mechanisms design mecn 4110

LectureLecture

77Mechanisms DesignMechanisms Design

MECN 4110 MECN 4110

Professor: Dr. Omar E. Meza CastilloProfessor: Dr. Omar E. Meza Castilloomeza@bayamon.inter.edu

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

Lecture 7Lecture 7MEC

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

Cam and FollowerCam and Follower

Topic: CAMsTopic: CAMs

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

mon Chapters ObjectivesChapters Objectives

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.

Follower

mon CamCam

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.

mon Design of Cam SystemsDesign of Cam Systems

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

mon Cam DesignCam Design

mon Types of CamsTypes of Cams

mon Types of Joint Closers (cam/follower joint)Types of Joint Closers (cam/follower joint)

mon Follower MotionFollower Motion

mon Types of FollowersTypes of Followers

mon Obtaining the S DiagramObtaining the S Diagram

mon Unwrapping/Linearizing a CamUnwrapping/Linearizing a Cam

mon The S DiagramThe S Diagram

mon Why S Diagram Cannot Have Negative ValuesWhy S Diagram Cannot Have Negative Values

mon SVAJ DiagramSVAJ Diagram

mon Type of Motion Constraints Type of Motion Constraints

mon Type of Motion ProgramType of Motion Program

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

mon Double-Dwell Cam Design- Choosing SVAJ FunctionsDouble-Dwell Cam Design- Choosing SVAJ Functions

mon How Not Meet Cam Design Specifications (Linear Function)How Not Meet Cam Design Specifications (Linear Function)

mon Cycloidal MotionCycloidal Motion

mon Cycloidal Motion – SVAJ DiagramCycloidal Motion – SVAJ Diagram

mon a Diagrama Diagram

mon v Diagramv Diagram

mon s Diagrams Diagram

mon Cycloidal Displacement FunctionCycloidal Displacement Function

mon Polynomial Function Polynomial Function

mon Polynomial FunctionPolynomial Function

mon Double Dwell Cam DesignDouble Dwell Cam Design

mon Single Dwell Cam DesignSingle Dwell Cam Design

Homework7 Homework7 Web Web

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

mechanisms design mecn 4110

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