Cam and Follower Mechanical Notes

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                Cam and Follower

Cam- 

Cam is a rotating mechanical part used to provide rotating, reciprocating or oscilating motion to other part attached with it.   this other part is called follower. the easy example is shown in  diagram.

                 cam & follower figure.

              

1) Cams are widely used in automatic machines, IC engines for open or closing the valves.

2) Cams & follower make point contact between them (as shown above)  therefore they come in Higher pair.

   basically the main function of cam follower in IC engines is to control the inlet & outlet valves, in easy language the procedure of supplying fuel or ejecting gas from piston cyclinder is done with the help of cam & follower.

 or it can be used in other machines where oscilation and reciprocating mechanism is required.

                                                                               TYPES OF CAM

Types of cams (according to shape) accd to shape cams are many types but important 5 are shown below-

1) Wedge & Flat cam-
   These cams have generaly translation or oscilation motion.

                    wedge & flat cam

2) Radial or Disc cam & Plate cam-
   The cam in which follower move radially from the centre of rotation of the cam is known as radial or Dsc cam. The radial cam is generally used in ic engines.

  

           Radial and disc or plate cam

3) Spiral cam-

   Spiral cam consist of Teeth attached with pin gear follower they are very lessly use.

   

                          Spiral cam

4) Cyclinder Cam-

                     Cyclindrical Cam

5) Globoidal Cam-

                      Globoidal cam

 TYPES OF CAMS (according to follower function)

  The function of follower is to be only Rise upward, return downward   or dwell(static) now we discuss types of accd to follower motion

1) Rise-Return-Rise (R-R-R)

   This means firstly follower move upward then return back and then again rise and so on.

2) Dwell-Rise-Return-Dwell (DRRD)

   This mean firstly follower is at rest(dwell) means there is no motion in follower but cams always rotates then after some time follower rise up and then return back and rest at some time this rest position of follower is called Dwell.

3) Dwell-Rise-Dwell-Return (DRDR)

   first follower is at rest then rise up as the cam profile changes then again dwell(rest) then return back.. so on......

 Hence the types of cams are discussed above now we discuss Types of the Follower

TYPES OF FOLLOWER (accd. to shape)

1) Knife Edge follower-

                   Knife edge follower

  

2) Roller Follower                                            3) Flat Surface follower

           Roller & Flat surface follower

4) Mushroom Follower-

    TYPES OF FOLLOWER (accd to movement)

1)   Reciprocatory follower-         
     In this follower, the follower folow only reciprocatory motion.  

        Reciprocatory knife edge follower

                  
   

2) Oscilating follower-
   In this folower, the follower folow only oscilation motion.

             Oscilation roller follower

 

                 TYPES OF FOLLOWER     

            (accd to line of movement)

1)  Radial Follower-                   2) Offset follower-
   
   In radial follower,the line of movement of follower is meet  the axis of the center of cam.  

Radial and offset follower

       
   In Offset Follower the line of action of follower does not meet  with the axis of hte centre of cam.

                                         TERMINOLOGYY of CAM

        
Now we discuss about cam and the term used to working with cam. these term helpful for designing and to drawing the cam profile. these term are disus below in both Hindi or english language.


CAM Profile- 

  The surface boundries of the cam or designing of the cam is known as cam profile. it is different for different cam & follower.

  (Cam ka boundry ka jo designing or layout hota hai usse hum cam profile khte h.)

trace point,camprofile,basecircle,pitch curve.

Trace Point or Pitch Point-

  It is the reference point on the follower, it is present at the centre of the roller follower.
  In case of knife edge follower it is present at edge corner(tip).

  (roller follower ka jo centre point hota h wo trace point or pitch point hota hai. agar hummare pas knife edge follower hai to uska  trace point uski edge par hoga. trace point or pitch point dono ek  hi term hain.)

Base Circle-

  It is the imaginary circle drawn inside the cam profile by taking  minimum or shortest radius of the cam profile.

  (yah ek kalpanic circle hota h jise hum cam profile k andar bnate hain lekin cam profile k undar base circle ka radius kam se kam or shortest hona chaiye.)

Pitch curve

Prime Circle-
  It is also a imaginary circle drawn outside the base circle such that  its radius is equal to sum of radius of base circle or follower  roller.
  In case of knife edge follower there is no roller so the radius of  prime circle is same as radius of base circle.

 ( (yah bhi ek kalpnic circle hota hai jo base circle se bda hota hai is   circle radius {base circle radius + follower roller radius} k brabar    hota   hai. agar hummare pas knife edge follower jisme koi rooler nhi   hota to is case me prime circle base circle k equal hoga kyonki rooler radius to h nhi wo zero ho jayega.) )                     


Pitch Curve-
  It is the curve drawn outside the cam profile,to made this curve  let we supoose cam is at rest and the trace point/pitch point of the follower moves around the cam profile the curve obtain is called pitch curve.
  In case of knife edge follower pitch curve is same as cam profile.

 ( (manlo ki cam rest position mein hai. or hum roller follower ko uske around rotate karte hain to follower ka trace point jo curve bnayega    wo pitch curve hota h. agar hamare pas knife edge follower hai to   uska  pitch curve cam profile jaisa hoga. ab khud hi socho knife edge   follower ka to koi radius hi nhi hota to uska trace point to uska edge  hi hoga use rotate karne par humme cam profile curve hi   milega.) )

Pressure angle

Pressure Angle-
  let suppose we draw a tangent to the pitch curve then draw a  perpendicular/normal to that tangent. then the angle between that normal and line of motion of follower is called pressure angle.
  It is seen that presure angle canot greater than 30 degree.

  (pitch curve par ek tangent draw karo or us tangent par perpendicular draw karo jise normal khte hain. to us normal or follower ke motion k axis k bich mein jo angle hoga wo pressure angle hota h. draw karne k   bad apko ache se samaj aega.) 


Angle of Asent-
  When the follower moves in maximum upward direction, the corresponding angle formed by cam w.r.t the line of motion of   follower   is called angle of asent.

  (Asent ka matlab upar ki taraf move krna hota hai.jab foolower upar  ki taraf move krta hai to obious si bat hai cam me bhi rotation hogi  to folower k maximum upar jane par cam mein jo angle bnta hai use   angle of asent khte hain.)

Angle of Desent-
  Similarly when cam move downward, and angle formed by cam w.r.t. the line of motion of follower is called angle of desent.

  the angle of asent or desent both are called angle of action.

  (desent ka matlab niche ki taraf  move krna hota hai. same follower k niche move karne par cam mein jo angle bnta hai usse angle of desent  khte hain. angle of asent or desent dono ko hum angle of action khte   hain.)