阅读说明：本技术 一种金属零件增材制造过程中变形控制系统及方法 (Deformation control system and method in metal part additive manufacturing process ) 是由 来五星 陶春伟 史铁林 于 2019-08-26 设计创作，主要内容包括：本发明属于增材制造技术领域,并具体公开了一种金属零件增材制造过程中变形控制系统及方法,其包括回转工作台、应力消除装置、频率检测装置、成形装置和应力检测装置,其中：应力消除装置包括激振台和激振器,激振台固定在所述激振器上,且其上固定有基板,激振器固定在所述回转工作台上；频率检测装置、成形装置和应力检测装置安装在基板上方；系统工作时,成形装置每堆积数层待成形零件后,频率检测装置获取此时零件的固有频率,应力消除装置以此固有频率振动以消除零件内应力,然后由应力检测装置对零件内应力进行检测,从而在零件逐层堆积的过程中控制零件变形,提高零件的形状尺寸精度。(The invention belongs to the technical field of additive manufacturing, and particularly discloses a deformation control system and method in the additive manufacturing process of metal parts, which comprises a rotary worktable, a stress relief device, a frequency detection device, a forming device and a stress detection device, wherein: the stress relieving device comprises an excitation platform and a vibration exciter, wherein the excitation platform is fixed on the vibration exciter, a base plate is fixed on the excitation platform, and the vibration exciter is fixed on the rotary working table; the frequency detection device, the forming device and the stress detection device are arranged above the substrate; when the system works, after each layer of parts to be formed is stacked by the forming device, the natural frequency of the parts at the moment is obtained by the frequency detection device, the stress relief device vibrates at the natural frequency to relieve the internal stress of the parts, and then the internal stress of the parts is detected by the stress detection device, so that the deformation of the parts is controlled in the process of stacking the parts layer by layer, and the shape and size precision of the parts is improved.)

1. The utility model provides a metal parts vibration material disk in-process warp control system which characterized in that, includes swivel work head (1), stress relief device, frequency detection device, forming device and stress detection device, wherein: the stress relieving device comprises an excitation platform (15) and a vibration exciter (16), wherein the excitation platform (15) is fixed on the vibration exciter (16), a base plate (14) is fixed on the excitation platform, and the vibration exciter (16) is fixed on the rotary working table (1); the frequency detection device, the forming device and the stress detection device are arranged above the substrate (14);

when the forming device works, the forming device deposits the part (12) to be formed on the substrate (14) layer by layer, after each layer is deposited, the frequency detection device obtains the natural frequency of the part (12) to be formed at the moment, and the vibration exciter (16) vibrates at the same frequency as the natural frequency to eliminate the internal stress of the part (12) to be formed; and then the stress detection device detects the internal stress of the part (12) to be formed, if the stress value is greater than or equal to a preset stress threshold value, the vibration exciter (16) repeatedly vibrates until the stress value is less than the preset stress threshold value, and if the stress value is less than the preset stress threshold value, the forming device continues to stack the part (12) to be formed.

2. The system for controlling deformation in the process of metal part additive manufacturing according to claim 1, wherein the frequency detection device comprises a knocking device (6) and a sensor (13), the knocking device (6) is positioned above the base plate (14), and the sensor (13) is mounted on the base plate (14); during detection, the knocking device (6) knocks the part (12) to be formed, the sensor (13) acquires the vibration return characteristic of the part (12) to be formed at the moment, and the natural frequency of the part (12) to be formed at the moment is obtained according to the vibration return characteristic.

3. The system of claim 1, wherein the stress-detecting device is an ultrasonic stress-detecting device.

4. The system for controlling deformation in the metal part additive manufacturing process according to claim 3, wherein the ultrasonic stress detection device comprises an ultrasonic transmitting probe (5), an ultrasonic receiving probe (11), an ultrasonic signal generator (4) and an echo processor (7), the ultrasonic transmitting probe (5) and the ultrasonic receiving probe (11) are arranged on two sides of the part (12) to be formed, the ultrasonic signal generator (4) is connected with the ultrasonic transmitting probe (5), and the echo processor (7) is connected with the ultrasonic receiving probe (11).

5. A method for controlling deformation in the process of metal part additive manufacturing, which is realized by the system according to any one of claims 1-4, and is characterized by comprising the following steps:

s1 the forming device deposits a plurality of layers of parts (12) to be formed on the substrate (14) according to a preset track, and the frequency detection device acquires the natural frequency of the parts (12) to be formed;

the S2 vibration exciter (16) vibrates at the same frequency as the natural frequency, so that the part to be formed (12) is driven to vibrate by the vibration exciting table (15) to eliminate the internal stress of the part to be formed (12);

s3, detecting the internal stress of the part (12) to be formed by the stress detection device, and if the detected stress value is greater than or equal to the preset stress threshold value, repeating S2 until the detected stress value is less than the preset stress threshold value; if the detected stress value is smaller than the preset stress threshold value, the step S4 is executed;

s4 repeats S1 to S3 several times until the manufacture of the part is completed.

6. The method for controlling the deformation of a metal part during the additive manufacturing process according to claim 5, wherein the step of obtaining the natural frequency of the part (12) to be formed comprises the following steps: the knocking device (6) knocks the part (12) to be formed at a preset knocking point, the sensor (13) acquires the vibration return characteristic of the part (12) to be formed at the moment, and the natural frequency of the part (12) to be formed at the moment is further obtained according to the vibration return characteristic.

7. The method for controlling deformation in the process of manufacturing the metal part with the additive according to claim 5, wherein the number of stacked layers in the step S1 is preferably three.

Technical Field

The invention belongs to the technical field of additive manufacturing, and particularly relates to a deformation control system and method in a metal part additive manufacturing process.

Background

The traditional manufacturing method of the metal parts adopts a casting, forging, milling and separating process, firstly, a forging blank is cast, then, repeated forging and milling are carried out to manufacture each part, and finally, the parts are assembled. Although the machining process for reducing the material can obtain parts meeting the quality and precision requirements, the machining process has the defects of long machining period, low material utilization rate, low efficiency and the like.

The metal additive manufacturing technology is a novel manufacturing technology which directly processes a digital model into a solid part by adopting a material layer-by-layer accumulation method, and the technology opens the design limitation, releases the design imagination space and provides possibility for the integral manufacturing of large metal complex parts. The basic process comprises the following steps: the wire material is melted by a high-energy beam (electric arc, laser and the like) heat source, then the small metal molten drops are stacked or deposited layer by layer through a nozzle, and forging and milling are assisted in the process of follow-up, so that the large metal integral part with controllable performance is obtained. As the additive manufacturing is a multi-physical-field composite process, the additive manufacturing is a process of mutual influence and interaction of a temperature field, a force field and a stress field, and comprises heat sources such as electric arcs, plasmas or lasers, thermal contraction in a molten drop forming process, thermal temperature difference between layers, forging when the performance is improved, and later milling and grinding. The mass of large metal parts, particularly bearing parts, not only requires that the mechanical property reaches the standard, but also requires that the shape, the size and even the precision of the manufactured parts meet the design requirements. Because the additive manufacturing process is the accumulation of molten drops layer by layer, the heat, force and stress interaction stress is also formed and accumulated layer by layer, and the stress can be slowly released to generate deformation in the manufacturing process or after the manufacturing process is finished. Particularly, the dimensional accuracy of the large part is guaranteed layer by layer in the whole manufacturing process, stress is slowly generated and accumulated in the layer by layer manufacturing process, some stress can be naturally released along with time to bring a dimension error of a front layer, and along with the completion of the whole manufacturing process, the stress of a formed part in a natural state is released, and the accumulated deformation quantity of the large part can cause the deformation of the large part to exceed the design allowable range, even generate buckling deformation, which is an unacceptable result for the large metal part.

In order to solve the quality problems, the current researchers combine the metal additive manufacturing technology with the parallel control and ultrasonic strengthening technology, so as to improve the mechanical property and the surface size precision of a formed part. For example, patent CN109746443A discloses a method for controlling part deformation and precision in an additive manufacturing process in parallel, which realizes high-precision and high-performance additive manufacturing with a one-step in-place type ultra-short process by controlling the position of a part to be processed to be unchanged and simultaneously performing different processes on different processing layers or the same processing layer in the processing process, but this method cannot eliminate the influence of stress on the deformation of a formed part. Patent CN106735967B discloses a method for controlling shape and control performance in additive manufacturing of electric arc by ultrasonic vibration, which applies non-contact ultrasonic vibration in the additive manufacturing process to increase nucleation rate so as to refine molten pool crystal grains, and simultaneously reduces the generation of internal defects of the formed part, thereby improving the mechanical properties of the part, but this method cannot fundamentally eliminate the internal stress generated in the production process of the formed part. At present, the stress relief and deformation control in the additive manufacturing process are blank.

Disclosure of Invention

Aiming at the defects or improvement requirements in the prior art, the invention provides a deformation control system and a deformation control method in the metal part additive manufacturing process, and aims to eliminate stress in the additive manufacturing process through the matching of a frequency detection device and a stress elimination device, and detect the internal stress of a part to be formed by the stress detection device, so that the part deformation is controlled in the process of stacking the parts layer by layer, and the shape and size precision of the part is improved.

In order to achieve the above object, according to an aspect of the present invention, a deformation control system in an additive manufacturing process of a metal part is provided, including a rotary table, a stress relief device, a frequency detection device, a forming device, and a stress detection device, wherein: the stress relieving device comprises an excitation platform and a vibration exciter, wherein the excitation platform is fixed on the vibration exciter, a base plate is fixed on the excitation platform, and the vibration exciter is fixed on the rotary working table; the frequency detection device, the forming device and the stress detection device are arranged above the substrate;

when the forming device works, the forming device accumulates parts to be formed on the substrate layer by layer, after each layer is accumulated, the frequency detection device acquires the natural frequency of the parts to be formed at the moment, and the vibration exciter vibrates at the same frequency as the natural frequency to eliminate the internal stress of the parts to be formed; and then detecting the internal stress of the part to be formed by the stress detection device, if the stress value is greater than or equal to a preset stress threshold value, repeatedly vibrating the vibration exciter until the stress value is less than the preset stress threshold value, and if the stress value is less than the preset stress threshold value, continuously accumulating the part to be formed by the forming device.

As a further preferred, the frequency detection device comprises a tapping device and a sensor, the tapping device is located above the substrate, and the sensor is mounted on the substrate; during detection, the knocking device knocks the part to be formed, the sensor obtains the back vibration characteristic of the part to be formed at the moment, and the natural frequency of the part to be formed at the moment is obtained according to the back vibration characteristic.

More preferably, the stress detection device is an ultrasonic stress detection device.

Preferably, the ultrasonic stress detection device comprises an ultrasonic transmitting probe, an ultrasonic receiving probe, an ultrasonic signal generator and an echo processor, wherein the ultrasonic transmitting probe and the ultrasonic receiving probe are arranged on two sides of the part to be formed, the ultrasonic signal generator is connected with the ultrasonic transmitting probe, and the echo processor is connected with the ultrasonic receiving probe.

According to another aspect of the invention, a deformation control method in a metal part additive manufacturing process is provided, which is implemented by using the system, and comprises the following steps:

s1 the forming device deposits several layers of parts to be formed on the base plate according to the preset track, the frequency detecting device obtains the natural frequency of the part to be formed;

the vibration exciter of S2 vibrates with the same frequency as the natural frequency, so that the part to be formed is driven to vibrate by the vibration exciting table to eliminate the internal stress of the part to be formed;

s3, detecting the internal stress of the part to be formed by the stress detection device, and if the detected stress value is greater than or equal to the preset stress threshold value, repeating S2 until the detected stress value is less than the preset stress threshold value; if the detected stress value is smaller than the preset stress threshold value, the step S4 is executed;

s4 repeats S1 to S3 several times until the manufacture of the part is completed.

As a further preferred, the step of obtaining the natural frequency of the part to be formed specifically includes the following steps: the knocking device knocks the part to be formed at a preset knocking point, the sensor obtains the back vibration characteristic of the part to be formed at the moment, and the natural frequency of the part to be formed at the moment is obtained according to the back vibration characteristic.

More preferably, the number of stacked layers in S1 is three.

Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1. the invention integrates additive manufacturing, stress relief and detection into the same machine tool, improves the part processing efficiency compared with the traditional method of separately processing the additive manufacturing, the stress relief and the stress detection, realizes the direct layer-by-layer manufacturing of the metal integral part meeting the use requirement on the same equipment and the same position, is particularly suitable for the processing of large high-performance complex special-shaped parts, realizes the integral in-situ manufacturing of the large part which is formed by splicing a plurality of parts originally, and controls the deformation of a large structural part.

2. The deformation control system is compact and stable in overall structure, and reduces overturning moment of the rotary table when the rotary table needs to be overturned due to working conditions of parts.

3. The vibration exciter with the gradually-changed adjustable frequency is utilized, and the vibration exciter can adapt to the situation that the natural frequency is continuously changed along with the layer-by-layer growth of a part, so that the stress is eliminated in the machining process in the additive manufacturing process, the internal stress of the part is greatly reduced, the shape and the size precision of the surface of the part are improved, and the deformation of a large metal part is controlled in the additive manufacturing process; meanwhile, aiming at the difference of the natural frequencies of parts made of different materials, the vibration frequency of the vibration exciter is adjusted by using a computer so as to adapt to different working conditions; and according to the vibration aging principle, the vibration is carried out under the natural frequency of the part, so that the vibration treatment time can be shortened, the effects of stress relief and precision stabilization are better, and the energy consumption is minimum.

4. In the invention, the condition of layer-by-layer manufacturing (including accumulation, rolling and milling and grinding) of additive manufacturing is considered, and the ultrasonic stress detection equipment detects the internal stress of the current manufacturing layer of the part, so that the detection precision is ensured while a certain detection depth is ensured; and the ultrasonic detection has low cost, convenient carrying and small limitation, and is very suitable for realizing the stress layer-by-layer online detection in the additive manufacturing process.

Drawings

FIG. 1 is a schematic diagram of an overall structure of a deformation control system in an additive manufacturing process of a metal part according to an embodiment of the present invention;

FIG. 2 is a three-dimensional view of a rotary table and a stress relief device in an embodiment of the invention;

fig. 3 is a flowchart of a deformation control method in an additive manufacturing process of a metal part according to an embodiment of the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-rotary table, 2-pneumatic chuck, 3-computer, 4-ultrasonic signal generator, 5-ultrasonic transmitting probe, 6-knocking device, 7-echo processor, 8-nozzle, 9-rolling mechanism, 10-control device, 11-ultrasonic receiving probe, 12-part to be formed, 13-sensor, 14-base plate, 15-excitation table and 16-vibration exciter.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The deformation control system provided by the embodiment of the invention in the metal part additive manufacturing process comprises a rotary worktable 1, a stress relieving device, a frequency detection device, a forming device, a stress detection device and a computer 3, wherein as shown in fig. 1:

the rotary worktable 1 is an electromechanical universal rotary worktable and comprises a horizontal worktable and a double-shaft displacement mechanism, wherein the horizontal worktable can move along the directions of three dimensions of x, y and z, and a pneumatic chuck 2 is fixed on the horizontal worktable through a positioning pin; the double-shaft displacement mechanism is arranged below the horizontal workbench and is used for enabling the horizontal workbench to axially rotate along the y direction and the z direction;

the stress relieving device comprises an excitation platform 15 and a vibration exciter 16, the lower end of the excitation platform 15 is a cylindrical bulge, the radius of the cylindrical bulge is the same as that of the vibration exciter 16, the cylindrical bulge and the vibration exciter 16 are fixed through an annular chuck, a base plate 14 is fixed on the excitation platform 15 through a clamp, and the base plate 14 is used for placing a part 12 to be formed; the lower end of the vibration exciter 16 is fixed on the pneumatic chuck 2, and specifically, the vibration exciter 16 is a gradual change adjustable frequency vibration exciter, such as a piezoelectric ceramic vibration exciter;

the frequency detection device comprises a sensor 13 and a knocking device 6, the sensor 13 is an acceleration vibration sensor and is arranged on a substrate 14, and the knocking device 6, the forming device and the stress detection device are positioned above the substrate 14; the forming device comprises a nozzle 8, a roller mechanism 9 and a control device 10, wherein the nozzle 8 and the roller mechanism 9 are connected with the control device 10, and part accumulation and roller rolling are carried out under the control of the control device 10;

the computer 3 is connected with the stress relieving device, the frequency detection device and the ultrasonic detection device.

Furthermore, the stress detection device is an ultrasonic stress detection device and comprises an ultrasonic emission probe 5, an ultrasonic receiving probe 11, an ultrasonic signal generator 4 and an echo processor 7, wherein the ultrasonic emission probe 5 and the ultrasonic receiving probe 11 are arranged on two sides of a part 12 to be formed, the ultrasonic signal generator 4 is connected with the ultrasonic emission probe 5, and the echo processor 7 is connected with the ultrasonic receiving probe 11.

The deformation control by using the system comprises the following steps as shown in fig. 3:

s1, layering the three-dimensional model of the part 12 to be formed, and generating a forming track suitable for the structure of the part according to the shape characteristics and the processing parameters of each layer;

s2 the forming device deposits several layers of parts 12 to be formed on the substrate 14 according to the forming track under the control of the control device 10; the knocking device 6 knocks the part 12 to be formed at a preset knocking point, meanwhile, the sensor 13 acquires the back vibration characteristic of the part 12 to be formed at the moment and transmits the back vibration characteristic to the computer 3, and the computer 3 processes the back vibration characteristic to generate a frequency response characteristic diagram of the part, so that the inherent frequency of the part 12 to be formed at the moment is determined; specifically, the knocking device 6 performs knocking for multiple times to determine accurate natural frequency, and meanwhile, whether the part achieves the expected strength and toughness can be judged according to the result of the knocking test;

the vibration exciter 16 of S3 vibrates at the same frequency as the natural frequency, so that the part 12 to be formed is driven to vibrate by the vibration exciting table 15 to eliminate the internal stress of the part 12 to be formed; meanwhile, the relative positions of the part 12 to be formed and the vibration exciter 16 are adjusted by turning over the rotary table 1, and the detection and manufacturing positions are changed.

S4, starting the ultrasonic signal generator 4, transmitting the generated excitation signal to the ultrasonic transmitting probe 5 to enable the ultrasonic signal to be transmitted and form critical refraction longitudinal waves in the part, receiving an echo signal by the ultrasonic receiving probe 11 after transmitting a certain distance, converting the echo signal into an analog signal and transmitting the analog signal to the echo processor 7, amplifying, filtering, shaping and AD converting the analog signal by the echo processor 7 and transmitting the analog signal to the computer 3, and calculating the internal stress value of the part by the computer 3; if the detected stress value is greater than or equal to the predetermined stress threshold, repeating S3 until the detected stress value is less than the predetermined stress threshold; if the detected stress value is smaller than the preset stress threshold value, the step S5 is executed;

s5 repeats S2 to S4 several times until the manufacture of the part is completed.

Preferably, frequency detection and stress relief are performed once after three layers of the part 12 to be formed are stacked in S2, and stress relief and detection are also performed if the part is subjected to subsequent processing such as milling and grinding for improving surface accuracy.

Further, the natural frequency of the part 12 to be formed in S2 may also be obtained by performing finite element analysis after line laser scanning, or by detecting the stress of the tool during machining and performing spectrum analysis.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.