Thermal measuring and testing – Leak or flaw detection
Reexamination Certificate
2000-06-16
2002-08-27
Gutierrez, Diego (Department: 2859)
Thermal measuring and testing
Leak or flaw detection
C374S005000
Reexamination Certificate
active
06439764
ABSTRACT:
The invention concerns a device and a process for rapid and simple thermographic examination of functional surfaces of forming tools according to the pre-characterizing portion of Patent claims
1
and
11
. A device for examination of the thermal load of functional surfaces of forming tools is already known from EP 685297 A1.
The optimization of the forming processes and work tools associated therewith is the focus of intensive research and development activity. Of particular interest is measurement of temperature in the work area during the work process. This allows determination in situ of the loading and the friction condition of the work tool. Ever-increasing requirements of work tools dictate higher loads and require more suitable new materials for these work tools. Conventionally, these new materials are applied to the work tools in the form of coatings as in EP 685297 A1. It has been proposed to integrate one (or more) thin film sensors in a functional or wear protective layer of the work tool for determination of the temperature of the wear surface of a forming or machining work tool. This however requires much technical effort and high costs. Besides this, thin film sensors enable temperature measuring only at one point. The determination of the temperature distribution would here be possible only with a multiplicity of sensors, and would require higher technical investment and costs. Besides this, no high dynamic measurement can be accomplished with the integration of a thin film sensor in a work tool.
SUMMARY OF THE INVENTION
The task of the present invention is comprised therein, to provide a device for rapid and simple thermographic examination of functional surfaces in forming tools in situ, which makes possible the determination of the temperature distribution without hindering the work process or the goal of the optimization of the wear and structure relationship of the employed work tool without increasing investment and costs, as well as the development of a process with the same advantages.
With respect to the device to be achieved, the inventive task is preferably inventively solved whereby, that the device for thermographic examination of functional surfaces of forming work tools is designed in such a manner,
that it contains a temperature measurement device,
that the forming tool in the area of the functional surface contains at least one channel,
which respectively exhibits one opening facing the work piece,
and
into which thermal radiation emitted from the functional surface to be examined is conducted,
whereby the thermal radiation conducted through a channel is detectable at least indirectly by the temperature measuring device,
so that the work piece side opening of each channel is provided with a window, which is transparent yo thermal radiation.
The fundamental principle of the inventive device is comprised therein, that the thermographic examination of the functional surface occurs from the work tool internal side, through the one or more provided channels. Thereby there is made possible for the first time unimpeded and uninterrupted measurement of the absolute temperatures and two-dimensional temperature distribution of the work piece outer surface directly in the contact area of the work tool-work piece in situ. Thereby the forming process itself can be examined and optimized with respect to the processing parameters, the work tool geometry and the tribo system (material of work tool, work tool coating, lubricant, outer surface topography). The measurements can be carried out not only in the experimental operation, but rather also in be employed series production for dynamic process regulation or feedback control.
The investiture and the costs of the inventive device are small when compared to the application of a measurement field comprised of a plurality of thin layer sensors. Besides this, such a measurement field would only make possible or permit an approximate determination of the spatial temperature distribution, since the thin layer sensors only measure at points.
Depending upon the size of the opening of the channel on the side of the work piece, this may or may not be provided with a window.
In an advantageous embodiment of the inventive device, the work piece side opening of each channel is provided with a window and upon this window a layer or coating or overlay is applied.
Thereby, the determination of the utilization relationship and in particular the employment limits of various work tool coatings under real application conditions is made possible. If IR transparent coatings are employed, for example diamond or similar coatings or overlays, then the contact area of work tool-work piece can be examined in situ. If IR—opaque coatings are employed, then the temperature distribution is first conveyed from the contact area out via conductive paths through the coating to the underside and only thereafter is further relayed by means of thermal radiation in the direction of the temperature measuring device. Work tool coatings are conventionally only a few micrometers thick, thus the warmth conducted through them falsifies the measurement of the temperature distribution only within an acceptable magnitude.
In a further advantageous embodiment of the inventive device, there is over the window, or in place of the window, a covering secured, which is comprised of a tool material conventionally employed in forming processes, for example a chrome-containing tool steel.
The advantage of this embodiment is comprised in the simple, rapid and economical exchangeability of the covering and therewith the tool material and the tool surface.
In a further advantageous embodiment of the inventive device, a coating is applied to the covering.
The advantage of this embodiment is comprised therein, that the covering is easily exchangeable and independent from the rest of the tool, or the measuring device can be coated. This leads to a time and cost saving and makes possible direct or immediate comparative measurements with a basic device. As a result of the comparative measurements, it becomes possible to develop iteratively in the optimizing increments an optimal coating suited for the use for each application case of the forming technique.
Beyond this, the coating—of a conventional tool steel employed in forming processes—allows itself to be coated better and with greater bonding strength with the materials interesting for forming techniques than most of the other outer surfaces, which must withstand the loads during a forming process, for example a diamond outer surface, on which because of the covalent bonding character a sufficient adhesion is achieved. An adequate adhesion is, however, a precondition for temperature measurements over longer periods of time during the forming processes, without suffering from a breaking off of the coating. This makes possible durability testing of the forming process with parallel temperature measurements.
The window situated below the coating supports this superficially, and this prevents a deformation or a breaking of a thin covering on the basis of the loading during the forming process. In the use of coverings with sufficient mechanical load resistance, it becomes possible to dispense with the window.
Generally, a calibration of the device, in particular the temperature-measuring device to the emission characteristics of the material or, as the case may be, the coating, is necessary. The calibration expenditure for various materials or tool coatings can, however, be reduced to a single calibration, in which respectively one coating of a single material conventionally employed in the forming processes is applied over or in place of the window on the channel.
In an advantageous embodiment of this device, the material and the thickness of the coating is so selected, that the image of the temperature distribution of the functional surface (or as the case may be, the lower side of the coating), which via thermal conductivity is directed through the covering, is not adulterated perpendicular to this intended image direc
Engering Gerrit
Hortig Dirk
Lahres Michael
Daimler-Chrysler AG
Gonzalez Madeline
Gutierrez Diego
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