Numerical control machine tool workbench thermal displacement correction method and structure

Abstract

The invention discloses a numerical control machine tool workbench thermal displacement correction method and structure, a reading head assembly is fixed on a machine tool body, a measuring scale assembly is fixed on a workbench, the reading head assembly and the measuring scale assembly are located on the same straight line, the axis of a main shaft and the reading head assembly are located in the same plane, and the plane is perpendicular to the moving direction of the workbench. The screw rod generates heat to generate thermal displacement, the coordinates of the workbench integrally deviate, and the measuring scale assembly automatically aligns the originally set coordinates after detecting the deviation of the coordinates, so that the thermal displacement generated by the screw rod is corrected; when the working table deforms, the measuring scale assembly deforms together, the coordinate position of the working table is corrected through the measuring scale assembly, the position of the reading head assembly relative to the machine tool spindle in the moving direction of the working table is accurate, at the moment, the relative size between machining features of parts on the working table is accurate, and therefore the effect of correcting the thermal displacement of the working table is achieved. Thermal displacement correction is conducted on the numerical control machine tool workbench in real time, and the positioning accuracy of the workbench is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of machine tools, and in particular to a method for correcting the thermal displacement of a CNC machine tool worktable and a structure for correcting the thermal displacement of a CNC machine tool worktable by implementing the above method. Background Technology

[0002] Measuring ruler reading heads can automatically identify the accuracy errors of machine tools during the machining process and automatically compensate for these errors through a feedback system, thereby improving machining accuracy. Therefore, measuring ruler reading heads are widely used in CNC machine tools.

[0003] The existing measuring scale reading head structure has the reading head, measuring scale, and drive unit nut seat on the same side of the worktable. The drive unit drives the worktable to reciprocate along the machine bed. After prolonged reciprocating motion, the lead screw heats up, causing thermal displacement. Simultaneously, the nut also heats up, and this heat is transferred to the worktable, causing localized temperature rise and thermal displacement. Because the reading head and measuring scale are relatively close to the nut in the direction of worktable movement, the relative thermal displacement error between them is negligible. The thermal displacement of the lead screw pushes the worktable to change accordingly. The grating ruler reading head will continuously adjust its position to eliminate the thermal displacement caused by the lead screw. However, the thermal displacement of the worktable itself due to heat cannot be eliminated. With a long worktable, the value of the worktable's thermal displacement is significant, severely affecting the machining accuracy of parts. Furthermore, thermal displacement of the worktable caused by changes in ambient temperature cannot be corrected. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a method for correcting the thermal displacement of a CNC machine tool worktable that can improve the machining accuracy of parts.

[0005] In order to overcome the shortcomings of the prior art, the second objective of this invention is to provide a thermal displacement correction structure for a CNC machine tool worktable that can improve the machining accuracy of parts.

[0006] One of the objectives of this invention is achieved through the following technical solution:

[0007] A method for correcting the thermal displacement of a CNC machine tool worktable includes the following steps:

[0008] Structural Installation: The worktable is slidably mounted on the bed, the spindle is fixed to the worktable, the drive unit is fixed to the bed, the drive unit is connected to the lead screw and drives the lead screw to rotate, the nut is installed on the lead screw, the worktable is fixedly connected to the nut, the reading head assembly is fixed to the bed, the measuring scale assembly is fixed to the worktable, the reading head assembly and the measuring scale assembly are located on the same straight line, the spindle axis and the reading head assembly are in the same plane, and the plane is perpendicular to the direction of movement of the worktable;

[0009] Correcting the thermal displacement of the lead screw: During the operation of the drive component, the lead screw generates thermal displacement due to heat, causing the coordinates of the worktable to shift as a whole. At this time, the measuring scale assembly detects the coordinate shift and automatically corrects the originally set coordinates, thereby correcting the thermal displacement generated by the lead screw.

[0010] Correcting thermal displacement of the worktable: When the worktable receives heat transfer from the lead screw or expands or contracts as a whole due to environmental changes, the measuring scale assembly installed on the worktable expands or contracts together. The worktable corrects its coordinate position through the measuring scale assembly. At this time, the relative position of the reading head assembly with respect to the measuring scale assembly is accurate, that is, the relative position of the spindle axis with respect to the worktable is accurate. At this time, the relative dimensions between the machining features of the parts placed on the worktable are accurate, thereby correcting the thermal displacement of the worktable.

[0011] Furthermore, in the structure installation step, along the moving direction of the worktable, the nut is located at one end of the worktable, and the reading head assembly and the measuring scale assembly are located at the other end of the worktable.

[0012] Furthermore, in the structure installation step, the main shaft is set vertically, the line containing the reading head assembly and the measuring scale assembly is parallel to the sliding direction of the worktable, and the axis of the main shaft is perpendicular to the plane containing the reading head assembly and the direction of movement of the worktable.

[0013] The second objective of this invention is achieved by the following technical solution:

[0014] A CNC machine tool table thermal displacement correction structure is provided for implementing any of the aforementioned CNC machine tool table thermal displacement correction methods. The CNC machine tool table thermal displacement correction structure includes a bed, a table slidably mounted on the bed, and a spindle fixed to the bed's column frame. The structure further includes a drive assembly, a connecting seat, a reading head assembly, and a measuring scale assembly. The drive assembly includes a drive component, a lead screw, and a nut. The drive component is fixed to the bed and is drively connected to the lead screw. The nut is mounted on the lead screw and fixedly connected to the table via the connecting seat. The reading head assembly is fixed to the bed, and the measuring scale assembly is fixed to the table. Along the table's movement direction, the nut is located at one end of the table, and the reading head assembly and measuring scale assembly are located at the other end of the table. The reading head assembly and measuring scale assembly are on the same straight line. The spindle axis and the reading head assembly are in the same plane, and this plane is perpendicular to the table's movement direction.

[0015] Furthermore, the coefficient of thermal expansion of the measuring ruler assembly is the same as that of the worktable.

[0016] Furthermore, the reading head assembly includes a fixed base, a bracket, and a reading head. The fixed base is fixed to the bed, the bracket is fixed to the fixed base, and the reading head is fixed to the bracket.

[0017] Furthermore, the measuring scale assembly includes a mounting base and a measuring scale, the mounting base being fixed to the worktable and the measuring scale being fixed to the mounting base.

[0018] Furthermore, the measuring ruler is an optical grating ruler or a magnetic grating ruler.

[0019] Furthermore, the driving component is a motor.

[0020] Compared to existing technologies, the present invention's CNC machine tool table thermal displacement correction method fixes the reading head assembly to the machine bed and the measuring scale assembly to the table. The reading head assembly and the measuring scale assembly are located on the same straight line, with the spindle axis and the reading head assembly in the same plane. This plane is perpendicular to the direction of table movement. During operation, the lead screw heats up, generating thermal displacement and causing an overall shift in the table coordinates. The measuring scale assembly detects this shift and automatically corrects the previously set coordinates, thus correcting the thermal displacement generated by the lead screw. When the table receives heat from the lead screw or expands or contracts due to environmental changes, the measuring scale assembly mounted on the table expands or contracts along with it. The worktable corrects its coordinate position through the measuring scale assembly. At this point, the relative position of the reading head assembly with respect to the measuring scale assembly is accurate, meaning the relative position of the spindle axis with respect to the worktable is accurate. Therefore, the relative dimensions between the machining features of the parts placed on the worktable are accurate, thus correcting the thermal displacement of the worktable and improving the machining accuracy of the parts. Through the above steps, the thermal displacement of the CNC machine tool worktable is corrected in real time, ensuring the accuracy of the worktable positioning. This method uses purely mechanical connections, without additional detection units to monitor thermal displacement, making it simple to install and highly reliable. It can adapt to harsh machining environments, has a simple structure, and is more reliable than schemes that use algorithms for thermal displacement compensation. Attached Figure Description

[0021] Figure 1 This is a flowchart of the CNC machine tool worktable thermal displacement correction method of the present invention;

[0022] Figure 2 This is a schematic diagram of the thermal displacement correction structure of the CNC machine tool worktable according to the present invention;

[0023] Figure 3 for Figure 2 Enlarged view of point A of the thermal displacement correction structure of the CNC machine tool worktable.

[0024] In the diagram: 10. Bed; 20. Worktable; 30. Spindle; 40. Drive assembly; 41. Drive component; 42. Lead screw; 43. Nut; 50. Connecting seat; 60. Reading head assembly; 61. Fixed seat; 62. Bracket; 63. Reading head; 70. Measuring scale assembly; 71. Mounting seat; 72. Measuring scale; 80. Column. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or it can be fixed through another intermediate component. When a component is said to be "connected to" another component, it can be directly connected to the other component or it may be fixed through another intermediate component. When a component is said to be "set on" another component, it can be set directly on the other component or it may be set through another intermediate component. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] Please see Figures 1 to 3 The present invention provides a method for correcting the thermal displacement of a CNC machine tool worktable, comprising the following steps:

[0029] Structural Installation: The worktable 20 is slidably mounted on the bed 10, the spindle 30 is fixed to the worktable 20, the drive unit 41 is fixed to the bed 10, the drive unit 41 is connected to the lead screw 42 and drives the lead screw 42 to rotate, the nut 43 is mounted on the lead screw 42, the worktable 20 is fixedly connected to the nut 43, the reading head assembly 60 is fixed to the bed 10, the measuring scale assembly 70 is fixed to the worktable 20, the reading head assembly 60 and the measuring scale assembly 70 are located on the same straight line, and the axis of the spindle 30 and the reading head assembly 60 are located in the same plane;

[0030] Correcting the thermal displacement of the lead screw 42: During the operation of the drive component 41, the lead screw 42 generates thermal displacement due to heat, causing the coordinates of the worktable 20 to shift as a whole. At this time, the measuring scale assembly 70 detects the coordinate shift and automatically corrects the originally set coordinates, thereby correcting the thermal displacement generated by the lead screw.

[0031] Correcting the thermal displacement of the worktable 20: When the worktable 20 receives heat transfer from the lead screw 42 or expands or contracts as a whole due to environmental changes, the measuring scale assembly 70 installed on the worktable 20 expands or contracts together. The worktable 20 corrects its coordinate position through the measuring scale assembly 70. At this time, the relative position of the reading head assembly 60 with respect to the measuring scale assembly 70 is accurate, that is, the relative position of the spindle 30 axis with respect to the worktable 20 is accurate. At this time, the relative dimensions between the machining features of the parts placed on the worktable 20 are accurate, thereby achieving the effect of correcting the thermal displacement of the worktable 20.

[0032] Specifically, in the structural installation process, along the moving direction of the worktable 20, the nut 43 is located at one end of the worktable 20, and the reading head assembly 60 and the measuring scale assembly 70 are located at the other end of the worktable 20. The spindle 30 is set vertically, and the line containing the reading head assembly 60, the measuring scale assembly 70, and the spindle 30 is perpendicular to the sliding direction of the worktable 20. The coefficient of thermal expansion of the measuring scale assembly 70 is the same as that of the worktable 20, so that measuring scale assemblies 70 of the same length will have the same thermal displacement distance as the temperature rise of the worktable 20. The reading head assembly 60 includes a fixed base 61, a bracket 62, and a reading head 63. The fixed base 61 is fixed to the bed 10, the bracket 62 is fixed to the fixed base 61, and the reading head 63 is fixed to the bracket 62. The measuring scale assembly 70 includes a mounting base 71 and a measuring scale 72. The mounting base 71 is fixed to the worktable 20, and the measuring scale 72 is fixed to the mounting base 71.

[0033] Specifically, in the step of correcting the thermal displacement of the lead screw 42, the lead screw 42 will generate a temperature rise during long-term use, and the resulting thermal displacement will be transmitted to the worktable 20 through the connecting seat 50. At this time, the measuring scale assembly 70 will move along with the worktable 20. The measuring scale 72 has an automatic correction function and will feed back coordinate information to the CNC system. The CNC system will send a command to the drive component 41 to automatically correct the coordinates, thereby achieving the effect of correcting the thermal displacement generated by the lead screw 42. The final manifestation of the thermal displacement generated by the lead screw 42 is the thermal displacement generated by the worktable 20.

[0034] Specifically, in the step of correcting the thermal displacement of the worktable 20, when the worktable 20 experiences a temperature change, regardless of the cause of the change, the worktable 20 itself will generate thermal displacement, which manifests as overall expansion or contraction. The measuring scale assembly 70 has the same coefficient of expansion as the worktable 20. At this time, the measuring scale assembly 70 will also generate thermal displacement along with the worktable 20. The reading head 63 remains in its original fixed position during this process. At this time, the machine tool performs positioning detection through the measuring scale 72. The coordinates between any two points of the worktable 20 in the direction of movement are relatively accurate, that is, the coordinates of the machine tool spindle 30 relative to the workpiece on the surface of the worktable 20 are accurate, thereby correcting the thermal displacement and improving the machining accuracy of the parts.

[0035] Please continue reading. Figure 2 as well as Figure 3 This application also discloses a thermal displacement correction structure for a CNC machine tool worktable, used to implement the aforementioned thermal displacement correction method for a CNC machine tool worktable. The thermal displacement correction structure for a CNC machine tool worktable includes a bed 10, a worktable 20, a spindle 30, a drive assembly 40, a connecting seat 50, a reading head assembly 60, a measuring scale assembly 70, and a column 80.

[0036] The bed 10 is equipped with a slide rail, and the worktable 20 is slidably mounted on the slide rail of the bed 10. The column 80 is fixed to one end of the bed 10, and the spindle 30 is mounted on the top of the column 80. The spindle 30 is set in a vertical direction, and the end of the spindle 30 is located on one side of the worktable 20.

[0037] The upper surface of the worktable 20 is used to place the parts to be processed.

[0038] The drive assembly 40 includes a drive component 41, a lead screw 42, and a nut 43. The drive component 41 is fixed to the bed 10. In this embodiment, the drive component 41 is a motor. The lead screw 42 is connected to the drive component 41 for transmission. The drive component 41 drives the lead screw 42 to rotate. The nut 43 is installed on the lead screw 42. The rotation of the lead screw 42 causes the nut 43 to move linearly.

[0039] The connecting seat 50 is fixed to the nut 43, and the end of the worktable 20 is fixed to the connecting seat 50.

[0040] The reading head assembly 60 includes a fixed base 61, a bracket 62, and a reading head 63. The fixed base 61 is fixed to the bed 10, the bracket 62 is fixed to the fixed base 61, and the reading head 63 is fixed to the bracket 62.

[0041] The measuring scale assembly 70 includes a mounting base 71 and a measuring scale 72. The mounting base 71 is fixed to the worktable 20, and the measuring scale 72 is fixed to the mounting base 71. The measuring scale 72 is an optical scale or a magnetic scale. The coefficient of thermal expansion of the measuring scale assembly 70 is the same as that of the worktable 20.

[0042] Along the moving direction of the worktable 20, the nut 43 is located at one end of the worktable 20, the reading head assembly 60 and the measuring scale assembly 70 are located at the other end of the worktable 20, and the reading head assembly 60, the measuring scale assembly 70 and the spindle 30 are located on the same straight line.

[0043] When using the thermal displacement correction structure of the CNC machine tool worktable, during the operation of the drive component 41, the lead screw 42 generates thermal displacement due to heat, causing the coordinates of the worktable 20 to shift as a whole. At this time, the measuring scale assembly 70 detects the coordinate shift and automatically corrects the originally set coordinates, thereby correcting the thermal displacement generated by the lead screw. When the worktable 20 receives heat transfer from the lead screw 42 or expands or contracts as a whole due to environmental changes, the measuring scale assembly 70 installed on the worktable 20 expands or contracts together. The worktable 20 corrects its coordinate position through the measuring scale assembly 70. At this time, the relative position of the reading head assembly 60 with respect to the measuring scale assembly 70 is accurate, that is, the relative position of the spindle 30 axis with respect to the worktable 20 is accurate. At this time, the relative dimensions between the machining features of the parts placed on the worktable 20 are accurate, thereby achieving the effect of correcting the thermal displacement of the worktable 20. The CNC machine tool worktable thermal displacement correction structure performs real-time thermal displacement correction on the CNC machine tool worktable to ensure the accuracy of the worktable's 20 positioning; it adopts a purely mechanical connection, without additional detection units to detect thermal displacement, making it simple to install and highly reliable in use; it can adapt to harsh machining environments, has a simple structure, and is more reliable than solutions that use algorithms for thermal displacement compensation.

[0044] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These are all equivalent modifications and improvements made to the above embodiments based on the essential technology of the present invention, and all of these fall within the protection scope of the present invention.

Claims

1. A method for correcting the thermal displacement of a CNC machine tool worktable, characterized in that, Includes the following steps: Structural Installation: The worktable is slidably mounted on the bed, the spindle is fixed to the bed column frame, the drive unit is fixed to the bed, the drive unit is connected to the lead screw and drives the lead screw to rotate, the nut is installed on the lead screw, the worktable is fixedly connected to the nut, the reading head assembly is fixed to the bed, the measuring scale assembly is fixed to the worktable, the reading head assembly and the measuring scale assembly are located on the same straight line, the spindle axis and the reading head assembly are in the same plane, and the plane is perpendicular to the direction of worktable movement; Correcting the thermal displacement of the lead screw: During the operation of the drive component, the lead screw generates thermal displacement due to heat, causing the coordinates of the worktable to shift as a whole. At this time, the measuring scale assembly detects the coordinate shift and automatically corrects the originally set coordinates, thereby correcting the thermal displacement generated by the lead screw. Correcting thermal displacement of the worktable: When the worktable receives heat transfer from the lead screw or expands or contracts as a whole due to environmental changes, the measuring scale assembly installed on the worktable expands or contracts together. The worktable corrects its coordinate position through the measuring scale assembly. At this time, the relative position of the reading head assembly with respect to the measuring scale assembly is accurate, that is, the relative position of the spindle axis with respect to the worktable is accurate. At this time, the relative dimensions between the machining features of the parts placed on the worktable are accurate, thereby correcting the thermal displacement of the worktable.

2. The method for correcting the thermal displacement of a CNC machine tool worktable according to claim 1, characterized in that: During the structure installation step, along the direction of movement of the worktable, the nut is located at one end of the worktable, and the reading head assembly and the measuring scale assembly are located at the other end of the worktable.

3. The method for correcting thermal displacement of a CNC machine tool worktable according to claim 1, characterized in that: In the structure installation step, the main shaft is set vertically, the line containing the reading head assembly and the measuring scale assembly is parallel to the sliding direction of the worktable, and the axis of the main shaft and the plane containing the reading head assembly are perpendicular to the direction of movement of the worktable.

4. A thermal displacement correction structure for a CNC machine tool worktable, used to implement the thermal displacement correction method for a CNC machine tool worktable as described in any one of claims 1-3, wherein the CNC machine tool worktable thermal displacement correction structure comprises a bed, a worktable slidably mounted on the bed, and a spindle fixed to the bed column frame, characterized in that: The CNC machine tool table thermal displacement correction structure further includes a drive assembly, a connecting seat, a reading head assembly, and a measuring scale assembly. The drive assembly includes a drive component, a lead screw, and a nut. The drive component is fixed to the machine bed and is connected to the lead screw via a transmission connection. The nut is installed on the lead screw and is fixedly connected to the table via the connecting seat. The reading head assembly is fixed to the machine bed, and the measuring scale assembly is fixed to the table. Along the movement direction of the table, the nut is located at one end of the table, and the reading head assembly and the measuring scale assembly are located at the other end of the table. The reading head assembly and the measuring scale assembly are located on the same straight line, and the spindle axis and the reading head assembly are in the same plane, which is perpendicular to the movement direction of the table.

5. The thermal displacement correction structure for a CNC machine tool worktable according to claim 4, characterized in that: The coefficient of thermal expansion of the measuring scale assembly is the same as that of the worktable.

6. The thermal displacement correction structure for a CNC machine tool worktable according to claim 4, characterized in that: The reading head assembly includes a fixed base, a bracket, and a reading head. The fixed base is fixed to the bed, the bracket is fixed to the fixed base, and the reading head is fixed to the bracket.

7. The thermal displacement correction structure for a CNC machine tool worktable according to claim 4, characterized in that: The measuring scale assembly includes a mounting base and a measuring scale. The mounting base is fixed to the workbench, and the measuring scale is fixed to the mounting base.

8. The thermal displacement correction structure for a CNC machine tool worktable according to claim 7, characterized in that: The measuring ruler is either an optical grating ruler or a magnetic grating ruler.

9. The thermal displacement correction structure for a CNC machine tool worktable according to claim 4, characterized in that: The driving component is a motor.

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