A three-dimensional printing method and 3D printing device for polymer composite powder material

Abstract

A three-dimensional printing method and 3D printing equipment for polymer composite powder materials, wherein the three-dimensional printing method includes: using a laser with a wavelength of 1500nm-2800nm, and a galvanometer system with a lens aperture of 25mm or less to perform laser scanning on the polymer composite powder material to form a three-dimensional product, wherein the laser is a continuous laser, and the coating reflectivity of the X lens and the Y lens of the galvanometer system are both above 85%. The three-dimensional printing method and 3D printing equipment for polymer composite powder materials of the present invention use a laser with a wavelength of 1500nm-2800nm, and the functional groups of the polymer powder material, carbonyl and imino groups, have certain absorption peaks for the above wavelengths. After the above chemical bonds absorb laser energy, the temperature rises and melts the powder material, so it can be printed layer by layer in conjunction with the galvanometer system to finally form a three-dimensional workpiece; the laser of this wavelength does not require special treatment of the optical path, such as anhydrous treatment, so the production cost is relatively low.

Description

Technical Field

[0001] The present application relates to the field of additive manufacturing technology, and in particular to a three-dimensional printing method and a 3D printing device for polymer composite powder materials. Background Art

[0002] Additive manufacturing technology is a rapid manufacturing technology that forms three-dimensional objects by controlling the laser to scan layer by layer and stacking layer by layer. The process flow is as follows: first, the three-dimensional model of the workpiece is sliced ​​to obtain the cross-sectional information of each layer of the workpiece; the powdered material is evenly spread on the surface of the work platform, and the laser selectively melts the powder according to the system instructions; after a section is completed, a new layer of material is spread, and the scanning continues to be selective according to the cross-sectional information corresponding to the three-dimensional object; according to this method, the next section is scanned for powder spreading, and finally a three-dimensional object is obtained.

[0003] At present, 3D printing of polymer composite powder materials generally uses CO2 lasers with a wavelength of 10μm or CO lasers with a wavelength of 5μm. The cost of the above lasers is relatively high, especially CO lasers. Because water has a high absorption rate for infrared light with a wavelength of 5.5μm, the cost of anhydrous treatment of the optical path is relatively high when using CO lasers. Once water molecules enter the optical path, the stability of the laser power will be greatly affected.

[0004] Due to the relationship between wavelengths, the minimum focused spot size of CO2 lasers in the above wavelength band for 3D printing is generally only about 400μm, while the minimum focused spot size of CO lasers for 3D printing is generally only about 200μm, which limits the prospects of 3D printing of fine parts.

[0005] Due to the relationship between wavelength and the use of CO2 laser for 3D printing, in order to obtain the smallest focused spot, the XY lens of the galvanometer system used is generally a 30mm lens. The galvanometer motor drives the lens to have difficulty in responding quickly, so the CO2 laser scanning efficiency is not high.

[0006] Moreover, the output stability of the above-mentioned CO2 or CO laser itself is generally plus or minus 5%, which is not stable enough for materials that require high laser output stability; the response time of the CO2 or CO laser on and off is generally 60-120us, which will cause the end point of the scanning line to fail to turn off the laser in time when the galvanometer speed is fast, causing smear or overburning, which affects the quality of the parts; the cross-section of the light output of the CO2 or CO laser has a random shape, and even side spots appear, and even the beam cross-section is different at different powers, which limits the application of high-precision 3D printing; the electro-optical conversion efficiency of C02 or C0 laser is relatively low, generally around 10%-25%, which increases the customer's usage cost.

[0007] The above-mentioned C02 or C0 laser uses a pulse signal to turn on and off the laser, and adjusts the laser power by pulse width modulation or pulse number modulation. Therefore, the molten pool is actually composed of many laser pulse points, which is discontinuous and has poor stability. Therefore, high-quality sintering effect cannot be obtained.

[0008] In addition, many polymer composite powder materials have high transmittance at wavelengths around 1μm, which is not conducive to 3D printing of polymer composite powder materials, because 1μm lasers will pass through the material instead of being absorbed; additives need to be added to the polymer to increase the absorbency at 1μm wavelength, but this makes the manufacturing process more complicated. On the other hand, many polymer composite powder materials have strong absorption near wavelengths around 10μm, which can cause effective surface heating, but it is not the local heating required for precise processing, and cannot form fine 3D printing. Summary of the invention

[0009] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a three-dimensional printing method and a 3D printing device for polymer composite powder materials. The three-dimensional printing method for polymer composite powder materials has a faster scanning speed, a smaller focus spot on the target surface, a stable molten pool, and more refined workpiece printing.

[0010] In order to achieve the above object, the present invention provides a three-dimensional printing method of a polymer composite powder material, comprising:

[0011] A laser with a wavelength of 1500nm-2800nm ​​and a galvanometer system with a lens aperture of 25mm or less are used to perform laser scanning on polymer composite powder materials to form a three-dimensional product, wherein the laser is a continuous laser, and the coating reflectivity of the X lens and the Y lens of the galvanometer system are both above 85%.

[0012] As a further preferred embodiment of the present invention, the coating reflectivity of the X lens and the Y lens of the galvanometer system are both above 99.5%.

[0013] As a further preferred embodiment of the present invention, the scanning speed of the galvanometer system is 2rad / s-35rad / s, the jump and scanning delay is 0us-1500us, the spot diameter of the laser focused on the target surface is 50μm-1000μm, and the scanning layer thickness is 5μm-200μm.

[0014] As a further preferred embodiment of the present invention, the diameter of the spot of the laser focused on the target surface is 100 μm-300 μm.

[0015] As a further preferred embodiment of the present invention, the clear aperture of the lens of the galvanometer system is 14 mm or less.

[0016] As a further preferred embodiment of the present invention, the polymer composite powder material at least includes a polymer powder material containing carbonyl and imino functional groups.

[0017] As a further preferred embodiment of the present invention, the wavelength of the laser is 2 μm.

[0018] As a further preferred embodiment of the present invention, the laser is a fiber laser, a solid laser, or a semiconductor laser; and the galvanometer system is a two-dimensional galvanometer or a three-dimensional galvanometer.

[0019] As a further preferred embodiment of the present invention, the laser is a thulium-doped fiber laser with a wavelength of 1.5447 W / m.

[0020] The present invention also provides a three-dimensional printing device for polymer composite powder materials, comprising:

[0021] A laser, which is a continuous laser with a wavelength of 1500nm-2800nm;

[0022] Galvanometer system, the aperture of the lens is 25mm or less, and the coating reflectivity of the X lens and Y lens is more than 85%;

[0023] A working cylinder is flatly spread with polymer composite powder material by a powder spreader, so that the laser emitted by the laser sintering the polymer composite powder material under the deflection of the galvanometer system to print layer by layer to obtain a three-dimensional product.

[0024] The three-dimensional printing method and 3D printing device of the polymer composite powder material of the present invention, by adopting the above technical solution, have the following beneficial effects:

[0025] 1. Using a laser with a wavelength of 1500nm-2800nm, the carbonyl and imino functional groups of polymer powder materials have certain absorption peaks for the above wavelengths. After the above chemical bonds absorb the laser energy, the temperature rises and melts the powder material. Therefore, it can be printed layer by layer in conjunction with the galvanometer system to form a three-dimensional workpiece. Moreover, the production cost of the laser with this wavelength is relatively low because the optical path does not need special treatment, such as dehydration treatment;

[0026] 2. The laser with a wavelength of 1500nm-2800nm ​​is used, and the aperture of the lens of the matching galvanometer system is only 25mm or less, so that the motor-driven lens responds quickly and can complete the scanning of a single layer of 3D printing at high speed and efficiency; and the laser target surface can obtain a focused spot of 50μm-1000μm, so that small details can be formed, that is, the workpiece printing is more refined;

[0027] 3. The laser with a wavelength of 1500nm-2800nm ​​of the present invention not only has good power output stability, with a fluctuation range within plus or minus 1% of the set power, making the scanning molten pool stable, but also has an electro-optical conversion efficiency of up to 40%;

[0028] 4. Since the laser used in the present invention is a continuous laser, a modulation signal can be used to switch the laser, and an analog quantity can be used to continuously adjust the laser power, so that a stable molten pool can be obtained, thereby improving the printing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the structure of an embodiment of a 3D printing device provided by the present invention;

[0030] Figure 2 To ensure uniformity of the molten pool using CO2 or CO laser;

[0031] Figure 3 This is the energy distribution diagram of the molten pool using CO2 or CO laser in skywriting mode;

[0032] Figure 4 The present invention uses a fiber laser to achieve uniform molten pool.

[0033] Markings in the figure:

[0034] 1. Computer, 2. Control card, 3. Laser, 4. Fiber optic head, 5. Collimator, 6. Dynamic divergence mirror, 7. Focusing mirror, 8. Galvanometer system, 9. Laser, 10. Working area, 11. Powder return cylinder piston, 12. Working cylinder piston, 13. Powder delivery cylinder piston, 14. Working chamber, 15. Polymer powder material. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0036] To achieve the above object, the present invention provides a three-dimensional printing method of a polymer composite powder material, comprising:

[0037] A laser 3 with a wavelength of 1500nm-2800nm ​​and a galvanometer system 8 with a lens aperture of 25mm or less are used to perform laser 9 scanning on the polymer composite powder material to form a three-dimensional product, wherein the laser 3 is a continuous laser 3, and the coating reflectivity of the X lens and the Y lens of the galvanometer system 8 are both above 85%.

[0038] The cost of the laser 3 in this band is much lower than that of CO2 or CO laser at the same power. Compared with the wavelength of CO2 laser 3 (for example, 10.6μm), single fundamental mode M2=1, BPP=λ / Π=3.38mm*mrad, the laser 3 with the above wavelength (for example, 2μm) adopted in the present invention has single fundamental mode M2=1, BPP=λ / Π=0.637mm*mrad. If the divergence angles θ of the above two light beams are consistent, it can be deduced from BPP=W×θ that the focused spot diameter obtained by the laser 3 with a wavelength of about 2μm adopted in the present invention is about 1 / 5 of that of the CO2 laser. Similarly, it can be deduced that it is about 1 / 3 of that of the CO laser. This means that the present invention can print more detailed workpieces and features, and can achieve fine printing.

[0039] In 3D printing, CO2 lasers generally use XY lenses with a light aperture of 30mm for scanning, and the galvanometer response time and scanning speed are difficult to improve. The wavelength of the laser 3 in this application is relatively short, approximately equal to 1 / 5 of the wavelength of the CO2 laser, so an XY lens with a light aperture of less than 25mm can be used for scanning. The response time of the XY lens with a light aperture of 25mm is only 1 / 2 of that of the 30mm XY lens, which can increase the scanning speed, that is, improve the scanning efficiency.

[0040] Since the present application adopts a continuous laser 3, it can use a modulation signal to switch the laser 9 and use an analog quantity to continuously adjust the laser power. Compared with CO2 or CO, which adjusts the laser power by pulse width modulation or pulse number modulation, the molten pool is composed of pulse points and the molten pool is unstable (see Figure 2 ), the three-dimensional printing method of the present application can obtain a stable molten pool, thereby improving the printing quality.

[0041] Specifically, the polymer composite powder material at least includes a polymer powder material 15 containing carbonyl and imino functional groups, so that the carbonyl, amino and carbon-hydrogen bonds in the polymer composite powder material have certain absorption peaks for the above wavelengths, and the above chemical bonds absorb the energy of the laser 9 and heat up to melt the powder material, and realize layer-by-layer printing by cooperating with the galvanometer system 8, and finally form a three-dimensional workpiece. It can be understood that the above polymer composite powder material can be a polymer powder material 15, or it can be composed of several polymer powder materials 15. Of course, it can also be composed of polymer powder materials 15 and other non-polymer powder materials 15 (such as ceramic materials), which are not listed one by one here.

[0042] Preferably, in order to further improve the printing quality, the coating reflectivity of the X lens and Y lens of the galvanometer system 8 is above 99.5%, and the transmittance of other optical lenses, such as diverging mirror, focusing mirror 7, field mirror, and plane mirror, is also above 99.5%. The scanning speed of the galvanometer system 8 is 2rad / s-35rad / s, the jump and scanning delay is 0us-1500us, the spot diameter of the laser 9 focused on the target surface is 50μm-1000μm, and the scanning layer thickness is 5μm-200μm. Further preferably, the spot diameter of the laser 9 focused on the target surface is 100μm-300μm.

[0043] In order to further improve the 3D printing speed, the clear aperture of the lens of the galvanometer system 8 is 14 mm or less.

[0044] Specifically, the laser 3 is a fiber laser, a solid laser, or a semiconductor laser. Of course, it can also be other types of lasers 3, which are not listed here one by one. Preferably, the wavelength of the laser 3 is 2 μm. The galvanometer system 8 is a two-dimensional galvanometer or a three-dimensional galvanometer.

[0045] like Figure 2 As shown, CO2 or CO laser uses pulse width adjustment to adjust the energy of laser 9. Because the pulse has a period and pulse width, it is discontinuous in timing. Finally, the molten pool formed by laser 9 shooting at the powder surface is also discontinuous and uneven. If the period and pulse width are not well controlled, the light emitted by the pulse cannot overlap continuously in the molten pool, and the molten pool will be periodically disconnected, which has a significant impact on the printing quality of 3D printing. Figure 3 As shown in the figure, in the skywriting mode, when the galvanometer is scanning, the speed is uniform at the light-emitting position. When the speed is fast, when the CO2 or CO laser switches the laser 9 through the pulse width modulation signal, there is a certain delay in the actual response of the laser 9 energy, resulting in the laser 9 energy rising in a slope during the delay time. However, at this time, the scanning speed is high and uniform. At the head of the molten pool formed in this scanning path, the molten pool energy gradually increases. Figure 3 The black color is the required energy density, and the gray color is the energy density that does not meet the standard. The energy density that does not meet the standard will affect the printing quality. Similarly, when the laser is turned off, the energy density that does not meet the standard will also be formed at the end of the molten pool, which will also affect the printing quality.

[0046] Further preferably, the laser 3 is a thulium-doped fiber laser with a wavelength. The laser 3 has good power output stability, and the fluctuation range is within plus or minus 1% of the set power, so that the scanning molten pool is stable. The laser 3 has a good spot shape, and the ellipticity of the target surface focused spot can reach more than 98%, ensuring dimensional stability; the laser 9 is switched by a modulation signal, and the laser power is adjusted by an analog signal. Because the analog quantity is a continuous quantity, the laser 9 signal it emits is continuous, so the molten pool of the powder surface is also continuous, which can well control the quality of the three-dimensional printed workpiece, such as Figure 4 shown.

[0047] The present invention also provides a three-dimensional printing device for polymer composite powder materials, comprising:

[0048] Laser 3, which is a continuous laser with a wavelength of 1500nm-2800nm;

[0049] Galvanometer system 8, the aperture of its lens is 25 mm or less, and the coating reflectivity of its X lens and Y lens is more than 85%;

[0050] The working cylinder is flatly spread with polymer composite powder material by a powder spreader, so that the laser 9 emitted by the laser 3 sintering the polymer composite powder material under the deflection of the galvanometer system 8 to print layer by layer to obtain a three-dimensional product.

[0051] It can be understood that, in a specific implementation, the above-mentioned 3D printing equipment also includes a computer 1, a control card 2, an optical fiber head 4, a collimating lens 5, a dynamic diverging lens 6, a focusing lens 7, a powder return cylinder, a powder return cylinder piston 11, a working cylinder piston 12, a powder delivery cylinder, a powder delivery cylinder piston 13, a working chamber 14 and a powder spreader, etc. Since the core of the invention of this application is: using the laser 3 and the galvanometer system 8 with the above-mentioned specific structure and parameters to print polymer composite powder materials, other existing components included in the 3D printing equipment will not be introduced in detail.

[0052] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the technical solution of the present application is described in detail below in the form of embodiments and drawings.

[0053] like Figure 1 As shown, the 3D printing device includes a computer 1, a control card 2, an optical fiber head 4, a collimating lens 5, a dynamic diverging lens 6, a focusing lens 7, a laser 3, a galvanometer system 8, a powder return cylinder, a powder return cylinder piston 11, a working cylinder, a working cylinder piston 12, a powder delivery cylinder, a powder delivery cylinder piston 13, a working chamber 14 and a roller (not shown in the figure). The laser 3 is a continuous laser with a wavelength of 2μm; the aperture of the lens of the galvanometer system 8 is 14mm or less, and the coating reflectivity of its X lens and Y lens is above 99.5%;

[0054] The specific printing process of the 3D printing device in this embodiment is as follows:

[0055] Inert gas is filled into the working chamber 14, the powder feeding cylinder piston 13 rises to a certain height, the working cylinder piston 12 decreases a layer thickness, and the roller moves from left to right to evenly spread the polymer powder material 15 to the working area 10 of the working cylinder. The computer 1 slices the three-dimensional model of the part to be printed layer by layer to obtain the slice data of all layers, and transmits the current layer data to the control card 2. The control card 2 outputs a digital signal to control the movement of the galvanometer system 8. The wavelength of the laser 9 emitted by the laser 3 used in this embodiment is around 2μm, which is smaller than the wavelength of the CO2 laser 3. , if it is 10.6μm, single fundamental mode M2=1, BPP=λ / Π=3.38mm*mrad, the present invention adopts a wavelength of about 2μm, single fundamental mode M2=1, BPP=λ / Π=0.637mm*mrad, if the above two beam divergence angles θ are consistent, it can be deduced from BPP=W×θ that the focal spot diameter obtained by the laser 3 with a wavelength of about 2μm in this embodiment is about 1 / 5 of that of the CO2 laser, and similarly it can be deduced that it is about 1 / 3 of the CO laser, which means that more detailed workpieces and features can be printed. Moreover, because the wavelength is 1 / 5 of that of the CO2 laser, in the 3D printing process, the CO2 laser generally uses an XY lens with a clear aperture of 30mm for scanning, and the galvanometer response time and scanning speed are difficult to improve. Since the wavelength of the laser 3 used in this embodiment is relatively short, an XY lens with a light aperture of less than 14 mm can be used for scanning. The response time of the 14 mm XY lens is only 1 / 3 of that of the 30 mm XY lens, and the scanning speed can also be faster, so the scanning of a single layer can be completed efficiently. One channel outputs a modulation signal and an analog signal to control the switch and power of the laser 3. The laser 9 is emitted from the optical fiber head 4 into the collimator 5. After the collimator 5 converts the laser 9 into parallel light, the laser 9 is emitted to the dynamic divergent mirror 6. The laser 9 is emitted to the focusing mirror 7 module in a divergent form, and then to the galvanometer system 8 in a convergent form. The galvanometer system 8 then emits the laser 9 to the area to be scanned according to the instruction of the control card 2. After the current layer is scanned, the powder return cylinder piston 11 moves upward to push out the excess powder spread by the roller, and the working cylinder piston 12 moves downward by a layer thickness. The roller spreads powder from right to left, and then scans the area to be scanned. This step is repeated until the printing of the product to be printed is completed.

[0056] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A three-dimensional printing method of polymer composite powder material, characterized in that: include: A laser with a wavelength of 1500nm-2800nm ​​and a galvanometer system with a lens aperture of 25mm or less are used to perform laser scanning on polymer composite powder materials to form a three-dimensional product, wherein the laser is a continuous laser, and the coating reflectivity of the X lens and the Y lens of the galvanometer system are both above 85%.

2. The three-dimensional printing method of polymer composite powder material according to claim 1, characterized in that: The coating reflectivity of the X lens and the Y lens of the galvanometer system is both above 99.5%.

3. The three-dimensional printing method of polymer composite powder material according to claim 2, characterized in that: The scanning speed of the galvanometer system is 2rad / s-35rad / s, the jump and scanning delay is 0us-1500us, the spot diameter of the laser focused on the target surface is 50μm-1000μm, and the scanning layer thickness is 5μm-200μm.

4. The three-dimensional printing method of polymer composite powder material according to claim 3, characterized in that: The spot diameter of the laser focused on the target surface is 100μm-300μm.

5. The three-dimensional printing method of polymer composite powder material according to claim 1, characterized in that: The clear aperture of the lens of the galvanometer system is 14 mm or less.

6. The three-dimensional printing method of polymer composite powder material according to claim 1, characterized in that: The polymer composite powder material at least includes a polymer powder material containing carbonyl and imino functional groups.

7. The three-dimensional printing method of polymer composite powder material according to claim 1, characterized in that: The wavelength of the laser is 2 μm.

8. The three-dimensional printing method of polymer composite powder material according to any one of claims 1 to 7, characterized in that: The laser is a fiber laser, a solid laser, or a semiconductor laser; the galvanometer system is a two-dimensional galvanometer or a three-dimensional galvanometer.

9. The three-dimensional printing method of polymer composite powder material according to claim 8, characterized in that: The laser is a thulium-doped optical fiber laser with a wavelength.

10. A 3D printing device, characterized in that: include: A laser, which is a continuous laser with a wavelength of 1500nm-2800nm; Galvanometer system, the aperture of the lens is 25mm or less, and the coating reflectivity of the X lens and Y lens is more than 85%; A working cylinder is flatly spread with polymer composite powder material by a powder spreader, so that the laser emitted by the laser sintering the polymer composite powder material under the deflection of the galvanometer system to print layer by layer to obtain a three-dimensional product.

Images