Follow-up and linear axis compensation method for cut-off of groove square tube

Abstract

The invention discloses a follow-up and linear axis compensation method for beveled square tube truncation, which belongs to the technical field of beveled square tube truncation, and comprises the following steps of: before cutting, performing capacitance correction treatment; in the cutting process, Z-axis control mainly refers to an NC position command, meanwhile, the working temperature of a capacitor is monitored in real time through a Z-axis temperature rise compensation circuit, compensation of performance changes caused by temperature rise of the capacitor is achieved, and then height error compensation is conducted on the basis of the NC position command. Whether h is equal to a set value h0 or not is judged, if not, errors exist in the cutting position, and the Z axis follows the measured current actual height h to conduct PID closed loop control; in the beveling machining situation, if Z-axis follow-up is started at the same time under the condition that the swing head shaft has an angle, the Y-axis starts position compensation at the same time. The method takes NC as the main part and capacitance value feedback as the auxiliary part, and ensures that the cutting path meets the expectation. The problem of focus position deviation caused by swinging of the swinging head can be compensated, and the machining precision is high.

Description

Technical Field

[0001] The invention relates to the technical field of bevel square tube cutting, and in particular to a follow-up and linear axis compensation method for bevel square tube cutting. Background Art

[0002] When laser beveling square tubes, it is necessary to ensure the consistency of the processing path so that the cut workpiece will be flush at the cross section, which is of great help to the subsequent welding work.

[0003] In the process of bevel cutting, traditional methods make it difficult to accurately control key parameters such as the angle, width and depth of the bevel. For example, mechanical cutting is susceptible to tool wear and machine tool accuracy limitations; thermal cutting is affected by airflow and heat source stability, resulting in large deviations in bevel size. In conventional processing methods, when the cutting head swings, the focus position will shift, resulting in inconsistent cutting paths before and after the cutting head swings, and poor consistency in the cut paths.

[0004] Based on this, the present invention designs a follow-up and linear axis compensation method for beveled square tube truncation to solve the above problems. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, the present invention provides a follow-up and linear axis compensation method for beveled square tube truncation.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for following and linear axis compensation of beveled square tube truncation, comprising the following steps: Step 1: Before cutting, perform capacitance calibration; during cutting, monitor the capacitance value in real time and infer the distance h between the nozzle and the metal sheet in actual processing; Step 2: During the cutting process, the Z-axis control mainly refers to the position command of the NC. At the same time, the Z-axis temperature rise compensation circuit monitors the working temperature of the capacitor in real time to compensate for the performance change of the capacitor due to temperature rise, and then compensates for the height error based on the position command of the NC. Step 3: Determine whether h is equal to the set value h0. If so, there is no error in the cutting position. If not, there is an error in the cutting position. The Z axis follows the measured actual height h to perform PID closed-loop control. Step 4: In the case of bevel cutting, when the swing head axis is at an angle, if the Z-axis tracking is turned on at the same time, the Y-axis position compensation will be turned on at the same time.

[0007] Furthermore, in step one, before cutting, different capacitance values ​​are generated due to the different heights between the nozzle and the metal sheet. The capacitance value is 0 when the nozzle is in contact with the surface of the sheet, and then gradually moves away from the metal sheet, and the capacitance values ​​at different heights are recorded to generate a height-capacitance value relationship table.

[0008] Furthermore, in step one, while cutting is in progress, the capacitance value is monitored in real time, and the distance h between the nozzle and the metal sheet in actual processing is inferred based on the current capacitance value and the height-capacitance value relationship table.

[0009] Furthermore, in step 2, the Z-axis temperature rise compensation circuit includes a feedback circuit composed of an operational amplifier, a thermistor, etc.

[0010] Furthermore, a thermistor is used as a temperature sensor, and its resistance change is converted into an electrical signal and fed back to the operational amplifier. The operational amplifier outputs a corresponding control signal to adjust the voltage applied to the capacitor or the current flowing through the capacitor according to the set reference signal.

[0011] Furthermore, in step three, the Z axis follows the measured actual height h to perform PID closed-loop control to achieve h=h0 and realize position compensation.

[0012] Furthermore, in step 4, the position compensation command of the Y axis = (Z axis mechanical coordinate command - Z axis motor feedback) * tan (A axis absolute coordinate command).

[0013] Furthermore, in step 4, the Z-axis and A-axis commands use a velocity feedforward compensation strategy to compensate for servo lag and communication delay.

[0014] Compared with the prior art, the present invention has the following beneficial effects: the present invention mainly uses NC (Numerical Control) and supplemented by capacitance feedback to ensure that the cutting path meets expectations. The follow-up and Y-axis compensation strategies provided by the present invention can compensate for the focus offset caused by the swing of the swing head, ensuring that the focus of the cutting head is always at the same position of the pipe when the swing head swings arbitrarily, thereby ensuring the consistency of the processing path and improving the processing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1The schematic diagram of the present invention is a follow-up and linear axis compensation method for beveled square tube truncation. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: In some embodiments, please refer to the drawings of the specification Figure 1 A method for following and linear axis compensation of beveled square tube truncation includes the following steps: Step 1: Before cutting, perform capacitance calibration; during cutting, monitor the capacitance value in real time and infer the distance h between the nozzle and the metal sheet in actual processing; During the cutting process, the Z-axis control mainly refers to the position command of NC (Numerical Control). The goal is to make the original NC command roughly conform to the size and shape of the workpiece. If the workpiece itself has deformation and size deviation, the nozzle may hit the workpiece or the laser focus depth error may affect the processing when only referring to NC. Therefore, the Z-axis reference capacitor value is used to make corresponding position compensation to avoid the above situation.

[0019] Step 1 The specific steps are as follows: Step 1.1, before cutting, do capacitance calibration processing. Specifically, due to the different heights between the nozzle and the metal sheet, the generated capacitance values ​​are different. When the capacitance value is 0 when it is attached to the surface of the sheet, gradually move away from the metal sheet, record the capacitance values ​​at different heights, and generate a height-capacitance value relationship table; Step 1.2, during cutting, the capacitance value is monitored in real time, and the distance h between the nozzle and the metal sheet in actual processing is inferred based on the current capacitance value and the height-capacitance value relationship table; Step 2: During the cutting process, the Z-axis control mainly refers to the position command of the NC. At the same time, the Z-axis temperature rise compensation circuit monitors the working temperature of the capacitor in real time to compensate for the performance change of the capacitor due to temperature rise, and then compensates for the height error based on the position command of the NC. Specifically, at the same height from the surface of the plate, the capacitance value will change due to the change in temperature. The Z-axis temperature rise compensation circuit includes a feedback circuit composed of an operational amplifier, a thermistor, etc. The thermistor is used as a temperature sensor, and its resistance change is converted into an electrical signal and fed back to the operational amplifier. The operational amplifier outputs a corresponding control signal according to a set reference signal to adjust the voltage applied to the capacitor or the current flowing through the capacitor, etc., to achieve compensation for the performance change of the capacitor caused by temperature rise; Step 3: Determine whether h is equal to the set value h0. If so, there is no error in the cutting position. If not, there is an error in the cutting position. The Z axis follows the measured actual height h to perform PID closed-loop control to achieve h=h0 and realize position compensation. Step 4: Please refer to Figure 1 In the case of bevel cutting, when the swing axis (A axis) is at an angle (e.g. -45°), if the Z axis is turned on at the same time, it will cause the laser cutting position to be wrong (A axis). NC It is the position of the laser in the processing file. Laser is the actual position of the laser without the groove strategy), then the Y axis also needs to make a certain position compensation; Y-axis position compensation command = (Z-axis mechanical coordinate command - Z-axis motor feedback) * tan (A-axis absolute coordinate command); Among them, the Z-axis and A-axis commands need to take into account servo lag and communication delay, and are implemented through a speed feedforward compensation strategy to ensure that they match the timing of the motor feedback.

[0020] The present invention mainly uses NC (Numerical Control) and supplemented by capacitance feedback. The reason is that if the non-planar curvature of the workpiece being processed changes greatly (such as the R angle of a square tube), the height of the capacitance feedback is not reliable and the change is difficult to predict. If the capacitance height is used as the main tracking control, the result will be unstable tracking and height errors. The processing mode of laser bevel cutting of square tubes is affected by the square tube and nozzle geometry. The reliability of the capacitance value needs to be additionally provided on the basis of NC (Numerical Control) to consider the above influences to ensure that the cutting path meets expectations.

[0021] The follow-up and Y-axis compensation strategies provided by the present invention can compensate for the focus offset caused by the swing of the swing head, ensuring that the focus of the cutting head is always at the same position of the pipe when the swing head swings arbitrarily, thereby ensuring the consistency of the processing path and improving the processing accuracy. Precise groove processing ensures a good match of the welded joint, reduces the generation of welding defects (such as incomplete penetration, slag inclusions, pores, etc.), and makes the strength, toughness and other mechanical properties of the welded joint closer to the parent material, significantly improving the overall quality and reliability of the welded structure. For example, in the field of aerospace, the welding of parts after high-precision laser groove compensation processing can better withstand stress and loads in extreme environments and ensure flight safety.

[0022] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for follow-up and linear axis compensation of grooved square tube truncation, characterized in that: The following steps are involved: Step 1: Before cutting, perform capacitance calibration; during cutting, monitor the capacitance value in real time and infer the distance h between the nozzle and the metal sheet in actual processing; Step 2: During the cutting process, the Z-axis control refers to the position command of the NC, and the Z-axis temperature rise compensation circuit monitors the working temperature of the capacitor in real time to compensate for the performance change of the capacitor due to temperature rise, and then compensates for the height error based on the position command of the NC; Step 3: Determine whether h is equal to the set value h0. If so, there is no error in the cutting position. If not, there is an error in the cutting position. The Z axis follows the measured actual height h to perform PID closed-loop control. Step 4: In the case of bevel cutting, when the swing head axis is at an angle, if the Z-axis tracking is turned on at the same time, the Y-axis position compensation will be turned on at the same time.

2. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 1 is characterized in that: In step one, before cutting, the capacitance value generated is different due to the different heights between the nozzle and the metal sheet. The capacitance value is 0 when it is in contact with the surface of the sheet, and then gradually moves away from the metal sheet, recording the capacitance values ​​at different heights to generate a height-capacitance value relationship table.

3. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 2 is characterized in that: In step 1, while cutting is in progress, the capacitance value is monitored in real time, and the distance h between the nozzle and the metal sheet in actual processing is inferred based on the current capacitance value and the height-capacitance value relationship table.

4. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 3 is characterized in that: In step 2, the Z-axis temperature rise compensation circuit includes a feedback circuit formed by an operational amplifier and a thermistor.

5. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 4 is characterized in that: Thermistor is used as a temperature sensor, and its resistance change is converted into an electrical signal and fed back to the operational amplifier. The operational amplifier outputs a corresponding control signal to adjust the voltage applied to the capacitor or the current flowing through the capacitor based on the set reference signal.

6. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 5 is characterized in that: In step three, the Z axis follows the measured actual height h to perform PID closed-loop control to achieve h=h0 and realize position compensation.

7. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 6, characterized in that: In step 4, the position compensation command of the Y axis = (Z axis mechanical coordinate command - Z axis motor feedback) * tan (A axis absolute coordinate command).

8. The method for follow-up and linear axis compensation of grooved square tube truncation according to claim 7, characterized in that: In step 4, the Z-axis and A-axis commands use a velocity feedforward compensation strategy to compensate for servo lag and communication delay.

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