Machine Design 101: Cam and Roller

When it comes to transforming rotary motion into linear actuation, there is likely no better mechanism than that of a cam and roller.

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Cam and roller mechanisms are often used in engines, repeating machinery and other manufacturing applications. A cam consists of a rotating shaft that usually has some oblong or non-regular shape used to induce the desired linear motion. There are radial cams, which translate motion along one axis, and even cylindrical cams that can translate motion along 2-axis. The roller, sometimes called a follower, is the piece that follows along with the cam’s motion, and it is typically restricted to a strictly linear field of motion.

If you have done any sort of machine design over your time as an engineer, you know that translating rotational motion into linear motion is not always the easiest thing to do efficiently. Cams and rollers do this task with ease, but there also exists a subset of cam design that provides for very fluid and precise motion.

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Cams are not limited by simple shapes, rather they can be designed to have an organic or flowing interface with the roller mechanism. This results in more specialized radial cams. It’s this range of freedom in cam and roller design that gives engineers like you the ability to create unique mechanisms with only a simple rotational input.

Like any translation of motion, there will be a loss of some energy.

Cams and rollers have very minimal energy losses due to the fact that the interface between parts is such a small area, thus there is very little friction. There are two main follower contact types that interface with cams: flat-faced and roller. Flat-faced interfaces are simple and they resist jamming in the mechanism. The drawback is when designing more organic cam shapes or when a precise path is needed, a flat interface falls short. On the other hand, a roller interface can fit into precise cam shapes, but it can jam easily and is generally more complex to build and maintain. 280px-cam-disc-3_3d_animated

To dive even deeper into cam and roller design, we must consider the dynamic interface of all of the parts. As a design engineer for cam systems, you have to keep a close watch on the displacement and its derivatives therein, being velocity, acceleration, and jerk. Usually, cam mechanisms are used in machines that require a rather precise movement, and losing sight of any of these physics elements could result in ultimately a bad design. A good cam and roller design will result in the follower maintaining a fairly constant velocity and acceleration in all of its relative cycle phases. So, if you are ever faced with designing a cam and roller mechanism, remember that if you aren’t precise in the design, your end product likely will fail earlier due to fatigue – or not even work at all.

In the world of cams, there’s even more than what we discussed here. Theoretically speaking there is an infinite number of cam designs that can be used in a machine, but it often takes an ingenious engineer to design the correct parts. But, that’s what you are, right?

Sources: Machine DesignBright Hub EngineeringSlideShare

Images: [1][2][3]

Profile photo of Trevor English
Trevor is a civil engineer by trade and an accomplished internet blogger with a passion for inspiring everyone with new and exciting technologies. He is also a published children’s book author whose most recent book, ZOOM Go the Vehicles, is aimed at inspiring young kids to have an interest in engineering.


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