PRODUCTION USING A MACHINE TOOL OF FACES DEFINABLE BY CONE SEGMENTS

Abstract

In a method for producing and/or machining a non-conical face of a workpiece defined by a segment of a cone, in particular a sealing face of a multiple-eccentric shut-off valve, using a machine tool having at least two linear axes and at least one rotary axis controlled by a numerical controller for generating a relative movement between a tool and the workpiece, a cycle is provided on the numerical controller and retrieved by a user of the machine tool. The user parameterizes the cycle, whereafter a part program is generated by the cycle for execution by the numerical controller. The executed part program generates the relative movement along a path determined by the part program to produce and/or machine the face of the workpiece.

Claims

1-16. (canceled)

17. A method for producing or machining a non-conical sealing face of a closure part or a non-conical sealing face of a valve seat of a shut-off valve by a using a machine tool having at least two linear axes and at least one rotary axis for generating a relative movement between a tool and the closure part or the valve seat, said method comprising: retrieving a cycle by a user of the machine tool on a numerical controller which controls the linear and rotary axes; defining the non-conical sealing face by a segment of a cone; parameterizing the cycle by the user; detecting at least one parameter relating to the cone; using the cycle and the numerical controller to generate a parts program executable by the numerical controller; and executing the parts program to generate the relative movement along a path defined by the parts program for producing or machining the non-conical sealing face of the closure part or the non-conical sealing face of the valve seat of the shut-off valve.

18. The method of claim 17, wherein the non-conical sealing face is defined by the segment of an oblique cone, in particular of an oblique circular cone.

19. The method of claim 17, wherein the non-conical sealing face is defined by the segment of a cone, in particular of a straight circular cone, having a height line which is not parallel with a workpiece normal.

20. The method of claim 17, wherein the non-conical sealing face is embodied as a circular closed cone segment.

21. The method of claim 17, wherein the non-conical sealing face is machined by a turning operation.

22. The method of claim 17, wherein the shut-off valve is an eccentric, in particular a multiple-eccentric shut-off valve.

23. The method of claim 22, further comprising executing a radial compensating movement to compensate for an eccentricity in at least one linear axis of the machine tool.

24. The method of claim 17, wherein the parts program is generated at least partially in a polar coordinate format.

25. The method of claim 17, wherein the parts program is generated at least partially in a Cartesian format.

26. The method of claim 17, further comprising enabling the user to input geometric specifications for the non-conical sealing face or manufacturing specifications for producing or machining the non-conical sealing face by way of a cycle mask that can be displayed on a display device of the numerical controller.

27. The method of claim 17, wherein the cycle generates the path at least partially in the form of directly adjacent splines, in particular 5.sup.th-order splines.

28. The method of claim 17, wherein the tool defines a tool radius and the parts program takes into account the tool radius, in particular in form of a tool radius correction.

29. A cycle of a numerical controller configured to execute a method as set forth in claim 17.

30. A numerical controller comprising a cycle and configured to execute a method as set forth in claim 17.

31. A machine tool comprising a numerical controller configured to execute a method as set forth in claim 17.

Description

[0061] The invention is explained in greater detail below using exemplary embodiments. In this case:

[0062] FIG. 1 shows a machine tool for performing an inventive method,

[0063] FIG. 2 shows a triple eccentric shut-off valve,

[0064] FIG. 3 shows a triple eccentric shut-off valve in a schematic representation,

[0065] FIG. 4 shows a turning operation of a sealing face of a triple eccentric shut-off valve, shown in FIGS. 2 and 3, with a compensating movement through a linear axis of the machine tool,

[0066] FIG. 5 shows some parameters queried when the cycle is retrieved and relating to the geometry of the sealing face,

[0067] FIG. 6 shows a tool path composed of a plurality of directly adjacent splines,

[0068] FIG. 7 shows a representation of points on elliptical segments for the formation of a spline,

[0069] FIG. 8 shows a spline segment for one revolution,

[0070] FIG. 9 shows method steps in the performance of a method in accordance with the invention.

[0071] FIG. 1 schematically shows a machine tool 20. In the context of the exemplary embodiment the machine tool 20 has six machine axes, through which a relative movement can be performed between a tool 1, which in the context of the exemplary embodiment is present in the form of a turning tool 1, and a workpiece 5, in the exemplary embodiment indicated as a valve seat 5 of a multiple-eccentric shut-off valve. The tool 1 is in this case clamped in a tool holder 2, which is connected to a tool spindle 21 driven by a position-controlled motor 22. The workpiece 5 is fastened to a workpiece table 7 by clamping means 6.

[0072] The turning tool 1 can be moved with the machine 20 shown in the exemplary embodiment in a position-controlled translatory manner in the X, Y and Z direction 1 with drives not shown in FIG. 1 for the sake of clarity. Besides the three linear axes the machine tool 20 shown further comprises the two position-controlled rotary axes A and B, likewise shown in FIG. 1, with which the tool 1 can be turned about the respective axis and likewise can be aligned relative to the workpiece 5 in a position-controlled manner through the angular positions α and β.

[0073] In addition the machine 20 has a third position-controlled rotary axis C, which runs in parallel to the Z axis, and in respect of which the workpiece table 7 is mounted so as to be rotatable relative to a stationary machine frame 23. As a result the workpiece 5 can also be positioned in an angular position γ relative to the tool 1. Here too the drive has not been shown for the sake of clarity.

[0074] Depending on the machining to be carried out, speed-controlled operation with respect to the rotary axes A and/or C is also possible in the case of the machine tool 20 shown.

[0075] The machine tool 20 in accordance with the exemplary embodiment thus has six machine axes (the 3 linear axes X, Y and Z plus the 3 rotary axes A, B and C), i.e. it is what is known as a 6-axis machine tool (6-axis machine) 20.

[0076] It may be mentioned at this point that the machine tool 20 can of course also have more, or fewer, than six machine axes.

[0077] The machine tool 20 is connected to a numerical controller 30, which uses a parts program 33 and/or a manual input to determine position setpoint values x, y, z, α, β and γ to control a relative movement taking place between the tool 1 and the workpiece 5. The numerical controller 30 determines the position setpoint values using the parts program 33, in which the movement to be carried out by the tool 1 in respect of the workpiece 5 is defined in the form of commands. Alternatively or additionally the movement of the tool 1 and/or the workpiece 5 can also be specified by an operator on site at the machine tool 20 by means of a manual input via a control facility 31 in conjunction with a display device 32 of the numerical controller 30. To this end the control facility 31 has in particular input fields, buttons and rotary controls.

[0078] The parts program 33 is in this case normally generated outside the numerical controller 30 by an external CAM/CAD system (not shown) and what is known as a postprocessor (not shown) that may be connected downstream of the CAM/CAD system, and from there is transferred to the numerical controller 30.

[0079] During the execution of the parts program 33 the numerical controller 30 generates in a specific cycle, the interpolation cycle, both position setpoint values x, y and z for the linear axes and α, β and γ (angular positions) for the rotary axes. Thanks to these position setpoint values the tool 1 is moved along a movement path with a predefined orientation relative to the workpiece 5.

[0080] In accordance with the invention a cycle 34 for producing and/or machining non-conical faces of the workpiece 5 is present on the numerical controller 30 in accordance with the exemplary embodiment, and can be defined by a segment of a cone, i.e. can be described mathematically. As indicated in the figure, the workpiece 5 in the exemplary embodiment is a valve seat 5 of a triple eccentric shut-off valve. Thanks to a corresponding parameterization of the cycle 34, which will be looked at in greater detail later, the desired machining, in particular a turning operation of the sealing face, is possible.

[0081] Besides the aforementioned turning operation of the valve seat 5, the 6-axis machine shown could likewise be used, for example, to perform milling of the valve seat 5, in which the tool 1 is designed as a milling cutter (not shown) rotating about the spindle axis A, said milling cutter being positioned in a position-controlled manner in the X, Y and Z direction and in which the valve seat 5 is preferably fixed in place. The milling cutter would in this case be driven in a speed-controlled manner by the motor 22 and the spindle 21.

[0082] FIG. 2 shows a triple eccentric shut-off valve (triple offset butterfly valve), as is employed for example in the chemical industry, the oil and gas industry, or the water and wastewater industry. A particular challenge of these valves is the production of the requisite sealing faces, such as for example the valve seat indicated in FIG 1. The creation of parts programs for machine tools for producing these sealing faces has hitherto only been possible using CAD/CAM systems.

[0083] FIG. 3 illustrates a triple eccentric shut-off valve 40 in a schematic representation. The valve seat 41 of the shut-off valve 40 with the sealing face 42 can be seen in the figure. Furthermore, the rotatably mounted closure part 43 of the shut-off valve 40 with the sealing face 44 can be seen.

[0084] The geometry of the sealing faces 42 and 44 can be described using an oblique circular cone 50. likewise shown by way of example in FIG. 3, with the base area 51, the radius 52, the height 53, the tip 54 and the deviation 55. The two parallel surfaces of the valve seat 41 and of the closure part 43 result in an annuiarly closed cone segment 57 as an intersection on the lateral face of the cone 50. The sealing faces 42 and 44 lie on this annuiarly closed cone segment 57 of the lateral face of the cone 50 and can hence be precisely described mathematically.

[0085] Further, the three eccentricities of the shut-off valve 40 can be seen in FIG 3. A First eccentricity 45 results from an offset of a pivot point 48 of the closure part 43 compared to a first center line 59, running in the vertical direction, of the shut-off valve 40 in the direction of flow 49 of the shut-off valve 40. A second eccentricity 46 results from an offset of the pivot point 48 of the closure part 43 compared to a second center line 56, running in the horizontal direction, of the shut-off valve 40 in a direction perpendicular to the direction of flow 49 of the shut-off valve 40. A third eccentricity corresponds to an angle 47 between the second, horizontal center line 56 of the shut-off valve 40 and a cone axis 58 running through the center point of the base area of the cone 50 and the tip 54 of the cone 50.

[0086] FIG. 4 illustrates the turning operation of the valve seat 41 (only the substantially hollow-cylindrical part of the valve seat 41 that is essential for the machining is shown) of the triple eccentric shut-off valve 40 in accordance with FIG. 3. For machining, the valve seat 41 (corresponding to the workpiece 5 in FIG. 1) rotates at a preferably constant angular velocity about the axis of rotation C (see also FIG. 1) and a turning tool 60 that can be adjusted in at least two linear axes (corresponding to the tool 1 in FIG. 1) carries out metal-cutting machining. A compensating movement of the turning tool 60 to compensate for the aforementioned eccentricities along a first linear axis 61 is shown, for example the X axis shown in FIG. 1, the compensating movement taking place synchronously with the rotation of the valve seat 41 per revolution of the valve seat 41. Further, a second linear axis 62 for the infeed movement of the turning tool 60 is shown, for example the Z axis shown in FIG. 1.

[0087] Besides the aforementioned constant angular velocity of the rotation about the axis of rotation C, any angular velocity, even one that varies over time, can in principle come into consideration. In a preferred embodiment, the angular velocity of the rotation is defined—in a manner known per se—such that a constant cutting velocity results.

[0088] In accordance with the invention a corresponding cycle is started and executed for the corresponding machining of the valve seat 41 on the CNC machine. The machining is preferably performed starting on a hollow-cylindrical workpiece blank.

[0089] The geometric information required for manufacturing the sealing faces, as well as the manufacturing-related information, is in this case requested particularly conveniently by the operator using a cycle mask displayed on an HMI screen of the CNC controller. Alternatively the manufacturing cycle could also take place by the parameters being input manually in the parts program (without an HMI mask).

[0090] Table 1 below contains an exemplary summary of interactively editable parameters on the CNC controller, which can be requested using the cycle mask following a corresponding cycle retrieval. Besides a preferred designation of the respective parameter, Table 1 likewise shows a brief description and where appropriate a unit of measurement for the parameter in question. Depending on the form of description the actual parameter inputs required in each case may vary or may be derived from other specifications not mentioned here.

TABLE-US-00001 TABLE 1 Input parameters for the machining cycle on the CNC controller. Parameter Description Unit PRG Program name Name of the program to be generated RAX Rotary axis Rotary axis on which the workpiece is clamped IAX Infeed axis Linear axis which radially maps the eccentric compensating movement to the center of rotation MAX Machining axis Linear axis which maps the infeed movement along the lateral face of the cone (revolution feed) Contour This parameter can be used to define the contour preference reference Internal The machining takes place inside the defined cone, typically for the housing External The machining takes place outside the defined cone, typically for the valve Machining Machining direction Establishes in which direction the rotary axis (RAD) rotates; this should be selected to match the alignment of the turning tool Format Polar Cartesian RP Return plane mm During machining the tool travels in rapid motion from the tool change point to the return plane and then to the safety clearance. At this height a switch is made to the machining feed. On completion of machining the tool travels in the machining feed out of the workpiece to the height of the safety clearance. It then travels in rapid motion from the safety clearance to the return plane and further to the tool change point. The return plane is input as absolute. The reference point Z0 and the return plane RP generally have different values. The cycle assumes that the return plane is situated ahead of the reference point. SC Safety clearance mm The safety clearance establishes the distance to the material that is no longer traversed in rapid motion. The cycle automatically establishes the direction of working of the safety clearance. The safety clearance generally works in multiple directions. The safety clearance is input incrementally (unsigned). S Machining speed 1/min SR Reduced speed for the startup 1/min Z0 Reference point mm Reference point in Z Z1 End depth mm Depth in relation to Z0 F Machining feed mm/rev This parameter describes the feed per revolution DCX Distance between axis of rotation and tip of cone mm DCZ Distance between tip of cone and Z0 mm DCE1 Distance to cone corner 1 mm DCE2 Distance to cone corner 2 mm

[0091] FIG. 5 illustrates graphically some of the parameters that are requested during the cycle retrieval and that can be seen in Table 1.

[0092] The parameters shown provide all the specifications required to define the visible straight circular cone K and thus for the geometric description of the face to be produced. In particular, it can be seen in the figure that the cone K is pivoted (“turned”) in space in comparison to a surface normal of the workpiece running in the Z direction. This means that a height line h of the straight circular cone with the center point M of the base area is not aligned in parallel to the surface normal of the workpiece and thus not in parallel to the Z axis of the machine tool.

[0093] After entering all the requisite parameters, a (CNC) parts program is generated fully automatically using the CNC controller, and can either be started immediately on the machine tool or alternatively is generated and executed at runtime based on user inputs. Thus no specific postprocessor is required, as would be necessary when creating the program using a CAM system, since the machine information required (number, type and position of the axes; maximum traversing ranges of the axes, etc.) for the algorithm are directly available or known here.

[0094] The tool path to be traversed by the tool relative to the workpiece generally runs on the lateral face of the cone segment in question. In the exemplary embodiment the cone is a straight circular cone K and the cone segment is an annularly closed segment of the lateral face of the cone K produced by the intersection of the cone K with the workpiece W. The invention is however not restricted to this cone shape or lateral shape. Further relevant for technical applications are in particular faces that relate to an oblique cone, in particular an oblique circular cone. The face sought is generally produced by the intersection of the cone in question with the workpiece blank (see FIG. 5).

[0095] In the exemplary embodiment in accordance with FIG. 5, in which a straight circular cone K is rotated in comparison with a surface normal of the workpiece, i.e. is pivoted in space, an intersection of the cone through a plane parallel to the workpiece surface of the workpiece W generates an ellipse.

[0096] If the infeed movement (Z direction) is disregarded, the result would be elliptical paths for the machining. Taking account of the infeed movement results in substantially elliptical, spiral-shaped path sections running around the lateral face of the cone segment in question, as is indicated by the curve shown in FIG. 5. A tool path 70 such as this (also called a movement path or just a path) is also shown by way of example in FIG. 6, the infeed in the Z direction being shown as substantially enlarged for clarity compared to an infeed corresponding to an actual machining operation. For machining of the corresponding workpiece W the tool must hence move relative to the workpiece substantially along elliptical, spiral-shaped path sections.

[0097] In the cycle according to the invention the movement path 70 is advantageously described or generated in the form of a plurality of directly adjacent splines, in other words polynomials of the highest n.sup.th degree. This is particularly advantageous when such splines are processed directly by the CNC controller, i.e. can be used for the control of the relative movement between tool and workpiece by retrieving corresponding commands, as is the case for example with the SINUMERIK 840D CNC controller from Siemens for polynomials up to the 5.sup.th degree. The output format here is not a normal G code, consisting of straight lines or segments of a circle, but a polynomial code. Analogously to the G code customary in parts programs, the individual program instructions (commands) can in this way be generated block by block in the form of polynomial calls and can then be executed. The spline (polynomial) code generated in this way means that the individual spline segments can transition into one another “smoothly” (in a multiple continuously differentiable manner).

[0098] The movement path 70 path shown in FIG. 6 consists of many path segments in the form of splines 71, in other words polynomials, that transition into one another in a multiple differentiable manner. Thanks to the “smooth” transition between the splines, the start and end of an individual spline 71 cannot be seen in the movement path 70.

[0099] A preferred form of embodiment is described below for path generation on the lateral face of the cone and thus on the aforementioned splines.

[0100] For the technological description the path is (notionally) unrolled on the cone. In this case a certain infeed per revolution should be taken into account. As an illustration, a ball-end cutter can be imagined which rotates about the face of the cone and in this case moves continuously downward (or upward) on the cone.

[0101] To calculate a revolution from 0° to 360°, a subdivision is for example made into 32 angular segments. An angular segment is therefore 11.52° wide. Within an angular segment six equally divided horizontal intersections between the start height of the angular segment and the end height of the angular segment are calculated. Six points are then defined on the ellipses. The first point lies on the first ellipse at 0°. The second point lies on the second ellipse at 2.304°. The third point lies on the third ellipse at 4.608°. The further points are further defined in accordance with this pattern.

[0102] The procedure shown is illustrated in FIG. 7. The six aforementioned ellipse segments E1 to E6 and the points P1 to P6 lying respectively on the ellipse segments are shown. The points P1 to P6 lying on the ellipses E1 to E6 are connected to a spline 80. In a continuous definition of the splines for the further angular segments the continuous path can be defined for one revolution around the cone. A corresponding path section 81 is illustrated in FIG. 8. Many such continuous path sections of this type ultimately result in the path 70 illustrated in FIG. 6.

[0103] In connection with the invention, the tool path is advantageously not described in a Cartesian coordinate system, but in a polar coordinate system that is better suited for at least substantially circular movements. The SINUMERIK 840D CNC controller from Siemens is also ideal for this. A coordinate transformation between the different coordinate systems is also possible in one form of embodiment of a cycle according to the invention.

[0104] Further, in a preferred form of embodiment of the invention, a tool radius correction, known per se, is carried out during the machining of a workpiece by means of a tool. The tool radius correction permits the programming of the workpiece contour regardless of the geometry of the tool used. Hence during the parameterization of the cycle a tool radius can also advantageously be detected, which is taken into account during the path generation using the numerical controller.

[0105] The essential method steps in the performance of a method according to the invention are illustrated once again below in the form of a flow diagram in accordance with FIG. 9.

[0106] In a first method step S1 an executable cycle for producing and/or machining non-conical faces of a workpiece that can be defined by a segment of a cone is provided on a numerical controller of a machine tool connected to the controller.

[0107] In a method step S2 the cycle is retrieved by a user of the machine tool on a graphical user interface of the numerical controller of the machine tool.

[0108] In a method step S3 the user inputs the technology and geometry specifications required for the production or machining of the intended face of the workpiece on the graphical user interface of the numerical controller. The cycle is thereby “parameterized”.

[0109] In a method step S4 account is taken of the inputs made in method step S3 and a parts program that can be executed by the numerical controller is generated by the numerical controller and is stored in a memory of the numerical controller. Recourse can thereby once again be had to the parts program during the production or machining of structurally identical workpieces.

[0110] Besides the usual G code instructions, polynomial code instructions are advantageously also generated in the case of the parts program generated in this way, so that the individual segments of the tool path established by the parts program are made up not only of straight lines and segments of a circle, but at least in part also of polynomial segments (splines).

[0111] In a method step S5 the parts program created in this way is executed on the numerical controller and thus the machine tool for producing or machining the non-conical face of the workpiece that can be defined by a segment of a cone. Linked to this is the relative movement between the tool and the workpiece established by the parts program.