A design and forming method for cylindrical springs based on metal selective laser melting technology

Abstract

The present invention discloses a design and forming method for a cylindrical spring based on the selective laser melting technology of metals, which relates to the field of metal additive manufacturing. The method includes selecting a metal material according to the usage conditions of the spring and designing the relevant parameters of the spring; adjusting the 3D printing process parameters of the spring; involving the forming mode and the support structure of the spring; forming a printing file and adjusting the printing parameters; performing heat treatment and post-treatment after printing and forming, etc. The present invention overcomes the deficiencies of the prior art, can select the corresponding spring material according to the spring usage environment, and simultaneously perform selective laser melting forming on springs with different parameters, greatly shortening the iteration cycle and reducing the R & D cost.

Description

Technical Field

[0001] The invention relates to the field of metal additive manufacturing, and in particular to a cylindrical spring design and forming method based on metal laser selective melting technology. Background Art

[0002] Cylindrical compression spring is a mechanical part that works by utilizing elasticity. Its elastic properties can be used to realize functions such as mechanism movement, buffering, vibration, energy storage, and force measurement. It is widely used in machinery, instrumentation and other fields.

[0003] At present, the main process for spring processing is hot forming or cold forming on a spring machine. However, this process is suitable for mass production of springs. For small-batch trial production of springs, there are problems such as single spring parameters, large single production volume, long production cycle and high cost. In particular, for spring wire materials used in special environments (such as high temperature environments) and less common, the raw material procurement cost may be much higher than the trial production cost, which has formed a certain resistance to the rapid iteration of product development.

[0004] Additive manufacturing technology can break through the constraints of traditional mechanical manufacturing processes and can form complex structural parts in an integrated manner without the need for tooling and molds. It has the characteristics of short processing cycles and fast iterations, and has formed significant advantages in small-batch trial production and customized design. It has been widely used in aerospace, automotive industry, medical equipment and other fields, but it is rarely reported on the design of springs. Summary of the invention

[0005] The problem solved by the present invention is to overcome the resistance of traditional spring manufacturing processes to small-batch trial production and rapid parameter iteration of springs, and propose a design and forming method for cylindrical compression springs based on metal laser selective melting technology. Based on this method, the corresponding spring material can be selected according to the spring use environment, and springs with different parameters can be simultaneously laser selectively melted to form, which greatly shortens the iteration cycle and reduces R&D costs.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A cylindrical spring design and forming method based on metal laser selective melting technology, the design and forming method comprising the following steps:

[0008] (1) Material selection and spring design: Based on the use conditions of the spring, select the corresponding metal material powder, and design the spring stiffness coefficient and geometric parameters according to the mechanical properties of the metal material;

[0009] (2) Adjustment of 3D printing process: Based on the temperature field difference of the spring component during and after the laser selective melting forming process and the relationship between the characteristics of the metal material, the 3D printing process is adjusted for the pitch and inner diameter of the spring digital 3D model;

[0010] (3) Design of the spring printing support structure and forming method: The spring is formed horizontally along the axial direction. A single-channel grid support combined with a conical support is designed as the support structure of the printing process. A nested design method is used for the single-channel grid support, and the forming surface is parallel to the axial direction.

[0011] (4) Model import and printing: Generate a forming model including a support structure from the digital three-dimensional model of the cylindrical spring after process adjustment, further set the forming process parameters of the model on the forming model, generate a working file that can be used for 3D printing, import the working file into a laser selective melting metal 3D printer, set the forming process parameters of the laser selective melting metal 3D printer, and use high-quality mode for forming;

[0012] (5) Heat treatment: According to the mechanical performance requirements of the spring, the deposited spring after forming and the printed substrate are heat treated and tempered;

[0013] (6) Spring acquisition: The spring after heat treatment is subjected to post-processing to obtain the designed spring.

[0014] Preferably, the determination of the spring use conditions in step (1) includes environmental conditions, mechanical properties, and geometric constraints.

[0015] Preferably, the metal powder in step (1) is high-temperature alloy powder.

[0016] Preferably, the high temperature alloy powder is at least one of aluminum alloy powder, titanium alloy powder, stainless steel powder and copper alloy powder.

[0017] Preferably, the geometric parameters of the spring in step (1) include the spring major diameter, minor diameter, median diameter, wire width, wire height, wire diameter, free height, number of turns, and pitch.

[0018] Preferably, the 3D printing process adjustment in step (2) includes increasing the pitch by 0.05-0.2 mm, enlarging the minor diameter by 0.1-0.3 mm, and compensating the spot by +0.04-+0.09 mm.

[0019] Preferably, the forming process parameters of the model set on the forming model in step 4 include part entity parameters, grid support parameters, and support structure parameters with internal filling.

[0020] Preferably, the forming process parameters of the laser selective melting metal 3D printer in step (4) include: the oxygen content of the forming atmosphere is ≤300ppm, the laser spot diameter is 0.06-0.15mm, the beam quality M2 is ≤1.1, and the laser power is ≥500W.

[0021] Preferably, in step (5), the heat treatment and tempering method for the formed deposited spring together with the printed substrate is at least one of solid solution, solid solution plus double aging, aging, annealing, and hot isostatic pressing.

[0022] Preferably, the post-processing process in step (6) is, in order, separation of the spring from the printed substrate, removal of the support structure, grinding and polishing, and sandblasting.

[0023] Compared with the prior art, the present invention provides a cylindrical spring design and forming method based on metal laser selective melting technology, which has the following beneficial effects:

[0024] The present invention can select spring wire materials with excellent performance according to the use environment of cylindrical compression springs, and simultaneously form springs with different parameters (the different parameters include spring stiffness coefficients, geometric parameters, etc.) in a single laser selective melting forming process. The printing process is usually completed within 24 hours depending on the size of the spring, which greatly shortens the iteration cycle and reduces R&D costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of the method for designing and forming a cylindrical compression spring using the metal laser selective melting technology. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] Example:

[0028] A method for designing and forming a cylindrical compression spring based on metal selective laser melting technology comprises the following steps:

[0029] (1) Select the appropriate metal powder according to the use conditions of the spring. The use conditions that affect the design of the spring usually include the temperature and mechanical properties (such as the strength and stiffness required at the use temperature) in the use environment. Based on this, select the appropriate 3D printing metal powder; commonly used metal powders are high-temperature alloy powders, including aluminum alloy powders, titanium alloy powders, stainless steel powders, copper alloy powders, etc.; in addition, the use environment should also include geometric constraints; after selecting the metal material, the stiffness coefficient and geometric parameters of the compression spring can be designed according to the mechanical properties parameters of the material (mainly including shear modulus, tensile strength, yield strength, etc.), referring to the mechanical manual. The main geometric parameters include the major diameter, minor diameter, middle diameter, wire width, wire height, wire diameter, free height, number of turns, pitch, etc. of the compression spring;

[0030] (2) According to the geometric parameters of the spring, a three-dimensional digital model of the spring is drawn using three-dimensional CAD software; and based on the temperature field difference of the spring component during and after the laser selective melting forming process and the relationship with the characteristics of the metal material, the 3D printing process is adjusted for the pitch and inner diameter of the spring digital three-dimensional model (mainly dimensional parameter compensation); usually, the dimensional parameter compensation range for the geometric deformation of the spring wire is an increase of 0.05~0.2mm in pitch, an increase of 0.1~0.3mm in inner diameter (minor diameter), and a spot compensation of +0.04~+0.09mm.

[0031] (3) Further design and planning of the printing forming direction and support structure of the spring: In order to minimize the temperature gradient of the axial section of the spring during the forming process, effectively reduce the local mutation of the spring along the axial direction during the laser selective forming process, and at the same time ensure the stability, efficiency and reliability of the forming process, a horizontal forming method along the axial direction of the spring is adopted (that is, the forming surface is parallel to the axial direction), and the support structure is designed in the form of a combination of single-channel grid support and conical support, and a nested design method is adopted for the single-channel grid support;

[0032] (4) Generate a forming model containing a support structure from the digital three-dimensional model of the cylindrical spring after process adjustment, such as a MatAMX forming model, which includes a grid support structure, a conical support structure, an anti-deformation lattice structure, and a compensated three-dimensional solid structure of the spring; further set the forming process parameters on the forming model (for the MatAMX forming model, it is necessary to set the forming process parameters such as the part entity, grid support, and support structure with internal filling), generate a working file that can be used for 3D printing, and import the working file into a laser selective melting metal 3D printer; adopt high-quality mode forming to ensure the comprehensive mechanical properties of the spring; set the laser selective melting forming parameters on the laser selective melting forming metal 3D printer, including: forming atmosphere oxygen content ≤300ppm, laser spot diameter 0.06~0.15mm, beam quality M2≤1.1 (dimensionless), laser power ≥500W, etc.;

[0033] (5) After laser selective melting, the deposited spring is connected to the substrate and taken out of the 3D printer. Since the spring generates stress during the laser selective melting process, it is necessary to perform overall heat treatment and tempering on the deposited spring after forming together with the printed substrate to meet the mechanical property requirements of the spring. According to different mechanical property requirements of the spring, the heat treatment modulation methods include solid solution, solid solution + double aging, aging, annealing, hot isostatic pressing, etc.

[0034] (6) After heat treatment and tempering, the spring and the substrate are taken out of the heat treatment furnace, and the spring is separated from the substrate by wire cutting. The support structure on the surface of the spring is removed and ground and polished. Finally, it is sandblasted to complete the post-printing processing process of the spring.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A cylindrical spring design and forming method based on metal selective laser melting technology, It is characterized in that The design forming method comprises the following steps: (1) Material selection and spring design: Based on the use conditions of the spring, select the corresponding metal material powder, and design the spring stiffness coefficient and geometric parameters according to the mechanical properties of the metal material; (2) Adjustment of 3D printing process: Based on the temperature field difference of the spring component during and after the laser selective melting forming process and the relationship between the characteristics of the metal material, the 3D printing process is adjusted for the pitch and inner diameter of the spring digital 3D model; (3) Design of the spring printing support structure and forming method: The spring is formed horizontally along the axial direction. A single-channel grid support combined with a conical support is designed as the support structure of the printing process. A nested design method is used for the single-channel grid support, and the forming surface is parallel to the axial direction. (4) Model import and printing: Generate a forming model including a support structure from the digital three-dimensional model of the cylindrical spring after process adjustment, further set the forming process parameters of the model on the forming model, generate a working file that can be used for 3D printing, import the working file into a laser selective melting metal 3D printer, set the forming process parameters of the laser selective melting metal 3D printer, and use high-quality mode for forming; (5) Heat treatment: According to the mechanical performance requirements of the spring, the deposited spring after forming and the printed substrate are heat treated and tempered; (6) Spring acquisition: The spring after heat treatment is subjected to post-processing to obtain the designed spring.

2. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The determination of the spring use conditions in step (1) includes environmental conditions, mechanical properties, and geometric constraints.

3. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The metal powder in step (1) is high temperature alloy powder.

4. According to claim 3, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The high temperature alloy powder is at least one of aluminum alloy powder, titanium alloy powder, stainless steel powder and copper alloy powder.

5. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The geometric parameters of the spring in step (1) include the spring major diameter, minor diameter, median diameter, wire width, wire height, wire diameter, free height, number of turns, and pitch.

6. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The 3D printing process adjustment in step (2) includes increasing the pitch by 0.05-0.2 mm, enlarging the minor diameter by 0.1-0.3 mm, and compensating the light spot by +0.04-+0.09 mm.

7. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The forming process parameters of the model set on the forming model in the step (4) include part entity parameters and support structure parameters combining single-channel grid support and conical support.

8. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The forming process parameters of the laser selective melting metal 3D printer in step (4) include: the oxygen content of the forming atmosphere is ≤300ppm, the laser spot diameter is 0.06-0.15mm, the beam quality M2 is ≤1.1, and the laser power is ≥500W.

9. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: In the step (5), the method of heat treating and tempering the formed deposited spring together with the printed substrate is at least one of solid solution, solid solution plus double aging, aging, annealing, and hot isostatic pressing.

10. According to claim 1, a cylindrical spring design and forming method based on metal selective laser melting technology, Features: The post-processing processes in step (6) are, in order, separation of the spring from the printing substrate, removal of the support structure, grinding and polishing, and sandblasting.

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