OPTIMISATION OF CHIP REMOVAL PROCESSES ON MACHINE TOOLS

Abstract

In a method for operating a machine tool system with a machine tool for machining a workpiece using a tool, a control device is connected to the machine tool for generating a relative movement between the workpiece and the tool using a program executable by the control device. The control device includes an operating unit having a display device, allowing an operator to interact with the control device. The operator can manually alter with the operating unit a technology parameter. However, the operator generally does not know how a manual alteration of a technology parameter will affect productivity. Therefore, a measure for a change to production-related characteristics variable resulting from the manual alteration is determined and displayed to the operator on the display device directly or in relation to an associated relative measure.

Claims

1.-15. (canceled)

16. A method for operating a machine tool system, the machine tool system comprising a machine tool with a tool for machining a workpiece, and a control apparatus connected to the machine tool for generating a relative movement between the workpiece and the tool using a program which can be executed by the control apparatus, with the control apparatus comprising an operating facility with a display apparatus for interaction between an operator and the control apparatus, said method comprising: altering manually by the operator using the operating facility a technology parameter; determining a change to a production-related characteristic variable brought about by the altered technology parameter; displaying the changed production-related characteristic variable on the display apparatus directly or in relation to an associated relative measure; determining the changed production-related characteristic variable with the control apparatus or with an external computing facility connected to the control apparatus; storing in the control apparatus or in the external computing facility a tool change time provided for a tool change or tool costs required for procuring the tool or a machine hour rate associated with operating the machine tool; and determining a measure for the change to the production-related characteristic variable as a function of at least one of the tool change time, the tool costs and the machine hour rate.

17. The method of claim 16, further comprising: employing for machining the workpiece or for machining a batch of the workpiece a number of identical tools, with the number of identical tools changing as a result of the manual alteration of the technology parameter; successively inserting with a tool changing apparatus the tools into a tool holder of the machine tool; and determining the change in the production-related characteristic variable as a function of the number of tools and a number of tool changes associated therewith.

18. The method of claim 16, further comprising after the measure for the change to the production-related characteristic variable is displayed on the display apparatus, requiring a further manual interaction of the operator with the operating facility before the machining of the workpiece is adapted to the altered technology parameter.

19. The method of claim 16, wherein at least one of the tool change time, the tool costs and the machine hour rate can be adjusted by interaction between the operator and the control apparatus or the external computing facility.

20. The method of claim 16, wherein the tool change time is measured and preferably continuously updated during the actual operation of the machine tool.

21. The method of claim 16, wherein the measure for the change to the production-related characteristic variable is determined as a function of measured values generated during the operation of the machine tool.

22. The method the claim 16, further comprising manually changing a feed rate or a spindle speed by the operator.

23. The method of claim 16, wherein the measure for the change to the production-related characteristic variable is displayed as an absolute value.

24. The method of claim 16, wherein the measure for the change to the production-related characteristic variable is displayed relative to an optimum of the relevant production-related characteristic variable.

25. The method of claim 16, wherein the production-related characteristic variable is a machining time necessary for machining the workpiece or machining costs associated with machining the workpiece.

26. A machine tool system, comprising: a machine tool with a tool for machining a workpiece; and a control apparatus connected to the machine tool for generating a relative movement between the workpiece and the tool, said control apparatus comprising an operating facility with a display apparatus for interaction between an operator and the control apparatus, said control apparatus, by using a program which can be executed by the control apparatus, configured to alter manually by the operator using the operating facility a technology parameter, determine a change to a production-related characteristic variable brought about by the altered technology parameter, display the changed production-related characteristic variable on the display apparatus directly or in relation to an associated relative measure, determine the changed production-related characteristic variable with the control apparatus or an external computing facility connected to the control apparatus, store in the control apparatus or in the external computing facility a tool change time provided for a tool change or tool costs required for procuring the tool or a machine hour rate associated with operating the machine tool, and determine a measure for the change to the production-related characteristic variable as a function of at least one of the tool change time, the tool costs and the machine hour rate.

27. The machine tool system of claim 26, wherein the external computing facility determines a measure for a machining time required for machining the workpiece or a measure for machining costs associated with machining the workpiece.

28. A control apparatus for a machine tool system having a machine tool with a tool for machining a workpiece, the control apparatus connected to the machine tool for generating a relative movement between the workpiece and the tool, and comprising an operating facility with a display apparatus for interaction between an operator and the control apparatus, the control apparatus, by using a program which can be executed by the control apparatus, configured to alter manually by the operator using the operating facility a technology parameter, determine a change to a production-related characteristic variable brought about by the altered technology parameter, display the changed production-related characteristic variable on the display apparatus directly or in relation to an associated relative measure, determine the changed production-related characteristic variable with the control apparatus or an external computing facility connected to the control apparatus, store in the control apparatus or in the external computing facility a tool change time provided for a tool change or tool costs required for procuring the tool or a machine hour rate associated with operating the machine tool, and determine a measure for the change to the production-related characteristic variable as a function of at least one of the tool change time, the tool costs and the machine hour rate.

Description

[0060] FIG. 1 shows a machine tool system with a numerically controlled machine tool,

[0061] FIG. 2 shows a display according to the invention on a display of a user interface,

[0062] FIG. 3 shows method steps for carrying out a method according to the invention,

[0063] FIG. 4 shows productivity as a function of technology parameters,

[0064] FIG. 5 shows a preferred operating range of the machine tool.

[0065] FIG. 1 shows a diagrammatic view of a machine tool system according to the invention in the form of a machining center 1 for the 5-axis machining of a workpiece 2 by at least one tool 3. The machining center 1 comprises a machine tool 5 which is fastened to a machine frame 4. The machine tool 5 comprises a stand 8 which is movable along the axis X, and a slide 9 which is movably mounted thereon along the axes Y and Z, and which carries a spindle 10. The spindle 10 can be driven in rotation about the axis C and is provided for receiving a tool 3. Moreover, the spindle 10 is mounted so as to be pivotable about an axis S, the spindle axis C describing a movement on a conical surface during pivoting. The angle between the spindle axis C and the pivot axis S is 45°, resulting in a cone angle of 90°. As a result of this arrangement, the spindle 10 can assume any desired angle of inclination between a horizontal and a vertical extreme position.

[0066] The machine tool 5 further comprises a slide 11 which is movable along the axis Z and carries a workpiece table 12 which can be driven in rotation about the axis B and is provided with corresponding fastening and clamping means (not shown) for receiving a workpiece 2.

[0067] A CNC controller 14 is provided for controlling the machining center 1. The CNC controller 14 executes a control function by processing a part program in real time and thereby controls the relative movement between the tool 3 and the workpiece 2 in real time. In this case, input data or input signals (“actual values”) of the machine tool 5 are continuously recorded by the controller 14, and the CNC controller 14 generates output signals in the form of control commands for the drives (not shown) of the machine tool 5, including these actual values.

[0068] The CNC controller 14 has, inter alia, as essential components a real-time kernel NCK (Numerical Control Kernel), a PLC (Programmable Logic Control) and an HMI unit 15 (Human-Machine Interface) with a display 16 for the operation of the machining center 1 by an operator 6.

[0069] The machining center 1 enables machining processes to be carried out by cutting technology with geometrically determined cutting edges, such as for example milling, turning, drilling, thread cutting, rotary milling, honing, etc., but also machining processes with geometrically undefined cutting edges, such as for example, grinding. Furthermore, chipless manufacturing methods such as roller burnishing or thread forming can be carried out. The production of a desired workpiece shape takes place within the working space 13 of the machine tool 5 by means of a sequence of different machining processes, for which tools 3 are moved with the workpiece 2 relative to one another along programmed paths and brought into engagement with one another. The tools 3 required for carrying out the machining processes are held in a tool magazine 7 and, in accordance with the machining sequence, are successively inserted into the spindle 10 by means of a tool changing facility (not shown).

[0070] With the machining center 1 shown, 5-axis machining operations can be carried out, which are required, for example, during the milling of free-form surfaces—for example, during the milling of turbine blades.

[0071] The controller 14 is designed such that initially predetermined technology parameters relating to the machining can be changed by manual actuation of the user interface 15 by the user 6. For example, a feed rate can be specified in a part program stored in the controller 14 and can be changed by the user 6 by actuating an override controller present at the user interface.

[0072] According to the invention, the effects of this change are first determined and displayed to the user in the form of a change in a production-related characteristic variable on the display 16 of the controller 14.

[0073] By way of example, FIG. 2 shows such a display on the display 16. In the example, the feed rate was increased from normal 100% to 120% (diagram 20). It can be seen from the display that this change in the feed rate would result in an increase in the total machining time to approx. 106% (diagram 21) and the total machining costs to approx. 119% (diagram 22). These initially unexpected effects can be explained, for example, by the fact that, during the intended machining, the tools used wear faster as a result of increasing the feed rate, which in turn causes a higher consumption of tools and increased, and more frequent, tool changes.

[0074] It is particularly advantageous if the manual change in a technology parameter, in the example the feed rate, does not have an immediate effect on the machining currently being carried out, but instead, for the implementation of the control function, the original value of the technology parameter is initially retained and the change in the production-related characteristic variable caused by the change is determined only in a simulation. The operator thus has the possibility of incorporating this feedback into his considerations and, if appropriate, not carrying out the change or carrying it out differently before anything at all changes with regard to the machining of the workpiece. For example, it is possible to prevent the user from inadvertently reducing the productivity of the machine by his manual intervention. In order that the manual parameter change performed actually affects the actual machining, in this exemplary embodiment, the “confirm” button 23 shown in FIG. 2 must first be actuated to confirm the change, for example by touching the button 23 on the display 16 embodied as a touch display.

[0075] FIG. 3 illustrates an exemplary embodiment for carrying out a method according to the invention. In a first method step S1, by means of interaction between an operator and the control apparatus, the operator manually changes a specific technology parameter.

[0076] In a second method step S2, a measure of a change in a production-related characteristic variable caused by the change carried out in step S1 is determined and displayed on the display of the controller.

[0077] In a step S3, the user makes a further manual input to confirm the change in the technology parameter made in step S1.

[0078] In a step S4, the changed technology parameter in the control apparatus is taken into account when generating the relative movement between the workpiece and the tool.

[0079] FIG. 4 illustrates the relationship between production-related characteristic variable such as productivity and some technology parameters which can be changed by an operator on the machine tool (feed rate v.sub.f, cutting speed v.sub.c, intervention depth a.sub.p or intervention width a.sub.e). The curve K1 (dashed line), in this case a straight line, illustrates the chip removal volume for the unrealistic application that no tool changes are required. The chip removal volume increases here, for example, in a linear manner with the feed rate.

[0080] The number of tool changes required for a specific actual machining operation is shown in the curve 2 (dotted line), Due to wear and tear, a disproportionately large number of tools are required as the chip removal volume of the tool in engagement increases.

[0081] The curve K3 illustrates productivity taking into account the wear-related tool change. It can be seen from this that productivity initially increases to an optimum with increasing chip removal volume (per unit of time) and decreases again after this optimum.

[0082] FIG. 5 illustrates, by way of example, a preferred range with regard to the feed rate v.sub.f, which is preferably in a range between the values v.sub.f1 and v.sub.F2 and is thus determined in such a way that the productivity P deviates from its maximum at most by a predetermined value ΔP. The operator preferably receives an additional warning message on the machine if the machine is located at an operating point outside the preferred operating range defined in this way.

[0083] On the basis of the procedure proposed here, the employee who determines the process receives business data relevant to the process which supports him in his decision-making. Although the non-linear dependencies are still present in the process, decisions made in the past, for example, are clearly mirrored to the employee with regard to the mode of action, so that he can better make the upcoming decisions.

[0084] The invention leads to an incremental improvement of the processes and has considerable potential in terms of savings, increased effectiveness and optimization of the cost situation.

[0085] On the basis of such an online process evaluation, it is even possible to optimally adjust the processes to the current utilization situation, for example by specifying a guideline or an abstract target variable (for example, TCO/base chip removal rate).