Workpiece, system and method for thermal error measurement of five-axis machining center

Abstract

The invention provides a workpiece for thermal error measurement of a five-axis machining center, the surface of the workpiece is provided with a plurality of blind holes, the blind holes extend into the workpiece from the surface of the workpiece, the cross section of each blind hole is circular, the number of the blind holes is at least three, and the blind holes at least meet two of a first arrangement mode, a second arrangement mode and a third arrangement mode, according to the first arrangement mode, the connecting line of the circle centers of at least two blind holes is perpendicular to the first direction; according to the second arrangement mode, the connecting line of the circle centers of at least two blind holes is perpendicular to the second direction, and the second direction is perpendicular to the first direction; according to the third arrangement mode, the connecting line or the extension line of the circle centers of at least two blind holes passes through the rotating center point of the workpiece. The invention further provides a system and a method for measuring the thermal error of the five-axis machining center.

Description

Technical Field

[0001] This application relates to the field of machine tool precision measurement technology, and more specifically, to a workpiece, system, and method for measuring thermal errors in a five-axis machining center. Background Technology

[0002] As a foundation of current manufacturing development, the development level of machining centers is an important indicator of the modernization level of equipment. Thermal error accounts for approximately 40% to 70% of the machining error in machining centers, making it one of the main sources of machine tool error. Compared to three-axis machining centers, five-axis machining centers add two rotary axes, thus making the formation mechanism of thermal error more complex and its measurement more difficult.

[0003] Currently, thermal errors in five-axis machining centers are mainly detected using displacement sensors, laser trackers, R-test measuring instruments, and trigger probes. GB / T17421.3 specifies a method for detecting machine tool thermal errors using displacement sensors; however, this method can only measure thermal error changes at a single point in the machine tool's workspace and cannot reflect the overall thermal error level across the entire workspace. Laser trackers can reflect machine tool thermal errors by measuring changes in the spindle tool's position; however, laser trackers are primarily mounted on a bracket, and their measurement results reflect the positional change of the spindle tool relative to the ground, not the error relative to the workpiece. R-test measuring instruments can reflect machine tool thermal errors by measuring changes in the position of standard balls on the worktable, and multiple standard balls can be used to reflect the overall thermal error level across the entire workspace. However, R-test measuring instruments are expensive to manufacture and technically challenging. Trigger probes operate on a similar principle to R-test measuring instruments, reflecting the overall thermal error level across the entire workspace by measuring changes in the position of standard balls at different locations on the worktable. However, trigger probes require long measurement times, leading to variations in the machine tool's temperature field at different measurement points, which affects measurement accuracy. Summary of the Invention

[0004] In view of the above problems, this application provides a workpiece, system and method for measuring thermal error in a five-axis machining center.

[0005] According to a first aspect of this application, a workpiece for thermal error measurement in a five-axis machining center is provided. The workpiece surface has a plurality of blind holes extending from the workpiece surface into the workpiece interior. The cross-section of each blind hole is circular. The number of blind holes is at least three, and the blind holes satisfy at least two of a first arrangement, a second arrangement, and a third arrangement.

[0006] The first arrangement includes a line connecting the centers of at least two blind holes that is perpendicular to a first direction; the second arrangement includes a line connecting the centers of at least two blind holes that is perpendicular to a second direction, the second direction being perpendicular to the first direction; the third arrangement includes a line or extension of the line connecting the centers of at least two blind holes that passes through the rotation center of the workpiece.

[0007] According to an embodiment of this application, the blind hole is cylindrical.

[0008] According to an embodiment of this application, the blind hole has at least one stepped surface, and along the axial direction of the blind hole, the stepped surface divides the blind hole into at least two coaxial measuring holes, the measuring holes being cylindrical; from the top surface to the bottom surface of the blind hole, the diameter of the measuring holes decreases sequentially.

[0009] According to a second aspect of this application, a system for measuring thermal errors in a five-axis machining center is provided, comprising:

[0010] A five-axis machining center, wherein the five-axis machining center has a worktable;

[0011] The workpiece is fixed on the worktable, and the workpiece is the workpiece for thermal error measurement of a five-axis machining center as described in any of the above-mentioned items;

[0012] The scanning probe is mounted on the machine tool spindle of the five-axis machining center.

[0013] The machining tools are placed in the tool magazine of the five-axis machining center.

[0014] A tool changing mechanism for replacing the scanning probe located on the machine tool spindle with the machining tool, and / or replacing the machining tool located on the machine tool spindle with the scanning probe.

[0015] According to a third aspect of this application, a method for measuring thermal error in a five-axis machining center is provided, comprising:

[0016] A workpiece is provided and fixedly installed in the working area of ​​the worktable of a five-axis machining center, wherein the workpiece is the workpiece for thermal error measurement of a five-axis machining center as described in any of the above claims;

[0017] A scanning probe is installed on the spindle of the five-axis machining center, and machining tools are placed in the tool magazine of the five-axis machining center.

[0018] When the five-axis machining center is in the initial position, the scanning probe is used to fit the center coordinates of the bottom surface of the blind hole as initial data;

[0019] The workpiece is machined using the machining tool in five-axis linkage. After machining, the workpiece returns to the initial position and the scanning probe is used again to fit the center coordinates of the bottom surface of the blind hole as measurement data. This step is repeated M times to obtain 1 to M batches of measurement data, where M is an integer greater than or equal to 1.

[0020] The thermal error of each batch (1 to M) is calculated by referring to the initial data.

[0021] According to an embodiment of this application, after installing the scanning probe on the machine tool spindle, the method further includes: using the scanning probe to establish a workpiece coordinate system at the center of the bottom surface of each blind hole.

[0022] According to an embodiment of this application, fitting the center coordinates of the bottom surface of the blind hole using the scanning probe includes:

[0023] The scanning probe extends into the blind hole, closely follows the inner wall and bottom surface of the blind hole, and circles around to obtain circumferential data of the blind hole;

[0024] The center coordinates of the bottom surface of the blind hole are fitted based on the circumferential data of the blind hole.

[0025] According to an embodiment of this application, when measuring the circumferential data of the blind hole, the measurement speed of the scanning probe is between 3000 mm / min and 10000 mm / min.

[0026] According to an embodiment of this application, before performing five-axis linkage machining, the scanning probe is replaced with the machining tool by a tool changing mechanism; after performing five-axis linkage machining, the machining tool is replaced with the scanning probe by a tool changing mechanism.

[0027] According to an embodiment of this application, before performing five-axis linkage machining on the workpiece, the method further includes: calculating the tool changing error of the five-axis machining center, and adjusting the tool changing mechanism and the machine tool spindle according to the tool changing error until the tool changing error is less than a preset value.

[0028] The above one or more embodiments have the following beneficial effects:

[0029] 1. The workpiece surface used for thermal error measurement in a five-axis machining center has multiple blind holes with circular cross-sections. During measurement, the scanning probe closely follows the inner wall and bottom surface of the blind hole, circling it to obtain the coordinates of various points around the circumference of the blind hole, which serve as the basis for subsequent thermal error calculation. This measurement method enables rapid measurement of multiple blind holes, avoiding differences in temperature fields due to excessively long measurement times, thus improving the accuracy of the measurement results.

[0030] 2. During the measurement process, ensuring that the workpiece covers the actual machining space of the machine tool allows the measurement results to reflect the thermal error level of the entire working space of the machine tool, preventing incomplete thermal error assessment caused by localized machining.

[0031] 3. Before performing thermal error measurement, the workpiece is machined in five-axis linkage using machining tools to make the generated thermal error close to the thermal error generated in actual operation. This provides more realistic thermal error data for the subsequent measurement process, so that the measurement results can truly reflect the performance of the five-axis machining center.

[0032] 4. The workpiece and system for measuring thermal errors in five-axis machining centers provided in this application have low manufacturing costs, and the method for measuring thermal errors in five-axis machining centers using this workpiece and system is relatively simple, which helps to reduce measurement costs and improve measurement efficiency. Attached Figure Description

[0033] The above-mentioned contents, other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0034] Figure 1 This illustration schematically shows a structural diagram of a workpiece for thermal error measurement in a five-axis machining center according to an embodiment of this application;

[0035] Figures 2a-2b A schematic cross-sectional view of a workpiece for measuring thermal error in a five-axis machining center according to an embodiment of this application is shown.

[0036] Figure 3 The schematic diagram illustrates the structure of a system for measuring thermal errors in a five-axis machining center according to an embodiment of this application;

[0037] Figure 4 The schematic diagram illustrates the steps of measuring thermal error in a five-axis machining center according to an embodiment of this application;

[0038] Figure 5 A schematic diagram illustrating the thermal error measurement sequence of a five-axis machining center according to an embodiment of this application is shown.

[0039] It should be noted that, for clarity, the dimensions of the overall / partial structure or the overall / partial region in the drawings used to describe the embodiments of this application may be enlarged or reduced, that is, these drawings are not drawn to actual scale.

[0040] Component designation explanation

[0041] 10 workpiece 100 blind hole 101 Step surface 102 First measuring hole 103 Second measuring hole 110 Fixing hole 20 5-axis machining center 21 workbench 30 Scanning probe Detailed Implementation

[0042] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0043] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0044] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0045] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0046] A five-axis CNC machine tool is an advanced machining equipment that adds two rotary axes (any two of the A, B, and C axes) to the conventional three-axis (X, Y, and Z axes). This allows the cutting tool to approach the workpiece at complex angles and directions, enabling single-set machining of complex-shaped workpieces, such as blades and molds. It significantly improves machining efficiency, reduces the number of setups and errors, and achieves high machining accuracy, making it widely used in high-end manufacturing fields such as aerospace, automotive, and shipbuilding. However, in related technologies, thermal error measurement in five-axis machining centers suffers from problems such as incomplete measurement, reference deviation, high technical difficulty, and relatively low measurement accuracy.

[0047] This application provides a workpiece, system, and method for measuring thermal error in a five-axis machining center. The workpiece surface has multiple blind holes extending from the workpiece surface into the workpiece interior. The cross-section of each blind hole is circular, and the number of blind holes is at least three. The blind holes satisfy at least two of the following arrangements: a first arrangement, a second arrangement, and a third arrangement. The first arrangement includes a line connecting the centers of at least two blind holes that is perpendicular to a first direction. The second arrangement includes a line connecting the centers of at least two blind holes that is perpendicular to a second direction, which is perpendicular to the first direction. The third arrangement includes a line or extension of the line connecting the centers of at least two blind holes that passes through the rotation center of the workpiece.

[0048] According to an embodiment of this application, the workpiece surface has multiple blind holes with circular cross-sections. During measurement, the scanning probe closely follows the inner wall and bottom surface of the blind hole, circling around to obtain the coordinates of various points on the circumference of the blind hole, which serve as the basis for subsequent thermal error calculation. This measurement method enables rapid measurement of multiple blind holes, avoiding differences in temperature fields due to excessive measurement time. During the measurement process, the workpiece covers the actual machining space of the machine tool, and the measurement results reflect the thermal error level of the entire working space of the machine tool. Before thermal error measurement, the workpiece is machined using a machining tool in a five-axis linkage manner to make the generated thermal error close to the thermal error generated in actual operation, providing more realistic thermal error data for subsequent measurement. The workpiece and system for thermal error measurement of a five-axis machining center provided in this application have low manufacturing costs and simple measurement methods, which help reduce measurement costs and improve measurement efficiency.

[0049] Figure 1 The schematic diagram illustrates the structure of a workpiece for thermal error measurement in a five-axis machining center according to an embodiment of this application.

[0050] like Figure 1 As shown, the surface of the workpiece 10 has a plurality of blind holes 100, which extend from the surface of the workpiece to the interior of the workpiece.

[0051] According to an embodiment of this application, the cross-section of the blind hole 100 is circular. When performing thermal error measurement, it is necessary to obtain the center point of the blind hole 100. Therefore, the cross-section of the blind hole 100 is designed to be circular, which facilitates the scanning probe to obtain the circumferential data of the blind hole 100, thereby fitting the center of the blind hole 100.

[0052] According to embodiments of this application, the number of blind holes 100 is at least three, and their arrangement satisfies at least two of the following arrangements: a first arrangement, a second arrangement, and a third arrangement. The first arrangement includes a line connecting the centers of at least two blind holes 100 perpendicular to a first direction. Figure 1The X-axis direction is shown to facilitate the measurement of the thermal error of the five-axis machining center in the A-axis direction, where the A-axis direction represents the direction of rotation about the X-axis. The second arrangement includes at least two blind holes 100 whose centers are connected by a line perpendicular to the second direction (…). Figure 1 The first arrangement (shown in the Y-axis direction) facilitates the measurement of the thermal error of the five-axis machining center in the B-axis direction, where the B-axis direction represents the direction of rotation around the Y-axis. The third arrangement includes a line or extension connecting the centers of at least two blind holes 100 passing through the workpiece's rotation center point, facilitating the measurement of the thermal error of the five-axis machining center in the C-axis direction, where the C-axis direction represents the direction of rotation around the Z-axis. When the arrangement of multiple blind holes 100 satisfies two of the first, second, and third arrangement methods, the thermal error of any two of the A, B, and C axes of the five-axis machining center can be measured using the workpiece 10.

[0053] In one optional embodiment, the number of blind holes 100 is set to nine, and the nine blind holes 100 are arranged in a rectangular and uniform manner on the surface of the workpiece 10. In other optional embodiments, the multiple blind holes 100 can have other arrangement forms, such as triangular, circular, irregular shapes, etc., and the multiple blind holes 100 can also be non-uniformly arranged. In addition, the distribution of blind holes 100 can be adjusted according to the commonly used machining areas of the machine tool. For example, more blind holes 100 should be arranged in the commonly used machining areas of the machine tool, and fewer blind holes 100 should be arranged in the less commonly used machining areas of the machine tool. By more rationally distributing the blind holes 100, the thermal error information of the machine tool in the commonly used and less commonly used machining areas can be obtained more accurately.

[0054] According to embodiments of this application, the depth of the blind hole 100 is between 3mm and 40mm, and the diameter of the blind hole 100 is at least 10mm. The depth of the blind hole 100 can be designed according to actual measurement needs. At different heights, the thermal deformation of the machine tool may vary. Designing the blind hole 100 to have different depths allows for the measurement of the thermal error of the machine tool at different heights in the Z-axis direction. However, during the same measurement process, data from multiple blind holes 100 at the same height needs to be collected to ensure the accuracy of the measurement results and avoid additional error factors caused by height variations.

[0055] like Figure 2a As shown, in one alternative embodiment, the blind hole 100 is cylindrical, and the depths of the multiple blind holes 100 are the same. In this case, the workpiece 10 can be used to measure the thermal error of the machine tool at a fixed height. In another alternative embodiment, the blind hole 100 is cylindrical, and the depths of the multiple blind holes 100 may be different. In this case, the workpiece 10 can be used to measure the thermal error of the machine tool at different fixed heights.

[0056] In another alternative embodiment, the blind hole 100 may have at least one stepped surface 101 along the axial direction of the blind hole 100. Figure 2b (As shown in the Z-axis direction), the stepped surface 101 divides the blind hole 100 into at least two coaxial cylindrical measuring holes, and the diameter of the measuring holes decreases sequentially from the top surface to the bottom surface of the blind hole 100. Taking a blind hole 100 with one stepped surface 101 as an example, as... Figure 2b As shown, the stepped surface 101 divides the blind hole 100 into a first measuring hole 102 and a second measuring hole 103. The first measuring hole 102 is located above the second measuring hole 103, and the diameter of the first measuring hole 102 is larger than the diameter of the second measuring hole 103. In this case, the scanning probe can be closely attached to the inner wall of the stepped surface 101 and the first measuring hole 102 to measure the thermal error of the machine tool at the height of the stepped surface 101. In addition, the scanning probe can also be closely attached to the bottom surface and inner wall of the second measuring hole 103 to measure the thermal error of the machine tool at the height of the bottom surface of the second measuring hole 103. This enables comprehensive detection of the thermal error of the machine tool at different height positions, meeting different measurement needs.

[0057] According to an embodiment of this application, the surface of the workpiece 10 also has a fixing hole 110. When performing thermal error measurement, a fastener is inserted into the fixing hole 110 to fix the workpiece 10 on the worktable of the five-axis machining center.

[0058] Figure 3 The schematic diagram illustrates the structure of a system for measuring thermal errors in a five-axis machining center according to an embodiment of this application.

[0059] like Figure 3 As shown, the system for measuring thermal error in a five-axis machining center includes a workpiece 10, a five-axis machining center 20, a scanning probe 30, a machining tool (not shown in the figure), and a tool changer (not shown in the figure).

[0060] According to an embodiment of this application, a five-axis machining center 20 has a worktable 21, and a workpiece 10 is fixed to the worktable 21 by fasteners (not shown in the figure). The workpiece 10 should cover the actual machining space of the machine tool, including the entire working space inside and outside the worktable 21. The workpiece 10 is the workpiece used for thermal error measurement of the five-axis machining center as described above, and the specific details can be found in the above description, which will not be repeated here.

[0061] According to an embodiment of this application, the scanning probe 30 is mounted on the machine tool spindle of a five-axis machining center 20 for measuring the blind hole 100 on the surface of the workpiece 10. During the measurement process, the machining tool and the scanning probe 30 can be switched by operating the tool changing mechanism of the machine tool's CNC system.

[0062] According to an embodiment of this application, a machining tool (not shown in the figure) is placed in the tool magazine of a five-axis machining center for five-axis simultaneous machining of the area outside the blind hole 100 on the surface of the workpiece 10 to generate thermal error.

[0063] According to an embodiment of this application, a tool changing mechanism (not shown in the figures) is used to replace the scanning probe 30 located on the machine tool spindle with a machining tool, and / or to replace the machining tool located on the machine tool spindle with the scanning probe 30.

[0064] Figure 4 The diagram illustrates the steps for measuring thermal error in a five-axis machining center according to an embodiment of this application.

[0065] like Figure 4 As shown, the method for measuring thermal error in a five-axis machining center in this embodiment includes operations S210 to S250.

[0066] In operation S210, a workpiece is provided and fixedly mounted in the working area of ​​the worktable of the five-axis machining center.

[0067] According to the embodiments of this application, referring to Figure 3 As shown, workpiece 10 is fixed to the worktable 21 by fasteners. Workpiece 10 should cover the actual machining space of the machine tool, including the entire working space inside and outside the worktable 21. Workpiece 10 is the workpiece used for thermal error measurement of the five-axis machining center as described above, and will not be repeated here. By ensuring that the workpiece covers the actual machining space of the machine tool, the subsequent measurement results can reflect the thermal error level of the entire working space of the machine tool, preventing the problem of incomplete thermal error assessment caused by local machining.

[0068] When operating the S220, a scanning probe is installed on the spindle of the five-axis machining center, and machining tools are placed in the tool magazine of the five-axis machining center.

[0069] Reference Figure 3 As shown, a scanning probe 30 is installed on the spindle of a five-axis machining center, and a workpiece coordinate system is established at the center of the bottom surface of each blind hole 100 using the scanning probe 30. Additionally, machining tools are placed in the tool magazine of the five-axis machining center to replace the scanning probe 30 during the measurement process.

[0070] When operating S230, with the five-axis machining center in its initial position, the center coordinates of the blind hole bottom surface are fitted using the scanning probe as initial data.

[0071] According to an embodiment of this application, the scanning probe 30 extends into the blind hole 100, closely follows the inner wall and bottom surface of the blind hole 100, and circles around to obtain circumferential data of the blind hole 100. The circumferential data is the coordinates of each point on the circumference. The center coordinates of the bottom surface of the blind hole 100 are fitted based on the circumferential data of the blind hole 100 as initial data.

[0072] According to an embodiment of this application, fitting the center coordinates of the bottom surface of the blind hole 100 includes: fitting a circle to the circumferential data of the blind hole 100 using the least squares method, establishing the equation of the circle, optimizing the parameters in the equation based on the known point coordinates, so that the sum of the squares of the distances from these points to the fitted circle point is minimized, and obtaining the center coordinates of the bottom surface of the blind hole 100.

[0073] In an optional embodiment, the surface of workpiece 10 has nine blind holes 100, such as Figure 5 As shown, measurements were taken sequentially at the nine blind holes 100 in the order indicated by the arrows. The initial coordinates of the first measuring point of the first blind hole were marked as follows: , And so on.

[0074] According to an embodiment of this application, when measuring the circumferential data of the blind hole 100, the measurement speed of the scanning probe 30 is between 3000 mm / min and 10000 mm / min. When the measurement speed is 3000 mm / min, the measurement time for measuring the center of the bottom surface of the blind hole 100 with a diameter of 20 mm is less than or equal to 1.5 s, which can achieve rapid measurement and avoid the situation where different characteristic temperature fields are different due to excessive measurement time.

[0075] In operation S240, the workpiece is machined using a five-axis linkage tool. After machining, the workpiece returns to the initial position and the scanning probe is used again to fit the center coordinates of the bottom surface of the blind hole as measurement data. This step is repeated M times to obtain 1 to M batches of measurement data, where M is an integer greater than or equal to 1.

[0076] According to an embodiment of this application, before performing five-axis linkage machining, the method further includes: calculating the tool changing error of the five-axis machining center, and adjusting the tool changing mechanism and the machine tool spindle according to the tool changing error until the tool changing error is less than a preset value. Specifically, the scanning probe 30 on the machine tool spindle is replaced with a machining tool using the tool changing mechanism, and then the machining tool is replaced with the scanning probe 30. The scanning probe 30 is then fitted to the center coordinates of the bottom surface of the blind hole 100 again. The measurement result is compared with the initial data in step S230 to calculate the tool changing error. If the tool changing error is less than the preset value, five-axis linkage machining can be performed; otherwise, the tool changing mechanism and the machine tool spindle need to be adjusted until the tool changing error is less than the preset value. In an optional embodiment, the preset value is 0.01 mm.

[0077] According to an embodiment of this application, the scanning probe 30 is replaced with a machining tool via the tool changing mechanism of the machine tool. Following a set operating program, the machining tool performs five-axis simultaneous machining in the area outside the blind holes 100 on the surface of the workpiece 10 for approximately 15 minutes, causing the various components of the machine tool to heat up. After machining, the machine tool stops moving, and the scanning probe 30 is removed from the machine tool magazine via the tool changing mechanism. The circumferential data of multiple blind holes 100 are measured again to fit the center coordinates of the bottom surfaces of the multiple blind holes 100. The measurement sequence is as follows: Figure 5 As indicated by the arrow; repeat this step M times to obtain batches of measurement data from 1 to M. By using machining tools for five-axis simultaneous machining, the generated thermal error is made close to the thermal error generated in actual operation, thus providing more realistic thermal error data for subsequent measurement processes, enabling the measurement results to truly reflect the performance of the five-axis machining center.

[0078] According to an embodiment of this application, the measurement data is recorded as , , where j is the j-th blind hole of the workpiece, j = 1, 2...N, and k is the batch of measurement data, k = 1, 2...M.

[0079] When operating S250, the thermal error of the corresponding batch is calculated by referring to the initial data for the measurement data of batches 1 to M.

[0080] According to the embodiments of this application, the X-axis thermal deformation of the j-th blind hole in the k-th batch is calculated using formula (1), the Y-axis thermal deformation of the j-th feature in the k-th batch is calculated using formula (2), and the Z-axis thermal deformation of the j-th feature in the k-th batch is calculated using formula (3).

[0081] (1),

[0082] (2),

[0083] (3),

[0084] Where, k j .

[0085] According to the embodiments of this application, the A-axis thermal deformation of the j-th blind hole in the k-th batch is calculated using formula (4), the B-axis thermal deformation of the j-th blind hole in the k-th batch is calculated using formula (5), and the C-axis thermal deformation of the j-th blind hole in the k-th batch is calculated using formula (6).

[0086] (4),

[0087] (5),

[0088] (6),

[0089] Where, k j a and b are two distinct numbers in [1, N], and the line connecting the centers of the a-th blind hole and the b-th blind hole is perpendicular to the X-axis; c and d are two distinct numbers in [1, N], and the line connecting the centers of the c-th blind hole and the d-th blind hole is perpendicular to the Y-axis; e and f are two distinct numbers in [1, N], and the line connecting the centers of the e-th blind hole and the f-th blind hole, or their extension, passes through the rotation center of the workpiece 10.

[0090] According to the embodiments of this application, by calculating the thermal error of batches 1 to M, the thermal error of the machine tool at different times can be reflected; in addition, multiple blind holes 100 are distributed at different positions on the surface of the workpiece 10, and M measurements are performed on each blind hole 100 to calculate the corresponding thermal error amount, which can reflect the thermal error level of the entire working area of ​​the machine tool.

[0091] The embodiments of this application have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of this application. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this application is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this application, and all such substitutions and modifications should fall within the scope of this application.

Claims

1. A workpiece for measuring thermal error in a five-axis machining center, characterized in that, The workpiece surface has multiple blind holes extending from the workpiece surface into the workpiece interior. Each blind hole has a circular cross-section, and the number of blind holes is at least three. The blind holes satisfy at least two of the following arrangements: a first arrangement, a second arrangement, and a third arrangement. The first arrangement includes a line connecting the centers of at least two blind holes that is perpendicular to a first direction; the second arrangement includes a line connecting the centers of at least two blind holes that is perpendicular to a second direction, the second direction being perpendicular to the first direction; the third arrangement includes a line or extension of the line connecting the centers of at least two blind holes that passes through the rotation center of the workpiece.

2. The workpiece for thermal error measurement in a five-axis machining center according to claim 1, characterized in that, The blind hole is cylindrical.

3. The workpiece for thermal error measurement in a five-axis machining center according to claim 1, characterized in that, The blind hole has at least one stepped surface, which divides the blind hole into at least two coaxial measuring holes along the axial direction of the blind hole. The measuring holes are cylindrical. The diameter of the measuring holes decreases sequentially from the top surface to the bottom surface of the blind hole.

4. A system for measuring thermal error in a five-axis machining center, characterized in that, include: A five-axis machining center, wherein the five-axis machining center has a worktable; The workpiece is fixed on the worktable, and the workpiece is the workpiece used for thermal error measurement of a five-axis machining center as described in any one of claims 1 to 3; The scanning probe is mounted on the machine tool spindle of the five-axis machining center. The machining tools are placed in the tool magazine of the five-axis machining center. A tool changing mechanism for replacing the scanning probe located on the machine tool spindle with the machining tool, and / or replacing the machining tool located on the machine tool spindle with the scanning probe.

5. A method for measuring thermal error in a five-axis machining center, characterized in that, include: A workpiece is provided and fixedly installed in the working area of ​​the worktable of a five-axis machining center, wherein the workpiece is the workpiece used for thermal error measurement of a five-axis machining center as described in any one of claims 1 to 3; A scanning probe is installed on the spindle of the five-axis machining center, and machining tools are placed in the tool magazine of the five-axis machining center. When the five-axis machining center is in the initial position, the scanning probe is used to fit the center coordinates of the bottom surface of the blind hole as initial data; The workpiece is machined using the machining tool in five-axis linkage. After machining, the workpiece returns to the initial position and the scanning probe is used again to fit the center coordinates of the bottom surface of the blind hole as measurement data. This step is repeated M times to obtain 1 to M batches of measurement data, where M is an integer greater than or equal to 1. The thermal error of each batch (1 to M) is calculated by referring to the initial data.

6. The method for measuring thermal error in a five-axis machining center according to claim 5, characterized in that, After installing the scanning probe on the machine tool spindle, the method further includes: using the scanning probe to establish a workpiece coordinate system at the center of the bottom surface of each blind hole.

7. The method for measuring thermal error in a five-axis machining center according to claim 5, characterized in that, Fitting the center coordinates of the bottom surface of the blind hole using the scanning probe includes: The scanning probe extends into the blind hole, closely follows the inner wall and bottom surface of the blind hole, and circles around to obtain circumferential data of the blind hole; The center coordinates of the bottom surface of the blind hole are fitted based on the circumferential data of the blind hole.

8. The method for measuring thermal error in a five-axis machining center according to claim 7, characterized in that, When measuring the circumferential data of the blind hole, the measurement speed of the scanning probe is between 3000 mm / min and 10000 mm / min.

9. The method for measuring thermal error in a five-axis machining center according to claim 5, characterized in that, Before performing five-axis linkage machining, the scanning probe is replaced with the machining tool by a tool changing mechanism; after performing five-axis linkage machining, the machining tool is replaced with the scanning probe by a tool changing mechanism.

10. The method for measuring thermal error in a five-axis machining center according to claim 9, characterized in that, Before performing five-axis linkage machining on the workpiece, the method further includes: calculating the tool changing error of the five-axis machining center, and adjusting the tool changing mechanism and the machine tool spindle according to the tool changing error until the tool changing error is less than a preset value.

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