ASME B89.4.21.1 pdf free download
ASME B89.4.21.1-2020 pdf free download.Environmental Effects on Coordinate Measuring Machine Measurements.
This Tech,iical Repoit discusses unportant iniluenu’s of the environnient on (limensional and geometric measurements performed using coordinate measuring machines (CMMs). including influences on both the machine and the workpeces to h measured. This Report discusses the thermal eflects related to the use ot tactile (:MMs, hut many of these effects are also applicable to optical and other noncontact coordinate measurement systems.
2 INTRODUCTION AND BACKGROUND
2.1 Operating Conditions
PUM 200 (ref. I I J) LiefineS rated operating conditions (4.9) and limiting operating conditions (4.10). Machine speci— fications, typically stated as maximum permissible errors (MPEs). are intended to be applical)le to a CMM that is used within its rated operating conditions These rated operating conditions are the conditions that must be fulfilled for the machine to perform as designed (i.e., meet the M Pls). These conditions include, but are not limited to. environmental conditions. Liminngoperating conditions are the extreme at which a machine can he operated without sustaimiingdamnage and withoLit degradation of specifications when subsequently operated within its rated operating conditions.
2.2 Definition of Environment
kir the purpose of this Technical Report. the (:MM environment includes those elements in the machine surroundings that ailed CMM system performance; effects of operators are not &Id(lressed in this Report. The environmental effects included are temperature and humidity. illumination, vibration, electrical efTects, and contamination. These effects are caused or transmitted by surrounding air, building structure, other equipment, supply air, and the electrical System.
For (lie purpose of this Technical Report, environments are classified as i.ihoratury or “shop,” A laboratom)’ dlvironnwnt is controlled in order to perform measurements at an acceptable accuracy level. A shop environment is controlled only to the level required to produce acceptable workpieces. A shop environment may nut be acceptable for performing measurement tasks.
2.3 EnvironmentaL Effects
The influence oenvironment.iI variables on the measurement results obtained using the CMM are classified as environmental effects. The variables are identified in para. 2.2, and their infhiencecan varygreatlyamong different facilities, or even within one facility. Whereas temperature and humidity may vary depending on the time of day or season of the year, influences such as illumination, electrical noise, and vibration may be lairly constant for a given CMM installation. (:omltanhin.ltion, either airborne or on the CMM and workpieces. may be either a steady-state or varying condition. The ability to manage contamination will depend on the nature of (lit’ installation and the perceived impact of the conLimilmnation on measurement resLilts.
Three main methods are employed to mitigate the influence of the environmental effects, as follows:
(ci) Auenipt to Remove the Source of the Influence. This may he done by shutting down or moving equipment causing vibration or removing heat sources from the immediate vicinity of the measuring equipment.
(h) Aueimuae the ff’cs of the Inlhiemee. Vibration isolators may he used between the fiictory or laboratory lion.’ and the CMM, or barnes may be installed to block radiation from a heat source that cannot be moved.
(c compensate for the Influence. By using knowledge about how a l)artictllar influence effects the measurement and Sensors to quantity theenvironniental state, the measurement results cami beadjusted to compensate for the environmnemit,
After mitigation, simply evaluate the influence; the uncertainty of measurement can be increased to accommodate the effect of environmnL’mltal influences where these methods are not employed.ASME B89.4.21.1 pdf download.
