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?