69584_40-英文版机械设计手册.pdfVIP

CHAPTER 40 CAM MECHANISMS Andrzej A. Ol?dzki, D.Sc.f Warsaw Technical University, Poland SUMMARY / 40.1 40.1 CAM MECHANISM TYPES, CHARACTERISTICS, AND MOTIONS / 40.1 40.2 BASIC CAM MOTIONS / 40.6 40.3 LAYOUT AND DESIGN; MANUFACTURING CONSIDERATIONS / 40.17 40.4 FORCE AND TORQUE ANALYSIS / 40.22 40.5 CONTACT STRESS AND WEAR: PROGRAMMING / 40.25 REFERENCES / 40.28 SUMMARY This chapter addresses the design of cam systems in which flexibility is not a consid- eration. Flexible, high-speed cam systems are too involved for handbook presenta- tion. Therefore only two generic families of motion, trigonometric and polynomial, are discussed. This covers most of the practical problems. The rules concerning the reciprocating motion of a follower can be adapted to angular motion as well as to three-dimensional cams. Some material concerns circu- lar-arc cams, which are still used in some fine mechanisms. In Sec. 40.3 the equations necessary in establishing basic parameters of the cam are given, and the important problem of accuracy is discussed. Force and torque analysis, return springs, and con- tact stresses are briefly presented in Sees. 40.4 and 40.5, respectively. The chapter closes with the logic associated with cam design to assist in creating a computer-aided cam design program. 40.7 CAM MECHANISM TYPES, CHARACTERISTICS, AND MOTIONS Cam-and-follower mechanisms, as linkages, can be divided into two basic groups: 1. Planar cam mechanisms 2. Spatial cam mechanisms In a planar cam mechanism, all the points of the moving links describe paths in par- allel planes. In a spatial mechanism, that requirement is not fulfilled . The design of mechanisms in the two groups has much in common. Thus the fundamentals of pla- nar cam mechanism design can be easily applied to spatial cam mechanisms, which f Prepa