1、BRITISH STANDARD BS 4656-28: 1988 Incorporating Amendment No. 1 Accuracy of machine tools and methods of test Part 28: Specification for numerically controlled turning machines up to and including 1500 mm turning diameter UDC 621.9.01-187:001.4:621.941:681.5BS4656-28:1988 This British Standard, havi
2、ng been prepared under the directionof the Machine, Engineers and Hand Tools Standards Committee, was published under the authority ofthe Board of BSI and comes intoeffect on 31 August 1988 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference MTE/1 Draft
3、for comment 87/74259 DC ISBN 0 580 16661 9 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Machine, Engineers and Hand Tools Standards Committee (MTE/-) to Technical Committee MTE/1, upon which the following bodies were represented: Adva
4、nced Manufacturing Technology Research Institute Cranfield Institute of Technology Department of Trade and Industry Health and Safety Executive Institution of Production Engineers Ministry of Defence University of Aston in Birmingham Amendments issued since publication Amd. No. Date of issue Comment
5、s 6665 March 1991 Indicated by a sideline in the marginBS4656-28:1988 BSI 07-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Application of test methods 1 4 Abbreviations 2 5 Diagrams 2 6 Machine size ranges 2 Figure 1 Test piece for test P4: be
6、tween centres machines 15 Figure 2 Test piece for test P4: chucking machines 16 Figure 3 Test piece for tests G18 and P5 17 Table 1 Geometrical tests for numerically controlled turning machines 3 Table 2 Practical tests for numerically controlled turning machines 12 Publications referred to Inside b
7、ack coverBS4656-28:1988 ii BSI 07-1999 Foreword This Part of BS 4656 has been prepared under the direction of the Machine, Engineers and Hand Tools Standards Committee and is based on a draft submitted by the former Machine Tool Industry Research Association now known as the Advanced Manufacturing T
8、echnology Research Institute. This standard is being used in support of discussions by the International Organization for Standardization (ISO). NOTENumerically controlled turning machines are manufactured in a variety of configurations and sizes for both bar and chucking work. This standard include
9、s suitable tests for differing spindle nose and turret configurations. This Part is a revision of BS4656-28:1981 which is withdrawn. For this type of machine, 3.5 now gives independent status to both geometrical and practical tests and therefore the latter no longer override the former. Other change
10、s are as follows. Tests. Instrumentation test. An instrumentation test G18 to assess contouring accuracy under no load conditions, together with test P5, is included as an optional addition to tests P1 to P4. Figure 3 shows test piece dimensions for test P5. The test involves checking the circular m
11、ovement produced by two linear axes that are nominally perpendicular to each other, by the use of circle comparison standards. The circle comparison standards can take different forms, namely a ball bar fixed at points corresponding to the tool and workpiece positions or a master disc fixed at the w
12、orkpiece position and a linear displacement probe attached at the tool position. With some form of data acquisition system interfaced to the circle comparison standard, it is possible to obtain graphs which show the radial deviations of the machines circular interpolation. This test can be used for
13、checking the stated tolerances in relation to the accuracy of the machine, and as an aid to machine diagnostics in defining the causes of the deviation in terms of geometric error, servo drive error or control system error. Unlike a cutting test this instrumentation test is analysed on a statistical
14、 basis using a number of runs from differing directions of travel. The operating conditions can be changed after each test to establish the optimum contouring accuracy of the machine. All this is achieved in situ with the time required to assess each change kept to a minimum and with the knowledge t
15、hat the results are not influenced by cutting problems. Test piece for practical test P5. The main criteria in selecting the shape of the special test piece for test P5 are as follows: a) maximum verification of contouring accuracy; b) simplicity of shape generation (programming); c) ease of measure
16、ment. G8. Measuring instruments. G12. Statement in column 4 amplified. G17. Alternative method introduced as G 17(b). G18. Repeatability test. Deleted now that BS 4656-16 is published even though Part 16 does not specify tolerances. G19. Test renumbered as G 18. P1 and P3. Permissible deviations tig
17、htened. Figure 3. Editorial comment.BS4656-28:1988 BSI 07-1999 iii The test pieces (for tests P1 to P4) as shown in Figure 1 and Figure 2 only meet the first requirement, i.e. maximum verification of contouring accuracy. The over-centre test piece (in test P5) readily meets all three requirements. B
18、y using a105 arc segment a range of information can easily be derived using standard metrology equipment. The shape of the test piece is easy to generate on most types of machine and, as previously stated, relatively straight-forward to measure. Additionally, by imposing intermediate programmable bl
19、ocks, e.g. every15 , the dynamic transition of block to block information can be observed. A positive witness at points of transition would indicate the form characteristics of a multi-block contour. A British Standard does not purport to include all the necessary provisions of a contract. Users of
20、British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 18, an inside back cover and a back co
21、ver. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS4656-28:1988 BSI 07-1999 1 1 Scope This Part of BS 4656 specifies, with reference to BS3800, both geometrical and pract
22、ical tests for numerically controlled turning machines up to and including1500mm turning diameter over the bed, and gives corresponding permissible deviations which apply. This standard is applicable to machines of general purpose use and normal accuracy. It deals only with the verification of accur
23、acy of the machine. It does not apply to the testing of the running of the machine (vibrations, abnormal noises, stick-slip motion of components, etc.) nor to its characteristics (speeds, feeds, etc.) which should be generally checked before testing accuracy. This standard does not apply to sequence
24、 controlled lathes, such as those with plug-boards or decade switches. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 4656 the following definitions apply. 2.1 numerically controlled machine tool
25、a machine tool that operates in accordance with the instructions and numerical data introduced, usually as its operations proceed, from a machine readable data medium or from a computer, without direct human control other than in the initiation of command signals 2.2 primary plane the plane in which
26、 errors in tool positioning have the major effect on workpiece diameter sizing, parallelism and repeatability. In general, this will be the plane containing the tool cutting path 2.3 secondary plane the plane perpendicular to the primary plane, i.e. of secondary importance in workpiece diameter sizi
27、ng, etc. 3 Application of test methods 3.1 In applying the tests detailed in Table 1 and Table 2, reference should be made to BS3800, especially concerning the installation of the machine before testing, warming up of spindles and other moving parts, the description of measuring methods and the reco
28、mmended accuracy of testing equipment. 3.2 The tests may be applied in any order that is practicable and that makes for ease of mounting of instruments or gauging. The sequence in which the geometrical tests are listed in Table 1 is related to the sub-assemblies of the machine and it is not intended
29、 to impose the practical order in which the tests are to be done. 3.3 It is not always necessary for all the tests specified in this standard to be carried out. The purchaser shall be at liberty to select, in agreement with the manufacturer, those tests relating to the properties that are of interes
30、t to him. The appropriate tests are to be clearly stated when the machine is ordered. 3.4 When establishing the tolerance for a measuring range different from that given in this standard (see2.311 of BS3800:1964), it should be taken into consideration that the minimum value of tolerance is0.01mm for
31、 geometrical and practical tests. 3.5 Practical tests should be made with finishing cuts (e.g. depth0.1mm, feed0.1mm per revolution) and not with roughing cuts, which are liable to generate appreciable cutting forces. The manufacturer shall select the actual feeds and speeds for the practical tests
32、to suit the particular machine. The results obtained from practical tests shall be independent of those obtained from geometrical tests where these check the same feature.BS4656-28:1988 2 BSI 07-1999 4 Abbreviations For the purposes of this Part of BS4656, various methods of expressing permissible d
33、eviations are employed, each having a particular type of application. The methods employed are as follows. 5 Diagrams For reasons of simplicity the diagrams in this standard illustrate only one type of machine. 6 Machine size ranges For the purposes of this Part of BS4656, machines are divided in tw
34、o size ranges. In general, permissible deviations are applied according to the machines size. Machine size ranges are based on the maximum diameter that can be machined over the bed thus: Range 1. Maximum turning diameter less than or equal to500mm. Range 2. Maximum turning diameter greater than500m
35、m but less than or equal to1500mm. Where appropriate, allowances are also made for the distance between centres (DC). / This type of expression applies to deviations of perpendicularity that are ratios. for any length of This type of expression applies to deviations of straightness and parallelism,
36、and is used in fact for local permissible deviations, the measurement length being obligatory. per This type of expression applies to deviations of straightness and parallelism and is used to recommend a measurement length, but in this case the proportionality rule comes into operation if the measur
37、ement length differs from that indicated.BS 4656-28:1988 BSI 07-1999 3 Table 1 Geometrical tests for numerically controlled turning machines All dimensions are in millimetres. 1 2 3 4 5 6 No. Diagram Object Permissible deviation Measuring instruments Observations and references to the test code BS 3
38、800:1964 Range 1 Range 2 G1 Checking of straightness of the bed slideways This is only for bed type machines with longitudinal slideways 500 (seecolumn 6) a) longitudinally b) transversely a) DC a 500 and DC u 1000 0.020 DC 1000 0.02 plus 0.01 for each additional 1000 b) 0.04/1000 a) DC 500 and DC u
39、 1000 0.030 DC 1000 0.03 plus 0.02 for each additional 1000 b) 0.04/1000 Precision levels, optical or other methods 3.11, 5.212.21, 5.212.22 This test is replaced by G11 for machines with longitudinal movements less than 500 Measurements shall be made at positions equally distributed throughout the
40、length of the slideway. The level may be placed on the saddle Local differences in a) shall not exceed the specified deviation over any longitudinal length less than300 5.412.7 In b) readings on levels shall not exceed the permissible deviations at any position along the length of the slideways G2 C
41、hecking of parallelism of the outside of the tailstock sleeve to the movement of the principal toolholding slide: a) in the primary plane b) in the secondary plane a) 0.015 per 300 b) 0.02 per 300 a) 0.03 per 500 b) 0.04 per 500 Dial gauge 5.422.3 After the tailstock has been sufficiently extended,
42、it shall be locked as under normal working conditions, when taking measurements a DC means distance between centres.BS 4656-28:1988 4 BSI 07-1999 Table 1 Geometrical tests for numerically controlled turning machines All dimensions are in millimetres. 1 2 3 4 5 6 No. Diagram Object Permissible deviat
43、ion Measuring instruments Observations and references to the test code BS 3800:1964 Range 1 Range 2 G3 Measurement of run-out of the revolving tailstock centre 0.015 FIM (Full indicator movement) 0.02 FIM Dial gauge 5.612.2, 5.621.2 The value of the force F shall be the minimum value to eliminate en
44、d play and shall be specified by the manufacturer Dial gauge is to be mounted with the stylus at right angles to the surface being checked. Centre to be rotated whilst taking measurements G4 Checking of parallelism of axis of centres with the movement of principal toolholding slide: a) in the primar
45、y plane b) in the secondary plane a) DC au 500 0.015 DC 500 and DC u 1000 0.02 a) DC u 500 0.02 DC 500 and DC u 1000 0.025 a) Dial gauge and mandrel between centres or straightedge for DC 500 or taut wire and microscope or optical methods for all values ofDC b) Dial gauge and test mandrel or optical
46、 methods a) 5.232.3, 5.232.1 or 5.212.3, 5.232.3 Length of mandrel to equal maximum distance between centres b) 5.422.3 Readings are to be taken at extremities of the test mandrel with tailstock sleeve locked as under normal working conditions when taking measurements For each 1000 increase in dista
47、nce between centres, add 0.005 up to a maximum permissible tolerance of 0.03 b) 0.04 0.05 b) 0.06 a DC means distance between centres.BS 4656-28:1988 BSI 07-1999 5 Table 1 Geometrical tests for numerically controlled turning machines All dimensions are in millimetres. 1 2 3 4 5 6 No. Diagram Object
48、Permissible deviation Measuring instruments Observations and references to the test code BS3800:1964 Range 1 Range 2 G5 a) Measurement of periodic axial slip of the work spindle b) Measurement of camming of the chuck locating face of the spindle nose a) 0.01 b) 0.02 a) 0.015 b) 0.025 Dial gauge and
49、possibly a special device 5.62 and 5.63 The value of the force F shall be the minimum value to eliminate end play and shall be specified by the manufacturer The spindle shall be rotated whilst taking measurements, Dial gauge mounted on a fixed part of the machine including periodic axial slip G6 Measurement of run-out of the chuck locating diameter of the spindle nose 0.01 FIM 0.015 FIM Dial gauge and possibly a special device 5.61 The value of the force F shall be the minimum value to eliminate end play and shall be speci
