CN113899541A - Abrasive belt grinding experiment table based on constant force control and experiment method thereof - Google Patents
Abrasive belt grinding experiment table based on constant force control and experiment method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of abrasive belt grinding, in particular to an abrasive belt grinding experiment table based on constant force control and an experiment method thereof. The method is based on constant force control abrasive belt grinding, and has the function of calibrating the coefficient of a local material removal rate model and the relative modulus between a grinding belt wheel and a test piece material; it may also verify the accuracy of the material removal prediction. This laboratory bench is by the abrasive band machine, clamping device, pressure sensor, numerical control guide rail and control software are constituteed, but the four corners chuck that is connected with pressure sensor centre gripping test piece is close to and contacts the abrasive band and grinds, pressure sensor can measure the pressure between test piece and the contact wheel in real time and feed back to the controller, the controller carries out the comparison with measured pressure and preset's target pressure, control numerical control guide rail according to the deviation between the two and advance or retreat according to certain speed, thereby keep the contact pressure between test piece and the abrasive band wheel unchangeable, the laboratory bench can realize clamping device's the free movement of X, Y, Z three directions.
Description
Technical Field
The invention relates to the technical field of abrasive belt grinding, in particular to an abrasive belt grinding experiment table based on constant force control and an experiment method thereof.
Background
In recent years, with the development of scientific technology in China, the domestic manufacturing level is continuously improved, and the mechanical processing equipment is promoted to be continuously developed towards high precision and high efficiency. Some major devices require high-precision machining, such as aero-generators, gas turbines and other high-end equipment are assembled by tens of thousands of parts, the parts require precision and ultra-precision machining, and the precision problem affects the service life and safety of the devices. Therefore, improving the dimensional accuracy of each part contributes to improving the overall performance of the equipment, and the problem of machining accuracy is crucial.
In the mechanical processing method, the numerical control abrasive belt has the advantages of high grinding efficiency, wide processing range, strong pertinence, low use cost, safe and convenient operation and the like, and is widely applied to the mechanical manufacturing industry. The abrasive belt grinding technology is originally used for manual rough grinding and polishing, and along with the improvement of abrasive belt quality and the development of technology, the abrasive belt grinding technology surpasses the limitation that the abrasive belt grinding technology can only be used for grinding and polishing at the beginning of the invention, the improvement of abrasive belt manufacturing technology and the appearance of novel wear-resistant abrasive materials, the efficiency, the precision and the service life of abrasive belt grinding are continuously improved, the abrasive belt grinding technology is gradually applied to semi-mechanical and mechanical grinding processing, the abrasive belt grinding technology is also applied to precision or ultra-precision processing at present, and therefore, the abrasive belt grinding technology plays an increasingly important role in the modern equipment manufacturing industry.
The abrasive belt grinding is a high-precision and high-efficiency process technology in the manufacturing industry, and can process precise parts in major equipment, but the abrasive belt grinding technology is still developed in many aspects, many problems are urgently needed to be solved or optimized, the abrasive belt grinding problem is a problem which is worth paying attention all the time, on the basis of constant force grinding, more functions which are beneficial to processing are realized, the abrasive belt grinding technology is perfected, and the universality and the applicability of abrasive belt grinding are improved, which is also a key point and a difficult point to be broken through by the abrasive belt grinding technology. The invention is provided for realizing more functions of an abrasive belt grinding experiment table, controls abrasive belt grinding based on constant force, and has the function of calibrating the coefficient of a local material removal rate model and the relative modulus between an abrasive belt wheel and a test piece material; it may also verify the accuracy of the material removal prediction.
Disclosure of Invention
In view of the above, the invention provides a belt grinding experiment table based on constant force control and an experiment method thereof. The method is based on constant force control abrasive belt grinding, and has the function of calibrating the coefficient of a local material removal rate model and the relative modulus between a grinding belt wheel and a test piece material; it may also verify the accuracy of the material removal prediction.
In order to solve the problems, the technical scheme adopted by the invention is as follows: the utility model provides an abrasive band grinding laboratory bench based on constant force control which characterized in that: the device comprises an abrasive belt machine with adjustable rotating speed, a clamping device, a pressure sensor, a numerical control guide rail driven by a stepping motor and a controller; the abrasive belt of abrasive belt machine contacts with the test piece, the test piece centre gripping is on clamping device, clamping device sets firmly the central point who puts in pressure sensor, pressure sensor sets up on the numerical control guide rail, be provided with the backing plate on the numerical control guide rail, clamping device's horizontal is realized to the numerical control guide rail, vertical and vertical three orientation's free movement, be provided with the spring between pressure sensor and the backing plate, pressure sensor real-time measurement test piece and the abrasive belt wheel between pressure and feed back to the controller through the data line, pressure sensor, numerical control guide rail and abrasive belt machine pass through controller control.
Furthermore, the belt sander with the adjustable rotating speed comprises an abrasive belt wheel, a tension wheel, a driving wheel and an abrasive belt, wherein the abrasive belt is wound on the abrasive belt wheel, the tension wheel and the driving wheel, and the driving wheel drives the abrasive belt to perform closed-loop transmission through a driving motor.
Further, clamping device includes four-jaw chuck and connecting rod, and four-jaw chuck and connecting rod are connected, and the test piece centre gripping is on four-jaw chuck, and the connecting rod sets up in pressure sensor's center.
Furthermore, the center planes of the abrasive belt wheel, the tensioning wheel and the driving wheel are positioned on the same plane.
Further, the numerical control guide rail is arranged on the workbench.
An experimental method of an abrasive belt grinding experiment table based on constant force control comprises the following steps:
firstly, a test piece is arranged on a clamping device, an abrasive belt is sleeved on the surfaces of a tension wheel and a driving wheel and is tensioned and adjusted, a controller presets target pressure and grinding time, and after the test piece starts to work, the test piece is free in the transverse direction, the longitudinal direction and the vertical direction on three guide rails, so that the center of the test piece and the center of the abrasive belt wheel are in the same level; the linear velocity of the abrasive belt is changed by adjusting the rotating speed of the driving wheel, and the four-corner chuck connected with the pressure sensor can clamp a test piece to be close to and contact with the abrasive belt moving at high speed for grinding; the pressure sensor measures the pressure between the test piece and the abrasive belt wheel in real time and feeds the pressure back to the controller, the controller compares the measured pressure with a preset target pressure, and when the pressure between the test piece and the abrasive belt wheel is greater than or less than a preset pressure, the controller controls the numerical control guide rail to move forwards or backwards at a certain speed according to the deviation between the test piece and the abrasive belt wheel, so that the contact pressure between the test piece and the abrasive belt wheel is kept unchanged; the numerical control guide rail automatically compensates the contact pressure change caused by factors such as test piece abrasion, machine vibration and the like, and automatically removes the pressure after the grinding time is reached, and finally the precision grinding processing of the test piece is completed.
The invention has the following advantages:
1) the constant-force control abrasive belt grinding is realized through the pressure sensor, the pressure sensor can measure the pressure between the test piece and the abrasive belt wheel in real time and feed the pressure back to the controller, the controller compares the measured pressure with the preset target pressure, and controls the numerical control guide rail to move forward or backward at a certain speed according to the deviation between the measured pressure and the target pressure, so that the contact pressure between the test piece and the abrasive belt wheel is kept unchanged, and the precise grinding processing of the test piece is completed.
2) The pressure sensor and the backing plate paper piece are provided with the springs, so that the buffer is provided for the clamping device, and the control precision of the contact pressure is improved.
3) The invention is provided with 3 modules, and can realize three-dimensional numerical control modules moving in three directions.
4) The method controls the abrasive belt grinding based on the constant force, and can calibrate the coefficient of a local material removal rate model and the relative modulus between the abrasive belt wheel and a test piece material; it may also verify the accuracy of the material removal prediction.
5) The experiment table is simple in structure and easy to operate, related components are easy to obtain, and expensive instruments are not needed.
6) The grinding pressure can be set in advance according to experiment requirements, a man-machine interaction function can be realized, and convenience is provided for actual grinding experiment requirements.
7) The invention ensures the basic constancy of the contact pressure in the grinding test process, realizes the constant-force grinding of the test piece, effectively avoids the serious abrasion of the abrasive belt caused by the overlarge pressure between the abrasive belt and the test piece, is beneficial to relieving the accumulation of the frictional heat of the abrasive belt and prolongs the service life of the abrasive belt.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 shows a clamping device with a buffer structure according to the present invention;
FIG. 3 is a schematic diagram of an abrasive belt machine of the present invention;
FIG. 4PID control algorithm principle;
FIG. 5 is a constant force belt grinding controller based on a PID algorithm;
FIG. 6 pressure distribution of an elliptical contact area;
FIG. 7 shows the distribution of the grinding paths and the detection points of the test piece to be ground;
reference numerals: 1-a controller, 2-a numerical control guide rail, 3-a pressure sensor, 4-a clamp, 5-a base plate, 6-a spring, 7-a connecting rod, 8-a four-jaw chuck, 9-a test piece, 10-a bolt, 11-a data line, 12-a workbench, 13-an abrasive belt wheel, 14-an abrasive belt, 15-a tension wheel, 16-a driving wheel and 17-a base.
Detailed Description
The present invention will be described in detail with reference to specific embodiments.
The invention provides the method for realizing more functions of the abrasive belt grinding experiment table, controls abrasive belt grinding based on constant force, has the function of calibrating the coefficient of a local material removal rate model and the relative modulus between an abrasive belt wheel and a test piece material, and can also verify the accuracy of material removal amount prediction.
The invention discloses an abrasive belt grinding experiment table based on constant force control, which comprises an abrasive belt machine with adjustable rotating speed, a clamping device, a pressure sensor 3, a numerical control guide rail 2 driven by a stepping motor and a controller 1, as shown in figure 1.
The structure of the belt sander with the adjustable rotating speed is shown in fig. 3, and comprises a belt sander 13, a sanding belt 14, a tension pulley 15, a driving wheel 16 and a base 17; the abrasive belt wheel 13, the driving wheel 16 and the tension wheel 15 are all installed on the frame, the driving wheel 16 is sequentially in closed-loop transmission connection with the abrasive belt wheel 13 and the tension wheel 15 through an abrasive belt 14, an output shaft of an abrasive belt driving motor is connected with the driving wheel 16, the abrasive belt driving motor drives the driving wheel 16 to rotate, the driving wheel 16 drives the abrasive belt wheel 13 and the tension wheel 15 to rotate through the abrasive belt 14, and the test piece 9 is ground through the abrasive belt 14 moving at a high speed; the center surfaces of the abrasive belt wheel 13, the tension wheel 15 and the driving wheel 16 are positioned on the same plane.
The structure of the clamping device is shown in fig. 2, and comprises a four-jaw chuck 8 and a connecting rod 7, wherein the connecting rod 7 is connected with a pressure sensor 3 and is connected with the chuck 8 through the connecting rod 7, the four-jaw chuck 8 is connected with the connecting rod 7, the connecting rod 7 is fixed at the central position of the pressure sensor 3, a test piece 9 is clamped on the four-jaw chuck 8, the four-jaw chuck 8 can generally clamp the test piece with a regular cross section, and the clamping and the loosening of the test piece are realized.
Above-mentioned pressure sensor 3 sets up on numerical control guide rail 2, backing plate 5 sets up on numerical control guide rail 2, numerical control guide rail 2 can realize clamping device's horizontal, vertical and vertical three direction's free movement, pressure between pressure sensor 3 real-time measurement test piece 9 and abrasive band wheel 13 to feed back to the controller through data line 11, the controller carries out the comparison with the target pressure of presetting in advance with the actual measurement pressure, in time adjust pressure between the two, make grinding pressure reach invariable in the course of working. A spring 6 is arranged between the pressure sensor 3 and the backing plate 5, so that a buffering effect is provided for the clamping device, and the control precision of the contact pressure can be improved. Due to the presence of the spring 6, the test piece 9, the four-jaw chuck 8 and the pressure sensor 3 will move backwards together somewhat when the test piece held by the four-jaw chuck 8 is subjected to an axial pressure. The numerical control guide rail 2 is arranged on the workbench 12, and the workbench 12 is placed at a proper position away from the belt sander, so that the clamping device can be controlled to freely move in the transverse direction, the longitudinal direction and the vertical direction. The flexible clamping device is matched with the numerical control guide rail and a constant force control algorithm, the PID control is adopted in the constant force control algorithm, the algorithm principle is shown in figure 4, and the axial pressure acting on the test piece can be kept stable.
The workbench 12 of the numerical control guide rail is provided with the ABC three modules which are connected together through the screws, the nuts and the connecting assembly to form the three-dimensional numerical control module moving in the three directions of the transverse direction, the longitudinal direction and the vertical direction, the numerical control guide rail controls the clamping device to translate on the transverse guide rail, the longitudinal guide rail and the vertical guide rail through the motion controller, so that the transverse movement, the longitudinal movement and the vertical movement of a test piece can be controlled, and the four-corner chuck can clamp the test piece to be close to and contact with an abrasive belt to perform abrasive machining.
The pressure sensor 3, the numerical control guide rail 2 and the abrasive belt machine are controlled by the controller 1. As shown in fig. 5, these are basic functions of a constant-force abrasive belt grinding controller, the controller is constant-force control grinding software designed according to parameters provided by a numerical control guide rail, a pressure sensor and an abrasive belt machine, firstly, a connection controller is clicked, a desired target pressure and grinding time are set after the connection controller is connected, constant-force grinding can be performed according to the target pressure by clicking a grinding start button, and the pressure is automatically removed after the grinding time is reached.
The control software sends a series of signals to the motion controller; the controller receives the signal, converts the signal into information such as pulse frequency and the like through internal stored logic operation, and outputs the information to the driver; the driver receives the pulse signal and converts the pulse signal into phase current for driving the stepping motor to accurately rotate; the stepping motor receives phase currents with different frequencies and magnitudes output by the driver, converts the phase currents into information such as angular displacement and angular acceleration of the stepping motor, and finally can realize normal work of the numerical control guide rail.
The working process of the invention is as follows: firstly, a test piece 9 is installed on a clamping device, an abrasive belt 14 is sleeved on the surfaces of a tension wheel 15 and a driving wheel 16 and is tensioned and adjusted, target pressure and grinding time are preset through a controller 1, after the work is started, the controller 1 sends a series of signals to a motion controller, the signals are converted into phase currents for controlling a stepping motor after a series of transformations, the stepping motor is controlled to realize the free movement of the test piece on three guide rails in three directions, and the center of the test piece 9 and the center of a sand belt wheel 13 are in the same level; the linear velocity of the abrasive belt 14 is changed by adjusting the rotating speed of the driving wheel 13, the four-corner chuck 8 connected with the pressure sensor 3 can clamp the test piece 9 to be close to and contacted, and the sand 14 moving at high speed is ground; the pressure sensor 3 measures the pressure between the test piece 9 and the abrasive belt wheel 13 in real time and feeds the pressure back to the controller 1, the controller 1 compares the measured pressure with a preset target pressure, and when the pressure between the test piece 9 and the abrasive belt wheel 13 is greater than or less than a preset pressure, the numerical control guide rail 2 is controlled to move forwards or backwards at a certain speed according to the deviation between the test piece 9 and the abrasive belt wheel 13, so that the contact pressure between the test piece 9 and the abrasive belt wheel 13 is kept unchanged; the numerical control guide rail 2 automatically compensates the contact pressure change caused by factors such as abrasion of the test piece 9 and machine vibration, automatically removes the pressure after the grinding time is reached, and finally completes the precise grinding processing of the test piece.
The pressure sensor is used for actually measuring the pressure between the test piece and the abrasive belt wheel, the pressure between the test piece and the abrasive belt wheel is timely adjusted, the grinding pressure is constant in the processing process, the influence of the change of the grinding pressure on the grinding effect is eliminated, on the basis of controlling the abrasive belt grinding by constant force, the experiment table can measure the removal rate of the standard test piece under the multi-factor grinding parameters through orthogonal tests, and the coefficient of a local material removal rate model is calibrated by combining a statistical method; the relative modulus between the abrasive belt wheel and the test piece material can be calibrated through a contact test under variable pressure, so that a contact model for grinding a complex curved surface by the abrasive belt is established; the experiment table can also be used for comparing the actual material removal depth and the theoretical removal depth of each target point on the surface of the test piece by grinding the test piece with the cylindrical surface, and analyzing the precision of the prediction result relative to the actual result.
The grinding pressure can be set in advance according to experiment requirements, a man-machine interaction function can be realized, the adjustment is simple, the implementation is convenient, the applicability is strong, and convenience is provided for actual grinding experiment requirements.
The experiment table can verify the accuracy of prediction of the material removal amount. In the grinding experiment process, a constant-force grinding experiment table is adopted to clamp a test piece to be ground to be in contact with the abrasive belt wheel, so that constant pressure in the feeding process is kept. And the abrasive belt wheel makes relative motion along the axial direction of the test piece according to the set feeding speed, and the axial direction of the test piece with the cylindrical surface to be ground is kept vertical to the axial direction of the abrasive belt wheel. And grinding the material of the test piece, comparing the actual material removal depth and the theoretical removal depth of each target point on the surface of the test piece, and analyzing the precision of the predicted result relative to the actual result.
The model prototype of the local material removal rate of abrasive belt grinding adopted by the invention is as follows:
in the formula:
r-depth of material removal per unit time (mm/s), also known as local material removal rate;
p is the uniform distribution pressure (Mpa) of the contact area;
vsbelt line speed (m/s);
CA-a correction constant for the grinding process;
KA-the complex constant of the test piece resistance coefficient and the abrasive belt grinding capacity;
Kt-the wear factor of the abrasive belt.
Due to CAAnd KAThe value of (A) is only related to the determined factors of the belt type, the material of the test piece and the like, and the abrasion coefficient K of the belttIs not significantly changed during the early and middle stages of belt use, so most researchers will do CA·KA·KtAs a whole constant, and this is also the practice of the invention, and let K ═ CA·KA·KtThe above equation becomes:
the above formula is the basis for the selection of grinding parameters according to the invention, wherein three coefficients K, b are involved2，b3Calibration by experiment is required.
According to the invention, the relative modulus between the abrasive belt wheel and the test piece material can be calibrated through the experiment table, and the relative modulus between the abrasive belt wheel and the test piece material is calibrated through a contact test under variable pressure, so that a contact model for grinding a complex curved surface by using an abrasive belt is established.
The abrasive belt wheel used for abrasive belt grinding is a standard cylinder, the geometric shape of a test piece researched by the experiment table is a blade, and the normal grinding force FnWhen the abrasive belt acts on the surface of the test piece, the contact area of the abrasive belt and the test piece is a typical ellipse according to the Hertz contact equation, and the contact pressure distribution of the abrasive belt and the test piece is semi-ellipsoidal as shown in figure 6.
The boundary formula of the elliptical contact area according to the hertzian contact equation is:
in the formula: a and b are the lengths of the half shaft of the long shaft and the half shaft of the short shaft of the contact ellipse respectively, and the solving formula is respectively as follows:
f is the normal contact force between the abrasive belt wheel and the surface of the test piece;
is the relative modulus of the abrasive belt wheel to the test piece, E1V and v1Respectively representing Young's modulus and Poisson's ratio, E of the abrasive belt wheel material2V and v2Respectively representing the Young modulus and the Poisson ratio of the test piece material;
a and B are relative curvatures of contact points, and the calculation formula is as follows:
in the formula R1' and R1"represents the maximum and minimum radii of curvature, R, of the abrasive belt wheel at the point of contact2' and R2"represents the maximum and minimum curvature radius of the surface of the test piece at the contact point, alpha is the included angle between the abrasive belt wheel at the contact point and the main direction of the surface of the test piece, and the solving formula of other relevant parameters is as follows:
in the above formula kappa2Is the ratio of the major and minor semi-axes, epsilon (kappa)2) Is the second type of elliptic integral.
The pressure distribution of the test piece and the abrasive belt in the oval contact area is as follows:
in the formula P0Is the maximum pressure in the contact area, the position of the maximum pressure is located at the center point of the elliptical contact area, P0The calculation formula of (2) is as follows:
according to the contact model, the shape and the contact pressure distribution of the contact area between the abrasive belt wheel and the engine blade in the abrasive belt grinding process can be calculated, but the relative modulus E of the two materials is obtained in advance*Thus relative modulus E*It also needs to be determined experimentally.
The experiment table can obtain the relative modulus between the abrasive belt wheel and the test piece material in the abrasive belt grinding process and the shape and the contact pressure distribution of the contact area between the abrasive belt wheel and the test piece material by using the summarized formula.
The accuracy of the prediction of the material removal amount can be verified through a laboratory bench. In the grinding experiment process, a constant-force grinding experiment table is adopted to clamp a test piece to be ground to be in contact with the abrasive belt wheel, so that constant pressure in the feeding process is kept. And the abrasive belt wheel makes relative motion along the axial direction of the test piece according to the set feeding speed, and the axial direction of the test piece with the cylindrical surface to be ground is kept vertical to the axial direction of the abrasive belt wheel. And grinding the material of the test piece, comparing the actual material removal depth and the theoretical removal depth of each target point on the surface of the test piece, and analyzing the precision of the predicted result relative to the actual result.
The pressure sensor is a main component for constant force control and regulation, the pressure sensor can measure the pressure between a test piece and the abrasive belt wheel in real time and feed back the pressure to the controller, the controller compares the measured pressure with a preset target pressure, and controls the numerical control guide rail to move forward or backward at a certain speed according to the deviation between the measured pressure and the target pressure, so that the contact pressure between the test piece and the abrasive belt wheel is kept unchanged, and the precise grinding processing of the test piece is completed. The method has the advantages that on the basis of ensuring that the contact pressure in the grinding test process is basically constant, the coefficient of a local material removal rate model and the relative modulus between the abrasive belt wheel and the test piece material can be calibrated, and the accuracy of material removal prediction can be verified.
The invention ensures the basic constancy of the contact pressure in the grinding test process, realizes the constant-force grinding of the test piece, effectively avoids the serious abrasion of the abrasive belt caused by the overlarge pressure between the abrasive belt and the test piece, is beneficial to relieving the accumulation of the frictional heat of the abrasive belt and prolongs the service life of the abrasive belt. The experiment table controls abrasive belt grinding based on constant force, and can calibrate the coefficient of a local material removal rate model and the relative modulus between the abrasive belt wheel and a test piece material; it may also verify the accuracy of the material removal prediction. The experiment table is simple in structure and easy to operate, involved components are easy to obtain, expensive instruments are not needed, and self-adaptive grinding pressure adjustment can be achieved.
The coefficient for calibrating the local material removal rate model can be calibrated through an experiment table, and can be obtained through the following experiments: three coefficients K, b in the local material removal rate model2，b3Calibration by orthogonal experiments is required. The orthogonal test adopts a standard test piece with the section side length D being 7mm, and the test piece is contacted with the abrasive belt under the control of a constant-force grinding test bed and is kept for a time length delta t being 20 s. The height variation delta H of the standard test piece within delta t duration can be measured by a screw micrometer, and the material removal rate r under the grinding parameter combination can be further calculated:
the material removal rate r measured at different combinations of grinding parameters is reported in the table below, with r in mm/s.
TABLE 1 removal of Material at different combinations of contact pressure and line speed
According to the 9 sets of calibration test results in Table 1, b can be compared2,b3And K, and processing the test data as follows.
Let y ═ lg (r), b0＝lg(K)，x2＝lg(P)，x3＝lg(vs) Then the corresponding linear regression equation is
y＝b0+b2x2+b3x3
The linear equation contains 2 independent variables x in total2,x3And independent variables are mutually independent, y is a test measurement result, 9 groups of tests are respectively carried out on 2 independent variables according to the design, and the independent variable of the ith group of tests is marked as xi,2,xi,3And the test result is recorded as yi。
Is provided with
Are respectively a parameter b0,b2,b3Obtaining a sample regression equation of
Observed value yiAnd the regression value
Residual error e ofiIs composed of
b0,b2,b3Should be chosen such that all eiHas the smallest sum of squares, i.e.
According to the theorem of extreme values of multivariate function, Q is respectively paired with b0,b2,b3First order partial derivatives are calculated and made equal to 0, i.e.
Is simple and easy to obtain
Written in matrix form as
Order to
The above formula can be written as
The coefficient estimate is therefore
Processing the test results in Table 1 according to the data processing method, and finally calibrating K is approximately equal to 0.0401194, b2≈1.162000，b3R 1.087408. Therefore, under the test environment of the present item, the local material removal rate r can be calculated according to the following formula:
r＝0.0401194·P1.162000·Vs 1.087408
the relative modulus coefficient between the abrasive belt wheel and the workpiece material can be calibrated through an experiment table, and can be obtained through the following experiments: considering test cost, complexity, etcThe relative modulus E of the abrasive belt wheel and the workpiece material can be indirectly measured in the following way*：
Coating a coloring agent on an abrasive belt, adopting a spherical surface (the material is the same as that of a blade) with a radius R, contacting the abrasive belt wheel (including the abrasive belt) under different normal pressures F, measuring the sizes of the long axis and the short axis of an elliptical contact area after removing the pressure, and taking the contact pressure suitable for experimental design as a reference value, wherein the maximum normal pressure recorded by a pressure sensor in each contact process is actually used as the standard; the contact area size refers to the major axis a and the minor axis b of the contact ellipse.
TABLE 2 relative modulus calibration test results
Since the spherical and abrasive wheel radii are known, A, B, κ for each test2,ε(κ2) Can be calculated according to the formula in the previous section, and the major axis and the minor axis of the ellipse are assumed to be [ a ] measured in the ith testi,bi]Then the relative modulus E of the abrasive belt wheel and the workpiece material can be calculated according to the principle that the theoretical area is equal to the actually measured area of the contact areai *The calculation method is as follows:
according to the above formula, the relative modulus obtained by 10 sets of calibration tests can be respectively calculated
The results of the 10 groups of tests are averaged to finally obtain the relative modulus E between the abrasive belt wheel and the workpiece material adopted by the project*＝10.733Mpa。
The accuracy of prediction of the material removal amount can be verified through an experiment table, and the following experiment can be adopted to obtain a prediction result: the verification experiment grinds 4 workpieces together, and the grinding path on each workpiece is a section of bus of a cylindrical surface. The points to be measured are 25 detection points of the surface of the workpiece, the 25 detection points are distributed on 5 sections of the workpiece, and each section has 5 detection points. The corresponding experimental parameters were as follows:
workpiece parameters: materials: steel No. 45; length: 175 mm; width: 30 mm; radius of cylindrical surface: 100 mm.
Grinding parameters: contact pressure: 20N; feeding speed: 2 mm/s; grinding path length: 125mm × 4.
The distribution of the grinding path and the detection points of the workpiece to be ground is shown in fig. 7, wherein a blue dotted line is the grinding path, a yellow dotted line is the movement track of the contact point on the abrasive belt wheel when the grinding of each workpiece starts and ends, and a red dot point is the detection point. According to the contact model established by the project, the theoretical values of the long half axis and the short half axis of the contact area can be calculated to be a ≈ 6.722mm and b ≈ 6.502mm respectively, so that the detection points are set to five points which are spaced by 2.5mm and are symmetrical to the grinding path on each section.
According to the grinding and contact model with the material removal rate constructed by the project, the theoretical material removal depth (unit mm) distribution of 25 detection points in the five sections can be predicted and is shown as the following table:
TABLE 3 theoretical Material removal depth at various inspection points
The actual material removal distribution at 25 test points of the five measured cross sections is shown in the following table:
TABLE 4 actual material removal depth test results at each test point
The final result shows that the predicted average deviation of the material removal amount on 5 sections is lower than 20%, and the rationality of the local material removal rate model and the contact model adopted by the invention is proved.
The invention is not limited to the examples, and any equivalent changes to the technical solution of the invention by a person skilled in the art after reading the description of the invention are covered by the claims of the invention.
Claims (6)
1. The utility model provides an abrasive band grinding laboratory bench based on constant force control which characterized in that: the device comprises an abrasive belt machine with adjustable rotating speed, a clamping device, a pressure sensor (3), a numerical control guide rail (2) driven by a stepping motor and a controller (1); abrasive band (13) of abrasive band machine contact with test piece (9), test piece (9) centre gripping is on clamping device, clamping device sets firmly the central point in pressure sensor (3) and puts, pressure sensor (3) set up on numerical control guide rail (2), be provided with backing plate (5) on numerical control guide rail (2), clamping device's horizontal is realized in numerical control guide rail (2), the free movement of vertical and three direction, be provided with spring (6) between pressure sensor (3) and backing plate (5), pressure sensor (3) real-time measurement test piece (9) and abrasive band wheel (13) between feed back to controller (1) through data line (11), pressure sensor (3), numerical control guide rail (2) and abrasive band machine pass through controller (1) control.
2. A belt grinding test bench based on constant force control as claimed in claim 1, characterized in that: the belt sander with the adjustable rotating speed comprises a belt sander (13), a tension pulley (15), a driving wheel (16) and a belt sander (14), wherein the belt sander (14) is arranged on the belt sander (13), the tension pulley (15) and the driving wheel (16) in a winding mode, and the driving wheel (16) drives the belt sander (14) to perform closed-loop transmission through a driving motor.
3. A belt grinding test bench based on constant force control according to claim 1 or 2, characterized in that: clamping device include four-jaw chuck (8) and connecting rod (7), four-jaw chuck (8) and connecting rod (7) are connected, test piece (9) centre gripping is on four-jaw chuck (8), connecting rod (7) set up in the center of pressure sensor (3).
4. A belt grinding test bench based on constant force control as claimed in claim 3, characterized in that: the center planes of the abrasive belt wheel (13), the tension wheel (15) and the driving wheel (16) are positioned on the same plane.
5. A belt grinding test bench based on constant force control as claimed in claim 4, characterized in that: the numerical control guide rail (2) is arranged on the workbench (12).
6. The experimental method of the belt grinding experiment table based on the constant force control as claimed in claim 1, wherein: the method comprises the following steps:
firstly, a test piece (9) is installed on a clamping device, an abrasive belt (14) is sleeved on the surfaces of a tension wheel (15) and a driving wheel (16) and is tensioned and aligned, a controller (1) presets target pressure and grinding time, and after the test piece (9) starts to work, the test piece (9) freely moves in the transverse direction, the longitudinal direction and the vertical direction on three guide rails, so that the center of the test piece (9) and the center of an abrasive belt wheel (13) are in the same level; the linear velocity of the abrasive belt (14) is changed by adjusting the rotating speed of the driving wheel (16), and the four-corner chuck (8) connected with the pressure sensor (13) can clamp the test piece (9) to approach and contact the abrasive belt (4) moving at high speed for grinding; the pressure sensor (3) measures the pressure between the test piece (9) and the abrasive belt wheel (13) in real time and feeds the pressure back to the controller (1), the controller (1) compares the measured pressure with a preset target pressure, and when the pressure between the test piece (9) and the abrasive belt wheel (13) is greater than or less than the preset pressure, the numerical control guide rail (2) is controlled to move forwards or backwards at a certain speed according to the deviation between the test piece (9) and the abrasive belt wheel (13), so that the contact pressure between the test piece (9) and the abrasive belt wheel (13) is kept unchanged; the numerical control guide rail (2) automatically compensates the contact pressure change caused by factors such as abrasion of the test piece (9), machine vibration and the like, and automatically removes the pressure after the grinding time is reached, thereby finally finishing the precise grinding processing of the test piece (9).
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107962480A (en) * | 2017-11-28 | 2018-04-27 | 华中科技大学 | Force control method is processed in a kind of blade robot sbrasive belt grinding |
| CN110561237A (en) * | 2019-10-08 | 2019-12-13 | 华中科技大学 | Robot abrasive belt grinding method and system combining active and passive power control |
| CN216208490U (en) * | 2021-10-29 | 2022-04-05 | 西安工业大学 | Abrasive belt grinding experiment table based on self-adaptive pressure control |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107962480A (en) * | 2017-11-28 | 2018-04-27 | 华中科技大学 | Force control method is processed in a kind of blade robot sbrasive belt grinding |
| CN110561237A (en) * | 2019-10-08 | 2019-12-13 | 华中科技大学 | Robot abrasive belt grinding method and system combining active and passive power control |
| CN216208490U (en) * | 2021-10-29 | 2022-04-05 | 西安工业大学 | Abrasive belt grinding experiment table based on self-adaptive pressure control |
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