国 上泽克通大学 e-国b口 Covered LECTURE 9 Cha8 in Design of Machinery CAM DESIGN 凸轮机构设计 国 上泽充通大学 Lectures Power/Energy Conversion Power/Energy (Electrical Motors) Transmission (Gears,Cam,Linkage, Belt Drives Power Serews) Joints Transmission (Fasteners, Support (Bearings) Structural Connectors) Support (Frames) Tools Statics,Dynamics, Stress Analysis,etc. 1
1 CAM DESIGN 凸轮机构设计 LECTURE 9 Covered : Cha8 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)
上泽文廷大学 CAM Design ©Topics What is a cam mechanism How does a cam mechanism work? Classification and construction of a cam mechanism Timing diagram and motion program How to design a cam according to the motion program? What are kinematic characteristics of a cam mechanism? Reading---Chapter 8 in Design of Machinery Handouts---Dynacam software students'edition 圆上泽大华 What is a cam mechanism? .Where can we find cams? >Convenient device for transforming one motion into another >Has a curved or grooved surface that mates with a follower =Imparts motion to follower Follower oscillation.translation,or both 2
2 CAM Design Topics • What is a cam mechanism • How does a cam mechanism work? • Classification and construction of a cam mechanism • Timing diagram and motion program • How to design a cam according to the motion program? • What are kinematic characteristics of a cam mechanism? Reading --- Chapter 8 in Design of Machinery Handouts--- Dynacam software students’ edition •Where can we find cams? Convenient device for transforming one motion into another Has a curved or grooved surface that mates with a follower =Imparts motion to follower Follower oscillation, translation, or both What is a cam mechanism?
上活成大峰 What is a cam mechanism? Pitch curve Cam surface Prime circle Roller follower Base circle WWWWW 国 上泽充通大警 What is a cam mechanism? Reciprocating roller follower Trace point Total follower travel Maximum pressure Pitch circle angle 2 Follower motion Cam shaft Pitch point 3/ Base. circle Pitch point Prime circle Pitch curve Cam profile 3
3 What is a cam mechanism? What is a cam mechanism?
园 上活我大峰 What is a cam mechanism? 1.Base circle.It is the smallest circle that can be drawn to the cam profile 2.Trace point.It is a reference point on the follower and is used to generate the pitch curve. In case of knife edge follower,the knife edge represents the trace point and the pitch curve corresponds to the cam profile.In a roller follower,the centre of the roller represents the trace point. 3.Pressure angle.It is the angle between the direction of the follower motion and a normal to the pitch curve.This angle is very important in designing a cam profile.If the pressure angle is too large,a reciprocating follower will jam in its bearings. 4.Pifch point.It is a point on the pitch curve having the maximum pressure angle. 5.Pitch circle.It is a circle drawn from the centre of the cam through the pitch points. 6.Pifch curve.It is the curve generated by the trace point as the follower moves relative to the cam.For a knife edge follower,the pitch curve and the cam profile are same whereas for a roller follower,they are separated by the radius of the roller. 7.Prime circle.It is the smallest circle that can be drawn from the centre of the cam and tangent to the pitch curve.For a knife edge and a flat face follower.the prime circle and the base circle are identical.For a roller follower.the prime circle is larger than the base circle by the radius of the roller. 8.Lif or stroke.It is the maximum travel of the follower from its lowest position to the opmost position. 圈上清庆大坐 Cams compare with linkages .Linkage advantages >Reliability >Ease of construction >Lower cost .Cam-follower systems more compact than linkages >For same output motion >Can generate a true dwell >Intermittent motion ME371 Design Manufacturing ll 4
4 What is a cam mechanism? ME371 Design & Manufacturing II Cams compare with linkages •Linkage advantages Reliability Ease of construction Lower cost •Cam-follower systems more compact than linkages For same output motion Can generate a true dwell Intermittent motion
国 上游充通大学 Classifications of Cam Mechanisms D TONG 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 the cam(radial and cylindrical) 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) ME371 Design Manufacturing ll 圈上清支大学 Classifications of Cam Mechanisms Type of Follower Motion Follower- Half joint Translating and oscillating followers Cam Spring Depends on motion required 02 Half joint Cam h2aaad4 02 Spring Follower 5
5 ME371 Design & Manufacturing II Classifications of Cam Mechanisms 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 the cam(radial and cylindrical) 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) ME371 Design & Manufacturing II Type of Follower Motion Translating and oscillating followers Depends on motion required Classifications of Cam Mechanisms