The first article inspection report determines whether the corresponding tool can be released for production. For a hardware manufacturer, this extensive part evaluation used to take several days using conventional 3D measurement technology. Using computer tomography, the company was able to reduce the time required to a few hours.

Since 1952, Blum in Vorarlberg in Höchst has produced high quality hardware for high end furniture.  With about 5,000 employees worldwide, the company is a reliable partner for furniture manufacturers and aftermarket hardware dealers. In order to meet their customers’ high quality standards, this hardware manufacturer has used Werth multisensor coordinate measuring technology for many years. The measuring machines, which are used in great numbers, include models from the VideoCheck, Inspector, and TomoScope series. All measuring machine are equipped with the WinWerth software package for machine control and measurement data evaluation.

The company previously used conventional 3D measurement technology for first article inspection in order to release the final tool for production. This process often took several days. In order to significantly reduce the time required, they changed to coordinate measuring machines with tomography sensors for some time now. The measurement results are available in a few hours in the form of meaningful color-coded 3D presentations of deviations. In order to guarantee the measuring process capability of this measurement equipment, high quality technology is needed.

Integration in a coordinate measuring machine

The high requirements for mechanical and thermal stability for reliable computer tomography measurements can only be met by complete integration of this sensor into a coordinate measuring machine. In addition to the stable granite base, proven components and methods from coordinate measuring technology are used.

The TomoScope 200 combines computer tomography and multisensor coordinate measurement in one machine
The TomoScope 200 combines computer tomography and multisensor coordinate measurement in one machine

These include, for example, the guides and drives of standard measuring machines. High accuracy is achieved by intelligent reconstruction processes and a raster principle in imaging. This method allows measurements with increased resolution for determining the smallest features, even on large parts, and expands the measurement range of computer tomography. Traceable measurement results can be obtained by a calibration comparable to VDI/VDE 2617 part 13 using standards, such as spheres, gage blocks, or ballbar standards. The precision’s that are achieved thereby, in the form of specified maximum permissible error (MPE) are on the order of 4.5 μm or better. The application of these specifications to real measured objects, however, is possible only for “cooperative” parts. Variation in wall thicknesses of actual components, complex geometries, and different material properties influence the measurement results. This is caused by physical measurement deviations, known as artifacts, which arise due to X-rays penetration of the measured object. Artifact deviations depend heavily on the object geometry and the object material itself, and therefore cannot be corrected analytically with sufficient precision. However, because the errors are systematic, Werth AutoCorrection (patent pending) provides the ability to capture corresponding measurement points with high-precision optical or tactile sensors and correct errors in the tomography using these measurement points. In practice, the deviations between the tomography scan and a reference sensor are simply determined – only for dimensions with appropriately precise tolerances, of course – and any systematic errors are then fully automatically compensated by the software for all subsequent parts.

New Technology At a glance

The tomography process detects and measures all internal and external geometries of a part. The color-coded presentation of the deviations allows rapid evaluation of dimensional accuracy. Both the deviations from a CAD model, and the deviations between the current part and a master part (actual to actual comparison) can be visualized.

Plastic part from the Blumotion series left to to right: 3D point cloud, triangulated surface representation, and color-coded deviation plot relative to the CAD model)
Plastic part from the Blumotion series left to to right: 3D point cloud, triangulated surface representation, and color-coded deviation plot relative to the CAD model)

Simple standard measurements

In order to evaluate regular geometries with classical dimensioning, areas of the 3D point cloud are automatically assigned to the corresponding surfaces of the desired feature. This makes it very easy to determine dimensions, such as a diameter of a cylinder within the 3D point cloud.

Definition of cross sections in the 3D point cloud for determining dimensions in a 2D section
Definition of cross sections in the 3D point cloud for determining dimensions in a 2D section

In addition, cross sections can be freely defined within the measured CT point cloud. The sections are evaluated using 2D contour evaluation. This eliminates the need to cut and destroy components, saving time and money. Measurement times of many hours to a few days can thus be reduced to a few hours or even minutes.

 The increase in efficiency that can be achieved due to the particularly fast generation of first article  inspection reports enabled Blum to amortize its first measuring machine in about one year. Another machine was purchased just after the ROI of the first one.

Measurement using the 3D point cloud (left: patch selection using the CAD model, right: dimensional check of a cylinder)
Measurement using the 3D point cloud (left: patch selection using the CAD model, right: dimensional check of a cylinder)

 Although, classical optical and tactile measurement techniques will remain indispensable for rapid sample inspection during production, modern computer tomography provides new solutions.  It will continue to develop in the future.

About Werth Inc.

For over 50 years the name Werth has stood for the highest quality and precision in the field of dimensional measurement technology. The company has its headquarters in Giessen, in a region with a long tradition in the industry of precision mechanics and optics.
 
The company’s goal is to attain a high degree of customer satisfaction through worldclass technical solutions and unlimited user-orientation.
 
Through innovative developments in the field of high precision mechanics, image processing and software, Werth Messtechnik GmbH is now the world leader in the area of multisensor coordinate measurement technology. This is also reflected in a range of world firsts and patents.
A highly qualified team assures skill in terms of both advice and technical execution in all areas of the company, including development, construction, manufacturing, quality assurance and sales.
 
By active participation on standardization committees, we support product specifications and quality standards which promote competition.
Consistent quality assurance and acceptance to VDI/VDE 2617 and/or ISO 10360 are guarantees of the reliability, accuracy and comparability of the equipment.
 
Contact Info:
Werth, Inc.
8 Custom Drive
Old Saybrook, CT 06475
Phone 1.860.399.2445
http://www.werthinc.com

 

 

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