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  2. Procedure for discreet exploration of roundness/cylindricity, or   (15/12/2001)

This news article was originally written in Spanish. It has been automatically translated for your convenience. Reasonable efforts have been made to provide an accurate translation, however, no automated translation is perfect nor is it intended to replace a human translator. The original article in Spanish can be viewed at Procedimiento para la exploración discreta de redondez y/o cilindricidad
Dimensional Metrology - Tutorial

Procedure for discreet exploration of roundness/cylindricity, or

To the continuing need to evaluate geometric tolerances in the Department of metrology in the Ascamm Foundation various procedures of exploration, acquisition and data processing have been developed to respond to needs of GD & T.
José Valero García - Chief of metrology in the Ascamm Foundation / / Francesc Rivillas Cañaveras - technical specialist in metrology of the Ascamm Foundation

These developments are based on the use of our means of acquiring 3D best uncertainty. Means of acquisition by continuous scanning of equivalent uncertainty present on the market represent an investment without feasibility for our current needs, so these developments were also started from the need to complement the benefits of our resources with innovative functions of own development. This is the case of the procedure for scanning by means of which we can assess - according to needs - roundness and/or the cylindricity.

These were the requirements of item in the course of the procedure:

  • Repeatability and traceability of the data collected
  • Ability to adapt to the variability of demand
  • Automaton implementation to reduce errors and improve execution time
  • Compatibility of output with the leaves of calculation and the graphical environment.
  • Local reference system to start the process

The acquisition of data can be in any of our MMC in autorun, governed by CN of the Brown & Sharpe family. At the beginning of the program is passed through a phase of dialogue in which the operator answers the questions:

  • Name for the file of results?
  • Diameter to explore?
  • Total number of points to explore?
  • Initial height of exploration?
  • By how many levels?
  • Step between levels?

The program written with parametrizadas variables is able to calculate the path of exploration by input parameters, govern the movements of the machine and head PH9, open results file, save all acquired data and finally evaluate the roundness if he explored a single level or the cylindricity explored two or more levels.

The writing of exploration data format is compatible with the leaves of calculation in Excel. It is there where the end-points, marking the angular position and the height of the nearest point to the Centre and the same applies to the farthest point are identified. For all the points lie between these two limits applies a radial extension 10 X in order to achieve a graphic representation emphasizing areas with error of form.

The processed results are saved in a format that is compatible with the Unigraphics CAD system. The explored contour is represented in this system as a curve Splinegoing through all the correlative points located on the same level. Then, there are the two concentric circles corresponding to extreme rays of which unfolds all around. Representation concludes by tracing lines which mark the angular positions of minimum and maximum diameters.

The synthetic result occurs as in the following figure:

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Extreme diameters can result from combinations of radios that do not necessarily involve the points of tangency with the boundary circles

You can see that the extreme diameters can result from combinations of radios that do not necessarily involve the points of tangency with the boundary circles. This type of graphic information is useful in the corrective metrology. The moldista uses this information to make the local corrections needed to improve the product.

The versatility of this procedure has provided the possibility of applying it in different projects:

  • Solution for the improvement of water-tightness conical couplings for tubes of transfusion in medical applications - Motecsa
  • Solution for the improvement of roundness in the area of coupling of the deposits of radiators for cooling in car engine system - Tramec.
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The table of the processed results points out the farthest point in red the point closest to the Center and blue.
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