Adam Gaska, Jerzy Sladek, Ksenia Ostrowska, Robert Kupiec, Marcin Krawczyk, Wiktor Harmatys, Piotr Gaska, Maciej Gruza, Danuta Szewczyk, Renata Knapik, Artur Kmita
DETERMINATION OF COORDINATE MEASURING MACHINES ACCURACY CHANGES MADE BY DIFFERENT NODES DENSITY IN CAA MATRIX

Advances in modern manufacturing techniques implies more efficient production but also new tasks for coordinate metrology and producers of Coordinate Measuring Machines (CMMs). Main aim here is accuracy improvement. The solutions used regarding CMM construction are easy and it is hard to improve it now. So accuracy improvement is done mainly using sophisticated mathematical algorithms that are responsible for correction of relevant errors. Different types of errors could be compensated, including: probe head errors, machine dynamics errors and most of all machines geometrical errors. Almost all coordinate measuring machines produced nowadays are equipped with geometrical errors compensation matrix known as CAA matrix (Computer Aided Accuracy).
CAA matrices are based on grid of reference points (nods) in which certain values of components of geometrical errors are experimentally determined. Values between this nodes are estimated using simple interpolation methods. Theoretically, the more dense is the grid on which CAA matrix is described, the better is the accuracy of the machine on which the matrix was used. On the other side, increased number of nods implies bigger costs of matrix determination connected with greater amount of time and workload.
This work presents experiments aiming in determination of CAA matrix using LaserTracer system done for different densities of matrix nodes. The relations between maximum permissible errors obtained on machine using matrices with different densities of nodes will be shown. Authors would also try to answer the question how to determine the most appropriate nodes density regarding the ratio of time spent for matrix creation and obtained accuracies.

Ingo Lindner, Tim Eichner, Jerzy Sladek, Michal Wieczorowski
IN-PROCESS QUALITY CONTROL APPROACH IN METAL FORMING OF SPLINED MACHINE ELEMENTS

The increasing demand of high precision machine elements manufactured in mass production results in a target conflict with respect to quality control of the production lots, esp. if metal forming techniques are the production principles.
Due to high process forces, kinematic movements of forming tools and imprinted change of material properties during tool and workpiece interaction, a change of the workpiece position within the manufacturing processes generates quality losses in the resulting geometries.
Today, SPC based post-process or in-situ measurements are the basis for the quality control on such production processes. This paper will give an outlook on in-process monitoring of geometrical features based on the targeted component feature specification to be observed. The borderzone quality prediction combined with the collection of relevant process parameters, integrated into an overall inprocess measurement system approach are further intellectual aspects. Initial results out of an ongoing development initiative will be presented.

Siniša Delcev, Jelena Gucevic, Vukan Ogrizovic
NECESSITY OF INVOLVEMENT OF CALIBRATION LABORATORIES IN PROFICIENCY TESTING SCHEMES

During the accreditation, but also in its maintenance, calibration laboratories must prove their competence. According to the ISO/IEC 17025:2005 standard competence is proved by participating in interlaboratory comparisons or participation in PT (proficiency testing) schemes. However, some accreditation bodies, such as Serbia, insist on participation in PT schemes and not accredit calibration laboratory, or even take away accreditation, unless they are involved in these activities. Of course, participation in interlaboratory comparisons is default.
Unfortunately, PT schemes are not organized for all types of measure and methods as there are no accredited PT providers (for example - for the geodetic measures are not any). To some measures there is only one provider of PT, and if there are any more they charge for their services, which are not negligible. In such situations calibration laboratory located in a very difficult situation because they can not obtain or may lose accreditation.
On the other hand, participation in interlaboratory comparisons, according to the standard, also proves competence, but are easier to maintain and less costly - usually do not cost anything because all involved laboratories have the same benefit. Also, these activities can be organized between laboratories in the same state.
This paper aims to stimulate discussion and debate about ways of proving competence of calibration laboratories. We believe that, in the interpretation of ISO/IEC 17025, the laboratory can demonstrate competence by participating in any activity, PT schemes or interlaboratory comparisons, and they are equal to this need.

Robert Schmitt, Martin Peterek
GUIDELINES FOR TRACEABLE MEASUREMENTS ON MACHINE TOOLS

Flexible manufacturing processes for high quality products at low costs are one of the main research objectives in the field of production technology. The quality inspection of large or complex workpieces manufactured on machine tools often takes place beside the production line. To assure the traceability of the quality inspection the features are measured on a CMM in an isolated measurement room. The high invest for a CMM and influences like transport, handling and the loss of the original set up show the need for a machine tool integrated traceable measuring process for product’s quality assurance.
Touch probes can be found in many new machine tools and shall provide the possibility of testing product characteristics right after the manufacturing process. But due to disturbances like machine defects or temperature fluctuations, the measurement process on the machine tool is not traceable. The measurement data are not comparable and cannot be used for process improvements or process control.
New approaches at WZL are aiming to assure the traceability of the inspection processes on machine tools and Multi Technology Platforms (MTP). The fusion of appropriate methods for the traceability of CMM’s and innovative calibration methods for machine tools will allow the determination of a measurement uncertainty for the measurement system “touch probe and machine tool”. Different methods for the uncertainty evaluation of CMMs have been examined and validated for machine tools. Within the research activities a guideline has been developed that will allow the implementation of a traceable measurement process on machine tools.
The objectives of the research activities are part of the Cluster of Excellence ‘Integrative Production Technology for high Wage Countries’ at the RWTH Aachen.

Wieslaw Grabon, Pawel Pawlus, Rafal Reizer
COMPARISON OF METHODS OF OIL CAPACITY CALCULATION

The aim of this work is to compare various methods of oil capacity calculation for surfaces with isolated pockets. These surfaces were measured by stylus profilometer. In reference method, oil capacity was calculated by summation of volume contained in all the separate dimples from measured surface. Oil capacity was calculated also on the basis of material ratio curve using the Svk and Sr2 parameters from the Sk group (areal extension of ISO 13565-2 standard). The second procedure was developed on the basis of Sq parameter group (areal extension of ISO 13565-3 standard). The third method is bases on determination of point of maximum curvature of the normalized material ratio curve. It was found that in most cases it is possible to obtain correct values of oil capacity using the Sk family parameters. However when the slope of material ratio curve in its middle part is small or high, the errors of oil capacity estimation using this approach may be large. In this case the other methods gave better results.