A high-precision 3D printed polymer foam part and its application

Abstract

The present invention discloses a polymer foam part for high-precision 3D printing and its application, relating to the technical field of 3D printing. The high-precision 3D printed part provided by the present invention is prepared by the method of melt extrusion-3D printing stacking. By controlling the linear velocity of the extruded wire during stacking and the speed of the extruded wire, the precision of the obtained 3D printed part is greatly improved. The obtained part has a size error of ≤3%, high forming precision, no obvious protrusions and depressions on the appearance, and stable extrusion and uniform strand stacking during the preparation process. The density of the part also reaches below 0.6 g / cm<supgt;3< / supgt;, achieving a good weight reduction effect, and having broad application prospects in many fields such as aerospace and sports protection.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a high-precision 3D printed polymer foam product and application thereof. Background Art

[0002] Polymer 3D printing technology has free structural design, can realize mold-free molding, and has a short processing cycle. It has become an important development direction in the field of polymer material processing. Polymer-related 3D printing technologies include FDM technology that processes filaments, SLS technology characterized by micro-powder sintering, and SLA technology that forms through photocuring. Among them, the equipment involved in FDM technology is cheap and easy to obtain, and has been widely used in many technical fields.

[0003] Currently, polymer parts obtained through FDM 3D printing are usually solid structures with heavy texture. Although weight reduction can be achieved through hollowing out and other structures and methods, it is far from meeting the weight requirements of many fields including aerospace, sports protection, etc. Foaming the parts formed by FDM 3D printing is a way to achieve weight reduction, but there are problems such as difficulty in resin foaming, uneven regional foaming, and difficulty in controlling the size of foamed parts, which makes it difficult to apply in practice.

[0004] Existing literature reports a method of using supercritical fluid or high-pressure fluid to impregnate polymer wires, and then extrude the impregnated wires through the extrusion die of the FDM 3D printing device, and controllably stack the wires on the equipment workbench to achieve 3D printing, thereby preparing a polymer foamed part. This is equivalent to foaming the raw materials during the 3D printing process (supercritical fluid or high-pressure fluid can be used as a fluid foaming agent to make the wire foam and expand at the moment of being extruded from the extrusion die of the 3D printing device). This method can also achieve weight reduction, and the parts foamed by this method have more uniform pore distribution, and the morphology and size of the parts can also be controlled. However, during the 3D printing process, the extrusion die will move at high speed as the printing path is set, and the extruded wire will also have significant inertia, especially for wires with lighter hardness. When the inertia is too large, it will produce a "drift" phenomenon, which will affect the dimensional accuracy of the printed parts. How to improve the dimensional accuracy of 3D printed foam parts still needs to be solved. Summary of the invention

[0005] In order to address the deficiencies in the prior art, the present invention provides a high-precision 3D-printed polymer foam product. First, raw material particles are melted and extruded, and at the same time, the die used for extruding the filament is moved under the drive of a motor of a 3D printing device. The obtained filament can complete foaming and controllable stacking at the moment of extrusion. In this process, by controlling the speed of melt extrusion and the linear speed of stacking, the present invention achieves the reduction of the dimensional error of the 3D-printed polymer foam product to within 3%, with excellent precision.

[0006] Another object of the present invention is to provide an application of the above-mentioned high-precision 3D-printed polymer foamed parts.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A high-precision 3D-printed polymer foamed part, which is prepared by sequentially melt-extruding and 3D-printing stacking polymer particles containing a foaming agent, wherein the melt-extrusion speed is 0.1-3 kg / h, and the linear speed of the 3D-printing stack is ≤180 mm / s;

[0009] The melt extrusion is carried out using a single-screw extruder, which includes a first heating section, a second heating section and a third heating section. The temperature of the first heating section is 0-30°C, the temperature of the second heating section is 160-320°C, and the temperature of the third heating section is 230-390°C, wherein the real-time temperature of the third heating section is higher than that of the second heating section.

[0010] It should be noted that in the present invention, the temperature of the first heating section is controlled to be 0-30° C. by connecting the first heating section to a temperature control system. Specifically, the temperature control system includes at least one of an air cooling system and a water cooling system.

[0011] In a specific embodiment of the present invention, the melt extrusion and 3D printing stacking in the present invention are performed in a 3D printing device in which the filament extrusion unit includes a screw extruder.

[0012] In the existing process of extrusion foaming using a single screw extruder, the temperature of the extruder feeding section (i.e., the first heating section) is usually as high as 100°C or above. However, the inventors of this application have found through a large number of experimental studies that if the temperature in the extruder feeding section is too high, it will lead to excessive loss of the foaming agent in the polymer matrix, and the raw materials will be difficult to be stably transported to the second and third heating sections, resulting in uncontrollable foaming and expansion of the foaming material in the subsequent 3D printing process, affecting the dimensional accuracy of the obtained parts. Therefore, the present invention reduces the temperature of the feeding section in the process of raw material extrusion, reduces the loss of the foaming agent, and enables stable material transportation. The particles containing the foaming agent are melted and compacted in the second heating section to achieve densification between the particle structure and prevent the escape of the foaming agent; the particles containing the foaming agent continue to melt and foam in the third section of the screw, and the stable transportation of the foaming melt to the extrusion die is achieved through the metering properties of the screw structure.

[0013] During the FDM 3D printing process, the printing nozzle (in the present invention, the extrusion die of the extruder) will move at high speed as the printing path is set, and the extruded wire will also have significant inertia, especially when the hardness of the wire is low. The existence of inertia causes the extrusion speed to be too high, which will affect the dimensional accuracy of the printed parts. The inventors of this application have found through a large number of experimental studies that on the basis of adjusting the extrusion process, in the subsequent 3D printing process, by controlling the amount of raw materials extruded by the extrusion die per unit time and controlling the movement speed of the extrusion die within a certain range, the inertia of the extruded wire can be significantly reduced. The influence of the shape, size, etc. of the part can be greatly improved, thereby greatly improving the printing accuracy of the resulting 3D printed parts and reducing dimensional errors.

[0014] In a specific embodiment of the present invention, the loss rate of the foaming agent in the polymer particles containing the foaming agent in the first heating section during the melt extrusion process is less than 10%, preferably less than 5%.

[0015] In a specific embodiment of the present invention, the temperature control accuracy of the second and / or third heating section during the melt extrusion process is 0.5-5°C, preferably 1-3°C.

[0016] In a specific embodiment of the present invention, the residence time of the polymer particles containing the foaming agent in the second and / or third heating sections during the melt extrusion process is 0.1 to 1.5 s, preferably 0.2 to 1.0 s, and more preferably 0.3 to 0.8 s. In a specific embodiment of the present invention, the screw speed of the single screw extruder in the melt extrusion is 5 to 30 rpm.

[0017] Preferably, the melt extrusion speed is 0.2-2 kg / h.

[0018] In a specific embodiment of the present invention, the polymer particles containing a foaming agent are melt-extruded to obtain a foamed filament, and the diameter of the foamed filament is 0.2-0.8 mm. More specifically, in the present invention, the diameter of the foamed filament is 0.3-0.8 mm by controlling the diameter of the extrusion die to 0.4-1.0 mm.

[0019] Preferably, the temperature of the 3D printing stack is 30-150°C.

[0020] In a specific embodiment of the present invention, the temperature of the 3D printing stack is the cavity temperature of the 3D printing device, and is also the temperature of the extrusion die. By controlling the temperature of the printer cavity (inside the printer housing), the interfacial bonding degree of the stacked foaming melt streams can be improved, and a polymer lightweight foamed part with improved interlayer interfacial bonding can be obtained.

[0021] More preferably, the temperature of the 3D printing stack is 70-90°C.

[0022] More preferably, the temperature of the 3D printing stack has a temperature control accuracy of 1-5°C, and further preferably 1-3°C.

[0023] Preferably, the linear speed of the 3D printing stack is 110-140 mm / s.

[0024] In a specific embodiment of the present invention, the rotation angle of the 3D printed stack is 0-80°. Preferably, the rotation angle of the 3D printed stack is 0-10°. Preferably, the rotation angular velocity of the 3D printed stack is 0-3 rad / s.

[0025] By controlling the rotation angle of the stacking platform, the curved stacking molding of the foamed melt can be achieved, and 3D printed lightweight parts with curved structures can be prepared. However, rotation during the printing and stacking process will also bring inertia. Printing and stacking at a lower rotation angle will help further improve the accuracy.

[0026] In a specific embodiment of the present invention, the melt extrusion and 3D printing stacking are carried out in a 3D printing device, and the 3D printing device includes the following structural units: a feeding unit, an extrusion unit, a printer motion bracket, a stacking platform, and a printer housing; the extrusion unit is a single-screw extruder.

[0027] In a specific embodiment of the present invention, the feeding unit includes a raw material bin and a conveying pipeline, and the extrusion unit, namely a single-screw extruder, includes a screw structure, a temperature control component and an extrusion die.

[0028] When preparing a high-precision 3D printed polymer foam part in the above 3D printing device, the following steps are included:

[0029] Polymer particles containing a foaming agent are put into the raw material bin of the feeding unit, and the particles are quantitatively and regularly transported to the screw structure of the extrusion unit through the conveying pipeline. The temperature of different heating sections in the screw structure is controlled by the temperature control component to melt and foam the particles; the particle melt is transported to the extrusion die through the screw structure, and extruded and foamed through the die. Since the extrusion unit in the present invention is fixed on the moving bracket of the 3D printing device, the foaming melt extruded from the extrusion die can be stacked and formed on the stacking platform according to the designed path through the software program.

[0030] Preferably, the content of the blowing agent in the polymer particles containing the blowing agent is 0.1-10 wt%.

[0031] More preferably, the hardness of the polymer particles containing the foaming agent is Shore A80~Shore D85.

[0032] In a specific embodiment of the present invention, the shape of the polymer particles containing a foaming agent is at least one of circular, elliptical and cylindrical, the diameter of the particles is 0.5-5.0 mm, and the fluctuation range of the average diameter is ±0.5-1 mm.

[0033] Preferably, the foaming agent includes at least one of a fluid foaming agent and a solid foaming agent.

[0034] More preferably, the fluid blowing agent includes at least one of CO2, N2, gaseous alkanes, and hydrogenated chlorofluorocarbon (HCFC) blowing agents.

[0035] More preferably, the solid foaming agent includes at least one of expandable microspheres, carbonates, N,N'-dinitrosopentamethylenetetramine, and azodicarbonamide.

[0036] Preferably, the polymer includes at least one of a semi-crystalline polymer, a crystalline polymer, and an amorphous polymer.

[0037] More preferably, the amorphous polymer includes at least one of polystyrene, polymethyl methacrylate, polyetherimide, polyimide, and polysulfone.

[0038] More preferably, the semi-crystalline polymer includes at least one of polyethylene terephthalate, polylactic acid, and polyetheretherketone.

[0039] More preferably, the crystalline polymer includes at least one of polyethylene, polypropylene, polyurethane, polyester elastomer, and nylon elastomer.

[0040] Preferably, the polymer particles containing a foaming agent are prepared by blending a polymer with a foaming agent; wherein, when the foaming agent is a fluid foaming agent, the polymer and the foaming agent are blended by impregnation.

[0041] In a specific embodiment of the present invention, the blending is carried out at a temperature of -20 to 30°C, with a temperature control accuracy of 1°C and a humidity control of 1 to 30%.

[0042] In a specific embodiment of the present invention, the density of the 3D stacked product is 0.3-0.95 g / cm 3 .

[0043] The present invention also protects the application of the above-mentioned high-precision 3D-printed polymer foam parts in the fields of sports protection, aerospace, and precision manufacturing.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The high-precision 3D printed parts provided by the present invention have a dimensional error of ≤3%, high molding accuracy, no obvious protrusions and depressions in appearance, stable extrusion during the preparation process, uniform strand stacking, and the density of the obtained parts also reaches 0.6g / cm 3 The following has achieved a good weight reduction effect and has broad application prospects in many fields such as aerospace, sports protection, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic diagram of the structure of the 3D printing device in the present invention.

[0047] Figure 2 It is a schematic diagram of the structure of the 3D printed foamed part in the present invention. DETAILED DESCRIPTION

[0048] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents. Among them, the raw material information used in each embodiment and comparative example is as follows (the part involving hardness refers to Shore hardness):

[0049] Amorphous polymer A

[0050] A1, polystyrene PS, brand GPPS158K, BASF-Yangzi;

[0051] A2, polyetherimide PEI, grade 1000, SABIC;

[0052] Crystalline polymer B

[0053] B1, low-density polyethylene LDPE, brand 2426H, Maoming Petrochemical;

[0054] B2, thermoplastic polyurethane TPU, hardness 85A, Wanhua Chemical.

[0055] Semi-crystalline polymer C

[0056] C, PEEK, grade 1000, Mitsubishi Chemical.

[0057] Blowing agent: azodicarbonamide, commercially available.

[0058] Examples 1 to 11 and Comparative Example 1

[0059] This embodiment and the comparative example provide a series of high-precision 3D-printed polymer foam parts with different preparation parameters. The preparation process of the parts is carried out in a 3D printing device, and the 3D printing device includes the following structural units: a feeding unit, an extrusion unit, a printer motion bracket, a stacking platform, and a printer housing; the extrusion unit is a single-screw extruder, including a screw structure, a temperature control component and an extrusion die; the feeding unit includes a raw material bin and a conveying pipeline.

[0060] The method for preparing a high-precision 3D-printed polymer foam part in this embodiment comprises the following steps:

[0061] A foaming agent and polymer particles are blended at -20°C to obtain polymer particles containing 5 wt% of a foaming agent, the particles are put into a raw material bin of a feeding unit, the particles are quantitatively and regularly conveyed to a screw structure of an extrusion unit through a conveying pipeline, the temperature of different heating sections in the screw structure is controlled by a temperature control component, and the particles are melted and foamed; the particle melt is conveyed to an extrusion die through the screw structure, and is extruded and foamed through the die to obtain a foamed filament, wherein the diameter of the foamed filament is 0.3 mm (the diameter of the extrusion die is 0.4 mm). Through the software program, the foaming melt extruded from the extrusion die can be stacked and formed on the stacking platform according to the designed path, with a rotation angle of 5° and an angular velocity of 1 rad / s, to obtain high-precision 3D-printed polymer foam parts; among them, the loss rate of the polymer particles containing the foaming agent in the first heating section is less than 5%, the temperature control accuracy of the second heating section and the third heating section is 2°C, the residence time of the polymer particles containing the foaming agent in the second heating section and the third heating section is 0.5 s, and the screw speed is 10 rpm.

[0062] The high-precision 3D-printed polymer foam parts prepared in the embodiments and comparative examples have structures such as Figure 2 As shown, the model size is 150×150×1.2 mm, the filling method is "X" type, and the filling density is 30%.

[0063] The specific preparation parameters in Examples 1 to 11 and Comparative Example 1 are shown in Table 1 below:

[0064] Table 1. Specific preparation parameters in Examples 1 to 11 and Comparative Example 1

[0065]

[0066] Comparative Example 2

[0067] A high-precision 3D-printed polymer foamed part, which is different from Example 5 only in that:

[0068] The melt extrusion speed in the preparation process is 4 kg / h.

[0069] Comparative Example 3

[0070] A high-precision 3D-printed polymer foamed part, which is different from Example 5 only in that:

[0071] The stacking speed of the foaming melt in the preparation process is 200 mm / s.

[0072] Performance Testing

[0073] Dimension error test: It is calculated by the deviation between the actual size of the product and the modeling target size. Specifically, the dimension error φ = (V 制 -V 模 ) / V 模 ×100%, where volume V=length×width×height.

[0074] Part density test: Use a density balance to characterize the density of the part.

[0075] Processing behavior test: obtained through visual observation during the preparation process.

[0076] Part appearance test: obtained through visual observation of the part.

[0077] The specific performance test data is shown in Table 2 below:

[0078] Table 2. Processing behavior and other properties of the parts obtained in the examples and comparative examples

[0079]

[0080]

[0081] According to the data in Table 2 above, the high-precision 3D printed parts provided by the present invention have a dimensional error of ≤3%, high molding accuracy, no obvious protrusions and depressions in appearance, stable extrusion during the preparation process, uniform strand stacking, and the density of the obtained parts also reaches 0.6g / cm 3 The following has achieved a good weight reduction effect and has broad application prospects in many fields such as aerospace, sports protection, etc.

[0082] It can be seen from the data of Examples 5 to 8 in Tables 1 to 2 that when the melt extrusion speed is within the preferred range of 0.2 to 2 kg / h (Examples 5 to 6), the obtained product has lower dimensional error and density, high molding accuracy, and no obvious defects in appearance. At the same time, as the melt extrusion speed is increased to 3 kg / h (Example 7), the molding accuracy of the product begins to decrease due to the instability of the melt extrusion. According to the data of Examples 5, 9 to 11, as the stacking speed of the foaming melt increases from 100 mm / s (Example 11) to 120 mm / s (Example 5) and then to 140 mm / s (Example 10), and finally continues to increase to 160 mm / s (Example 9), the dimensional accuracy of the obtained 3D printed product first increases and then decreases (the dimensional error first decreases and then increases), and as the stacking speed is increased to 160 mm / s (Example 9), the molded product is prone to defects. Therefore, the preferred linear speed of 3D printing stacking in the present invention is 110 to 140 mm / s. According to the data comparison of Example 5 and Comparative Example 1, it can be seen that by adopting a specific extrusion process (Example 5) to extrude and foam the polymer, the obtained product has higher dimensional accuracy and better foaming performance, and the density is reduced while no defects are produced in the appearance.

[0083] According to Comparative Example 1, the conventional process of extruding and foaming the polymer particles containing the foaming agent will affect the precision and density of the product.

[0084] According to Comparative Examples 2-3, whether the extrusion speed of the foaming melt is too high or the stacking speed is too high, the inertia is too high and thus the stacking accuracy is greatly reduced.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A high-precision 3D printed polymer foam part, characterized in that: The polymer particles containing a foaming agent are prepared by melt extrusion and 3D printing stacking in sequence, wherein the melt extrusion speed is 0.1-3 kg / h, and the linear speed of the 3D printing stacking is 110-140 mm / s; The melt extrusion is carried out by a single screw extruder, the single screw extruder comprises a first heating section, a second heating section and a third heating section, the temperature of the first heating section is 0-30°C, the temperature of the second heating section is 160-320°C, the temperature of the third heating section is 230-390°C, wherein the real-time temperature of the third heating section is higher than that of the second heating section; The polymer particles containing the foaming agent are melt-extruded to obtain foamed filaments, wherein the diameter of the foamed filaments is 0.2-0.8 mm; The foamed melt extruded from the extrusion die is stacked and formed on the stacking platform according to the designed path through the software program; The speed of the melt extrusion is 0.2-2 kg / h.

2. The high-precision 3D-printed polymer foam part according to claim 1, characterized in that: The temperature of the 3D printing stack is 30~90℃.

3. The high-precision 3D-printed polymer foam part according to claim 1, characterized in that: The rotation angle of the 3D printed stack is 0~10°.

4. The high-precision 3D-printed polymer foam part according to claim 1, characterized in that: The melt extrusion and 3D printing stacking are performed in a 3D printing device, which includes the following structural units: a feeding unit, an extrusion unit, a printer motion bracket, a stacking platform, and a printer housing; the extrusion unit is a single-screw extruder.

5. The high-precision 3D-printed polymer foam part according to claim 1, characterized in that: The hardness of the polymer particles containing the foaming agent is Shore A80-Shore D85.

6. The high-precision 3D-printed polymer foam part according to claim 5, characterized in that: Include at least one of the following (a) to (b): (a) the foaming agent comprises at least one of a fluid foaming agent and a solid foaming agent; (b) The polymer includes at least one of a semi-crystalline polymer, a crystalline polymer, and an amorphous polymer.

7. The high-precision 3D-printed polymer foam part according to claim 6, characterized in that: Include at least one of the following (c) to (g): (c) the fluid blowing agent comprises at least one of CO2, N2, gaseous alkanes, and hydrogenated chlorofluorocarbon blowing agents; (d) the solid foaming agent comprises at least one of expandable microspheres, carbonates, N,N'-dinitrosopentamethylenetetramine, and azodicarbonamide; (e) the amorphous polymer comprises at least one of polystyrene, polymethyl methacrylate, polyetherimide, polyimide and polysulfone; (f) the semi-crystalline polymer comprises at least one of polyethylene terephthalate, polylactic acid, and polyetheretherketone; (g) The crystalline polymer includes at least one of polyethylene, polypropylene, polyurethane, polyester elastomer, and nylon elastomer.

8. Application of the high-precision 3D-printed polymer foam product according to any one of claims 1 to 7 in the fields of sports protection, aerospace, and precision manufacturing.

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