1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 26303:2012Machine tools Short-term capability evaluation of machining processes on metal-cutting machine toolsBS ISO 26303:2012 BRITISH STANDARDNational forewordThis Briti
2、sh Standard is the UK implementation of ISO 26303:2012.The UK participation in its preparation was entrusted to TechnicalCommittee MTE/1/2, Machine tools - Accuracy.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to i
3、nclude all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 77073 9ICS 25.080.01Compliance with a British Standard cannot confer immunity fromlegal obligations.This Br
4、itish Standard was published under the authority of theStandards Policy and Strategy Committee on 30 June 2012.Amendments issued since publicationDate Text affectedBS ISO 26303:2012Reference numberISO 26303:2012(E)ISO 2012INTERNATIONAL STANDARD ISO26303First edition2012-06-01Machine tools Short-term
5、 capability evaluation of machining processes on metal-cutting machine tools Machines-outils valuation de la capacit des procds dusinage des machines travaillant par enlvement de mtal BS ISO 26303:2012ISO 26303:2012(E) COPYRIGHT PROTECTED DOCUMENT ISO 2012 All rights reserved. Unless otherwise speci
6、fied, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ca
7、se postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2012 All rights reservedBS ISO 26303:2012ISO 26303:2012(E) ISO 2012 All rights reserved iiiContents Page Foreword iv Introduction . v 1 Scope 1 2 Norma
8、tive references 1 3 Terms and definitions . 2 4 Symbols 3 4.1 Upper case letters . 3 4.2 Lower case letters . 4 4.3 Greek letters . 5 5 Preliminary remarks 5 6 Procedure for short-term capability evaluation . 6 6.1 General . 6 6.2 Agreements 7 6.3 Warm-up procedure 9 6.4 Adjustment . 9 6.5 Productio
9、n 10 6.6 Measurement . 10 6.7 Computation and analysis 11 7 Factors influencing short-term capability evaluation 16 7.1 General . 16 7.2 Thermal influences 16 7.3 Influences due to measuring uncertainty . 18 7.4 Influences arising from statistical analysis 18 Annex A (informative) Additional informa
10、tion related to statistical evaluations . 19 Annex B (normative) Agreement form 26 Annex C (normative) Evaluation Forms . 30 Annex D (informative) Examples of capability agreements and analysis . 34 Bibliography 42 BS ISO 26303:2012 ISO 26303:2012(E) iv ISO 2012 All rights reservedForeword ISO (the
11、International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee
12、 has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnic
13、al standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bo
14、dies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying an
15、y or all such patent rights. ISO 26303 was prepared by Technical Committee ISO/TC 39, Machine tools, Subcommittee SC 2, Test conditions for metal cutting machine tools. BS ISO 26303:2012ISO 26303:2012(E) ISO 2012 All rights reserved vIntroduction The evaluation of the short-term capability of the ma
16、chining process is a different approach in machine tool assessment compared with machine tool performance testing methods, which are covered by a number of International Standards, e.g. ISO 230 (all parts) and other machine tool type specific standards. The main differences are machining a sample ba
17、tch of test pieces and definition of the relevant influencing factors as well as the statistical conditioning and analysis of the workpiece quality related data obtained during such tests. This International Standard is the result of a project guided closely by an international working group, and su
18、mmarized in order to make the information available to as many interested parties as possible. Especially for large batch production, short-term process capability estimates, as well as capacity measures, are very often applied in addition to testing of machine tool performances. In fact, machine to
19、ol users increasingly employ statistical process control (SPC) techniques in their activities and frequently ask the machine suppliers/manufacturers to become system suppliers as well, giving them responsibilities for the machining process too. Statistical methods in process management are covered b
20、y ISO 22514 (all parts). For the purposes of machine tool acceptance based on the test of its capability in machining a specified workpiece, both requirements and methods stated by individual users differ widely, due to the absence of a recognised International Standard. Long-winded discussions and
21、adaptation processes during the acceptance tests are, therefore, often necessary, delaying delivery to the customer and causing great time- and cost-related expenditure. This International Standard provides a unified procedure for the acceptance test of a machine tool based on its short-term process
22、 capability. It introduces the short-term capability of a given process, which employs the machine under test, the machining process, tooling and clamping applied, as well as the workpiece properties, and the estimate of relevant machine capability indexes. This International Standard adapts to and
23、complies with the specifications established in ISO 22514 (all parts). However, the term “process performance” specified in ISO 22514-3 corresponds to the term “short-term capability” in this International Standard. The term “short-term capability” has been widely used in the machine tool industry f
24、or many years; therefore, ISO/TC 39/SC 2 decided to maintain this term. Combined with the statistical evaluation, many influencing factors significantly restrict the fraction of tolerance interval covered by machine tool variations. As a consequence, the machine capability indices are specified in c
25、onjunction with the test conditions and the required tolerance limits. BS ISO 26303:2012 ISO 26303:2012(E) BS ISO 26303:2012INTERNATIONAL STANDARD ISO 26303:2012(E) ISO 2012 All rights reserved 1Machine tools Short-term capability evaluation of machining processes on metal-cutting machine tools 1 Sc
26、ope This International Standard defines procedures for acceptance of metal-cutting machine tools based on the tests of their capability in machining a specified workpiece (i.e. indirect testing). It gives recommendations for test conditions, applicable measurement systems and the requirements for ma
27、chine tools. This International Standard is consistent with ISO 22514 (all parts) describing statistical methods for process management and deals with the specific application of those methods to machine tools and machining of a sample batch of test pieces. This International Standard covers neither
28、 functional tests, which are generally carried out before testing the accuracy performance, nor the testing of the safety conditions of the machine. Annex A gives additional information related to statistical evaluation, (normative) Annexes B and C provide agreement and evaluations forms for short-t
29、erm capability tests, while Annex D gives an example. NOTE 1 Direct testing aims to investigate individual machine properties, such as geometric or positioning accuracy. Short-term capability evaluation is meant to prove that a machine has the capability to fulfil a specific process task. It is, the
30、refore, important to recognise that the short-term capability test is focused only on the manufactured product. This means that direct testing methods are more suited for the determination of error sources on the machine tool and for deriving constructive improvements of a machine tool that is used
31、in a wide production spectrum; a short-term capability test is less suited for detection of error sources of the machine tool. Therefore, it is expected that short-term capability evaluation for the acceptance of metal-cutting machine tools in machining processes be primarily carried out on workpiec
32、e-dependent special-purpose machines, e.g. working stations of transfer lines, with a process-determined cycle time of less than 10 min, so that at least 50 workpieces are manufactured in one shift as the statistical uncertainty increases strongly for a smaller number. In principle, short-term capab
33、ility evaluation can also be performed on universal machines, such as machining centres used for large batch production if they meet the above-mentioned statistical requirements. NOTE 2 The term “short-term capability”, which is a widely used term in machine tool industry, corresponds to the term “p
34、rocess performance” specified in ISO 22514-3. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any a
35、mendments) applies. ISO 4288, Geometrical Product Specifications (GPS) Surface texture: Profile method Rules and procedures for the assessment of surface texture ISO 22514-3:2008, Statistical methods in process management Capability and performance Part 3: Machine performance studies for measured da
36、ta on discrete parts ISO/TR 22514-4:2007, Statistical methods in process management Capability and performance Part 4: Process capability estimates and performance measures BS ISO 26303:2012ISO 26303:2012(E) 2 ISO 2012 All rights reserved3 Terms and definitions For the purposes of this document, the
37、 following terms and definitions apply. 3.1 short-term capability ability of a manufacturing unit to produce a given part within specified tolerances at a specified confidence level, a concept mainly applied to batch production NOTE 1 A manufacturing unit may be a single machine tool, one spindle of
38、 a multi-spindle machine tool, one station of a transfer line, etc. NOTE 2 Process capability is defined in ISO/TR 22514-4:2007, 2.2.1, as: statistical estimate of the outcome of a characteristic from a process which has been demonstrated to be in a state of statistical control and which describes t
39、hat processs ability to realize a characteristic that will fulfil the requirements for that characteristic. NOTE 3 In this International Standard, short-term capability indices, Csand Csk, are estimated under the assumption of normal distribution of the characteristic value considered. If this assum
40、ption is not fulfilled, short-term range values, RV,sand RV,sk, are evaluated instead of capability indices. NOTE 4 This International Standard adapts to and complies with the specifications established in ISO 22514 (all parts). However, the term “process performance” specified in ISO 22514-3 corres
41、ponds to the term “short-term capability” in this International Standard. The term “short-term capability” is widely used in the machine tool industry; therefore, ISO/TC 39/SC 2 decided to maintain this term. 3.2 short-term capability index Csratio of the specified tolerance itself to the standard d
42、eviation of the measured values quantifying the scatter NOTE Measured values are also known as characteristic values. 3.3 critical short-term capability index Csk ratio of the specified tolerance itself to the standard deviation of the measured values quantifying the scatter under consideration of t
43、he location of the mean value NOTE 1 If the mean value of the measured values is in the centre of the tolerance zone, this is called a centred distribution; if the mean value is not in the centre of the tolerance zone, this is called a shifted distribution. For the relationship between centred and s
44、hifted distributions, see A.1. NOTE 2 Measured values are also known as characteristic values. 3.4 short-term range value RV,s ratio of the range of the measured values to the specified tolerance itself 3.5 critical short-term range value RV,sk ratio of the range of the measured values to the specif
45、ied tolerance itself under consideration of the location of the mean value BS ISO 26303:2012ISO 26303:2012(E) ISO 2012 All rights reserved 33.6 control chart chart, with upper and lower control limits, on which values of some statistical measure for a series of samples, spiked samples and blanks, ar
46、e plotted, usually in date or sample number order ISO 5667-14:1998, 3.10 3.7 control chart control chart for individuals variables control chart for evaluating the process level in terms of the individual observations in the sample ISO 3534-2:2006, 2.3.15 3.8 control limit line on a control chart us
47、ed for judging the stability of a process ISO 3534-2:2006, 2.4.2 3.9 lower specification limit specification limit that defines the lowest value a quality characteristic may have and still be considered conforming ISO 22514-1:2009, 2.1.13 3.10 upper specification limit specification limit that defin
48、es the highest value a quality characteristic may have and still be considered conforming ISO 22514-1:2009, 2.1.12 4 Symbols 4.1 Upper case letters C Capability index Ck Critical capability index Cs Short-term capability index (corresponds to machine performance index Pmin ISO 22514-3:2008);Cs,nomno
49、minal short-term capability index Csk Csk,nom Critical short-term capability index Nominal critical short-term capability index Cact Actual capability index Ki ithclass (histogram) U Uncertainty (of measurement or capability index) CL, isU Upper control limit for the standard deviation is CL,xjU Upper control limit for the average values jx USL Upper specification limit BS ISO 26303:2012ISO 26303:2012(E) 4 ISO 2012 All rights reservedR Range RV,sRV,s,nomShort-term range value Nominal short-term range value RV,
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