1、AMERICAN NATIONAL STANDARD Ball Screws ANSI B5.48 - 1977 - - . -. - REAFFIRMED 1994 FOR CURRENT COMMIlTEE PERSONNEL PLEASE SEE ASME MANUAL AS11 SECRETARIAT SOCIETY OF AUTOMOTIVE ENGINEERS SOCIETY OF MANUFACTURING ENGINEERS NATIONAL MACHINE TOOL BUILDERS ASSOCIATION THE AMERICAN SOCIETY OF MECHANICAL
2、 ENGINEERS PUBLISHED BY THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS United Engineering Center 345 East 47th Street New York, N. Y. 1001 7 No part of this document may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Co
3、pyright 0 1977 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in U.S.A. ERRATA ANSI B5.48 - 1977 Ball Screws Page 13. Paragraph A1.2 Symbols, change 0 = helix angle, degrees to read 8 = lead angle, degrees. page 13. Paragraph A1.3 Axial Angle Deflection Equations change
4、0 = tan-1 nBCD 1 to read 0 =tan- - L nBCD Copyright 01979 by THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS All Rights Reserved Printed in USA. 36800B I1 llll I 1111llll FOREWORD In order to obtain a consensus opinion relative to proposals for standardization of ball screw assemblies within the ISO/TC
5、39 Subcommittee Working Group 7, a number of users within the machine tool industry and manufacturers of ball screws were assembled. It was determined by this group that there was a need for such standardization in the United States and application was made to AN Standards Committee B5-Machine Tools
6、, for the organization of a technical committee for this work. Accordingly, TC43 was organized and a scope was approved by AN Standards Committee B5. The first meeting was held on July 22, 1971. The members of the committee represented manufacturers, users of ball screws, and others of general inter
7、est balanced according to ANSI requirements for such committees. This document was approved as an American National Standard on April 7, 1977. iii AMERICAN NATIONAL STANDARDS COMMITTEE B5 MACHINE TOOLS, COMPONENTS, ELEMENTS, PERFORMANCE AND EQUIPMENT (The following is the roster of the Committee at
8、the time of the approval of the Standard) OFFICERS W. L. McCann, Chairman E. A. Munrhauer, Jr., Vice-chairman (Group A) Paul C. Ackermann, Vice-chairman (Group CJ C. T. Blake, Vice-chairman (Group BJ Harold Cooper, Vice Chairman (Group DJ E. J. Loeffler, Secretary STANDARDS COMMITTEE AMERICAN SOCIET
9、Y OF MECHANICAL ENGINEERS, THE f. S. Blackall, 111. The Taft-Pierce Manufacturing Company, Woonsocket, Rhode Island C. T. Blake, The Warner , NSK Corporation, New York, New York David A. Galonska, Saginaw Steering Gear Division, General Motors Corporation, Saginaw, Michigan J. Robert Henstenburg, Th
10、e Bullard Company, Bridgeport, Connecticut Richard F. Jennings, Jones 7.8,7.9 and 7.10 12 7.3 Imperial (Inch) System Symbols 12 7.4 Basic Load Rating (1 000 000 Inches Rated Life) . 12 7.5 Basic Static Thrust Capacity (Imperial) 12 7.7 SI Symbols 12 7.8 Basic Load Rating (25 400 Meters Rated Life) .
11、 12 7.9 Basic Static Thrust Capacity (Metric) . 12 7.10 Load Rating at Other Than 25 400 Meters of Travel . 12 7.6 Load Rating at Other Than One Million Inches of Travel 12 7.1 1 The Equivalent Load for Ball Bearing Screw Assemblies . 12 TABLES Table I Class and Deviation 3 Table I (a) Preferred Lea
12、d Error Measurement Interval-Inches . 3 Table I (b) Preferred Lead Error Measurement Interval-SI (Metric) 3 Table I1 Thread Length vs . “T” Factor for Classes 1. 2.4. and 5 4 Table 111 Full Indicator Movement. Classes 1 through 7 6 Table IV Diameter and Lead Combinations-Dimensions in Inches . 7 Tab
13、le V Diameter and Lead Combinations-Dimensions in Millimeters 7 FIGURES 1 Acceptance Template Construction 5 2 Ball Screw Specification Sheet . 8 3 Drawing Format . 10 3A Drawing Format . 11 vii APPENDICES AppendixAl 13 Al.3 Axial Deflection Equations . 13 A1.4 Approximate Deflection 14 Al.5 Drag To
14、rque (Maximum) 14 ChartAI 15 AppendixA2 16 Use-Classes 3,6,7, and 8 . 16 Fig . A2 Maximum Linear Deviation-Classes 2 and 5 17 Fig . A3 Maximum Permissible Lead Error-Classes 1 and 4 17 Al.l General 13 A1.2 Symbols . 13 . AI . 6 Length vs . Pitch Diameter Relation 14 Fig . A1 Maximum Rate Error and A
15、cceptance Template viii ANSI 65.48-1977 AMERICAN NATIONAL STANDARD BALL SCREWS 1.0 SCOPE 1.1 This standard covers definitions, classes of ball screws, recommended combinations of screw diame- ters and leads, recommended drawing format, and per- formance characteristics of ball screw and nut assem- b
16、lies as applied to machine tools. 1.2 The values stated in U.S. customary units are to be regarded as the standard. Metric values are con- verted from the customary values per recommenda- tions of “ASME Guide SI-1, ASME Orientation and Guide for Use of SI (Metric) Units”. 2.0 DEFINITIONS 2.1 Actual
17、Linear Deviation. The lead error rate, used as a reference line, for a ball screw assembly is determined by connecting the beginning and end points of the measured lead error. Maximum linear Meosured lead error Specified lead Actual linear deviation -. 1. Maximum linear3- devlation . 2.2 Backdriving
18、. Ability of screw or nut to rotate when thrust load is applied to the other member of the assembly. 2.3 Backlash. Axial free motion between the nut and screw. 2.4 Ball Nut. The member, containing the outer helical ball track of a ball screw assembly. 2.5 Ball Screw. The shaft member containing the
19、inner helical ball track, of a ball screw assembly. 2.6 Ball Screw Assembly. A device consisting of ball nut, ball screw and balls. 2.7 Ball Track. Specially designed helical groove in a ball nut or ball screw which transmits the load reac- tion between the ball nut or ball screw and the balls. 2.8
20、Basic Load Rating. That constant axial load which a group of apparently identical ball screw assemblies can endure for a rated life of one million inches (25 400 m) of travel. 2.9 Basic Static Thrust Capacity. The static thrust load, which will produce a permanent ball track defor- mation of 0.0001
21、times the ball diameter. 2.10 Circuit. A continuous closed path of recirculat- ing balls. 2.11 Column Strength. Maximum compressive axial load that can be applied to a screw without resulting in permanent structural deformation. 2.12 Conformity Ratio. Ratio of the ball track radius to the ball diame
22、ter. 2.13 Contact Angle. Nominal angle between a plane perpendicular to the screw axis, and a line drawn be- tween the theoretical points of tangency between a ball and the ball tracks and projected on a plane pass- ing through the screw axis and the center of the ball. 2.14 Critical Speed. Rotation
23、al speed, of nut or screw, that produces resonant vibration of the ball screw assembly. 2.15 Drag Torque. The torque required to rotate the nut relative to the screw in the absence of an external load. 2.16 End Seals. Closure element(s) affixed to the nut and in slideable contact with the screw in a
24、 man- ner which will inhibit foreign objects from entering the ball nut assembly and/or provide retention of the lubricant. 2.17 Equivalent Load. Mean load that will result in same life as a combination of varying loads. 2.18 Lead. Axial distance screw or nut travels in one revolution. 2.19 Lead Err
25、or (Deviation). The measured lead minus the specified lead. 2.20 Load Ball. A ball which carries a portion of the load. AMERICAN NATIONAL STANDARD BALL SCREWS 2.21 Maximum Linear Deviation. A maximum lead error rate applied to the total thread length. Moximum lineor deviation x, /2 +I Specified lead
26、 -. -. .Measured leod error Actuol linear deviotian JI Maximum - lineor deviotion J li - 2.22 Maximum Permissible Lead Error. The total allowable variation, peak-to-peak, in lead error over the total thread length. Maximum permissible leod error I f E:-% 4- Specified P T Threod leod - length -I 2.23
27、 Maximum Rate Error. The maximum permis- sible positive or negative slope, of the measured lead error line as plotted on a lead error versus thread length graph. It is normally specified in inches (mm) of error per 12 inches (300 mm) of thread length. + , 6 Maximum rate error Threod - lead 0 length
28、?- -I Moximum rote error 2.24 Measured Lead Error. The actual manufactured lead error including measurement error. 2.25 Multiple Circuit Nut. A ball nut with two or more closed paths of recirculating balls. 2.26 Multiple Start Screw. A ball screw in which the lead is an integral multiple of the pitc
29、h. 2.27 Nominal Lead. The lead chosen as a basic refer- ence. 2.28 Ogival (or Gothic) Groove. A ball track cross- section shaped like a Gothic Arch. 2.29 Pitch. The distance from a point on a ball track to a corresponding point on the next track, parallel to the ball screw or ball nut axis. ANSI 05.
30、48-1977 2.30 Pitch (Ball Circle) Diameter. The nominal diam- eter of a theoretical cylinderpassing through the cen- ters of the balls when they are in contact with the ball screw and ball nut tracks. 2.31 Preload. The use of one group of ball grooves in opposition to another to increase stiffness an
31、d elimi- nate backlash in a ball nut assembly. 2.32 Rated Life. The length of travel that 90 percent of a group of ball screw assemblies will complete or exceed before the first evidence of fatigue develops. 2.33 Root Diameter. Diameter of the screw measured at the bottom of the ball track. 2.34 Scr
32、ew Diameter. The outside diameter of the ball screw shaft. 2.35 Single Circuit Nut. A ball nut with only one closed path of recirculating balls. 2.36 Single Start Screw. A ball screw having the lead equal to the pitch. 2.37 Spacer Ball. A ball, an idler, smaller than the load balls. 2.38 Specified L
33、ead. The prescribed theoretical lead from which tolerances are applied. The specified lead is generally expressed as the nominal lead, or the nominal lead plus or minus a specified cumulative variance per 12 inches (300 mm). 2.39 Spring Rate. A measure of stiffness equal to load per unit deflection.
34、 2.40 Stiffness. Resistance to deflection. 2.41 Stops. Interference elements, effective at the end of nut travel, which prevent rotational motion be- tween nut and screw. Stops are designed to prevent accidental disassembly, and/or prevent excessive travel. 2.42 Thread Length. Total axial distance o
35、f usable threads. 2.43 Travel. The axial distance traversed by screw or nut in one direction. 2.44 Turns. The number of revolutions that the nut ball track makes about the screw axis for one circuit. 2.45 Wobble Error. The total variation, peak-to-peak, in lead error for one revolution of the nut. (
36、LO) 3.0 CLASSES OF BALL SCREWS 3.1 Preferred Classes The preferred classes of machine tool screw as- semblies are given in Table I. 2 . AMERICAN NATIONAL STANDARD BALL SCREWS Table I Class and Deviation ANSI 85.48-1977 Class Maximum Permissible Lead Error 12 xT 2 0.0002 X - X T 5 x - Lmm 12 Li 1 300
37、 xT I I 3 4 0.0005 x - X T 13 x - 12 300 Li Lmm xT 5 /O.OOO x E Li x T xT 71 81 Maximum Rate Error Inch Acceptance 127ch Template 300 rnrn +0.0002 t5 1 +0.0002 +5 1 .* +0.006 t 150 Maximum Wobble Linear Error Peak Deviation To Peak Inch 1 prn 1 Inch pr- 0.0002 1 0.0004 1 10 I I 0.0004 I 10 0.0015 38
38、 (1) Maximum linear deviation is to be determined by agreement between manufacturer and user. (3) Lmm =length of screw in millimeters (2) Li =length of screw in inches (4) T =value obtained in Table I1 (5) pm =micrometer, 0.001 mm. For maximum permissible runout, classes 1 through 7, see Table 111.
39、The full indicator movement for class 8 ball screw assem- blies shall not exceed 0.020 (0.5 mm) for each 120 inches (3000 mm) or less of length. For examples see Appendix A2; Figure A1 for classes 3, 6, 7, and 8; Figure A2 for classes 2 and 5; Figure A3 for classes 1 and 4. Table I (a) Preferred Lea
40、d Error Measurement Interval-inches Lead-Inches 0.080 Measuring lnterval- 6 8 12 15 16 12 16 20 25 16 20 25 Integral No.of Leads 1.000 0.750 0.500 0.400 0.375 0.333 0.250 0.200 0.160 0.125 0.100 Inches 2.0 2.0 2.0 4.0 6.0 6.0 6.0 6.0 6.0 4.0 4.0 4.0 Table I (b) Preferred Lead Error Measurement Inter
41、val-SI (Metric) Lead-mrn Measuring Interval- 8 10 10 12 15 20 24 30 20 16 20 Integral No.of Leads 20 16 12 10 8 6 5 4 3 2.5 2 mrn 40 40 60 160 160 120 120 120 120 120 120 3 AMERICAN NATIONAL STANDARD BALL SCREWS 3.2 Measured Lead The measured lead shall be of a ball screw as- sembly, ie., the displa
42、cement of the ball nut relative to the ball screw. Maximum permissible lead error, maximum rate error and maximum linear deviation are normally measured in a plane passing through the screw axis and on one side of the screw over an integral number of revolutions. The preferred interval between mea-
43、surements to be taken for lead error are given in Table I(a) for conventional units and Table I(b) for SI units. Wobble error measurements are made over small angular rotations during one revolution. Their cyclical nathre prevents them from appearing during maxi- mum measurements of permissible lead
44、 error, maxi- mum rate error and maximum measurements of linear deviation lead error. Measurements for wobble error, if required, should be taken for at least two revolu- tions and for as many positions along the screw as determined by agreement between manufacturer and user. Wobble error is in addi
45、tion to lead error mea- surements for maximum permissible lead error, maxi- mum rate error, and maximum linear deviation. i When maximum linear deviation is specified in classes 2 and 5, the vertical distance between the actual linear deviation line and the measured lead error line, in a chart plott
46、ing lead error versus screw length, must be transferred at each measured point to the abscissa before maximum permissible lead error, maximum rate error, and acceptance templates may be applied. See Figure A2 of Appendix A2 for illustration. The measurement of runout for classes 1 through 7 shall be
47、 taken in the ball groove with the screw mounted on centers. Runout measurements for class 8 screws shall be taken on the outside diameter with the screw supported on a surface plate. When the ball nut is in close proximity to the screw bearing journals good concentricity of the screw threads and be
48、aring journals is essential to protect the ball screw assembly from excessive forces. Figure 3, Note 1, shows a method of specifying this concentricity. 3.3 Templates For screw classes 2, 3, 5, 6, 7, and 8, the tem- plates shown in Figure 1 may be used to verify ac- curacy requirements. The template
49、 is superimposed and moved along the measured lead error line. The ac- ceptance template may be moved vertically but may not be rotated. For every possible horizontal position ANSI 85.48-1977 of the template, there must be at least one vertical position where the template contains the entire mea- sured lead error line. See Appendix A2 for illustration. Table I I Thread Length vs. “T“ Factor for Classes 1,2,4 and 5 Thread Length r Inches 12 to 18 18+to 24 24+ to 36 36+ to 48 48+ to 60 60+ to 72 72+to 84 84+to 96 96+ to 120 over 120 Millimeters 300 to 450 450+ to 6
