上海交通大学：《Design and manufacturing（ME371、ME337）》课程教学资源（讲义）Lecture11 Cam Design

圈上海夫通大华 e西b口 LECTURE 11 ME371/ME337 DESIGN AND MANUFACTURING Cam Design Covered: 漏 Ch8 in Design of Machinery SHAN 圈上泽夫通大学 Lectures Power/Energy Conversion (Electrical Motors) Power/Energy Transmission (Gears,Cam,Linkage, Belt Drives, Power Screws Transmission Joints (Fasteners, Support Connectors) (Bearings) Structural Support (Frames) Tools Statics,Dynamics, Stress Analysis,etc. 1

1 Cam Design LECTURE 11 ME371/ME337 DESIGN AND MANUFACTURING Covered: Ch8 in Design of Machinery Lectures Power/Energy Conversion (Electrical Motors) Transmission Support (Bearings) Joints (Fasteners, Connectors) Structural Support (Frames) Tools Statics, Dynamics, Stress Analysis, etc. Power/Energy Transmission (Gears, Cam, Linkage, Belt Drives, Power Screws)

国上海支大华 Outline © Cam Introduction ©Cam Motion Diagrams ®Cam Synthesis ©Sizing the Cam 国 上海充廷大学 Cam Introduction CAM:Has a curved or grooved surface that mates with a follower: Imparts motion to follower.The follower oscillation, translation,or both Cam-follower system advantages: Convenient device for transforming one motion into another >More compact than linkages 2

2 Outline Cam Introduction Cam Motion Diagrams Cam Synthesis Sizing the Cam  CAM: Has a curved or grooved surface that mates with a follower :  Imparts motion to follower. The follower oscillation, translation, or both  Cam-follower system advantages:  Convenient device for transforming one motion into another  More compact than linkages Cam Introduction

圈上海文通大华 Cam Introduction ▣Function generator Follower Fixture Cam 圈上泽夫道大学 Cam-follower Type ▣ Cam-follower systems can be classified by type of: >Type of the cam(radial and cylindrical) >Type of follower motion(rotation,translation) >Type of joint closure(force,form) >Surface of contact(roller,mushroom,flat) >Path of the motion of the follower(radial,axial) >Type of motion constraints(critical extreme position(CEP)and critical path motion(CPM)) >Type of motion program(rise-fall(RF),rise-fall- dwell(RFD),rise-dwell-fall-dwell(RDFD) 3

3 Cam Introduction Cam Follower Fixture  Function generator  Cam-follower systems can be classified by type of: Type of the cam(radial and cylindrical) Type of follower motion (rotation, translation) Type of joint closure (force, form) Surface of contact (roller, mushroom, flat) Path of the motion of the follower (radial, axial) Type of motion constraints (critical extreme position(CEP) and critical path motion (CPM)) Type of motion program (rise-fall (RF), rise-fall￾dwell (RFD), rise-dwell-fall-dwell (RDFD) Cam-follower Type

国上清文大华 Cam-follower Type 口Cam types Plate or disc Translating Cylindrical (盘形凸轮) (移动凸轮) (圆柱凸轮) 圈上泽夫道大学 Cam-follower Type Half joint 口 Follower motion Cam >Translation ·Radial 4 Offset from center of cam shaft >Oscillation(Rotation) Spring Follower 4

4  Cam types Plate or disc （盘形凸轮） Translating （移动凸轮） Cylindrical （圆柱凸轮） Cam-follower Type  Follower motion  Translation • Radial • Offset from center of cam shaft  Oscillation (Rotation) Cam-follower Type

国 上海文通大学 Cam-follower Type Shape of follower contact surface > Flat-face(平底从动件) Package smaller eg.Automotive valve) Roller(滚子从动件) Lower friction,but more expensive >Mushroom Roller Mushroom Flat-Faced Follower Follower Follower 4 Follower Follower Follower Spring Spring Spring Cam Cam a 圈上泽夫道大学 ▣ Follower types Cam (a)Cam with knife (6)Cam with roller (c)Cam with flat edge follower. faced follower. pherical faced ●tse (d)Cam with spherical (e)Cam with spherical 价Cam wit恤offset faced follower. faced follower. follower. 5

5  Shape of follower contact surface  Flat-face(平底从动件) • Package smaller ( eg. Automotive valve)  Roller（滚子从动件） • Lower friction , but more expensive  Mushroom Cam-follower Type Roller Follower Mushroom Follower Flat-Faced Follower Flat-Faced Follower Mushroom Follower Roller Follower  Follower types

圈上泽文通大华 Cam-follower Type ▣Joint closure types >Force closure Requires external force be applied to joint to keep cam and follower in contact >Form closure Closes joint by geometry,No external force required 4 用 -Track or groove Form-closed cam with Force-closed oscillating follower © 上海充廷大学 Cam-follower Type Common motion constraint types >Critical Extreme Position(CEP) Design specifications define the start and finish positions of follower Does not specify any constraint on path between extreme positions >Critical Path Motion(CPM) Path motion and/or derivatives defined overall or part of motion interval Analogous to function generation in the linkage design 6

6  Joint closure types  Force closure • Requires external force be applied to joint to keep cam and follower in contact  Form closure • Closes joint by geometry, No external force required Cam-follower Type Force-closed Form-closed cam with oscillating follower  Common motion constraint types  Critical Extreme Position (CEP) • Design specifications define the start and finish positions of follower • Does not specify any constraint on path between extreme positions  Critical Path Motion(CPM) • Path motion and/or derivatives defined overall or part of motion interval • Analogous to function generation in the linkage design Cam-follower Type

图 上海文通大学 Cam-follower Type 0 Common motion programs > Rise-fall(RF升程一回程) >Rise-fall-dwell(RFD升程-回程一休止) >Rise-dwell-fall-dwell(RDFD) ▣Dwell >No output motion for a specified period of input motion 圆上清支大华 Cams from the industry 7

7  Common motion programs  Rise-fall (RF升程－回程)  Rise-fall-dwell (RFD升程－回程－休止)  Rise-dwell-fall-dwell (RDFD)  Dwell  No output motion for a specified period of input motion Cam-follower Type Cams from the industry

圈上泽文通大华 Design Procedure ② 丈艺动作构思· 让动作协调起来 更好的方 9 ④ 选择合适的机构 圈上泽夫道大学 Cam Design Procedure 1.Type Synthesis P Selection of cam and follower type based on basic motion requirements >Geometric,environmental,and economic considerations 2.Follower Motion: >from timing diagram->motion program Based on specified rise,return,dwell 3.Dimensional Synthesis of Cam Profile >"Wrapping around"follower profile onto cam 4.Analysis Pressure Angle,Radius of Curvature, Dimensional Constraints... 8

8 Design Procedure Cam Design Procedure 1. Type Synthesis  Selection of cam and follower type based on basic motion requirements  Geometric, environmental, and economic considerations 2. Follower Motion: from timing diagram->motion program • Based on specified rise, return, dwell 3. Dimensional Synthesis of Cam Profile  “Wrapping around” follower profile onto cam 4. Analysis  Pressure Angle, Radius of Curvature, Dimensional Constraints

圈上活克通大华 Outline © Cam Introduction and Terminology © Cam Motion Diagrams ®Cam Synthesis ©Sizing the Cam 圈上泽夫道大学 Motion Diagram 口 Example follower displacement profile Obtained by linearizing cam-unwrapping it from its circular shape 口Abscissa(横坐标)can be >Time >Shaft angle C Developed Prime Circle Ris Dwell -Return Dwell- d 6 Transition or Inflection Points- 3 0 1 5 6 78 9 10 0 Station Point Numbers 9

9 Outline Cam Introduction and Terminology Cam Motion Diagrams Cam Synthesis Sizing the Cam Motion Diagram  Example follower displacement profile  Obtained by linearizing cam – unwrapping it from its circular shape  Abscissa(横坐标) can be  Time  Shaft angle

圈上泽文通大学 Choosing S VA J Functions Critical Extreme Position(CEP)case Does not specify functions to get from low dwell to high dwell or from one extreme to the other ▣Double dwell Cam ·What should we use for Motion our rise and fall functions? mm or in What qualities should we Hish look for? dwell 1 Low dwell Rise Fall 0 0 90 180 270 360 Cam angle deg 0 0.25 0.50 0.75 1.0 Time t sec 圈上泽夫道大学 Motion Diagram ▣ Cam design usually starts with sketch of: >Displacement >Velocity >Acceleration >Jerk Displacement Function? 10

10 Choosing S V A J Functions  Critical Extreme Position (CEP) case  Does not specify functions to get from low dwell to high dwell or from one extreme to the other  Double dwell Cam • What should we use for our rise and fall functions? • What qualities should we look for?  Cam design usually starts with sketch of:  Displacement  Velocity  Acceleration  Jerk Motion Diagram Displacement Function?