Quality control is a compulsory attribute of any production process. Embedded in the process, mature, smart and rapid?
Qsigma will be your partner in case of precise inspection of geometric shapes and dimensions. Optical inspection concepts comprising of lasers, dedicated illumination setups, cameras and other suitable sensors are potential tools for optimizing your measurement demands.
Diode laserThe active substance of a diode laser is a suitable doped semiconducting diode. The laser emission is generated by stimulated recombination of electrons and gaps in the semiconductor. For a stimulated emission a feedback by an optical resonator is required. In most cases (semi-)reflecting end faces of the semiconductor crystal serve as a resonator. To get laser radiation sufficient gaps and free electrons are required inside the active substance. This is achieved by applying a suitable voltage to the crystal.
Parallelism: An axis of the part must be located in a cylinder with preset (tolerated) radius, which is aligned parallel to the particular reference axis.
Perpendicularity: An axis of a part (e.g. the central axis of a cylindrical part) must be located in a cylinder with preset (tolerated) radius, which is perpendicular to the reference plane.
EvaluationIn a measurement process, beside the data capturing itself, the method of evaluation is important to gain a characterization of the device under inspection. By averaging, filtering of data as well as by data reduction results can be affected.
GBDAbbreviation for gap bulk density. It denotes the pressed density of substrate mat isolating the ceramic substrate from the metal shell of an automotive catalytic converter.
Least squares methodEvaluation method, fitting a contour to a measure point cloud. The type of the contour can be selected. For each measurement point the distance to fitting contour is computed. The fitting process will be continued until the sum of the distance squares will find its minimum.
Measurement fileA measurement file contains except the pure measured data preset values, nominal values and tolerance range with respect of the type of the part under investigation. In addition it contains a testing plan, operational parameters and parameters for displaying the measurement data.
Measurement system analysis
Inspection of the measurement reading variance.
Type 1 Study:
One part with known values is measured in 50 or 25 trials. The capability indices Cg and Cgk are determined. This study proofs the accuracy, repeatability and the short term stability of a measurement system.
Type 2 Study (Gauge R&R Study):
10 parts are measured by 3 persons with 3 trials each. Again Cg and Cgk are determined. It proofs the repeatability and the reproducibility of a measurement system.
Measurement system capability
Technical term in the field of quality management describing the capability of a measuring device. A measurement system analysis assumes a Gaussian distribution of measured data (a known part is measured several times)
The gauge capability Cg is defined as the ratio of the tolerance width to the measurement scatter range. The measurement scatter range is the standard deviation of all measurement values multiplied by six (i.e. 6x Sigma). The gauge capability gives a value for the general suitability of the particular measurement system.
The gauge capability index Cgk proofs additionally the position of the mean value of measurement data distribution.
Cgo is the difference of the upper tolerance limit and the mean value of the measurement data divided by half of the measurement scatter range (i.e. 3x Sigma).
Cgu is the difference of the mean value of the measurement data distribution divided by half of the measurement scatter range i.e. 3x Sigma).
The lower of both values is taken as the gauge capability index Cgk.
Minimum circumscribed circleA circle with minimum radius that circumscribes the cloud of measurement data.
Technical term of the quality management proofing the capability of a production process. The relation of the distribution of a measureable feature of the device under investigation to given tolerances is inspected. A Gaussian distribution of the measurement scattering is assumed. The process capability potential Cp values the quality capability of a production process. It is the ratio of the range of tolerance to the process scattering width. The process scattering width is determined by the standard deviation of the measurement data multiplied by 6 (i.e. 6x Sigma).
The process capability index Cpk proofs additionally the position of the mean value of measurement data distribution.
Cpo is the difference of the upper tolerance limit and the mean value of the measurement data divided by half of the measurement scatter range (i.e. 3x Sigma)
Cpu is the difference of the mean value of the measurement data distribution divided by half of the measurement scatter range i.e. 3x Sigma).
The lower of both values is taken as the gauge capability index Cpk.
qs-STATSoftware package from QDAS (www.qdas.de) commonly used by car producers and their suppliers for statistical evaluation (e.g. process capability, measurement system analysis) measurement data. InnoMeas systems can equipped with a data export software tool for qs-STAT.
By construction ideal geometrical dimensions and shape of a specimen are postulated. Putting to a production process, the real produced specimen may differ from the ideal dimensions and shape. To achieve reasonable output volume and reproducibility at acceptable costs tolerances in dimensions and shape are set. Examples for shape tolerance:
Straightness: the central axis of a cylindrical specimen must be inside a given (i.e. tolerated) cylinder.
Flatness: the plane of a specimen under inspection must be between a pair of parallel planes with given (i.e. tolerated) distance.
Roundness: all sectional planes of a cylindrical specimen, perpendicular to the central axis, must be within two concentric circles with a given (i.e. tolerated) difference in their radii.
Cylindricality: the lateral surface of a cylindrical specimen must be within a pair of concentric cylinders with a given (i.e. tolerated) difference in their radii.
Silhouette outline (also called light transmission mode)The device under investigation is side on illuminated. The silhouette outlines will be projected directly on a camera sensor or on a screen observed by a camera. Only the silhouette outline itself is to be analyzed. For illumination and imaging telecentric lenses are commonly used. This inspection method has its advantages in a high level detail accuracy and in a high-contrast image.
SPC (Statistical Process Control) measurement
It is a testing measurement to check e.g. measurement system capability. Usually a special SPC part with known values is used. Comparing the actual measurement values with the known features, it can be checked, if a measurement system has a proper operational system mode or if it has to be re-calibrated.
The known SPC part features are typically stored in the SPC measurement template.
Telecentric lensesTelecentric lenses are commonly used to avoid perspective-based distortions. The basic principle is to create a non-divergent parallel beam path. Thus the dimensional outlines are not changed, if object distance has been changed along the optical axis. Telecentric lenses can be used for illumination as well as for imaging.