3 Finger 1 Finger 2 M 饼干 4 饼干 4/ 2 2 A 饼干 饼干 4 2 A A 国 上净文通大学 3 Finger 1 Finger 2 M B 4 2 finger1 M finger2 M p0° 90° 180° 270° 360° 11
11 1 饼干 3 4 2 Finger 1 Finger 2 M B A 1 饼干 4 2 1 饼干 4 2 1 饼干 4 2 finger1 finger2 0º 90º 180º 270º 360º M M 1 饼干 3 4 2 Finger 1 Finger 2 M B A
® 上游充通大学 540 180 点火 国 上海充通大学 Type of Motion Constraints Critical Extreme Position(CEP)-start and end positions are specified but not the path between Does not specify any constraint on path between extreme positions © Critical Path Motion(CPM)-path or derivative is defined over all or part of the cam Comstant vekcity Retu 2 3 4 360Cgd 030 21020 360 cam angie deg 1.0 Time 0008 0580.67 1.00 ti8d于ee ME371 Design Manufacturing ll 12
12 排 门 闭 关 气 启 排 气 门 开 启 进 气 门 进 开 气 排 气 压 缩 膨 胀 闭 进 气 门 关 点 火 曲轴 0˚ 540˚ 360˚ 180˚ ① ② ③ ④ ⑤ ME371 Design & Manufacturing II Type of Motion Constraints Critical Extreme Position (CEP) – start and end positions are specified but not the path between Does not specify any constraint on path between extreme positions Critical Path Motion (CPM) – path or derivative is defined over all or part of the cam
国上人峰 Type of Motion Program From the CEP cam profile 运动规律 Dwell-period with no output motion with input motion Rise-Fall(RF)-no dwell (think about using a crank- rocker）(RF升程-回程) ©Rise-Fal-Dwell(RFD)-one dwell‖(RFD升程-回程-休) Rise-Dwell-Fall-Dwell(RDFD) -two dwells Coke bottling example: ME 圈上泽庆大坐 Type of Motion Program 运动规律 .Example follower displacement profile .Obtained by linearizing cam-unwrapping it from its circular shape C-Developed Prime Circle- Rise Dwell Return Dwell- -d Transition or Inflection Points- 5 10 Station Point Numbers Abscissa(横坐标)can be >Time >Shaft angle 13
13 ME371 Design & Manufacturing II Type of Motion Program 运动规律 From the CEP cam profile Dwell – period with no output motion with input motion. Rise-Fall (RF) – no dwell (think about using a crankrocker) (RF升程－回程) Rise-Fall-Dwell (RFD) – one dwell (RFD升程－回程－休止) Rise-Dwell-Fall-Dwell (RDFD) – two dwells Coke bottling example: Type of Motion Program 运动规律 •Example follower displacement profile •Obtained by linearizing cam – unwrapping it from its circular shape •Abscissa(横坐标) can be Time Shaft angle
园 上活大等 SVAJ Diagrams © Unwrapping the cam Plot of position(s/S), velocity(v/), acceleration(a/A)and jerk(j/J)verses cam angle Basis for cam design Handout-Dynacam 270 360 圈上清庆大坐 RDFD Cam Design Motion is between two dwells What should we use for our rise Motion and fall functions? mm or in ·What qualities High should we look for? dwell Low dwell Rise Fall 0 0 90 180 270 360 Cam angle 0 deg 0 0.25 0.50 0.75 1.0 Time t sec ME371 Design Manufacturing ll 14
14 ME371 Design & Manufacturing II Unwrapping the cam Plot of position(s/S), velocity(v/V), acceleration(a/A) and jerk(j/J) verses cam angle Basis for cam design SVAJ Diagrams Handout-Dynacam ME371 Design & Manufacturing II RDFD Cam Design Motion is between two dwells • What should we use for our rise and fall functions? • What qualities should we look for?
国上活大修 RDFD Cam,Naive Cam Design Connect points using Rise High dwell Fall straight line Low dwell Constant velocity ⑧Infinite acceleration。 and jerk ⑧Not an acceptable cam program 180 270 30 国 上净文通大学 Fundamental Law of Cam Design Any cam designed for operation at other than very low speeds must be designed with the following constraints The cam function must be continuous through the first and second derivatives of displacement across the entire interval(360 degrees). Corollary: The jerk must be finite across the entire interval (360 degrees). ME371 Design Manufacturing ll 15
15 ME371 Design & Manufacturing II RDFD Cam, Naive Cam Design Connect points using straight line Constant velocity Infinite acceleration and jerk Not an acceptable cam program ME371 Design & Manufacturing II Fundamental Law of Cam Design Any cam designed for operation at other than very low speeds must be designed with the following constraints The cam function must be continuous through the first and second derivatives of displacement across the entire interval (360 degrees). Corollary: The jerk must be finite across the entire interval (360 degrees)