Measuring and testing – Testing of apparatus
Reexamination Certificate
2002-06-27
2004-04-06
Williams, Hezron (Department: 2856)
Measuring and testing
Testing of apparatus
Reexamination Certificate
active
06715372
ABSTRACT:
TECHNICAL FIELD
The present invention relates partly to a method and apparatus for testing a machine tool.
STATE OF THE ART
In many contexts, industry uses various types of machine tools for processing and manufacturing various parts. This involves needing to be able to monitor the status of such machines in order, for example, to be able to do repairs and adjustments in time to avoid stoppages or bad precision of parts being manufactured. The objective is to be able to detect changes quickly and be able to rectify them before major and expensive defects develop.
A conventional method for testing a machine is to make representative parts and then check their dimensions in order to assess the machine's performance. Disadvantages observed in this respect include the need to use tools and testpieces and difficulty in comparing results from different tests. Using standardised testpieces certainly facilitates comparisons but still requires testpieces and tools.
Another method is to monitor the machine's rigidity in different directions by applying a suitable force by means of a hydraulic cylinder and measuring the resulting deflection by means, for example, of a micrometer. A disadvantage of this method is that it is time-consuming and measurement cannot be done with the machine in operation.
Another known practice is to use a special instrument, a so-called “ball bar”, fitted between workpiece holders and tool holders, to test the machine's ability to perform a circular movement. Measuring equipment in the instrument is used to record any deviations from a circle. Various such tests can be carried out at different times and compared to provide information on various characteristics of the machine, such as circularity, servo response, rectilinearity, play etc. Tests can also be done at various feed rates, in various feed directions and using bars of various lengths, and placing the workpiece holder at various different points.
There nevertheless remains the disadvantage of it not being easy to gain a proper assessment of the machine's characteristics under load.
OBJECTS OF THE INVENTION
The object of the invention is to make better machine testing possible. A further object is to achieve this by simple means.
DESCRIPTION OF THE INVENTION
The object of the invention is achieved by a method and an apparatus of the invention. On a machine tool in which a first element intended to support a machining tool, and a second element intended to support a workpiece, are mutually moveable, a special test arrangement may be placed between the first element and the second element. During a mutual displacement between the first and second elements, this test arrangement can apply a predetermined force between these elements while at the same time making it possible to record the resulting shift between them. The measured results may be used for analysis of the machine's condition.
Applying a predetermined force between the first and second elements during mutual displacement between them, and simultaneously measuring the resulting deformation, makes it possible to carry out machine testing in much more production-like conditions than was previously possible. Analysis can be further refined by also varying the manner in which the displacement takes place, as regards both movement configuration and direction of movement, and also by varying the magnitude of the force applied.
Further features and advantages of the invention are described in more detail with reference to embodiments depicted in the attached drawings.
REFERENCES:
patent: 4378660 (1983-04-01), Wiener
patent: 5111590 (1992-05-01), Park
patent: 5681981 (1997-10-01), McMurtry
patent: 5767380 (1998-06-01), Haas
patent: 5791843 (1998-08-01), Dreier
patent: 9718436 (1997-05-01), None
“Test Code for Machine Tools, Part 4: Circular Test For Numerically Controlled Machine Tools”. ISO 230-4:1996(E).
Kakino, et al. “Measuring Device” pp. 17-19 ofAccurancy Inspection Of NC Machine Tools By Double Ball Bar Methodedited by Dr. Johannes Heidenhain Gmbh, 1993.
Frank Rodney
Ostrolenk Faber Gerb & Soffen, LLP
Scania CV AB ((publ)
Williams Hezron
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