Apparatus for determining the contours of a work piece.

The invention relates to a device for extracting workpiece contours according to the preamble of claim 1.

Such a device is preferably used in numerically controlled machine tools in which the workpiece contour obtained is displayed on a screen for program checking and, if necessary, is generated as a workpiece after corrections.

This requires a workpiece program for which the input data for the workpiece contour should be read as directly as possible from the workpiece drawing. A typical workpiece drawing consists of a series of straight lines and circular arcs that are strung together or chained together to form the contour of the workpiece. If the starting point and the end point of each rectilinear curve piece on the drawing were given together with the starting and ending points of the circular arcs and their centers, the method for obtaining the desired workpiece contour on a numerically controlled machine tool was not difficult and would be trivial. In reality, however, the geometry of the workpiece is generally not sufficiently determined. The intersections of the circular arcs with each other and with straight curve pieces are generally not known.

The invention is based on the finding that the vast majority of the components or workpieces which are produced on numerically controlled machine tools can be constructed from selected geometric shapes which are lined up or linked together. The number of different contour pieces required to be able to define the majority of the work pieces is relatively small. These geometric shapes could be defined by the geometric dimensions of the contour pieces.

It is obvious to a person skilled in the art that the number of contour pieces and their specific properties can be changed.

If one looks at the workpiece drawing, it can be seen that the resulting workpiece contour can be described by a sequence or sequence of contour pieces, the complete geometry data of which can however only be taken directly from the workpiece drawing in the rarest of cases.

The invention has for its object to provide a device by means of which a complete workpiece contour can be obtained from contour pieces, the geometry data of which need not be complete.

This object is achieved by a device with the features of claim 1.

The particular advantages of the device according to the invention lie in the relatively simple handling, so that the operator can use the workpiece drawing with its data, which is in itself insufficient for NC programming, in dialogue with the device to adequately determine the data records for obtaining a complete workpiece contour, without that the operator has to make complicated considerations.

With the help of an embodiment, the invention will be explained in more detail with reference to the drawing.

It shows the<ul id="ul0001" list-style="none"><li>Figure is a block diagram of the device</li></ul>

With the help of an input unit E, which can have a keyboard, input data are input into an input memory SE. Geometry data for contour sections are obtained from the input data and stored in the data memory SD. The input memory SE, like the data memory SD, is connected to a computer C. Another memory SA for the contour algorithm is also connected to the computer C. The computer controls a result memory SR and a graphics unit G. The graphics unit G consists of a graphics memory GS and a graphics processor GP which controls a display module CRT. The result memory SR contains the result of the combined geometry data - which will be explained later - for use in NC machines.

The function of the device is ensured by the successive combination of geometry data, which is carried out by the computer C in accordance with the algorithm which is stored in the memory SA.

The geometry data stored in the data memory SD determine the geometry of the contour sections. As previously mentioned, these contour sections can be traced back to geometrically simple elements and are determined by information from the following data sets:<tables id="tabl0001" num="0001"><img file="EP0246422A2_D0001.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0246422A2_D0002.tif" /></tables><tables id="tabl0003" num="0003"><img file="EP0246422A2_D0003.tif" /></tables><tables id="tabl0004" num="0004"><img file="EP0246422A2_D0004.tif" /></tables><tables id="tabl0005" num="0005"><img file="EP0246422A2_D0005.tif" /></tables>

The contour algorithm stored in the memory SA determines the rules according to which the computer C combines the geometry data in the individual NC blocks in order to obtain higher-value data therefrom. The data of the adjacent NC blocks are preferably combined. Together with the data of the "predecessor" NC block or the "successor" NC block, the geometry data for the workpiece contour can be successively completed. However, it is also possible to use the geometry data of any NC block for combination if the reference data is not in the Cartesian coordinate system but in the incremental reference system. For this purpose, the block number of the NC block to which reference is made must be specified for the combination.

There are three ways to combine the geometry data of NC blocks:<ul id="ul0002" list-style="none"><li>1) the combination within an NC block;</li><li>2) the combination of two (neighboring) NC blocks (combination with "predecessor" or with "successor");</li><li>3) the combination of three (neighboring) NC blocks (combination with "predecessor" and "successor").</li></ul>

The corresponding combination takes place according to the contour algorithm stored in the memory SA, for example, according to 1), the incremental increase in the coordinates, based on the end point of the predecessor NC block, can be calculated for a straight line from the slope angle and length, or vice versa, as well as for one Circle from tangent angle at the starting point of the circle and incremental center angle the tangent angle at the end point can be calculated.

According to 2), the circular line on which the end point of the straight line lies is determined from the end point of the predecessor NC block and the length of a subsequent straight line.

Finally, according to 3), a straight line can be determined which is tangent to two circles, of which the center points and the radii are known, or a circle with a certain radius should connect tangentially between two straight lines.

Each combination converts a set of geometry data from an NC block into another set of geometry data by linking to a neighboring block or within the NC block according to the examples given above, with the aim of ultimately providing information about the end point or center point coordinates of the respective block Obtain contour section.

For this purpose, the computer C combines the geometry data of the memory SD in accordance with the contour algorithm from the memory SA in the following way:<ul id="ul0003" list-style="none"><li>With the last NC block read in, all combination rules are started to apply to this NC block, provided the corresponding geometry data for the NC block are available, then the next combination rules to it and its predecessor NC block or to the NC block for which there are incremental references, ie a block number. If this creates geometry data for the predecessor NC block, all the combination rules with the corresponding NC blocks are also used for this, and so on. If all originally undefined NC blocks have been run through to the start of the list, the direction is reversed and all combination rules are carried out until the end of the list, provided the corresponding geometry data is available for the rule application. This process from the end of the list to the beginning of the list and back with combinations is carried out until new geometry data can no longer be calculated. Then the next NC block is read in and the processing of the rules starts again.</li></ul>

Combination rules are rules that generate new geometry data for this NC block from the given geometry data of an NC block. There are also combination rules that generate new geometry data for one or both NC blocks from the geometry data of two NC blocks. Additional combination rules enable the generation of geometry data for one, two or three NC blocks from geometry data of three NC blocks.

An NC block is completely determined if none of the following geometry data can be calculated for this NC block:<ul id="ul0004" list-style="none"><li>with a straight line A, KL, U, V</li><li>with a circle A, R, hiA, MU, D9V, U, V.</li></ul>

Since ambiguities can arise when using the contour algorithm, a memory SB for a "backtrack" algorithm is connected to the computer C, which remembers every possible solution and continues to calculate with the first solution until there is a contradiction occurs with another entered or calculated value. In this case, the wrong solution and all resulting interim results will be undone and the next solution will be used. The same applies if there are more than two _Lthere are solutions. nation rules executed, provided the corresponding geometry data is available for the rule application. This process from the end of the list to the beginning of the list and back with combinations is carried out until new geometry data can no longer be calculated. Then the next NC block is read in and the processing of the rules starts again.

_KCombination rules are rules that generate new geometry data for this NC block from the given geometry data of an NC block. There are also combination rules that generate new geometry data for one or both NC blocks from the geometry data of two NC blocks. Additional combination rules enable the generation of geometry data for one, two or three NC blocks from geometry data of three NC blocks.

An NC block is completely determined if none of the following geometry data can be calculated for this NC block:<ul id="ul0005" list-style="none"><li>with a straight line A, KL, U # V</li><li>with a circle A, R, MA, MU, MV, U, V.</li></ul>

Since ambiguities can arise when using the contour algorithm, a memory SB for a "backtrack" algorithm is connected to the computer C, which remembers every possible solution and continues to calculate with the first solution until there is a contradiction occurs with another entered or calculated value. In this case, the wrong solution and all resulting interim results will be undone and the next solution will be used. The same applies if there are more than two _Lthere are solutions.

With the device described, complete workpiece contours can be determined in a particularly simple manner, and it goes without saying that these do not necessarily have to be displayed on the screen of an NC machine; they can also be generated directly by workpiece machining if the device according to the invention directly Machine feeds. The device can also be used advantageously at programming stations.