CAM MILLING
Cam Milling
The cam milling is the operation of producing cams in a milling machine by the use of universal dividing head and a vertical milling attachment. The cam blank is mounted at the end of the dividing head spindle and an end mill is held in the vertical milling attachment. The axis of the cam blank and the end mill spindle should always remain parallel to each other when setting for cam milling. The dividing head is geared to the table feed screw so that the cam is rotated
Cam and Follower Definition
A cam and follower system is a mechanical arrangement consisting of a cam, which is a specially shaped rotating element, and a follower, which is a device that follows the contour of the cam. The cam's shape dictates the motion of the follower, allowing for precise control and coordination in various applications.
Cam and Follower is also used in other machinery like gear systems. In the most basic form the system consists of three major components. A driving member is called the cam, a frame that holds the cam and the follower. The cam is controlled by the frame, and finally, the driven member is specified as the follower.
What Is Cam?
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 cam is directly in contact with the follower. A follower is another component of this machine, and it is made to oscillate or reciprocate by the cam.
The primary purpose of this component is to convert rotational motion into linear motion for another component. It is a machine component that can be connected to an electric wheel that rotates or a shaft that strikes different points on a lever along a circular route.
Camshafts for internal combustion engines have traditionally been produced by casting, steel forging, or cutting steel bar stock.
What is Follower?
A follower is a rotating or oscillating component of a device that directly tracks the motion of a cam. If a cam moves back and forth, the follower moves vertically with regard to the cam's axis.
The primary function of this machine component is to follow the cam, which may be oscillating or reciprocating. It alters the cam's rotary motion so that it now oscillates or reciprocates.
When building a cam-follower system, translating followers does not jam in a prismatic guide. The chances of restriction to the movement of the oscillating follower are much less.
Figure 2: Cam and Follower Design
Cam and Follower Nomenclature
Now let’s learn about Cam and Follower terminology. Refer to the figure below to understand the terminology better.
Cam and Follower Terminology
Trace Point
It is an imaginary point that is used to trace the profile of a cam. It is at the centre of a roller follower. Since the roller centre serves as the trace point, the movement of the follower will be explained in terms of how this roller centre moves.
If the follower has a flat face, the tracepoint is n the area of the follower's face that makes touch with the cam surface when it is in one of its extreme positions. Typically, the extreme position is when the follower is most closely situated to the cam centre.
Base Circle
The base circle is the smallest circle that can be created using the cam centre as its centre and touching the cam profile.
Pitch Curve
Consider kinematic reversal when defining the pitch curve. This four-link system has a fixed link, a cam, a roller, and a follower in the kinematic inversion. In this four-link mechanism, this link is fixed, but if we create a kinematic inversion holding cam fixed, it will move in the kinematic chain. A curve adjacent to the cam profile will be produced by the location of the roller's centre. After kinematic inversion with the cam set, this is where the tracepoint or roller centre is located.
Prime Circle
Prime circle is the smallest circle that can be drawn from the cam centre and which is tangential to the pitch curve. This circle is perpendicular to the pitch curve and has its centre at the camshaft axis.
Cam Profile
The surface of a cam where the follower joins is known as the cam profile.
Pressure Angle
A pressure angle is created between the normal to pitch curve and the line of motion of the follower.
Now, we will learn about different types of cam and followers
Types of Cam
There are different types of cam for different needs. Here is a list of different types of cam.
Disc or Plate Cam
The follower moves radially from the cam's rotational centre in the disc cam style of the cam. Due to its straightforward layout and size, which allow for installation in far-off places, this cam is very well-liked. Disc or plate cams are used in IC engines and machine tools.
Figure 4: Disc or Plate Cam
Cylindrical Cam
The circumferential outlines are cut on the cylinder's surfaces while the cylinder is rotated about its axis in the cylindrical cam. They also come in two varieties. In the first variety, a groove with a positive oscillating motion is cut into the surface of the cam and roller. The other has a cylinder as the working surface. The spring-loaded follower in this kind of cam corresponds to a cylinder rotating around a parallel plane.
Figure 5: Cylindrical Cam
Translating Cam
A cam that can move in a horizontal plane is referred to as a translating cam. The follower is also attached, in which the motion is interrupted with the aid of a spring. Occasionally, groove cams are used to accomplish follower motion without the need for a spring.
Figure 6: Translating Cam
Radial Cam
One of the most popular kinds of "cams" is the radial cam. A rotating plate or disc known as a "radial cam" has an outer circumference that is shaped to generate the necessary movement (typically linear) to a "follower" that is pressed up against it.
Figure 7: Radial Cam
Wedge Cam
If the cam has linear motion, we call it a wedge cam. The four-link wedge cam system consists of two fixed links and one link that resembles a cam wedge. Depending on the shape of this wedge, the follower will vacillate in the vertical direction alongside this prismatic pair or this guide as this cam oscillates in the horizontal direction.
Figure 8: Wedge Cam
Types of Followers
There are different types of followers for different needs. Here is a list of different types of followers.
Linear Follower
We refer to a follower as a linear follower if it moves linearly. Now let's talk about a translating follower, or what we refer to as radial translating since the axis of that prismatic pair goes through the cam centre. When the follower axis crosses the camshaft's centre, the follower is referred to as tangentially translating. It is referred to as an offset translation follower if there is a slight offset, which indicates that the follower's translation axis does not travel through the centre of the cam.
Figure 9: Linear Follower
Oscillating Follower
The cam continues to spin as before, but because of the shape of the cam, the follower oscillates instead, and this is where the follower is hinged. This is why it is known as an oscillating follower.
Figure 10: Oscillating Follower
Knife-edge Follower
We refer to a follower as a knife-edge follower if its only connection to the sensor is a knife-edge. Due to the extremely high wear rate, a knife-edge follower is never used, so the knife-edge is only notional. Too much contact tension will result.
Figure 11: Knife-edge Follower
Roller Follower
A roller follower is a follower that is hinged to a roller and in touch with a roller cam. The follower that is attached here oscillates, and the cam itself rotates. When a lot of electricity needs to be transmitted, like in stationary IC engines, it is used.
The roller needs a lot of areas if a larger roller can't be used because the pin needs to be big enough to transmit force between the cam and the follower, and the roller needs to be at least twice as big as the pin.
Figure 12: Roller Follower
Flat-Face Follower
A flat-face follower is one that has a follower surface that is flat and in touch with the cam. Instead of being flat, the trailing surface could also be curved. It is known as a curved face because the cam rotates and the follower that sits here oscillates. If there isn't much room available, as there was in the case of cars, we can use a flat-face follower.
Figure 13: Flat Face Follower
Advantages and Disadvantages of Cam and Follower
Here are some advantages and disadvantages of cam and follower:
Advantages of Cam and Follower
Benefits of Cam and Follower are:
- The device that changes rotary motion into reciprocating motion is straightforward.
- Any desired motion of the follower can be accomplished with proper design.
- The system can withstand strong shocks and vibrations.
- They are reliable and adaptable.
Disadvantages of Cam and Follower
Cons of Cam and Follower are:
- There is side thrust and friction resistance operating as the follower passes over the cam. This results in the cam experiencing frequent wear and tear.
- More room is needed for the cam and follower arrangement.
- The expense of manufacturing is high, and accuracy is required.
Cam and Follower Applications
There are lots of applications of cam and follower as mentioned below:
- In hanging clocks, Cam and Follower are utilised.
- They are utilised In automatic lathe tools in the feed mechanism.
- Screw equipment includes the Cam and Follower.
- Cam and Follower are gear-cutting machinery.
- This device in the printing equipment aids in screen printing. Both the push and the draw assist in positioning objects for printing and printing itself.
- These are the primary components that make up the hydraulic system.
- Even in machinery designed for the textile industry, the cam and follower mechanism enables the sewing of the fabric with just one press and pull.
- In that instance, fluid pressure affects the mechanism.
- Various components that are automatically in motion are used in automated equipment such as cams and followers.
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