Laser temperature control method and machining equipment

Abstract

A kind of laser temperature control method, according to the change of laser thermal load, first real-time large-scale adjustment is carried out to refrigerant target working temperature, then real-time fine adjustment is carried out to the target working temperature of refrigerant according to the temperature change of laser itself by PID control, and the actual temperature of refrigerant approaches and is constant to the target working temperature by PID algorithm control while the target working temperature of refrigerant is adjusted in large scale and finely.The method of the application significantly improves the stability and responsiveness of laser working temperature, and avoids the "false stability" phenomenon that the temperature of water chiller is stable while the temperature of laser is not stable.The refrigeration capacity is adjusted dynamically following the laser output power, so that the maximum temperature variation of laser is ≤±0.25℃ when the laser works in the range of zero to full power.

Description

Technical Field

[0001] The present invention relates to a temperature control method, in particular to a laser temperature notification method, which is beneficial to implement precision laser processing and improve processing accuracy. Background Art

[0002] Lasers, especially pulsed lasers, are widely used in industrial production. Due to their own characteristics, lasers release a lot of heat when working. Generally, the operating temperature range of lasers is ±5 to 10°C, but the heat (temperature) generated by lasers under actual working conditions far exceeds this range. Therefore, precise and constant temperature control is one of the technical obstacles to laser applications.

[0003] Water chillers are a widely used cooling mechanism, also widely used for constant temperature control of lasers. Lasers also come with pre-installed water-cooling connectors to facilitate user integration with water chillers and other cooling devices.

[0004] Generally speaking, a water chiller uses cooling water / liquid as a refrigerant. The low-temperature water output flows through the laser's internal circulation piping, removes heat, and then returns to the chiller. The chiller monitors the return water temperature and adjusts the cooling capacity to keep the high-temperature return water temperature stable near the set point. In general laser processing applications, this configuration is sufficient, maintaining a constant operating temperature of less than ±5°C during laser operation.

[0005] Precision laser processing differs from general laser applications in the following ways: 1) Precision laser processing requires real-time control of laser frequency and energy. The laser's output power and heat generation are constantly changing, creating a variable heat load. In contrast, in general laser processing, the laser only has an on-off function, with a single output power, and its heat generation remains constant, creating a constant heat load. 2) Precision laser processing requires precision at the micron to nanometer level, and even small changes in laser temperature can significantly affect processing accuracy, resulting in processing errors. In general laser processing, where processing is performed at the millimeter level, temperature changes are insufficient to significantly affect processing accuracy and remain within the allowable processing error range.

[0006] Therefore, the current common laser cooling systems used in precision laser processing have the following problems: 1) When the laser output power changes, the laser's operating temperature cannot be maintained constant, but fluctuates within a range of at least 3 to 5 degrees Celsius. This is because the temperature control is a typical time-delay control system. The change in laser power will immediately cause a change in heat generation. This heat change takes time for the water chiller to detect it through the refrigerant temperature increase. By the time the water chiller adjusts the cooling power based on the detected temperature change, the laser output power has already changed (multiple times). This makes it impossible for the water chiller's cooling power to coordinate with the laser power, causing the proportional-integral-derivative (PID) control parameters to oscillate. Similarly, for the same reasons mentioned above, even when the laser power remains unchanged, it is relatively slow to reach equilibrium in the controlled temperature, generally requiring more than 5 minutes.

[0007] In summary, the use of general laser cooling systems for precision laser processing will distort the constant temperature of the water-cooled machine. The temperature change rate and amplitude of the laser will be significantly greater than the changes perceived by the water-cooled machine sensor, which is extremely detrimental to the stable progress of precision laser processing and the realization of high-precision processing. Summary of the Invention

[0008] An object of the present invention is to provide a laser temperature control method, so that the actual temperature of the laser in a working state is maintained within a working range of less than ±1°C, thereby improving the laser processing accuracy.

[0009] Another object of the present invention is to provide a laser temperature control method, so that the cooling power of the water chiller is coordinated with the operating power of the laser, the PID parameter oscillation amplitude is reduced, and the laser temperature is kept constant.

[0010] Another object of the present invention is to provide a device for controlling the temperature of a laser, which is used to coordinate the cooling power of a water chiller with the operating power of the laser, thereby avoiding delays in laser temperature control and being suitable for the implementation of precision laser processing.

[0011] Another object of the present invention is to provide a machining device for performing precision laser processing.

[0012] The method of the present invention monitors the laser thermal load and dynamically adjusts the refrigerant temperature in real time based on changes in the laser thermal load, thereby achieving the effect of maintaining a constant laser temperature under different thermal loads. Specifically, the refrigerant target operating temperature is first significantly adjusted in real time based on changes in the laser thermal load, and then finely adjusted in real time based on changes in the laser's own temperature through PID control. While the refrigerant target operating temperature is being significantly and finely adjusted, the PID algorithm is used to control the actual refrigerant temperature to approach and maintain a constant temperature.

[0013] The method of the present invention adopts a constant temperature target temperature PID control, which forms a dual PID control system with the refrigerator's own refrigeration PID control, greatly reducing system coupling. The monitoring of laser power can monitor both the laser power and the laser control instructions with the same effect.

[0014] A laser temperature control method, comprising:

[0015] The heat load detection module and the temperature detection module detect the real-time heat load and real-time temperature of the laser respectively. When the output power of the laser changes, the pre-programmed set temperature that matches the current power of the laser is used as the cooling target temperature of the refrigerator.

[0016] The temperature detection module continuously detects the laser and obtains the temperature change curve, and dynamically changes the refrigerant target operating temperature of the refrigerator according to the pre-programmed PID control parameters. The refrigerator adjusts the actual refrigerant temperature based on the continuously updated refrigerant target operating temperature and internal PID algorithm.

[0017] A specific implementation of the method of the present invention monitors the heat load and temperature of the laser through a control system (including a power detection module and a temperature detection module), significantly adjusts the target operating temperature of the refrigerant of the refrigerator according to the heat load, and at the same time, based on the laser temperature, finely adjusts the target operating temperature of the refrigerator according to the laser PID algorithm, that is, if the current actual temperature of the laser is higher than the constant target temperature of the laser, the target operating temperature of the refrigerant of the refrigerator is lowered, and if the current actual temperature of the laser is lower than the constant target temperature of the laser, the target operating temperature of the refrigerant of the refrigerator is increased. The PID determines the high or low of the refrigerant target operating temperature according to the deviation between the current actual temperature of the laser and the constant target temperature of the laser;

[0018] The refrigerator maintains the temperature of the refrigerant at the target operating temperature of the refrigerant based on its own cooling PID algorithm. That is, if the current actual temperature of the refrigerant is higher than the target operating temperature of the refrigerant, the refrigerator will cool down. If the current actual temperature of the refrigerant is lower than the target operating temperature of the refrigerant, the refrigerator will heat up or stop cooling. The refrigerator PID determines the cooling power based on the deviation between the current actual temperature of the refrigerant and the target operating temperature of the refrigerant.

[0019] In the method of the present invention, the heat load detection module should be understood as a device for obtaining the output power of the laser, or a software module for obtaining the output power value, or a combination of the device and the software module.

[0020] In the method of the present invention, the temperature detection module should be understood as a device for obtaining the real-time temperature of the laser, or a software module for obtaining the real-time temperature value, or a combination of the device and the software module.

[0021] The method of the present invention implements independent temperature control on the laser body and the laser head.

[0022] The method of the present invention significantly improves the stability and responsiveness of the laser's operating temperature, avoiding the "false stability" phenomenon where the water chiller's temperature is stable but the laser's temperature is unstable. By dynamically adjusting the cooling capacity based on the laser's output power, the maximum temperature variation of the laser is guaranteed to be ≤±0.25°C when the laser operates within the zero to full power operating range. Furthermore, the responsiveness of laser temperature adjustment is significantly improved. When the laser output is stabilized at a certain power, the laser's temperature variation can be controlled within ±0.1°C within 180 seconds.

[0023] In order to implement the above method, the present invention also provides a device for controlling the temperature of the laser, comprising:

[0024] Temperature detection module, used to obtain real-time temperature data of the laser, such as the internal temperature of the laser head and the internal temperature of the laser body;

[0025] Thermal load detection module, used to obtain real-time thermal load related data of the laser, such as input / output voltage, input / output current and input / output power;

[0026] Refrigerator, including cooling mechanism, cooling mechanism and PID electronic control mechanism;

[0027] The master controller includes a programmable controller such as an industrial PC or embedded controller and a communication module.

[0028] The heat load detection module and the temperature detection module provide the obtained data to the master controller, which adjusts the cooling target temperature of the refrigerator based on the measured data.

[0029] The cooling mechanism of the device of the present invention includes a cooling medium, a monitoring and circulating pumping mechanism (such as a circulating pump, a pipeline and a flow sensor, etc.).

[0030] The cooling mechanism of the device of the present invention includes a refrigeration component (such as a semiconductor refrigeration plate or a compressor) and a heat exchange device (such as a heat exchange plate or a heat exchange copper tube).

[0031] The PID electronic control mechanism of the device of the present invention includes a controller (such as an embedded controller, a programmable controller and a temperature sensor) and a power supply.

[0032] In the device of the present invention, the master controller monitors the laser body and the laser head simultaneously, and the laser body and the laser head are respectively provided with coolers to independently adjust and control the temperature.

[0033] Machining equipment using the method of the present invention or equipped with the device of the present invention can achieve precision laser processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a temperature change diagram of the laser using a constant frequency water chiller for temperature control;

[0035] Figure 2 This is a temperature change diagram of the laser using a variable frequency water chiller to control the temperature;

[0036] Figure 3 This is a temperature change diagram of the laser using a semiconductor water cooler to control the temperature;

[0037] Figure 4 This is a temperature change diagram of a laser using the temperature control method of the present invention;

[0038] Figure 5 The figure is a schematic diagram of an embodiment of a device for temperature control according to the method of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below with reference to the accompanying drawings. The embodiments of the present invention are intended only to illustrate the technical solution of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the invention may be modified or replaced with equivalents without departing from the spirit and scope of the technical solution of the present invention, and all such modifications or equivalents should be included in the scope of the claims of the present invention.

[0040] A picosecond laser with a maximum heating power of 300 watts was used as the laser light source and a laser constant frequency water cooler (cooling capacity 1.5 kW, set target temperature 22°C, non-PID temperature control, temperature control range of ±0.1°C), a laser variable frequency water cooler (cooling capacity 0.6 kW, set target temperature 22°C, PID temperature control) and a laser semiconductor water cooler (cooling capacity 0.6 kW, set target temperature 22°C, PID temperature control) were configured to form a laser temperature control scheme. At a room temperature of 25°C and a preset water temperature of 22°C, the laser output power was continuously output from 25% to 100% for 30 minutes, and then switched back to 25% power for 30 minutes. The temperature control and adjustment capability of the refrigeration system was investigated. The results are shown in Table 1.

[0041] Table 1

[0042]

[0043] It can be seen that when the existing water chiller is used to cool the laser, the fluctuation range of the laser is about 3°C ​​or more, which cannot meet the needs of laser precision processing.

[0044] A picosecond laser with a maximum power of 300 watts is used as the laser light source, and a refrigerator (cooling capacity of 0.6 kW, set target temperature of 22°C, PID temperature control) and the method of this embodiment are used. That is, the laser heat load and temperature are monitored by a control system (including a power detector and a temperature detector). The cooling target temperature is significantly adjusted according to the heat load. Based on the laser temperature, the cooling target temperature of the refrigerator is finely adjusted according to the laser PID algorithm. That is, if the laser temperature is higher than the cooling target temperature, the set temperature of the refrigerator is lowered, and if the laser temperature is lower than the cooling target temperature, the set temperature of the refrigerator is increased. The PID determines the set temperature according to the degree of temperature deviation.

[0045] The refrigerator maintains the coolant temperature at the set temperature based on its own cooling PID algorithm. That is, if the refrigerant temperature is higher than the set temperature, it will cool, and if the refrigerant temperature is lower than the set temperature, it will heat. The refrigerator PID determines the cooling power based on the degree of temperature deviation.

[0046] To implement the method of this embodiment, the following method may be used: Figure 5 The device shown controls the laser temperature and includes

[0047] The temperature detection module 100 is used to obtain real-time temperature data of the laser 500, such as the internal temperature of the laser head and the internal temperature of the laser body;

[0048] Thermal load detection module 200, used to obtain real-time thermal load related data of the laser, such as input / output voltage, input / output current and input / output power;

[0049] Refrigerator 300, which includes a cooling mechanism, a cooling mechanism, and a PID electronic control mechanism;

[0050] The master controller 400 includes a programmable controller such as an industrial PC or an embedded controller and a communication module;

[0051] The cooling mechanism includes a refrigerant 600, a monitoring and circulation pumping mechanism, etc. The refrigerant 600 flows through the refrigerator 300 and the laser 500.

[0052] The heat load detection module and the temperature detection module provide the obtained data to the master controller, which adjusts the cooling target temperature of the refrigerator based on the measured data.

[0053] The temperature change of the laser is shown in the following figure: Figure 4As shown in Table 1, the temperature fluctuation during the entire process is ±0.2°C, and the temperature fluctuation during the stable output phase (after 10 minutes of output) is ±0.1°C. Compared with Table 1, the temperature fluctuation during the entire process is significantly reduced, and the temperature fluctuation during the stable output phase is only ±0.1°C, making the laser temperature more stable.

[0054] When the method and device of this embodiment are applied to machining equipment, the requirements of precision laser processing can be met.

Claims

1. A laser temperature control method, characterized in that: According to the changes in the laser's thermal load, the refrigerant's target operating temperature is first adjusted significantly in real time, and then the target operating temperature of the refrigerant is finely adjusted in real time through PID control according to the changes in the laser's own temperature. While making significant and fine adjustments to the refrigerant's target operating temperature, the PID algorithm is used to control the actual refrigerant's actual temperature to approach and maintain a constant temperature.

2. The laser temperature control method according to claim 1, characterized in that: Monitor the thermal load of the laser and make large adjustments to the target operating temperature of the refrigerant in real time according to its changes. Then, finely adjust the target operating temperature of the refrigerant in real time according to the temperature changes of the laser itself through PID control. While making large and fine adjustments to the target operating temperature of the refrigerant, the PID algorithm is used to control the actual temperature of the refrigerant to approach and maintain a constant temperature, thus forming a dual PID control system and reducing system coupling. The monitoring of the laser thermal load may be either the monitoring of the laser thermal load or the monitoring of the control instructions for adjusting the laser thermal load.

3. The laser temperature control method according to claim 1, wherein: The real-time heat load and temperature of the laser are measured through heat load monitoring and laser temperature monitoring respectively. When the heat load of the laser changes, the pre-programmed set temperature that matches the current heat load of the laser is used as the target operating temperature of the refrigerant of the refrigerator. The temperature detection module continuously detects the laser and obtains the temperature change curve, and dynamically changes the refrigerant target operating temperature of the refrigerator according to the pre-programmed PID control parameters. The refrigerator adjusts the refrigerant temperature based on the continuously updated refrigerant target operating temperature and the internal PID algorithm.

4. The laser temperature control method according to claim 1, characterized in that The laser body and laser head are temperature controlled separately.

5. A machining equipment, characterized in that The method comprises the laser temperature control method according to claim 1.

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