1 ME 302 DYNAMICS OF MACHINERY Cam Dynamics Dr. Sadettin KAPUCU © 2007 Sadettin Kapucu

Gaziantep University 2 Introduction to Cam Mechanisms A CAM changes the input motion, which is usually rotary motion (a rotating motion), to a reciprocating motion of the follower. They are found in many machines. A CAM has two parts, the FOLLOWER and the CAM PROFILE.

Gaziantep University 3 Introduction to Cam Mechanisms ONE CYCLEOne rotation/revolution of the cam. DWELLWhen the cam rotates but the follower does not rise or fall. THE RISEThat part of the cam that causes the follower to rise. THE RETURNThat part of the cam that causes the follower to fall.

Gaziantep University 4 Classification of cam mechanisms 1- Joint configurations

Gaziantep University 5 Classification of cam mechanisms 2- Cam Shape

Gaziantep University 6 Classification of cam mechanisms 3- Costraint on the Follower Force closed Form Closed

Gaziantep University 7 Classification of cam mechanisms 4- Modes of input/output and Follower arrangements In-line follower Off-line follower Rotating follower Translating follower Roller follower Spherical-faced follower Flat-faced follower

Gaziantep University 8 Cam Design Cam design 1- Low Speed Cam: Kinematic requirement 2- High Speed Cam: Not only kinematic requirement but also kinetics should be taken into consideration.

Gaziantep University 9 Cam Motions

Gaziantep University 10 Cam Motions

Gaziantep University 11 Motion Profiles 1- Linear Motion s  0  H V a

Gaziantep University 12 Motion Profiles 2- Simple Harmonic Motions   s H

Gaziantep University 13 Motion Profiles 2- Simple Harmonic Motions

Gaziantep University 14 Motion Profiles 3- Constant Acceleration Motion s H  

Gaziantep University 15 Motion Profiles 3- Constant Acceleration Motion

Gaziantep University 16 Motion Profiles 4- Cycloidal Motion Çapı H/ 

Gaziantep University 17 Motion Profiles 4- Cycloidal Motion

Gaziantep University 18 Motion Profiles 5- Trapezoidal Acceleration Motion Parabolik eğriye göre titreşimi ve gürültüsü daha az, aşınma ve şok etkisi daha uygun Üçünü derece hareket veya sikloidal harekete göre daha küçük kam ebatları ve daha düşük ivme değerleri elde edilir. Bağlama açısı, aynı taban dairesi için üçüncü derece hareket eğrisine nazaran daha iyidir.

Gaziantep University 19 Motion Profiles 6- Third Order Polynomial Motion

Gaziantep University 20 Motion Profiles 7- Third Order Polynomial Motion 2

Gaziantep University 21 Motion Profiles Polynomial Motion

Gaziantep University 22 Hareket Eğrileri

Gaziantep University 23 Eccentric Cam Mechanisms An eccentric cam is a disc with its centre of rotation positioned ‘off centre’. This means as the cam rotates the flat follower rises and falls at a constant rate. This type of cam is the easiest to make and yet it is one of the most useful. The diagrams (1 to 7) seen below show the cam rotating in an counterclockwise direction. As it rotates it pushes the flat follower upwards and then allows it to drop downwards. The movement is smooth and at a constant speed.

Gaziantep University 24 Eccentric Cam Mechanisms

Gaziantep University 25 Mathematical Models Cross section showing the overhead valve in an automotive engine and a mathematical model

Gaziantep University 26 Mathematical Models Cross section showing the overhead valve in an automotive engine and a mathematical model

Gaziantep University 27 Mathematical Models Cross section showing the overhead valve in an automotive engine and a mathematical model

Gaziantep University 28 Motion Profiles Shedding Mechanism Model of the shedding mechanism What type of profile should be used for high speed shedding??

Gaziantep University 29 Motion Profiles Model of the shedding mechanism Simple Harmonic Motion Cycloidal Profile Proposed Profile