) Figure 6-2 Classification of cam mechanisms4.2.1 Modes of Input/Output MotionRotating cam-translating follower. (Figure 6-2a,b,c,d,e)Rotating follower (Figure 6-2f):

The follower arm swings or oscillates in a circular arc with respectto the follower pivot.Translating cam-translating follower (Figure 6-3).Stationary cam-rotating follower:

The follower system revolves with respect to the center line of thevertical shaft.Figure 6-3 Translating cam - translating follower6.2.1 Follower ConfigurationKnife-edge follower (Figure 6-2a)Roller follower (Figure 6-2b,e,f)Flat-faced follower (Figure 6-2c)Oblique flat-faced followerSpherical-faced follower (Figure 6-2d)6.2.2 Follower ArrangementIn-line follower:

The center line of the follower passes through the center line of thecamshaft.Offset follower:

The center line of the follower does not pass through the center lineof the cam shaft. The amount of offset is the distance betweenthese two center lines. The offset causes a reduction of the sidethrust present in the roller follower.6.2.3 Cam ShapePlate cam or disk cam:

The follower moves in a plane perpendicular to the axis of rotation ofthe camshaft. A translating or a swing arm follower must beconstrained to maintain contact with the cam profile.Grooved cam or closed cam (Figure 6-4):

This is a plate cam with the follower riding in a groove in the faceof the cam.Figure 6-4 Grooved cam

Cylindrical cam or barrel cam (Figure6-5a):

The roller follower operates in a groove cut on the periphery of acylinder. The follower may translate or oscillate. If the cylindricalsurface is replaced by a conical one, a conical cam results.End cam (Figure 6-5b):

This cam has a rotating portion of a cylinder. The follower translatesor oscillates, whereas the cam usually rotates. The end cam is rarelyused because of the cost and the difficulty in cutting its contour.Figure 6-5 Cylindrical cam and end cam6.2.4 Constraints on the FollowerGravity constraint:

The weight of the follower system is sufficient to maintain contact.Spring constraint:

The spring must be properly designed to maintain contact.Positive mechanical constraint:

A groove maintains positive action. (Figure 6-4 and Figure 6-5a)For the cam in Figure 6-6, the follower has two rollers, separated by a fixeddistance, which act as the constraint; the mating cam in such an arrangement is often called a constant-diameter cam. Figure 6-6 Constant diameter cam

A mechanical constraint cam also be introduced by employing a dual orconjugate cam in arrangement similar to what shown in Figure 6-7.Each cam has its own roller, but the rollers are mounted on the samereciprocating or oscillating follower.Figure 6-7 Dual cam 6.2.5 Examples in SimDesign Rotating Cam, Translating FollowerFigure 6-8 SimDesign translating cam Load the SimDesign file simdesign/cam.translating.sim. If youturn the cam, the follower will move. The weight of the followerkeeps them in contact. This is called a gravity constraint cam.Rotating Cam/Rotating FollowerFigure 6-9 SimDesign oscillating cam The SimDesign file is simdesign/cam.oscillating.sim. Noticethat a roller is used at the end of the follower. In addition, aspring is used to maintain the contact of the cam and the roller. If you try to calculate the degrees offreedom (DOF) of the mechanism, you must imagine that the rolleris welded onto the follower because turning the roller does notinfluence the motion of the follower.6.3 Cam Nomenclature Figure 6-10 illustrates some cam nomenclature:Figure 6-10 Cam nomenclature

Trace point: A theoretical point on the follower, corresponding to the point of afictitious knife-edge follower. It is used to generate thepitch curve. In the case of a roller follower, the tracepoint is at the center of the roller.Pitch curve: The path generated by the trace point atthe follower is rotated about a stationary cam.Working curve: The working surface ofa cam in contact with the follower. For the knife-edge followerof the plate cam, the pitch curve and the working curvescoincide. In a close or grooved cam there is an innerprofile and an outer working curve.Pitch circle: A circle from the cam center through the pitchpoint. The pitch circle radius is used to calculate a cam of minimum sizefor a given pressure angle.Prime circle (reference circle): The smallest circlefrom the cam center through the pitch curve.Base circle: The smallest circle from the cam center throughthe cam profile curve.Stroke or throw:The greatest distance or angle throughwhichthe follower moves or rotates.Follower displacement: The position of the follower from aspecific zero or rest position (usually its the position when the follower contacts with the base circle of the cam) in relationto time or the rotary angle of the cam.Pressure angle: The angle at any point between the normal tothe pitch curve and the instantaneous direction of the follower motion. Thisangle is important in cam design because it represents the steepness of thecam profile.6.4 Motion events When the cam turns through one motion cycle, the follower executes aseries of events consisting of rises, dwells and returns. Riseis the motion of the follower away from the cam center, dwellis the motion during which the follower is at rest; and returnis the motion of the follower toward the cam center. There are many follower motions that can be used for the rises and thereturns. In this chapter, we describe a number of basic curves. Figure 6-11 Motion eventsNotation : The rotary angle ofthe cam, measured from the beginning of the motion event;: The range of therotary angle corresponding to the motion event;h : The stoke of the motion event of the follower;S : Displacement of the follower;V : Velocity of the follower;A : Acceleration of the follower.6.4.1 Constant Velocity Motion If the motion of the follower were a straight line, Figure 6-11a,b,c, it would have equal displacementsin equal units of time, i.e., uniform velocity from thebeginning to the end of the stroke, as shown in b. The acceleration,except at the end of the stroke would be zero, as shown in c. Thediagrams show abrupt changes of velocity, which result in large forcesat the beginning and the end of the stroke. These forces areundesirable, especially when the cam rotates at high velocity. Theconstant velocity motion is therefore only of theoreticalinterest. (6-1)6.4.2 Constant Acceleration Motion Constant acceleration motion is shown in Figure 6-11d, e, f. As indicated in e, the velocityincreases at a uniform rate during the first half of the motion anddecreases at a uniform rate during the second half of the motion. Theacceleration is constant and positive throughout the first half of themotion, as shown in f, and is constant and negative throughout thesecond half. This type of motion gives the follower the smallestvalue of maximum acceleration along the path of motion. In high-speedmachinery this is particularly important because of the forces thatare required to produce the accelerations. When

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