ASME B89.4.22:2004 pdf download

ASME B89.4.22:2004 pdf download Methods for Performance Evaluation of Articulated Arm Coordinate Measuring Machines
evaluation testing.The environment shall be consideredacceptable if the requirements of this paragraph andpara.4 are met. The user shall be responsible for con-ducting all of the environmental tests at their facility.The supplier shall have the right to witness this testing.The supplier shall, upon request, supply test equipment as specified in para. 6, as well as support for equipmentand tests, at a cost negotiated between the supplier and the user.The user is cautioned that failure to conformto the supplier’s recommendations on cleanliness andcleaning procedures can lead to significant performance degradation. For example, particulates, oils, and watercan significantly degrade the machine’s performance,increase friction, and accelerate wear.
3.2 Temperature and Humidity
3.2.1 General.Taking measurements when not at thestandard temperature of 20-C can have a significant andoften misunderstood influence on the quality of thosemeasurements.The provisions outlined in iSO/TR16015 form a part of this Standard, but interpretation isprovided for the application to the class of machine cov-ered by this Standard. It is recognized that some ma-chines, because of their portability,will be used inwidely varying thermal environments. The portable na-ture of these devices ensures that they will be used formeasurements in most of the wide spectrum of manu-facturing environments found today. ISO/TR 16015 de-fines two alternative conditions under which a test en-vironment is thermally acceptable.The first is that allmeasurements are taken at the standard temperature,which for all practical purposes can never be done.The
second condition is that the thermal error index (TEI; see
para.6.5,ASME B89.6.2) is a reasonable percentage ofthe working tolerance.This leads to the potential problem that errors, caused by differential thermal expan-sion, hysteresis,etc.. can be induced in machines when they are used at temperatures different from the tem-perature at which they were aligned and calibrated.Similarly, the measurement of a workpiece at a tem-perature different from its design temperature cancause the workpiece to change size or distort. How-ever, it is not within the current scope of this Standardto develop simple tests or procedures for quantifyingthese individual effects.In those cases where the ma-chine is to be operated at temperatures outside thesupplier’s specified temperature range, the user shouldrefer to the calculation of TE in Appendix H, for a bet-ter understanding of the potential effects this will haveon the machine’s performance.Acceptability of an en-vironment that does not comply with the supplier’sthermal parameters is therefore specified in terms ofits effect on the machine.
In general, nominal variations in humidity do nothave an adverse effect on the performance of the ma-chine, but over a period of time may be detrimental.
3.2.2 Thermal Environment Parameters.The suppliershall provide, as part of the machine specification, astatement of the acceptable thermal environment pa-rameters. It should be noted that the thermal environ-ment is not limited to the environment within the workrone, but includes the environment that is in contactwith the machine, i.e.,the impact of the external ther-mal influences on the machine itself.The thermal pa-rameters shall contain a specification on the range oftemperatures within which the specified performancewill be attained, as well as the maximum permissiblevertical and horizontal temporal and spatial gradients.while not part of the thermal testing, the safe operatingtemperature range and the thermal settling time shallalso be stated.
3.2.2.1 Thermal Radiant Energy. Care should betaken to minimize the machine exposure to direct sun-light or other powerful radiant energy sources.Otherdirect radiant energy sources (such as lighting) shall notbe, whenever possible, closer to any part of the machinethan twice the nominal arm length. wWhere this distancerequirement is impractical, indirect lighting designedfor diffuse reflection and increased path shall be used.
3.3 Vibration
3.3.1 General.The support surface (floor, founda-tion, tooling stand, etc.) upon which the machine ismounted can have motion induced as a result of exter-nal forces in the surrounding area (due to other ma-chines, transportation vehicles,compressors,motors,etc.).This motion can range from a continuous vibra-tion to interrupted shock or a combination of both. Suchmotion, if transmitted to the machine, has a degradingeffect on the overall performance and repeatability ofthe machine, causing relative motions between theprobe tip, the machine axes measuring system,and theworkpiece, resulting in increased measurement uncer-tainty. In addition, certain excessive amplitudes of mo-tion can cause damage to the machine.
3.3.2 Responsibilities.The user shall be responsiblefor site selection. environmental shock and vibrationanalysis,and for any additional special isolators deemednecessary to ensure compliance with the maximum per-missible vibration levels specified by the supplier.Allquestions of compliance shall be determined at the in-terface between the support system provided by theuser and the machine system provided by the supplier.3.3.3 Environmental Vibration Parameters.The sup-plier shall provide, as part of the machine specification,astatement of the acceptable seismic vibration spectraat the user- supplier interface.This interface may be verydifferent, depending upon details of the contractual
arrangement between supplier and user. This statementshall contain a complete description of the allowable to-