A base structure for improving the support of machine tools and its optimization design method

Abstract

The present invention relates to a base structure for improving the supportability of a machine tool, belonging to the technical field of machine tool optimization, comprising a plurality of spring feet and support holes arranged in conjunction with the plurality of spring feet, wherein the plurality of spring feet are respectively arranged at the four corners and the middle of the machine tool, any of the spring feet comprises a bolt, a nut and a spring sleeved outside the bolt stud, the nut is arranged above the support hole, the bolt passes through the support hole and is screwed into the nut, the bolt and the support hole cooperate to squeeze the spring, and the present invention also provides an optimization design method for a base structure for improving the supportability of a machine tool, comprising the following steps: step one: modeling; step two: importing simulation software, adjusting the elastic coefficients of different spring feet, and obtaining the variation relationship between different elastic coefficients and the deformation amount of the middle part of the base; step three: determining the optimal elastic coefficient of each part by using a MOGA algorithm according to the relationship between the deformation amount of the middle part of the base and the spring elastic coefficient.

Description

Technical Field

[0001] The invention belongs to the technical field of machine tool optimization, and in particular relates to a base structure for improving the support performance of a machine tool and an optimization design method thereof. Background Art

[0002] A machine tool is an automated processing equipment widely used in various production and life. A general machine tool includes a base and a processing machine above the base. In order to maintain the level of the base and separate the base that vibrates during work from the ground, there are usually feet at the bottom of the base to lift the base off the ground.

[0003] For the anchor, its supporting capacity needs to be optimized and designed to maximize the supporting performance. The general optimization method relies on experience to design the layout of the anchor bolts. At the same time, only the deformation of the bed is considered, and the change of the center of gravity of the bed and worktable components caused by the partial movement of the worktable is not considered. The degree of optimization is not high. For this reason, Chinese patent CN104794280B discloses a method for optimizing the layout of machine tool anchor bolts, including the following steps: 1) setting the number and spacing of machine tool anchor bolts; 2) calculating the deformation of the middle point of the worktable when the worktable and the workpiece are at various positions on the bed, and then selecting the maximum deformation and minimum deformation of the middle point of the worktable when the worktable and the workpiece are at various positions on the bed. The maximum deformation is then subtracted from the minimum deformation as the straightness error δ of the horizontal axis of the bed; 3) the straightness error δ of the horizontal axis of the bed is taken as the objective function, and the spacing and number of anchor bolts are taken as independent variables for optimization, and the corresponding spacing and number of anchor bolts when the straightness error δ of the horizontal axis of the bed is minimized are obtained, and then the anchor bolts of the machine tool are arranged according to the spacing and number of anchor bolts; the deformation of the middle point of the workbench and the workpiece at each position of the bed is calculated by the finite element simulation method, and the spacing and number of anchor bolts corresponding to the minimum straightness error of the horizontal axis of the bed are selected;

[0004] However, in order to expand the adjustment range of the supporting effect, it is sometimes necessary to use spring anchors instead of general bolt anchors. When the elastic coefficient of the spring anchor is too small, a slight external force will cause violent vibration, making it impossible to keep the machine tool level and the supporting performance is poor. When the elastic coefficient is too large, the spring pre-compression degree will be too high and the supporting effect will be poor. Therefore, it is necessary to adjust the elastic coefficient of each spring anchor according to the actual needs of the machine tool. The above scheme cannot calculate the elastic coefficients of several anchors, and the optimization effect is insufficient. Therefore, a base structure with good optimization effect and an optimization design method for improving the supporting performance of the machine tool are needed. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a base structure for improving the support performance of a machine tool and an optimization design method thereof, which has the characteristics of good optimization effect.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A base structure for improving the support of a machine tool comprises a plurality of spring feet and support holes matched with the spring feet. The spring feet are respectively arranged at the four corners and the middle of the machine tool. Any of the spring feet comprises a bolt, a nut and a spring sleeved on the outside of the bolt stud. The nut is arranged above the support hole. The bolt passes through the support hole and is screwed into the nut. A washer is arranged on the bolt head. The washer cooperates with the support hole to squeeze the spring.

[0008] The present invention also provides a method for optimizing the design of a base structure for improving the support performance of a machine tool, comprising the following steps:

[0009] Step 1: Modeling;

[0010] Step 2: Import the simulation software, and adjust only the elastic coefficients of different spring feet in the simulation software to obtain the changing relationship between different elastic coefficients and the deformation of the middle part of the base, until the changing relationship between the elastic coefficient and the deformation is reversed;

[0011] Step 3: Based on the relationship between the deformation of the middle part of the base and the spring elastic coefficient, the MOGA algorithm is used to determine the optimal elastic coefficient of each part.

[0012] As a preferred technical solution of the present invention, the step 3 of using the MOGA algorithm to determine the optimal elastic coefficient of each part also includes:

[0013] Define model material properties: density, Young's modulus, Poisson's ratio;

[0014] Define boundary conditions and forces required to load the model;

[0015] Divide the model into multiple unit grids;

[0016] Establish mechanical equations for each unit grid and solve them to obtain the deformation at the middle position of the base;

[0017] Define the range of variation of the elastic coefficient of the spring, and establish a response surface between the spring coefficient of each part and the maximum deformation and average deformation of the base;

[0018] The optimization objective is defined as minimizing the maximum deformation and average deformation of the base, and the MOGA multi-objective optimization algorithm is used to obtain the Pareto optimal frontier and the elastic coefficients of each object.

[0019] As a preferred technical solution of the present invention, step three also includes: dividing the model into multiple unit grids in the simulation software, measuring the local weight m of each grid, and upwardly correcting the elastic coefficient of the spring foot closest to the concentration point when the weight of a certain grid exceeds m0.

[0020] As a preferred technical solution of the present invention, the step three also includes: dividing the model into multiple unit grids in the simulation software, measuring the weight m of each grid part, and when the weight of a certain grid exceeds m0, correcting the elastic coefficient of the nearest spring foot to A1 times the original, where A1=m / m0×c, m≥m0, c is a pre-entered constant, and m0 is a pre-entered weight threshold.

[0021] As a preferred technical solution of the present invention, the step three also includes: calculating the point where the periodic motion of the equipment occurs in the simulation software, measuring the frequency of the periodic motion, and downwardly correcting the elastic coefficient of the spring foot closest to the concentration point.

[0022] As a preferred technical solution of the present invention, step three also includes: measuring the periodic motion frequency f at the point where the periodic motion of the computing device occurs, and correcting the elastic coefficient of the spring foot closest to the occurrence point to A2 times the original value, wherein A2=f0 / f×d, f≤f0, d is a pre-input constant, and d0 is a pre-input frequency threshold.

[0023] The beneficial effects of the present invention are:

[0024] (1) By using the simulation software, the relationship between different elastic coefficients and the deformation of the middle part of the base is obtained. Then, according to the relationship between the deformation of the middle part of the base and the spring elastic coefficient, the MOGA algorithm is used to determine the optimal elastic coefficient of each part. The support force of each spring foot on the machine tool can be accurately obtained, and the support force can be accurately adjusted, thereby improving the optimization effect of the design;

[0025] (2) By correcting upward the parts of the base with heavy weight and high simulation error rate, the design optimization effect is further improved;

[0026] (3) By correcting the elastic coefficient downward at the part of the base that is subject to more vibration and is more likely to deform due to vibration and thus affect the positioning accuracy of the machine tool, the vibration absorption effect of the spring foot is improved, further improving the optimization effect of the design. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0028] Figure 1 It is a structural schematic diagram of the present invention;

[0029] Figure 2 It is a schematic diagram of the structure of the spring foot of the present invention;

[0030] Description of main component symbols:

[0031] In the figure: 1. nut; 2. spring; 3. washer. DETAILED DESCRIPTION

[0032] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0033] See also Figure 1-2 A base structure for improving the support of a machine tool, comprising a plurality of spring feet and support holes matched with the plurality of spring feet, wherein the plurality of spring feet are respectively arranged at the four corners and the middle of the machine tool, wherein any spring foot comprises a bolt, a nut 1 and a spring 2 sleeved outside the bolt stud, wherein the nut 1 is arranged above the support hole, the bolt passes through the support hole and is screwed into the nut 1, and a washer 3 is arranged on the bolt head, wherein the washer 3 cooperates with the support hole to squeeze the spring 2;

[0034] Specifically, the machine tool base is in the shape of a quadrangular prism, and the bottom surface of the machine tool base close to the ground is a rectangle. At this time, the ground of the base automatically forms four corners and a middle part, and a plurality of spring feet are respectively arranged at the four corners and the middle part of the machine tool;

[0035] At the same time, a support hole is provided on the bottom surface of the base corresponding to the setting position of each spring foot. The support hole is a rectangular plate lower than the bottom. The two sides of the rectangular plate are connected to the bottom surface. The middle part is hollowed out to provide a screw hole. A nut 1 is provided at one end of the support hole near the base. At the same time, a spring 2 is provided on the stud sleeve of the bolt. One end of the spring 2 is connected to the washer 3 on the bolt nut, and the other end can be freely extended. At this time, the spring 2 can be compressed. Subsequently, the bolt passes through the screw hole of the support hole and is tightened with the nut 1 until the distance between the bolt head and the support hole is less than the natural length of the spring 2. At this time, the washer 3 cooperates with the support hole to squeeze the spring 2;

[0036] When in use, the squeezed spring 2 presses the bolt outward, so that the bolt and the support surface have a tendency to move away from each other. The gravity of the base acts on the support surface, giving the support surface a tendency to approach the bolt. At this time, the elastic force of the spring 2 counteracts the gravity of the base, completing the support of the base.

[0037] In the above structure, the supporting force on the middle part of the base depends on the elastic coefficient of spring 2 and the elastic force of spring 2. When the workpiece is too heavy, the deformation of the middle part of the base will be large, affecting the positioning accuracy of the machine tool. Therefore, the forces on the several spring feet in the middle of the machine tool are different, and the elastic coefficient needs to be adjusted according to actual needs. For this reason, this patent also provides an optimization design method for the base structure to improve the support of the machine tool, including the following steps:

[0038] Step 1: Modeling. Specifically, build a solidworks model of the spring foot and base according to the actual structure;

[0039] Step 2: Then import the simulation software, set different spring feet as several sampling points in the simulation software, adjust only the elastic coefficients of different spring feet for several sampling points, simulate deformation through simulation, record the elastic coefficients and corresponding deformation amounts, at the beginning, when the elastic coefficient of spring 2 increases, the deformation amount of the bottom decreases, until the elastic coefficient increases to a certain value, the deformation direction of the base changes; the elastic coefficient of spring 2 continues to increase, the deformation amount of the base increases, and the change relationship between different elastic coefficients and the deformation amount of the middle part of the base is obtained;

[0040] Step 3: According to the relationship between the deformation of the middle part of the base and the elastic coefficient of spring 2, the optimal elastic coefficient of each part is determined by using the MOGA algorithm. At this time, the elastic coefficients of several parts;

[0041] Specifically, the optimal elastic coefficient of each part determined by the MOGA algorithm also includes:

[0042] Define model material properties: density, Young's modulus, Poisson's ratio;

[0043] Define boundary conditions and forces required to load the model;

[0044] Divide the model into multiple unit grids;

[0045] Establish mechanical equations for each unit grid and solve them to obtain the deformation at the middle position of the base;

[0046] Define the range of variation of the elastic coefficient of spring 2, and establish a response surface between the coefficient of spring 2 at each position and the maximum deformation and average deformation of the base;

[0047] Finally, the optimization goal is defined as "minimum deformation of the base", and the MOGA multi-objective optimization algorithm is used to find the Pareto optimal frontier and the elastic coefficient of each object, and finally a set of solutions is obtained, which reflects the optimal elastic coefficient of the spring foot of each part. At this time, the elastic coefficient of each object in this solution is the target elastic coefficient of each spring foot in the middle of the machine tool. Under this elastic coefficient, the deformation of the middle part of the base can be minimized, thereby ensuring the positioning accuracy of the machine tool;

[0048] In some cases, the local weight of the base is large, and there is a probability that it cannot be fully simulated during simulation, the error rate is large, and it cannot be fully simulated, and the optimization effect is insufficient. Therefore, step three also includes: dividing the model into multiple unit grids in the simulation software, measuring the local weight m of each grid, and upwardly correcting the elastic coefficient of the spring foot closest to the concentration point when the weight of a certain grid exceeds m0;

[0049] Specifically, the model is divided into multiple unit grids in the simulation software, and the weight m of each grid is measured. When the weight of a grid exceeds m0, the elastic coefficient of the nearest spring foot is corrected to A1 times the original value, where A1=m / m0×c, m≥m0, c is a pre-entered constant, and m0 is a pre-entered weight threshold;

[0050] When the weight m of a certain grid is large, it is necessary to further correct the elastic coefficient of spring 2 upward to ensure the support effect. At this time, A1 is large. When the weight of a certain grid exceeds m0, the elastic coefficient of the nearest spring foot is corrected to A1 times the original, and the upward correction of the elastic coefficient is completed;

[0051] The design optimization effect is further improved by upwardly correcting the parts of the base that have heavier weight and higher simulation error rate.

[0052] Some parts of the machine tool need to withstand repeated vibrations. At this time, there is a high probability that the parts will be deformed under the influence of vibrations, thereby affecting the positioning accuracy of the machine tool. The spring feet of this part need to be corrected downward. For this reason, step three also includes: calculating the point where the equipment periodic motion occurs in the simulation software, measuring the periodic motion frequency, and correcting downward the elastic coefficient of the spring foot closest to the concentration point;

[0053] Specifically, at the point where the periodic motion of the computing device occurs, the periodic motion frequency f is measured, and the elastic coefficient of the spring foot closest to the occurrence point is corrected to A2 times the original value, where A2=f0 / f×d, f≤f0, d is a pre-entered constant, and d0 is a pre-entered frequency threshold;

[0054] When the periodic motion frequency f is high, the vibration generated by the periodic motion is large, and the elastic coefficient of spring 2 needs to be further corrected downward to ensure the support effect. At this time, A2=f0 / f×d is small, and the elastic coefficient of the spring foot closest to the occurrence point is corrected to the original A2 times to complete the downward correction of the elastic coefficient;

[0055] By correcting the elastic coefficient downward at the part of the base that is subject to more vibration and is more likely to deform due to vibration and thus affect the positioning accuracy of the machine tool, the vibration absorption effect of the spring foot is improved, further improving the optimization effect of the design.

[0056] The working principle and use process of the present invention:

[0057] When in use, the squeezed spring 2 presses the bolt outward, so that the bolt and the support surface have a tendency to move away from each other. The gravity of the base acts on the support surface, giving the support surface a tendency to approach the bolt. At this time, the elastic force of the spring 2 counteracts the gravity of the base, completing the support of the base.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An optimization design method for a base structure for improving the support of a machine tool, characterized in that: The base structure includes a plurality of spring feet and supporting holes matched with the spring feet. The spring feet are respectively arranged at the four corners and the middle of the machine tool. Any of the spring feet includes a bolt, a nut and a spring sleeved outside the bolt stud. The nut is arranged above the supporting hole. The bolt passes through the supporting hole and is screwed into the nut. A washer is arranged on the bolt head. The washer cooperates with the supporting hole to squeeze the spring. The optimization design method for the base structure to improve the support of the machine tool comprises the following steps: Step 1: Modeling, specifically, establishing a solidworks model of the spring foot and the base according to the actual structure; Step 2: Import the simulation software, and adjust only the elastic coefficients of different spring feet in the simulation software to obtain the changing relationship between different elastic coefficients and the deformation of the middle part of the base, until the changing relationship between the elastic coefficient and the deformation is reversed; Step 3: According to the relationship between the deformation of the middle part of the base and the spring elastic coefficient, the MOGA algorithm is used to determine the optimal elastic coefficient of each part. Specifically, it includes the following sub-steps: Define model material properties: density, Young's modulus, Poisson's ratio; Define boundary conditions and forces required to load the model; Divide the model into multiple unit grids; Establish mechanical equations for each unit grid and solve them to obtain the deformation at the middle position of the base; Define the range of variation of the elastic coefficient of the spring, and establish a response surface between the spring coefficient of each part and the maximum deformation and average deformation of the base; The optimization objective is defined as minimizing the maximum deformation and average deformation of the base, and the MOGA multi-objective optimization algorithm is used to obtain the Pareto optimal frontier and the elastic coefficients of each object.

2. The optimization design method for a base structure for improving the support performance of a machine tool according to claim 1, characterized in that: The step three also includes: dividing the model into a plurality of unit grids in the simulation software, measuring the weight m of each grid, and upwardly correcting the elastic coefficient of the spring foot closest to the concentration point when the weight of a certain grid exceeds m0.

3. The optimization design method for a base structure for improving the support performance of a machine tool according to claim 2, characterized in that: The step three also includes: dividing the model into multiple unit grids in the simulation software, measuring the weight m of each grid part, and when the weight of a grid exceeds m0, correcting the elastic coefficient of the nearest spring foot to A1 times the original value, where A1=m / m0×c, m≥m0, c is a pre-entered constant, and m0 is a pre-entered weight threshold.

4. The optimization design method for a base structure for improving the support performance of a machine tool according to claim 3, characterized in that: The step three also includes: calculating the point where the periodic motion of the equipment occurs in the simulation software, measuring the frequency of the periodic motion, and downwardly correcting the elastic coefficient of the spring foot closest to the concentration point.

5. The optimization design method for a base structure for improving the support performance of a machine tool according to claim 4, characterized in that: The step three also includes: calculating the point at which the equipment's periodic motion occurs, measuring the periodic motion frequency f, and correcting the elastic coefficient of the spring foot closest to the point of occurrence to A2 times the original value, where A2=f0 / f×d, f≤f0, d is a pre-entered constant, and d0 is a pre-entered frequency threshold.

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