Pulsed laser selective melting integrated forming system and method

Abstract

The present application relates to a pulse laser selective melting integrated forming system and method, and belongs to the field of laser composite manufacturing. The system comprises a laser composite manufacturing module, an online monitoring and control module, and a forming cavity. The pulse laser in the laser composite manufacturing module is incident on the forming cavity to melt the powder additive forming and to impact and / or subtract material in situ according to the monitoring results and the printing precision requirements. The online monitoring and control module is used to monitor the molten pool temperature, the forming process, and the printing appearance in real time, and to control the entire composite manufacturing process of the additive forming, the in-situ impact, and the in-situ subtracting. The pulse laser selective melting integrated forming method comprises using a pulse laser for additive forming, in-situ impact, and / or in-situ subtracting according to the monitoring results and the printing precision requirements, to obtain a high-precision and high-performance printing part. The system can be used for structure and performance integrated additive forming, and the method can be used to efficiently obtain a high-precision and high-performance printing part.

Description

Technical Field

[0001] This invention relates to the field of laser composite manufacturing, and in particular to a pulsed laser selective melting integrated forming system and method. Background Technology

[0002] Existing selective laser melting systems and methods primarily utilize continuous lasers or pulsed continuous lasers for melting. A few devices and methods employ nanosecond pulsed laser melting, and femtosecond laser selective melting for materials such as tungsten and iron has also been reported. The current problems with selective laser melting include: excessive temperature gradients during rapid melting, leading to significant thermal and residual stresses in the material, resulting in warping, deformation, and cracking; coarse columnar crystal structures in the printed parts; and anisotropic mechanical properties. Pulsed lasers, especially ultrafast lasers, have smaller heat-affected zones, and femtosecond lasers, being a cold processing method, are beneficial for reducing temperature gradients and improving material properties.

[0003] Currently, laser selective melting systems and methods (laser powder bed methods) produce printed parts with higher surface roughness and dimensional accuracy than powder / filament feeding methods and electron beam powder spreading methods, but still cannot reach the precision of traditional subtractive machining. Additive-subtractive composite manufacturing utilizes the advantages of additive manufacturing's layer-by-layer deposition and subtractive machining's high precision, especially in the high-precision machining of complex structures. Compared to subtractive machining using cutting tools, laser additive-subtractive composite manufacturing offers advantages such as non-contact with materials, no limitations on the size of the machined parts, and no cutting residue; while femtosecond lasers can directly vaporize materials without a heat-affected zone, giving them an advantage in subtractive machining involving material removal.

[0004] When the thermal and residual stresses within additively manufactured printed parts exceed the material's yield strength, deformation and cracking occur, particularly pronounced in high-melting-point, brittle materials. This has become a pressing issue hindering the application of printed parts. Micro-casting and forging, combined with additive manufacturing, can close microcracks in printed parts. For complex structures, laser shock stabilization (LSS) offers even greater advantages. Three-dimensional LSS can impact single-layer or multi-layer printed parts, affecting the entire part rather than just its surface; it can refine grains, close microcracks, and improve the material's fatigue resistance, corrosion resistance, and wear resistance. Previously, the Swiss Federal Institute of Technology in Lausanne (EPFL) and Jiangsu University in China implemented additive manufacturing and LSS separately in different subsystems, which reduced processing efficiency and accuracy, and increased system complexity.

[0005] Therefore, there is an urgent need for a system that can integrate additive manufacturing, laser blasting, and in-situ subtractive manufacturing to solve the problems of low precision of printed parts and low processing efficiency caused by performing additive manufacturing and laser blasting separately in different systems. Summary of the Invention

[0006] The purpose of this invention is to provide a pulsed laser selective melting integrated forming system and method to solve the problems of low precision of current additive manufacturing printed parts and low processing efficiency caused by performing additive manufacturing and laser shock in different systems.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A pulsed laser selective melting integrated forming system includes: a laser composite manufacturing module, an online monitoring and control module, and a forming cavity; the pulsed laser selective melting integrated forming system is used to realize additive forming, in-situ impact forming, and in-situ subtractive forming of printed parts.

[0009] In the laser composite manufacturing module, a pulsed laser is incident into the forming cavity to melt the powder and complete the additive manufacturing process. Based on the monitoring results and the accuracy requirements of the printed parts, the printed parts are subjected to in-situ impact and / or in-situ subtractive processing.

[0010] The online monitoring and control module is used to monitor the molten pool temperature, forming process, morphology of printed parts and powder spreading in real time, and to determine whether the printed parts are warped, cracked or raised based on the morphology of the printed parts. Based on the monitoring results and the accuracy requirements of the printed parts, the power, frequency and spot diameter of the pulsed laser are adjusted, and the entire composite manufacturing process of additive forming, in-situ impact and in-situ subtractive forming is controlled.

[0011] Optionally, the laser system includes a pulsed laser, a variable magnification beam expander, a first semi-transparent mirror, a galvanometer, and a field mirror arranged sequentially.

[0012] Optionally, the wavelength range of the pulsed laser is 193nm-1100nm, and the pulse width range is 30fs-2×10⁻¹⁰. 8 fs.

[0013] Optionally, the online monitoring and control module includes an online monitoring unit and a computer; the online monitoring unit is connected to the computer; the online monitoring unit includes a CCD camera, an infrared thermal imager, and a high-speed camera; the infrared thermal imager is used to monitor the melt pool temperature; the high-speed camera is used to monitor the printing process; and the CCD camera is used to monitor the powder spreading and the morphology of the printed parts.

[0014] Optionally, the molding cavity is provided with an illumination window, a laser incident window, and a high-speed camera observation window at the top, and a molding cavity door at the front; a protective gas inlet, a reaction gas inlet, and a vacuum pump are provided on the side of the molding cavity; a top powder chamber, a printing chamber, and a powder collection chamber are arranged sequentially inside the molding cavity and are respectively connected to the chamber lifting unit; a scraper is provided above the top plate of the top powder chamber; and a printing base plate is provided above the top plate of the printing chamber.

[0015] A pulsed laser selective melting integrated forming method, the method being applied to the aforementioned pulsed laser selective melting integrated forming system, the method comprising:

[0016] 1) Construct the geometric model of the printed part, slice the geometric model, and plan the scanning path of the slice model;

[0017] 2) Evacuate the molding cavity, fill it with a protective gas or a reactive gas, spread the powder, and melt the powder using a pulsed laser according to the scanning path;

[0018] 3) Determine whether the printed parts are warped, cracked, or bulging based on the monitored morphology, and obtain the monitoring results;

[0019] 4) Based on the monitoring results and the accuracy requirements of the printed parts, adjust the power, frequency and spot diameter of the pulsed laser to perform in-situ impact and / or in-situ subtraction on the printed parts;

[0020] 5) Lower the printing plate to the thickness of the slice model, and repeat step 2) "spread the powder and melt the powder with a pulsed laser according to the scanning path" to step 4) until the printed part is formed.

[0021] Optionally, the pulsed laser selective melting integrated forming method is characterized in that the reaction gas is nitrogen, oxygen, carbon source or a mixture of gases containing hydrogen.

[0022] Optionally, the pulsed laser selective melting integrated forming method is characterized in that the powder includes metal powder, ceramic powder, polymer powder, plastic powder, coated sand powder, biomaterial powder, and their slurries, gels, and composite materials; the particle size of the powder is 5 nm to 2 × 10⁻⁶. 5 nm.

[0023] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0024] The pulsed laser selective melting integrated forming system and method of this invention can monitor the forming process of the printed part in real time through an online monitoring system. Based on the shape of the printed part, the power, frequency, and spot diameter of the pulsed laser can be adjusted to perform in-situ impact and / or in-situ subtractive processing on the printed part until the printed part is formed. This invention integrates laser additive manufacturing, laser subtractive processing, and laser shock strengthening into one system. It utilizes a pulsed laser source with variable pulse width and variable spot diameter to complete additive, subtractive, and shock processing, improving processing efficiency, accuracy, and the performance of the printed part, while reducing system complexity. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a structural diagram of the pulsed laser selective melting integrated forming system provided by the present invention;

[0027] Figure 2 A flowchart of the pulsed laser selective melting integrated forming method provided by the present invention;

[0028] Figure 3 This is a flowchart of a method in one specific embodiment of the present invention.

[0029] Symbol Explanation: 1. Laser Composite Manufacturing Module; 2. Online Monitoring and Control Module; 3. Forming Cavity; 4. Computer; 11. Pulsed Laser; 12. Variable Magnification Beam Expander; 13. First Semi-transparent and Semi-reflective Mirror; 14. Galvanometer; 15. Field Mirror; 16. Pulsed Laser; 21. High-Speed ​​Camera; 22. Infrared Thermal Imager; 23. Lens; 24. Filter; 25. Second Semi-transparent and Semi-reflective Mirror; 26. CCD Camera; 27. Illumination Source; 31. Top Powder Tank; 32. Printing Tank; 33. Powder Collection Tank; 34. Tank Lifting Unit; 35. Scraper; 36. Printing Base Plate; 37. Observation Window; 38. Laser Incident Window; 39. High-Speed ​​Camera Observation Window; 40. Protective Gas Inlet; 41. Reactive Gas Inlet; 42. Vacuum Pump. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The purpose of this invention is to provide a pulsed laser selective melting integrated forming system and method to solve the problems of low processing efficiency and low precision of additive manufacturing printed parts when additive manufacturing and laser shock are performed separately in different systems.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1The pulsed laser selective melting integrated forming system provided by the present invention, such as Figure 1 As shown, the system includes: a laser composite manufacturing module 1, an online monitoring and control module 2, and a forming cavity 3.

[0034] The laser composite manufacturing module 1 is used to generate pulsed laser 16; the pulsed laser 16 is incident into the forming cavity 3, melting the powder to complete additive manufacturing, and performing in-situ impact and / or in-situ subtractive material processing on the printed part.

[0035] The online monitoring and control module 2 is used to monitor the melt pool temperature, forming process, powder spreading, and morphology of the printed part in real time. It controls powder spreading and atmosphere adjustment within the forming cavity 3, controls the pulsed laser 16 to melt the powder, and adjusts the power, frequency, and spot diameter of the pulsed laser according to the monitored morphology of the printed part to perform in-situ impact and / or in-situ subtraction until the printed part is formed. For example, in-situ impact strengthening is performed on parts with high residual stress such as microcracks and warping deformation, while in-situ subtraction is performed on parts with high roughness or high precision requirements of the printed part.

[0036] Furthermore, the molding cavity 3 contains, in sequence, a top powder chamber 31, a printing chamber 32, and a powder collection chamber 33. A chamber lifting unit 34 is installed at the bottom of the top powder chamber 31, the bottom of the printing chamber 32, and the bottom of the powder collection chamber 33. A scraper 35 is installed above the top plate of the top powder chamber 31. A printing base plate 36 is installed above the top plate of the printing chamber 32. Both the chamber lifting unit 34 and the scraper 35 are connected to the computer 4. The top powder chamber 31 supplies powder to the printing chamber 32 and spreads the powder on the printing base plate 36. The powder collection chamber 33 collects unmelted powder and powder after in-situ subtractive processing. In practical applications, powder is fed using a powder feeding system (top powder chamber 31) or pre-mixed powder is fed and then spread in a layer on the printing base plate 36. The powder can be metal powder, ceramic powder, polymer powder, plastic powder, coated sand powder, or biomaterial powder, or it can be a slurry, gel, or composite material of the above materials; the particle size of the powder is 5 nm to 2 × 10⁻⁶. 5 nm.

[0037] The molding cavity 3 has an observation window 37, a laser incident window 38, and a high-speed camera observation window 39 on its upper part; a molding cavity door is located at the front of the molding cavity 3; a protective gas inlet 40, a reaction gas inlet 41, and a vacuum pump 42 are provided on the side of the molding cavity 3. The molding cavity door is not located on... Figure 1 As shown in the diagram. In practical applications, the illumination source 27 illuminates the printed part through the observation window 37, providing illumination for the molding cavity 3.

[0038] As an optional implementation, the laser composite manufacturing module 1 includes a pulsed laser 11, a variable-magnification beam expander 12, a first semi-transparent mirror 13, a galvanometer 14, and a field mirror 15 arranged sequentially. The pulsed laser 16 generated by the pulsed laser 11 passes sequentially through the variable-magnification beam expander 12, the first semi-transparent mirror 13, the galvanometer 14, and the field mirror 15. The pulsed laser 16 emitted from the field mirror 15 is incident on the printing substrate 36 through the laser incident window 38. In practical applications, the pulsed laser 11 can be an ultrafast laser such as a nanosecond laser, picosecond laser, or femtosecond laser, and the variable-magnification beam expander 12 can achieve a 10-fold scaling of the spot diameter. The wavelength range of the pulsed laser is 193nm to 1100nm, and the pulse width range is 30fs to 2×10⁻¹⁰. 8 fs.

[0039] As an optional implementation, the online monitoring and control module 2 includes an online monitoring unit and a computer 4; the online monitoring unit is connected to the computer 4; the online monitoring unit includes a high-speed camera 21, an infrared thermal imager 22, and a CCD camera 26; wherein, the high-speed camera 21, the infrared thermal imager 22, and the CCD camera 26 are all connected to the computer 4. The connection relationship between the high-speed camera 21 and the computer 4 is not shown in Figure 1. The CCD camera 26 is used to monitor the morphology of the printed part and the powder spreading. The infrared thermal imager 22 is used to monitor the melt pool temperature; the high-speed camera 21 is used to monitor the forming process of the printed part. Figure 1 As shown, a lens 23, a filter 24, and a second semi-transparent mirror 25 are sequentially arranged in front of the infrared thermal imager 22. The second semi-transparent mirror 25 is placed at a preset angle and is located directly below the first semi-transparent mirror 13 and directly above the CCD camera 26.

[0040] This invention also provides a pulsed laser selective melting integrated forming method, which is applied to the above-mentioned pulsed laser selective melting integrated forming system, such as... Figure 2 and Figure 3 As shown, the method includes:

[0041] Step 201: Construct the geometric model of the printed part, slice the geometric model, and plan the scan path of the slice model.

[0042] In practical applications, a geometric model of the printed part is obtained using drawing software, and a slicing software is used to slice the model and plan the scanning path.

[0043] Step 202: Evacuate the molding cavity, fill it with a protective gas or a reactive gas, spread the powder, and melt the powder using a pulsed laser according to the scanning path.

[0044] In practical applications, the molding cavity is evacuated and filled with a protective gas to reduce the oxygen and water vapor content, or it is filled with gases that can react with the powder (reactive gases), such as nitrogen, carbon source, and oxygen, to obtain in-situ reinforced composite materials.

[0045] The powder spreading and atmosphere system within the forming cavity are controlled, and the powder is melted using a pulsed laser according to the scanning path. Powder is fed using a powder feeding system or pre-mixed before feeding and spread into a single layer on the printing substrate; the powder is then melted using a pulsed laser.

[0046] Step 203: Determine whether the printed part is warped, cracked, or bulging based on the monitored morphology of the printed part, and obtain the monitoring results.

[0047] Step 204: Based on the monitoring results and the accuracy requirements of the printed part, adjust the power, frequency and spot diameter of the pulsed laser to perform in-situ impact and / or in-situ subtraction on the printed part.

[0048] In-situ impact strengthening is performed on parts with high residual stress such as microcracks and warping deformation detected in real time, while in-situ material reduction is performed on parts with high roughness or parts with high precision requirements for printed parts.

[0049] Step 205: Lower the printing plate to the thickness of the slice model, and repeat the process of "spreading powder and melting the powder with a pulsed laser according to the scanning path" in step 202 to step 204 until the printed part is formed.

[0050] This invention integrates laser additive manufacturing, laser in-situ subtractive processing, and laser in-situ impact strengthening into a single system (i.e., the pulsed laser selective melting integrated forming system of this invention). It utilizes an ultrafast pulsed laser source with variable pulse width and variable spot diameter to complete additive, subtractive, and impact processing, thereby improving processing efficiency, accuracy, and the performance of the printed parts.

[0051] The pulsed laser selective melting integrated molding system of the present invention can also be used to mold liquid resins, biomaterials (cold processing), etc., similar to laser sintering.

[0052] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0053] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A system for integrated shaping by selective laser melting, characterized in that The integrated forming system comprises a laser composite manufacturing module, an online monitoring and control module, and a forming cavity. The pulse laser in the laser composite manufacturing module is incident into the forming cavity to melt the powder and complete additive forming, and to impact and / or subtract material in situ according to the monitoring result and the precision requirement of the printed part. The laser composite manufacturing module comprises a pulse laser, a variable magnification beam expander, a first semi-transparent half mirror, a galvanometer and a field lens arranged in sequence; the pulse laser generated by the pulse laser passes through the variable magnification beam expander, the first semi-transparent half mirror, the galvanometer and the field lens in sequence, and the pulse laser emitted by the field lens is incident into the forming cavity; the pulse laser is an ultrafast laser; the variable magnification beam expander can realize 10 times zoom of the spot diameter; the wavelength range of the pulse laser is 193nm-1100nm, and the pulse width range is 30fs-2x10 8 fs. The online monitoring and control module is used to monitor the temperature of the molten pool, the forming process, the morphology of the printed part, and the powder spreading in real time, to determine whether the printed part is warped, cracked, or raised according to the morphology of the printed part, to obtain a monitoring result, and to adjust the power, frequency, and spot diameter of the pulse laser according to the monitoring result and the precision requirement of the printed part, so as to control the entire composite manufacturing process of additive forming, in-situ impact, and in-situ subtracting.

2. The integrated pulsed laser selective melting system of claim 1, wherein, The online monitoring and control module comprises an online monitoring unit and a computer, and the online monitoring unit is connected to the computer.

3. The integrated pulsed laser selective melting system of claim 1, wherein, The top of the forming cavity is provided with an illumination window, a laser incidence window, and a high-speed camera observation window, and the front of the forming cavity is provided with a forming cavity door.

4. A method of integrated forming by selective laser melting, characterized in that The method comprises additive forming by using a pulse laser, in-situ impact and / or in-situ subtracting of the printed part according to the monitoring result and the precision requirement of the printed part, and obtaining a printed part with high precision and high performance. The method is applied to the pulse laser selective melting integrated forming system according to any one of claims 1-3, and the method comprises: 1) constructing a geometric model of the printed part, slicing the geometric model, and planning a scanning path of the sliced model; 2) vacuumizing the forming cavity, filling protective gas or reaction gas, spreading powder, and melting the powder by using a pulse laser according to the scanning path; 3) determining whether the printed part is warped, cracked, or raised according to the monitored morphology of the printed part to obtain a monitoring result; 4) adjusting the power, frequency, and spot diameter of the pulse laser according to the monitoring result and the precision requirement of the printed part to impact and / or subtract material in situ for the printed part; 5) lowering the printing base plate by the thickness of the sliced model, and repeating the step 2) of "spreading powder and melting the powder by using a pulse laser according to the scanning path" to step 4) until the forming of the printed part is completed.

5. The method of claim 4, wherein, The reaction gas is nitrogen, oxygen, a carbon source, or a mixed gas containing hydrogen.

6. The method of claim 4, wherein the laser power is varied in the range of 1- 10 kW. The powder includes metal powder, ceramic powder, polymer powder, coated sand powder, biomaterial powder, and their slurries, gels and composites; the particle size of the powder is 5nm-2x10 5 nm.

Images