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-falldwell (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?
