High-steady-state finishing control method for grinding wheel of centerless grinding machine

Abstract

The invention relates to the technical field of centerless grinding machines, in particular to a centerless grinding machine grinding wheel high-steady-state finishing control method which can stably finish a high-precision grinding wheel in the dynamic process, a machine tool is provided with an MPM dynamic balancing instrument and adopts a marble lathe bed, and a three-phase asynchronous motor or a spindle motor is selected as a grinding wheel motor. A servo motor with the rated rotating speed of 3000r / min is selected as a diamond roller motor; in the process of dressing the grinding wheel by the diamond roller, the same-direction dressing mode that the linear velocity value VRlr when the spindle of the diamond roller rotates divided by the linear velocity value VGW when the spindle of the grinding wheel rotates is a fixed value qd is adopted; the dressing feeding of the grinding wheel dresser is controlled by a U shaft, and a fixed grinding wheel dressing amount is carried out each time of dressing.

Description

Technical Field

[0001] This invention relates to the field of centerless grinding machine technology, specifically to a method for high-stability dressing control of grinding wheels in centerless grinding machines. Background Technology

[0002] Centerless grinders are widely used in metal processing, and with the development of technology, the requirements for workpiece machining accuracy are becoming increasingly stringent. The grinding process of a centerless grinder is a dynamic process in which the grinding guide wheel continuously grinds, removes grains, and dresses. Existing grinding processes suffer from problems such as significant vibration and low dressing accuracy and efficiency. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a high-stability dressing control method for centerless grinding wheels, which can stably dress high-precision grinding wheels during dynamic processes.

[0004] The technical solution is as follows: A high-stability-state dressing control method for centerless grinding wheels, characterized in that the machine tool is equipped with an MPM dynamic balancing instrument and uses a marble bed, a three-phase asynchronous motor or spindle motor is selected as the grinding wheel motor, and a servo motor with a rated speed of 3000 r / min is selected as the diamond roller motor; during the dressing process of the diamond roller, the linear velocity value V of the diamond roller spindle rotation is used. Rlr Divide by the linear velocity V of the grinding wheel spindle during rotation. GW The dressing method is a fixed value qd in the same direction; the dressing feed of the grinding wheel dresser is controlled by the U-axis, and each dressing operation moves a fixed amount of grinding wheel dressing.

[0005] Its further feature is that the speed V of the main axis of the diamond roller is calculated first. Rlr and grinding wheel motor dressing speed n GW-MOT V, the speed of the main axis of the diamond roller Rlr and grinding wheel motor dressing speed n GW-MOT From formulas 1 and 2, we get: Formula 1 Where D Rlr n is the diameter of the diamond roller. Rlr-MOT K represents the rotational speed of the diamond roller motor. Rlr-MOT K represents the diameter of the pulley of the diamond roller motor. Rlr The diameter of the main shaft pulley of the diamond roller; Formula 2 Where n GW-MOT To adjust the speed of the grinding wheel motor, V GW D is the speed of the grinding wheel spindle axis. GW K is the diameter of the grinding wheel. GW-MOT K is the diameter of the grinding wheel motor pulley. GWThe diameter of the grinding wheel spindle pulley; Then test grind the workpiece, and adjust the grinding wheel motor dressing speed according to the actual situation. Obtain the changing qd value according to formula 3 until qualified products are ground in batches. Lock the qd value. In subsequent batch grinding of workpieces, when dressing the grinding wheel, dress it with a constant qd value. in Formula 3.

[0006] Set the new grinding wheel diameter D according to the selected grinding wheel specifications. GW-NEW And determine the current diameter D of the grinding wheel. GW-CURRENT =D GW-NEW - 2×K GW-WEAR Formula 4, where D GW-WEAR This represents the wear amount of the grinding wheel; Substituting formulas 4 and 3 into formula 2, we get... Formula 5 Based on the real-time wear of the grinding wheel, the dressing speed of the grinding wheel motor is calculated using Formula 5 to achieve dressing of the grinding wheel with a constant qd value.

[0007] During trial grinding, the grinding wheel dressing reciprocating speed is set to the trial grinding wheel dressing reciprocating speed value. After successful trial grinding, according to... Formula 6, where D axis_w n is the current reciprocating speed of the grinding wheel dressing. GW-MOT Adjust the speed of the grinding wheel motor; The calculated cutting depth L per revolution for dressing the grinding wheel is locked; as the wear of the grinding wheel increases, the diameter of the grinding wheel decreases, and the dressing speed of the grinding wheel motor increases. Formula 7 calculates the current grinding wheel dressing reciprocating speed, and the CNC system controls the dressing action.

[0008] By adopting this invention, the overall mechanism is optimized to reduce vibration from a mechanical perspective, ensuring the long-term precision stability of the centerless grinder. During dressing, the qd value is changed, and the dressing speed of the grinding wheel motor changes with the current grinding wheel diameter and is adjusted in real time. The constant cutting amount per revolution during grinding wheel dressing ensures more stable grinding wheel hulling during dressing, enabling stable dressing of high-precision grinding wheels in dynamic processes. Attached Figure Description

[0009] Figure 1 A schematic diagram of the diamond roller dressing structure; Figure 2 Schematic diagram of a grinding wheel dresser Figure 3 This is the screen displaying the steady-state dressing parameters for the grinding wheel on the user interface. Detailed Implementation

[0010] A method for controlling the high-steady-state dressing of grinding wheels in a centerless grinder is mainly achieved through the following three aspects: 1. Overall mechanism optimized design to reduce vibration: The rotating grinding wheel motor and diamond roller motor are the main vibration sources during the dressing process of the entire centerless grinder. A three-phase asynchronous motor or spindle motor is selected as the grinding wheel motor, and a servo motor with a rated speed of 3000 r / min is selected as the diamond roller motor, featuring speed feedback and lower vibration. The diamond roller spindle is driven to rotate via a synchronous belt, such as... Figure 1 As shown.

[0011] The use of a marble bed can quickly absorb vibrations generated during grinding and dressing, providing excellent damping and shock absorption performance. It also boasts superior thermal stability, ensuring the long-term geometric and positioning accuracy of the centerless grinder. Furthermore, the absence of casting internal stress fundamentally avoids bed deformation caused by the slow release of stress, guaranteeing the long-term accuracy and stability of the centerless grinder.

[0012] After installing the grinding wheel on the grinding wheel spindle, perform a static balance on the balancing stand first. Then, install it on the main machine's grinding wheel head. The machine tool is equipped with an MPM dynamic balancing machine. Rotate the grinding wheel and use the dynamic balancing machine to balance it, reducing vibration. The preferred installation position for the vibration sensor of the dynamic balancing machine is at the front bearing housing of the grinding wheel spindle. Directly above or to the side of the spindle are also good choices. Generally, when the grinding wheel rotates at grinding speed or dressing speed, the vibration value should be less than 0.4 mm / s (RMS value).

[0013] Rotate the diamond roller and use a dynamic balancing machine in manual mode to check the vibration value of the running diamond roller. The preferred installation position of the vibration sensor of the dynamic balancing machine is at the front bearing housing of the roller spindle. Directly above or to the side of the spindle is also acceptable. Generally, the vibration value of the diamond roller should be less than 0.4 mm / s (RMS value) when it rotates.

[0014] 2. Dress the grinding wheel using a constant qd value (diamond roller linear velocity / grinding wheel linear velocity): During the dressing process of the diamond roller, the linear velocity V of the diamond roller spindle during rotation is used. Rlr Divide by the linear velocity V of the grinding wheel spindle during rotation. GW This is a same-direction trimming method for a fixed value qd.

[0015] The diamond roller motor is a servo motor with a rated speed of 3000 rpm. Considering the dressing efficiency, a speed between 2500-3000 rpm is generally selected. The specific setting value is selected based on the spindle vibration value, and it is important to avoid the dressing resonance point. Then, substitute into Formula 1 to obtain the current linear velocity of the diamond roller. Other parameters in the formula are known. Formula 1 Where D Rlr n is the diameter of the diamond roller. Rlr-MOT K represents the rotational speed of the diamond roller motor. Rlr-MOT K represents the diameter of the pulley of the diamond roller motor. Rlr The diameter of the main shaft pulley of the diamond roller is given.

[0016] When the grinding wheel rotates clockwise and the roller rotates counterclockwise, the contact point of the two moving in the same direction is called co-directional dressing, which is the most common method. However, when both the grinding wheel and the roller rotate clockwise, the contact point of the two moving in opposite directions is called reverse dressing. Reverse dressing causes excessive friction at the contact point, which can easily damage the roller, so it is generally not used.

[0017] The grinding wheel is dressed using a constant qd value method. That is, during the dressing process of the diamond roller, the linear velocity of the diamond roller is divided by the linear velocity of the grinding wheel to obtain a fixed value qd. Then, according to Formula 2, the grinding wheel motor speed (calculated value) during dressing is obtained, and the workpiece is tested. Formula 2 Where n GW-MOT To adjust the speed of the grinding wheel motor, V GW D is the speed of the grinding wheel spindle axis. GW K is the diameter of the grinding wheel. GW-MOT K is the diameter of the grinding wheel motor pulley. GW The diameter of the grinding wheel spindle pulley is given.

[0018] Because, during the steady-state control process of diamond roller dressing grinding wheels, the qd value is constant, i.e., Formula 3 exists: .

[0019] To perform constant qd value dressing, the new grinding wheel diameter D must first be set according to the selected grinding wheel specifications. GW-NEW Then, each time the grinding wheel is dressed, the control system automatically accumulates the amount of wear, K, to the grinding wheel wear level. GW-WEAR No additional settings are required. The control system automatically reduces the grinding wheel wear amount K by twice its normal value. GW-WEAR This will give you the diameter D of the current grinding wheel. GW-CURRENT When replacing the grinding wheel, the grinding wheel replacement process is performed, and the grinding wheel wear is K. GW-WEAR It will be reset to zero. This leads to formula 4: D GW-CURRENT =D GW-NEW - 2×K GW-WEAR .

[0020] Substituting formulas 3 and 4 into formula 2, we get formula 5:

[0021] The CNC system calculates and stabilizes the grinding wheel motor's dressing speed using Formula 5 based on the real-time wear of the grinding wheel, achieving constant qd value (diamond roller linear velocity / grinding wheel linear velocity) dressing. According to the applicant's extensive data analysis, during constant qd value dressing, the ratio of the diamond roller's rotational linear velocity to the grinding wheel's rotational linear velocity is a fixed value qd, ranging from 0.3 to 0.7. Here, the intermediate value of 0.5 is input into the operation interface. Then, according to Formula 2, the grinding wheel motor speed (calculated value) during dressing is obtained, and the workpiece is test-ground after dressing the grinding wheel.

[0022] A smaller qd value results in higher dressing accuracy, a smoother grinding wheel surface, and better workpiece roughness, making it suitable for fine grinding; a larger qd value results in higher dressing efficiency and a higher material removal rate, making it suitable for rough grinding.

[0023] Repeated trial grinding until qualified products are produced in batches. Press the "Lock QD Value" button on the operation interface to lock the QD value. The grinding wheel motor dressing speed n is then adjusted. GW-MOT It will change with the current grinding wheel diameter D GW-CURRENT Change with change.

[0024] Field tests showed that the diamond roller motor, driving the diamond roller to rotate, met the machine tool vibration requirements at 2800 r / min. Therefore, the speed n of the diamond roller motor here... Rlr-MOT Substituting 2800 r / min into the equation, the diameter n of the diamond roller... Rlr The diameter K of the diamond roller motor pulley is 125mm. Rlr-MOT The diameter of the diamond roller main shaft pulley is 50mm. Rlr The value is 45. The current speed V of the main axis of the diamond roller can be calculated using Formula 1. Rlr It is 20.352 m / s.

[0025] During dressing of the grinding wheel using a constant qd value, the linear velocity of the diamond roller divided by the linear velocity of the grinding wheel results in a fixed value qd, which is between 0.3 and 0.7. Here, we use the intermediate value of 0.5. The current spindle speed V of the diamond roller is then used. Rlr Substitute 20.352 m / s. The diameter D of the new grinding wheel... GW-NEW The diameter of the grinding wheel motor pulley is 600mm. GW-MOT The diameter of the grinding wheel spindle pulley is 168mm, and the diameter K is... GW The wear rate is 220mm, and the grinding wheel wear amount is K. GW-WEAR If the value is 15mm, substituting it into Formula 5, we can calculate the recommended rotational speed n for the grinding wheel motor during dressing. GW-MOT The speed is 1786 r / min.

[0026] After dressing the grinding wheel, test-grind the workpiece, and then adjust the rotation speed according to the actual situation on site. At this time, the qd value changes as the grinding wheel dressing speed is adjusted. This continues until qualified products are produced in batches. Then, the qd value is locked. For subsequent batch grinding of workpieces, grinding wheel dressing is performed using a constant qd value. The grinding wheel dressing speed is calculated and adjusted continuously as the amount of grinding wheel wear changes, achieving a relatively stable dressing method.

[0027] 3. The grinding wheel is dressed repeatedly, with a constant cutting depth per revolution.

[0028] Diamond grinding wheel dresser, see Figure 2 As shown, the dressing feed is controlled by the (U-axis), and each dressing operation involves moving a fixed amount of grinding wheel material. The reciprocating motion is controlled by a servo axis (W-axis), and its speed is adjustable. Because a locked qd value is used for dressing, the feed per revolution needs to be stably controlled to a constant value to ensure more stable grinding wheel desizing during dressing.

[0029] During trial grinding, the grinding wheel dressing reciprocating speed is set to the specified value. After successful trial grinding, press the "Dressing Amount per Revolution Lock" button on the screen, according to formula 6: Where L is the depth of cut per revolution for dressing the grinding wheel, and D axis_w n is the current reciprocating speed of the grinding wheel dressing. GW-MOT Adjust the speed of the grinding wheel motor; The calculated grinding wheel dressing depth per revolution is shown in [the original text]. Figure 3 (Screenshot of grinding wheel steady-state dressing parameters). As grinding wheel wear accumulates, the grinding wheel diameter decreases, and the dressing speed of the grinding wheel motor increases. Applying formula 7:

[0030] The current grinding wheel dressing reciprocating speed (W axis) is calculated, and the CNC system controls the dressing action.

[0031] In practice, the test grinding machine is set to a pre-set reciprocating speed of 30 mm / min for dressing the grinding wheel, and the grinding wheel motor is set to a dressing speed of n. GW-MOT With a speed of 1786 r / min, the cutting depth L per revolution of the grinding wheel is calculated to be 0.0168 mm. As the wear of the grinding wheel increases, the wheel diameter decreases, and the grinding wheel motor's dressing speed increases. To ensure consistent threshing during grinding wheel dressing, the cutting depth per revolution needs to be stably controlled to a constant value. For example, when the grinding wheel dressing speed is gradually adjusted to 2000 r / min, according to formula 7, the current grinding wheel dressing reciprocating speed will automatically adjust to 33.59 mm / min.

Claims

1. A method for controlling the high-steady-state dressing of a centerless grinding wheel, characterized in that, The machine tool is equipped with an MPM dynamic balancing instrument and uses a marble bed. A three-phase asynchronous motor or spindle motor is selected as the grinding wheel motor, and a servo motor with a rated speed of 3000 r / min is selected as the diamond roller motor. During the diamond roller dressing process, the linear velocity V of the diamond roller spindle rotation is used. Rlr Divide by the linear velocity V of the grinding wheel spindle during rotation. GW The dressing method is a fixed value qd in the same direction; the dressing feed of the grinding wheel dresser is controlled by the U-axis, and each dressing operation moves a fixed amount of grinding wheel dressing.

2. The method for controlling the high-steady-state dressing of a centerless grinding wheel according to claim 1, characterized in that, First calculate the speed V of the main axis of the diamond roller. Rlr and grinding wheel motor dressing speed n GW-MOT V, the speed of the main axis of the diamond roller Rlr and grinding wheel motor dressing speed n GW-MOT From formulas 1 and 2, we get: Official 1 Where D Rlr n is the diameter of the diamond roller. Rlr-MOT K represents the rotational speed of the diamond roller motor. Rlr-MOT K represents the diameter of the pulley of the diamond roller motor. Rlr The diameter of the main shaft pulley of the diamond roller; Official 2 Where n GW-MOT To adjust the speed of the grinding wheel motor, V GW D is the speed of the grinding wheel spindle axis. GW K is the diameter of the grinding wheel. GW-MOT K is the diameter of the grinding wheel motor pulley. GW The diameter of the grinding wheel spindle pulley; Then test grind the workpiece, and adjust the grinding wheel motor dressing speed according to the actual situation. Obtain the changing qd value according to formula 3 until qualified products are ground in batches. Lock the qd value. In subsequent batch grinding of workpieces, when dressing the grinding wheel, dress it with a constant qd value. in Official 3.

3. The method for controlling the high-steady-state dressing of a centerless grinding wheel according to claim 2, characterized in that, Set the new grinding wheel diameter D according to the selected grinding wheel specifications. GW-NEW And determine the current diameter of the grinding wheel. D GW-CURRENT =D GW-NEW - 2×K GW-WEAR Formula 4, where D GW-WEAR This refers to the wear of the grinding wheel. Will Substituting formulas 4 and 3 into formula 2, we get... Official 5 Based on the real-time wear of the grinding wheel, the dressing speed of the grinding wheel motor is calculated using Formula 5 to achieve dressing of the grinding wheel with a constant qd value.

4. The method for controlling the high-steady-state dressing of a centerless grinding wheel according to claim 3, characterized in that, During trial grinding, the grinding wheel dressing reciprocating speed is set to the trial grinding wheel dressing reciprocating speed value. After successful trial grinding, according to... Formula 6, where D axis_w n is the current reciprocating speed of the grinding wheel dressing. GW-MOT Adjust the speed of the grinding wheel motor; The calculated cutting depth L per revolution for dressing the grinding wheel is locked; as the wear of the grinding wheel increases, the diameter of the grinding wheel decreases, and the dressing speed of the grinding wheel motor increases. Formula 7 calculates the current grinding wheel dressing reciprocating speed, and the CNC system controls the dressing action.

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