mechanisms design mecn 4110

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LectureLecture

77Mechanisms DesignMechanisms Design

MECN 4110 MECN 4110

Professor: Dr. Omar E. Meza CastilloProfessor: Dr. Omar E. Meza [email protected]

http://facultad.bayamon.inter.edu/omezaDepartment of Mechanical EngineeringDepartment of Mechanical EngineeringInter American University of Puerto RicoInter American University of Puerto Rico

Bayamon CampusBayamon Campus

mailto:[email protected]

http://www.bc.inter.edu/facultad/omeza

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Tentative Lectures ScheduleTentative Lectures Schedule

TopicTopic LectureLectureIntroduction of Mechanism and KinematicsIntroduction of Mechanism and Kinematics 1, 2 and 31, 2 and 3Position AnalysisPosition Analysis 44

Velocity AnalysisVelocity Analysis 55

Acceleration AnalysisAcceleration Analysis 66

CAMSCAMS 77


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Cam and FollowerCam and Follower

Topic: CAMsTopic: CAMs

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One thing you learn in science is that One thing you learn in science is that there is no perfect answer, no perfect there is no perfect answer, no perfect measure.measure.

A. O. BeckmanA. O. Beckman


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Up on completion of this chapter, the Up on completion of this chapter, the student will be able tostudent will be able to Understand how to design a CAM-FOLLOWER Understand how to design a CAM-FOLLOWER

Systems.Systems.


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Cam

Follower

http://en.wikipedia.org/wiki/File:Nockenwelle_ani.gif


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A cam is a rotating or sliding piece in a mechanical A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary linkage used especially in transforming rotary motion into linear motion or vice versa. It is often a motion into linear motion or vice versa. It is often a part of a rotating part of a rotating wheel (eg. an eccentric wheel) or (eg. an eccentric wheel) or shaft (eg a cylinder with an irregular shape) that shaft (eg a cylinder with an irregular shape) that strikes a strikes a lever at one or more points on its circular at one or more points on its circular path. The cam can be a simple tooth, as is used to path. The cam can be a simple tooth, as is used to deliver pulses of power to a deliver pulses of power to a steam hammer, for , for example, or an example, or an eccentric disc or other shape that disc or other shape that produces a smooth reciprocating (back and forth) produces a smooth reciprocating (back and forth) motion in the motion in the followerfollower which is a lever making which is a lever making contact with the cam.contact with the cam.

The reason the cam acts as a lever is because the The reason the cam acts as a lever is because the hole is not directly in the centre, therefore moving hole is not directly in the centre, therefore moving the cam rather than just spinning. On the other the cam rather than just spinning. On the other hand, some cams are made with a hole exactly in hand, some cams are made with a hole exactly in the centre and their sides act as cams to move the the centre and their sides act as cams to move the levers touching them to move up and down or to levers touching them to move up and down or to go back and forth.go back and forth.

http://en.wikipedia.org/wiki/Wheel

http://en.wikipedia.org/wiki/Lever

http://en.wikipedia.org/wiki/Steam_hammer

http://en.wikipedia.org/wiki/Eccentric_(mechanism)


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The first stage in designing a cam system is the The first stage in designing a cam system is the creation of a displacement diagram. A typical plate creation of a displacement diagram. A typical plate cam with an in-line roller follower is shown below cam with an in-line roller follower is shown below with a displacement diagram. This figure shows the with a displacement diagram. This figure shows the following characteristic features.following characteristic features.Rise-Rise- This is when the follower is moving away This is when the follower is moving away from the cam centre. The slope reflects the follower from the cam centre. The slope reflects the follower velocity.velocity.Dwell-Dwell- the is the period when the follower is the is the period when the follower is stationary stationary Return - Return - This is when the follower moves back This is when the follower moves back towards the cam centre towards the cam centre Base circle Base circle on the cam is the smallest full on the cam is the smallest full diameter of the cam diameter of the cam Prime circle Prime circle is centered on the cam rotation is centered on the cam rotation centre with radius at the follower roller centre centre with radius at the follower roller centre when the follower is on the base circle when the follower is on the base circle Cam profile Cam profile is the shaped surface of the cam is the shaped surface of the cam defining the follower motiondefining the follower motion


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New


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RF = rise-fallRF = rise-fall RFD = rise-fall-dwellRFD = rise-fall-dwell RDFD = rise-dwell-fall-dwellRDFD = rise-dwell-fall-dwell


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Homework7 Homework7 Web Web

Omar E. Meza Castillo Ph.D.Omar E. Meza Castillo Ph.D.

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mechanisms design mecn 4110

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