阅读说明：本技术 一种激光沉积成形过程监测装置与双闭环控制方法 (Laser deposition forming process monitoring device and double closed-loop control method ) 是由 赵凯 杨萍 郝云波 朱忠良 梁旭东 张春杰 赵维刚 于 2020-12-01 设计创作，主要内容包括：一种激光沉积成形过程监测装置与双闭环控制方法,该装置包括测距传感器、熔池观测传感器和控制单元。该双闭环控制方法中,包括外环控制方法和内环控制方法。外环控制方法中,包括测距传感器,安装在加工头侧面,使激光束与工件加工面垂直,测量加工头与加工表面的距离,控制系统将所测距离与预设距离进行对比,得出加工头与加工表面的距离误差,距离误差作为闭环控制算法的输入,被控工艺参数提升量的调整变化值作为输出。内环控制方法中,包括熔池观测传感器,同轴或旁轴安装在加工头上,获取熔池的形状、尺寸信息,控制单元根据预存熔池数据库得出熔池数据偏差量,被控工艺参数的变化量激光功率、送粉速度的调整变化值作为输出。(A monitoring device for a laser deposition forming process and a double closed-loop control method are provided, the device comprises a distance measuring sensor, a molten pool observation sensor and a control unit. The double closed-loop control method comprises an outer loop control method and an inner loop control method. The outer ring control method comprises a distance measuring sensor which is arranged on the side surface of a processing head to enable a laser beam to be vertical to a processing surface of a workpiece, the distance between the processing head and the processing surface is measured, a control system compares the measured distance with a preset distance to obtain a distance error between the processing head and the processing surface, the distance error is used as the input of a closed-loop control algorithm, and the adjustment change value of the controlled process parameter lifting amount is used as the output. The inner ring control method includes the molten pool observation sensor, the coaxial or paraxial installation on the processing head, the acquisition of the shape and size information of the molten pool, the control unit according to the pre-stored molten pool database to obtain the deviation of the molten pool data, the controlled process parameter variation laser power, the powder feeding speed adjustment variation as output.)

1. A laser deposition modeling process monitoring apparatus, comprising: the device comprises a distance measuring sensor, a molten pool observation sensor and a control unit;

the distance measuring sensor is arranged on the side surface of the processing head, enables the laser beam to be vertical to the processing surface of the workpiece, is used for measuring the distance between the processing head and the processing surface and transmits height data to the control unit;

the molten pool observation sensor is coaxially arranged at the processing head, and the molten pool is coaxially observed by utilizing the light path to obtain the shape and the size of the molten pool;

and the control unit is used for processing the distance between the processing head and the processing surface and the shape and the size of the molten pool, which are measured by the distance measuring sensor and the molten pool observation sensor, calculating a deviation value, adjusting the technological parameters in the forming process in real time and feeding back the technological parameters to the control unit.

2. The apparatus as claimed in claim 1, wherein the distance measuring sensor has a sampling frequency of 500-1000 HZ, and is capable of measuring the distance between the processing head and the processing surface and outputting the measured distance as an analog value.

3. A laser deposition modeling process monitoring apparatus as claimed in claim 1 or claim 2 wherein the bath view sensor includes an image processor for processing the acquired bath image to output the bath shape parameters in analog form.

4. The apparatus of claim 3, wherein the weld puddle observation sensor processes the collected weld puddle image for less than 30 ms.

5. The device for monitoring the laser deposition forming process according to claim 4, wherein the control unit is a PLC or an embedded processor.

6. The double closed-loop control method based on the laser deposition forming process monitoring device as claimed in any one of claims 1 to 5, characterized by comprising the following steps:

step 1: before laser deposition forming begins, adjusting the position of a processing head to a preset height value, enabling a measuring visual angle of a distance measuring sensor to be vertical to a processing surface of a workpiece, enabling a measuring center of a molten pool observation sensor to coincide with a working focus center of laser processing, and inputting the height of the processing head and the preset size value of the molten pool in a parameter setting interface;

step 2: setting initial laser power, powder feeding amount and lifting amount, setting a laser deposition forming track, and starting a forming processing process;

and step 3: in the laser deposition forming process, the distance measuring sensor and the molten pool observation sensor set the same sampling frequency;

and 4, step 4: the control unit subtracts a set value from the current size of the molten pool and the distance between the processing head and the processing surface to obtain the distance between the processing head and the processing surface and the deviation value of the size of the molten pool in the current sampling period;

and 5: the control unit controls the movement mechanism to adjust the lifting amount in real time according to the obtained distance deviation amount between the processing head and the processing surface; and controlling a laser and a powder feeder according to the obtained size deviation quantity of the molten pool to adjust the laser power and the powder feeding quantity in real time.

7. The double closed-loop control method for the monitoring device of the laser deposition forming process as claimed in claim 6, wherein in the step 3, the distance measuring sensor obtains the distance between the current processing head and the processing surface according to the set sampling frequency; and the molten pool observation sensor acquires the current molten pool size data in the same period according to the set sampling frequency.

8. The method of claim 6, wherein if the deviation of the distance between the processing head and the processing surface in step 5 is positive, the moving mechanism needs to reduce the deviation in the direction perpendicular to the processing surface.

9. The method as claimed in claim 6, wherein the deviation of the distance between the processing head and the processing surface in step 5 is negative, and the moving mechanism is required to lift the deviation in the direction perpendicular to the processing surface.

10. The double closed-loop control method of the monitoring device for the laser deposition forming process as claimed in claim 6, wherein the deviation amount of the size of the molten pool in the step 5 is used as the input of a control algorithm, and the adjusted values of the laser power and the powder feeding amount are output; if the size deviation of the molten pool is a positive value, reducing the laser power and the powder feeding amount; if the size deviation of the molten pool is negative, the laser power and the powder feeding amount are increased.

Technical Field

The invention belongs to the field of advanced manufacturing, relates to the field of laser cladding and laser deposition forming, and particularly relates to a monitoring device and a double closed-loop control method for a laser deposition forming process.

Background

The laser deposition forming technology is one of additive manufacturing technologies, takes alloy powder as a raw material, takes synchronous feeding of the powder as a characteristic, and performs layer-by-layer deposition manufacturing through laser melting/rapid solidification, and a part CAD model completes near-net-shape manufacturing of a fully-compact and high-performance metal structural part in one step. Because of its unique technical advantages, it is praised as a "revolutionary" and "shape-controlling/controlling" integrated manufacturing technique, and has a wide development prospect in the manufacture of important equipment for aviation, aerospace and the like. The technology has high material utilization rate, can realize the manufacture of complex high-performance components with mechanical properties equivalent to those of forgings, has the synchronous material feeding characteristic, can realize the manufacture of gradient structures, and can be used for high-performance repair of damaged components.

In the laser deposition forming process, the lifting amount of a single layer of the cladding processing head needs to be consistent with the actual increasing height of the cladding layer, so that the laser focus is always positioned on the processing surface. During actual processing, the single-layer lifting amount is generally set to be a fixed value, and as the height of a formed part increases, errors are accumulated layer by layer, so that a defocusing phenomenon can occur. The positive defocusing and the negative defocusing can change the working focal length of the laser, so that the spot size of the laser, the size of a molten pool and the temperature are changed, and finally, the phenomenon that the size of a workpiece is not consistent with an actual model or the workpiece collapses and the like can be caused. Therefore, a device capable of accurately measuring the height of the cladding processing head and the size of a molten pool is needed, height and molten pool size information can be fed back in real time, and the lifting amount, laser power and powder feeding amount of each layer can be adjusted in real time according to deviation, so that the stability of the processing process is ensured, and the appearance and quality of the processed surface are improved.

The existing control mode for monitoring the stability of the laser deposition forming process generally only monitors the height of a cladding layer, adjusts the lifting amount, neglects the overlarge local heat accumulation of a molten pool and is easy to cause collapse; or only monitoring the molten pool, adjusting the laser power and the powder feeding amount, neglecting the defocusing phenomenon caused by the accumulated error of the height of the cladding layer, and causing the problems of inconsistent size, low precision, poor surface quality and the like of a formed part.

Disclosure of Invention

The invention aims to provide a device for monitoring a laser deposition forming process and a double closed-loop control method, so as to realize double closed-loop accurate control of single-layer lifting amount, laser power and powder feeding amount of a cladding layer, ensure the stability of a processing process and improve the appearance and quality of a processed surface.

In order to solve the problems, the technical scheme of the invention is as follows: a laser deposition modeling process monitoring apparatus, comprising: the device comprises a distance measuring sensor, a molten pool observation sensor and a control unit;

the distance measuring sensor is arranged on the side surface of the processing head, enables the laser beam to be vertical to the processing surface of the workpiece, is used for measuring the distance between the processing head and the processing surface and transmits height data to the control unit;

the molten pool observation sensor is coaxially arranged at the processing head, and the molten pool is coaxially observed by utilizing the light path to obtain the shape and the size of the molten pool;

the control unit is used for processing the distance between the processing head and the processing surface and the shape and the size of the molten pool, which are measured by the distance measuring sensor and the molten pool observation sensor, calculating a deviation value, adjusting process parameters in the forming process in real time and feeding back the process parameters to the control unit;

preferably, the sampling frequency of the distance measuring sensor is 500-1000 HZ, the distance between the processing head and the processing surface can be measured, and the distance is output by analog quantity values.

Furthermore, the molten pool observation sensor comprises an image processor, and can process the collected molten pool image and output the molten pool shape parameters in an analog quantity mode, wherein the whole processing process is less than 30 ms.

Further, the control unit is a PLC or an embedded processor.

Another technical solution of the present invention is to provide a double closed-loop control method based on the above laser deposition forming process monitoring apparatus, which is characterized by comprising the following steps:

step 1: before laser deposition forming begins, adjusting the position of a processing head to a preset height value, enabling a measuring visual angle of a distance measuring sensor to be vertical to a processing surface of a workpiece, enabling a measuring center of a molten pool observation sensor to coincide with a working focus center of laser processing, and inputting the height of the processing head and the preset size value of the molten pool in a parameter setting interface;

step 2: setting initial laser power, powder feeding amount and lifting amount, setting a laser deposition forming track, and starting a forming processing process;

and step 3: in the laser deposition forming process, the distance measuring sensor and the molten pool observation sensor set the same sampling frequency;

and 4, step 4: the control unit subtracts a set value from the current size of the molten pool and the distance between the processing head and the processing surface to obtain the distance between the processing head and the processing surface and the deviation value of the size of the molten pool in the current sampling period;

and 5: the control unit controls the movement mechanism to adjust the lifting amount in real time according to the obtained distance deviation amount between the processing head and the processing surface; and controlling a laser and a powder feeder according to the obtained size deviation quantity of the molten pool to adjust the laser power and the powder feeding quantity in real time.

Compared with the prior art, the laser deposition forming process monitoring device and the double closed-loop control method can monitor the height of the cladding layer, adjust the lifting amount and solve the defocusing phenomenon caused by the accumulated error of the height of the cladding layer; and the molten pool can be monitored, the laser power and the powder feeding amount can be adjusted, and the problems of collapse, inconsistent size of a formed part, low precision, poor surface quality and the like caused by overlarge local heat accumulation of the molten pool are solved.

Drawings

The invention is further described below with reference to the accompanying drawings:

FIG. 1 is a view showing the components of a monitoring apparatus for laser deposition modeling (paraxial installation of a bath observation sensor) according to an embodiment of the present invention.

FIG. 2 is a view showing the components of a monitoring apparatus for laser deposition modeling (a molten pool observation sensor is installed coaxially) according to an embodiment of the present invention.

Fig. 3 is a control schematic block diagram of a dual closed-loop control method in an embodiment of the present invention.

Detailed Description

The following will make a further clear description of the manufacturing method of a spherical storage tank based on laser near-net-shape forming technology, which is proposed by the present invention, with reference to the accompanying drawings and specific examples. Advantages and features of the present invention will become apparent from the following description and from the claims.

The invention is described in further detail below with reference to the figures and examples.

Referring to fig. 1 and 2, the monitoring device for the laser deposition forming process according to the embodiment of the invention is composed of a distance measuring sensor 3, a molten pool observation sensor 5 and a control unit 2.

The distance measuring sensor is arranged on the side surface of the processing head 1, enables the laser beam to be vertical to the processing surface of the workpiece, is used for measuring the distance between the processing head 1 and the processing surface 4, and transmits height data to the control unit;

the molten pool observation sensor is coaxially arranged on the machining head 1, and the molten pool is coaxially observed by utilizing a light path to obtain the shape and the size of the molten pool;

the control unit is used for processing the distance between the processing head and the processing surface and the shape and the size of the molten pool, which are measured by the distance measuring sensor 3 and the molten pool observation sensor 5, calculating a deviation value, adjusting process parameters in the forming process in real time and feeding back the process parameters to the control unit 2; (ii) a

The distance measuring sensor 3 can select a laser distance measuring sensor with a measuring range of 50-500 mm and a sampling frequency of 500-1000 HZ, measures the distance between the processing head 1 and the processing surface 4, and outputs the distance by analog quantity values.

The molten pool observation sensor 3 comprises an image processor, can process the collected molten pool image, and outputs the molten pool shape parameters in an analog quantity mode, and the whole processing process is less than 30 ms.

The control unit 2 is a PLC or an embedded processor.

Referring to fig. 3, the double closed-loop control method of the laser deposition forming process monitoring device includes the following steps:

step 1: before laser deposition forming begins, the position of a processing head 1 is adjusted to a preset height value, the measuring visual angle of a distance measuring sensor 3 is perpendicular to the processing surface of a workpiece, the measuring center of a molten pool observation sensor 5 is overlapped with the working focus center of laser processing, and the height of the processing head and the preset size value of the molten pool are input into a parameter setting interface.

Step 2: setting initial laser power, powder feeding amount and lifting amount, setting a laser deposition forming track, and starting a forming processing process.

And step 3: in the laser deposition forming process, the distance measuring sensor 3 and the molten pool observation sensor 3 set the same sampling frequency; the distance measuring sensor 3 acquires the distance between the current processing head 1 and the processing surface 4 according to a set sampling frequency; the molten pool observation sensor 5 acquires the size data of the molten pool in the same period at present according to the set sampling frequency; .

And 4, step 4: and the control unit 2 subtracts a set value from the current size of the molten pool and the distance between the processing head and the processing surface to obtain the distance between the processing head and the processing surface and the deviation of the size of the molten pool in the current sampling period.

And 5: the control unit 2 controls the motion mechanism to adjust the lifting amount in real time according to the obtained distance deviation amount between the processing head 1 and the processing surface 4; controlling a laser and a powder feeder according to the obtained size deviation of the molten pool to adjust the laser power and the powder feeding amount in real time, such as: if the distance deviation between the processing head 1 and the processing surface 4 is a positive value, the motion mechanism needs to reduce the deviation value along the direction vertical to the processing surface; if the distance deviation between the processing head 1 and the processing surface 4 is a negative value, the motion mechanism needs to lift the deviation value along the direction vertical to the processing surface;

the size deviation of the molten pool is used as the input of a control algorithm, and the adjustment values of the laser power and the powder feeding amount are output; if the size deviation of the molten pool is a positive value, reducing the laser power and the powder feeding amount; if the size deviation of the molten pool is negative, the laser power and the powder feeding amount are increased.