国上海支大学 西+口 LECTURE 8 ME371ME337 DESIGN AND MANUFACTURING Power Screws Covered: 11-1 and 11-2 in Mechanical Engineering Design 圆上泽大些 Lectures Power/Energy Conversion Power/Energy (Electrical Motors) Transmission (Gears,Cam,Linkage, Belt Drives, Rower Screws) Joints Transmission (Fasteners Support Connectors (Bearings) Structura Support (Frames) Tools Statics,Dynamics, Stress Analysis,etc. 1
1 Power Screws LECTURE 8 Covered: 11-1 and 11-2 in Mechanical Engineering Design ME371/ME337 DESIGN AND MANUFACTURING 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)
圆上清支大学 OUTLINE Power Screw Introduction © Basic Terminology ©Torque Loading ©Other issues 圈上泽夫道大学 Power Screw Principles The screw thread is one of the most important inventions ever made Power screw using the principle of a screw thread and its mating nut Used to convert rotation to linear motion in actuators,machines(Lead screws)and jacks,etc. Transmit power,exert the necessary force to move a machine element along a desired path. Capable of very large mechanical advantages,can lift or- move large loads,the speed is often slow. 2
2 OUTLINE Power Screw Introduction Basic Terminology Torque Loading Other issues The screw thread is one of the most important inventions ever made Power screw using the principle of a screw thread and its mating nut Used to convert rotation to linear motion in actuators, machines (Lead screws) and jacks, etc. Transmit power, exert the necessary force to move a machine element along a desired path. Capable of very large mechanical advantages, can lift or move large loads, the speed is often slow. Power Screw Principles
圆上泽文大学 Applications 1 ▣Power screws >Either screw can move,as in a jack or >Nut can move,as in a positioning device. Head servomotor Lever coupling Sq.threaded rod lead screw nut 圆上清支大华 Applications 1 3
3 Applications 1 Power screws Either screw can move, as in a jack or Nut can move, as in a positioning device. Applications 1
国 上海文通大学 Lead Screw(传导螺杆) ▣Lead screw Lead screws are essentially accurate screws used to move a nut attached to a load,and they have been used for centuries to convert rotary motion into linear motion Lead screws are commonly used on manual economy machine tools > Efficiency in a lead screw system may be 30-50% © 上海充廷大学 Ball Screws(滚珠螺旋) Ball screw is similar in function to lead screw.Sliding contact between the screw and nut is replaced by rolling contact using recirculating spherical balls,reduce the thread friction.do not suffer from the stick-slip characteristics of sliding joints Leads to higher efficiency,may have 95%efficiency >However,not self-locking. >Have a more limited fatigue life,but have very high load nitonis capacity 4
4 Lead Screw(传导螺杆) Lead screw Lead screws are essentially accurate screws used to move a nut attached to a load, and they have been used for centuries to convert rotary motion into linear motion Lead screws are commonly used on manual economy machine tools Efficiency in a lead screw system may be 30-50% Ball Screws（滚珠螺旋） Ball screw is similar in function to lead screw. Sliding contact between the screw and nut is replaced by rolling contact using recirculating spherical balls, reduce the thread friction, do not suffer from the stick-slip characteristics of sliding joints Leads to higher efficiency, may have 95% efficiency However, not self-locking. Have a more limited fatigue life, but have very high load capacity
圈上海充通大峰 Ball Screws(遠珠螺旋) Modern machine tools,automation equipment,and actuators on aircraft use ball screws for high precision,high efficiency, fast response,and smooth operation. Carriage Rotary Encoder AC Brushless Motor Flexible Coupling Rearing Housing Ballscrew Ballnut Support Bearings 5
5 Ball Screws（滚珠螺旋） Modern machine tools, automation equipment, and actuators on aircraft use ball screws for high precision, high efficiency, fast response, and smooth operation