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Calibration Services for Coordinate Measuring Machines


This page contains links to articles related to coordinate measuring machines and inspection.  All articles are provided in PDF format and can be opened using any PDF viewer.

Horizontal Arm Deflection

Horizontal Arm DeflectionThis article describes some of the effects of tower deflection on horizontal arm CMM's. All manufacturers of horizontal arm CMM's have provisions for dealing with tower deflection as this is a common problem for this type of machine.


Compliance Statements

Compliance StatementsOften the biggest question when performing any kind of measurement that has a tolerance is simply “is it in spec?”. In some cases it is very clear that the measurement is either inside or outside of tolerance and in other cases, particularly when the measurand is close to the tolerance limit, it is not so clear and cannot be stated with any kind of confidence. Measurements that are close to the tolerance limit can randomly fall on either side of it due to measurement repeatability. Measurement uncertainty widens up the grey area around the measurement tolerance beyond what can easily be seen from measurement repeatability.

This article is about compliance statements and the accepted practice for expressing compliance to a specification. When expressing an opinion of compliance from the performance tests on a coordinate measuring machines following ASME B89.4.10360 or ISO/IEC 10360, it is necessary to do this with a suitable level of confidence particularly if traceability is a requirement.


Applying Compensation Map Data

Applying Compensation Map DataThis article is written as an example of how to interpret compensation data from a coordinate measuring machine and create a correction value and tool coordinate system for any position in the measuring volume. This information can be used to build a working model for error map correction and can be useful for developing other utilities to allow interpretation or correction based on measurement data.


Compensation Error Map Rotation Point

Errormap Rotation PointThis article describes the significance of the position selected for the compensation error map rotation point for a coordinate measuring machine. In a perfect world the application of the compensation data will behave exactly the same as the mechanical error but there is usually a bit of difference as the compensation methods are often generic. For physical angular errors the measurable straightness error is always zero at the point where the mechanical rotation occurs. The rotation point of the compensation map is a description where rotational corrections are calculated from, and ideally the same, as the mechanical rotation point.


Calibration Sphere Form Error

Calibration Sphere Form ErrorThis article describes the effect of form error on a sphere when used as a calibration artifact on a CMM. The purpose of the calibration sphere is to determine the effective stylus tip diameter and relative probe offset between multiple probe positions. Multiple probe positions can be from a fixed head with more than one stylus or a single stylus on an articulating probe head.

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Comparison Between ISO/IEC 10360-2:2009 and ASME B89.4.1:1997 Performance Standards

ISO 10360 vs ASME B89.4.1This document describes the testing method and results from a comparison of the two major performance testing standards for coordinate measuring machines; ISO/IEC 10360-2:2009 and ASME B89.4.1:1997. The ASME B89.4.10360-2:2008 is identical to ISO/IEC 10360-2:2009 therefore the results apply to both standards.

The Renishaw Machine Checking Gauge is included in the comparison tests as a point of reference. This gauge is ideal for CMM interim checking due to its speed and ease of use so therefore a comparative test using this gauge to established standards seemed appropriate.


CMM Measurement Uncertainty Budget

CMM Measurement UncertaintyThis article describes a generic uncertainty budget when using a CMM for inspection. The estimation of measurement uncertainty is a requirement for ISO/IEC 17025.

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Temperature Compensation

Temperature CompensationThis article describes the reasons for having the environment of a coordinate measuring machine at the standard reference temperature of 20 ?C and the effects of using a CMM at a non-standard temperature. This article also looks at common methods used to compensate for temperature and the types of materials used in the construction of CMM's that have an impact on how the machine will perform when temperature changes.

Temperature variation in a lab environment, when using a coordinate measuring machine, can be a large source of measurement error. Partial solutions to temperature related problems exist but do not address all problems and may even introduce collateral problems in the process.


Compensation Map Increments

Map IncrementsThis article is written as a guide for the choice of compensation map increments used on coordinate measuring machines. Selecting a suitable increment is important since a step size that is too large or too small will result in a loss of machine accuracy. Often the actual compensation map increment is selected based on secondary reasons (i.e. matches the increment of a step gauge or is simply a round number). In some cases map increments are selected with the belief that using a very small increment will improve the performance of the CMM. Most calibrators only have one opportunity to fully map a machine so comparative tests where the map increment is adjusted are never performed.


CMM Interim Testing

Interim TestingInterim tests are performance checks of a CMM that are done regularly between calibrations. Interim checks are important as they can proactively indicate that a problem exists with a machine and can also provide confidence in the equipment.

This article is written to describe different methods for CMM interim checks.


CMM Kinematic Axis Order

Kinematic OrderTo describe the significance of the kinematic axis order of a CMM machine. The kinematic order defines how the machine axis are interconnected and is used as part of the machine compensation data to correct for known errors. An incorrect kinematic order means the software is not capable of compensating for the known machine errors properly and may actually increase the measurement error of a CMM.