CN111391306A

CN111391306A - 3D printing forming method for converting plane shape into three-dimensional structure

Info

Publication number: CN111391306A
Application number: CN202010204053.0A
Authority: CN
Inventors: 马云海; 吴千; 刘庆萍; 禹江涛; 刘炫廷; 吴思阳; 周雪莉
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2020-03-21
Filing date: 2020-03-21
Publication date: 2020-07-10

Abstract

The invention discloses a 3D printing forming method for converting a plane shape into a three-dimensional structure, which belongs to the field of additive manufacturing and adopts different printing speeds and/or different printing paths to control the final shape of a printed piece.

Description

3D printing forming method for converting plane shape into three-dimensional structure

Technical Field

The invention relates to the field of additive manufacturing, in particular to a 3D printing forming method for converting a plane shape into a three-dimensional structure.

Background

The structure and properties of the polymer material are affected by the process conditions in the processing process, and different processing processes and process parameters can result in different material structures, thereby forming different material properties. Such as polyethylene, can be manufactured into foam, tubing and fibers using different processing techniques and different processing parameters. Although the chemical compositions of these materials are the same, the differences in molecular, crystalline and crystalline structures of the materials result from different processes and parameters, resulting in variations in the strength of the materials across orders of magnitude, from 0.01GP for foams to 1GP for tubing to 200GP for fibers. The polymer material is usually subjected to hot forming at high temperature, such as injection molding, extrusion, calendering and the like, and parameters such as temperature, pressure, flow speed and the like in the processing process have important influence on the structure of the material, so that the structure and performance of the material can be regulated and controlled by controlling process parameters.

3D printing is also called additive manufacturing, and is a process of adding materials point by point (line by line or plane by plane) and accumulating and molding, and in the process of the 3D printing process, the properties of the materials are undoubtedly seriously influenced by the printing process parameters. For example, in the most common fused deposition modeling 3D printing, after the thermoplastic plastic wire is heated and melted and extruded from the extrusion head, the temperature is lowered to solidify and model the material on the modeling substrate (or on the solidified surface of the printing material), and the mechanical properties and geometric accuracy of the printing material are influenced by the printing parameters (such as material melting temperature, substrate temperature, extrusion speed and deposition direction). In a general fused deposition modeling 3D printing process, after the printing speed and the printing path are set, the printing speed and the printing path are not changed in the whole part printing process. If the printing parameters are not proper, after the printed piece is taken out from the printer after printing is finished, the printed piece can generate defects such as warping deformation, cracking, anisotropy and the like due to environmental changes such as environmental temperature and the loss of the constraint of the substrate on the parts after the parts are taken out of the substrate.

In the traditional manufacturing concept, the defects are undesirable and should be avoided as much as possible, so that the technical means adopted by people is to optimize the process parameters in thousands of square meters to minimize the manufacturing defects based on that the current 3D printing three-dimensional structure directly forms the three-dimensional structure according to the path given by the three-dimensional model. However, it is not recognized that such defects (e.g., distortion, warpage, etc.) due to inconsistencies in printing process parameters may be utilized. The inventors have found that if the relationship between the parameters and the defects is determined, we can deliberately create defects by controlling the parameters to achieve the material structure and properties we want.

Disclosure of Invention

Based on the technical background and the concept, the invention provides a method for controlling the final shape of a printed piece by using printing parameters (different printing speeds and/or different printing paths), a plane-shaped (or one-dimensional linear) object is printed, and a printed and molded sample completes deformation with different curvature radii under the action of external excitation (heating). The forming sample is composed of a single layer or two layers, different printing speeds and printing directions are adopted in different areas of each layer, so that anisotropic internal stress is generated on the material, then, driving force is generated under the stimulation of temperature, the sample is driven to complete deformation in different directions and curvature radiuses, and finally, a desired three-dimensional shape is formed.

In order to achieve the above object, the present invention provides a 3D printing molding method for converting a planar shape into a three-dimensional structure, comprising the steps of:

s1, model establishment: the printed sample piece is a planar two-dimensional shape and consists of one layer or a plurality of layers, and different areas of the same layer or different layers adopt different printing speeds and/or printing paths, so that the material generates anisotropic internal stress;

s2, 3D printing: performing fused deposition on a thermoplastic plastic wire on a printing table by an FDM (fused deposition modeling) method to finish the printing of a required sample;

s3, cooling: cooling the printing platform and the printing sample piece at room temperature, and separating the printing platform from the sample piece;

s4, curvature deformation: and heating the cooled sample piece under a specific area, sensing the temperature change of the specific area, generating stress response, and generating the change of curvature radius in different directions and/or different degrees, thereby completing the deformation.

Wherein the thermoplastic plastic is selected from one of polylactic acid, ABS, polycaprolactone and polypropylene materials. Polylactic acid, polycaprolactone, polypropylene and the like are thermoplastic plastics, have good mechanical properties, are nontoxic and tasteless and can be used as food and medical materials. The variable printing material is heated to the glass transition temperature, the glass state is converted into the rubber state, the shape change is completed, and the shape is kept unchanged after the variable printing material is cooled to the room temperature. Meanwhile, polylactic acid and polycaprolactone are biodegradable materials, can be completely degraded by organisms in the nature after being used, and are ideal green high polymer materials.

The invention is suitable for most semi-crystalline thermoplastic polymer materials, which are 1.75 mm or 3mm wires commonly used for 3D printing.

According to the 3D printing and forming method for converting the plane shape into the three-dimensional structure, the printing speed is changed suddenly or gradually in different areas of the same layer or different layers, and the range of the printing speed is 30-250 mm/s.

In the 3D printing and forming method for converting the planar shape into the three-dimensional structure, the printing path is composed of straight lines with different angles, or different curves, or a combination of the straight lines and the curves in different regions of the same layer or different layers.

As a specific embodiment, the mold is composed of two thermoplastic layers, including a mold active layer and a mold passive layer. The printing speed V1 of the model active layer material ranges from 30mm/s to 250mm/s, and the printing speed V2 of the model passive layer material ranges from 30mm/s to 250 mm/s. V1 and V2 are different. The printing temperature is set to be 195-210 ℃, the inner diameter of the extrusion head is 0.4mm, the printing table descends by one printing layer height when each layer of printing is finished, deposition is carried out according to the deposition path of the next printing layer, and the steps are repeated in a circulating mode until the required sample printing is finished. And finally heating at 60-120 ℃ for 5-60 minutes, sensing the temperature change of a specific area to generate stress response, and generating the change of curvature radii of different degrees, thereby finishing the deformation.

The invention has the beneficial effects that:

1. compared with the method of directly printing the three-dimensional shape, the method only prints the plane shape and converts the plane shape into the three-dimensional shape by heating, thereby having short manufacturing time and high efficiency;

2. materials are saved, supporting materials are often needed for directly printing a three-dimensional structure, and only a planar shape needs to be printed without supporting materials;

3. the strength of a printed piece is high, the direct printing of the three-dimensional structure is realized by layer-by-layer accumulation molding, the strength of the direct printing of the three-dimensional structure depends on the interlayer bonding strength, the invention adopts a two-dimensional shape to be converted into the three-dimensional structure, the three-dimensional structure is formed by continuous wires, two dimensions are bent into three dimensions, and the strength of the three-dimensional structure is higher than that of the layer-by-layer accumulation;

4. the method has the advantages that energy is saved, the fused deposition molding needs to heat and melt the material, electric energy is consumed, the processing time is short, less energy is consumed, and although the printed product needs to be heated, the time is short, and the energy consumption is low.

Drawings

Fig. 1 is a perspective view of a strip after 3D printing and forming according to an embodiment of the present invention.

Fig. 2 is a perspective view of a deformed strip after 3D printing and forming according to an embodiment of the present invention.

FIG. 3 shows a printing apparatus according to an embodiment of the present invention, in which FIG. 1 is a printing chamber, FIG. 2 is a feeding roller, FIG. 3 is a printing filament, FIG. 4 is a heating device, FIG. 5 is a fixing device, FIG. 6 is an extrusion head, FIG. 7 is a printing platform, FIG. 8 is a printing sample, H is a printing height, and d is a printing diameter.

Fig. 4 is a cross-sectional view of a strip after 3D printing and forming according to an embodiment of the present invention.

Fig. 5 is a cross-sectional view of a strip after 3D printing and forming according to an embodiment of the present invention.

Fig. 6 is a plan view of a deformed strip after 3D printing and forming according to an embodiment of the present invention.

Fig. 7 is a perspective view of a sample after 3D printing and forming of the table leg according to embodiment 1 of the present invention.

Fig. 8 is a perspective view of a sample after 3D printing and forming of the table leg according to embodiment 1 of the present invention, the sample being deformed.

Fig. 9 is a perspective view of a sample after 3D printing and forming of a "chair" according to embodiment 2 of the present invention.

Fig. 10 is a top view of a sample piece after 3D printing and forming of a "chair" according to embodiment 2 of the present invention.

Fig. 11 is a perspective view of a sample after 3D printing and forming of a "chair" according to embodiment 2 of the present invention.

Detailed Description

The invention adopts a fused deposition modeling 3D printing technology, namely thermoplastic plastic wires are used, the material is heated to be higher than the melting temperature through the heating of a liquefier, and the extruded material is cooled, solidified and molded.

In the current 3D printing method, once set, the printing speed is constant and constant throughout the printing process of a sample, and the printing speed of each part of the sample is the same.

Different from the current printing method, the printing line type or plane shape of the invention adopts different printing speeds (moving speeds of the extrusion head) and printing directions at different parts of the same part so as to control the internal stress of the material, and then the printing part is heated to release the internal stress to deform the printing part so as to obtain the expected three-dimensional structure.

A typical method provided by the embodiment of the present invention is to print a double-layer straight strip (as shown in fig. 1), each layer adopts different printing speeds, the printing speed is high, the accumulated internal stress is large, and the shrinkage generated during heating is large, so that the double-layer structure is bent to the side with the large speed (as shown in fig. 2). The degree of curvature is related to the absolute value of the printing speed of the two layers, the speed difference, the layer thickness, the extrusion temperature and the ambient temperature, and when other factors are fixed, the degree of curvature is related only to the printing speed, so that the printed straight pattern can be converted into a curved shape by controlling the printing speed of each layer.

The thermoplastic plastic material adopted by the embodiment of the invention is polylactic acid material, the structure of the printer is shown in figure 3, and the specific printing parameters of the double-layer linear structure are as follows: the diameter d of the extrusion head is 0.4mm, the layer thickness h is 0.3mm, the printing extrusion temperature is 195 ℃ and the forming chamber temperature is 42 ℃. The relationship between the deformation curvature and the printing speed is shown in tables 1, 2, and 3. The printed strip is composed of upper and lower layers, and as shown in fig. 4, the upper layer 9 has a printing speed of V1 and the lower layer 10 has a printing speed of V2.

TABLE 1 change in radius of curvature at a lower layer printing speed of 30mm/s

V₁(mm/s)	50	70	90	110	130	150	170	190	210
										V₂(mm/s)	30	30	30	30	30	30	30	30	30
R(mm)	128	101	81	66	55	43	34	27	21

TABLE 2 change in radius of curvature at lower layer printing speed of 50mm/s

V1(mm/s)	70	90	110	130	150	170	190	210	230
										V2(mm/s)	50	50	50	50	50	50	50	50	50
R(mm)	152	122	99	86	73	59	46	35	26

TABLE 3 change in radius of curvature at 70mm/s lower layer printing speed

V1(mm/s)	90	110	130	150	170	190	210	230	250
										V2(mm/s)	70	70	70	70	70	70	70	70	70
R(mm)	179	155	133	116	93	75	57	44	33

The cross-section of the print is shown in fig. 5, where the material after extrusion has an approximately elliptical cross-sectional shape due to the extrusion, and a thickness (height) that is less than the diameter of the extrusion head, which in this case is set to 80% of the extrusion diameter, and 0.4mm of the extrusion head, the layer thickness is approximately equal to 0.3 mm.

The printed article is heated to produce a bend, the bend diameter being denoted by R. The printed matter is curved to the side where the printing speed is fast, and in this example, the upper layer 9 is curved in the direction of the upper layer 9 because the printing speed is faster than the lower layer 10, as shown in fig. 6.

The present invention will be described in further detail with reference to the accompanying drawings and examples.

Embodiment 1 3D printing and forming method of table legs

A part consisting of two lines as shown in figure 7 was printed with different print speeds at specific locations of the lines. In the figure, the upper layer printing speed of the area 11 and the area 12 is 50mm/s, and the lower layer printing speed of the area 11 and the area 12 is 210 mm/s; the printing speeds of the upper and lower layers of the rest of the figure are both 50 mm/s.

The printing material is polylactic acid, the diameter of the extrusion head is 0.4mm, the layer thickness is 0.3mm, and the temperature of the forming bin is 40 ℃. The printed lines were heated at 90 ℃ for 10 minutes.

The three-dimensional structure after the heat treatment is shown in fig. 8, and the lower layer printing speed of the

areas

11 and 12 is higher than that of the upper layer printing speed corresponding to fig. 7, resulting in bending of the two areas toward the lower layer, so that the linear shape is formed into a shape of a table leg.

Example 2 'chair' 3D printing and forming method

A part of two-layer planar shape as shown in fig. 9 is printed, with different printing speeds being applied to specific portions of this planar shape. FIG. 10 is a top plan view of the print shown in FIG. 9, with the upper layer print speed being 50mm/s and the lower layer print speed being 210mm/s for region 13, region 14, region 15 and region 16 of FIG. 10; in FIG. 10, the upper layer of region 17 prints at a speed of 210mm/s and the lower layer at a speed of 50 mm/s; the printing speeds of the upper and lower layers of the rest of FIG. 10 are both 50 mm/s.

The printing material is polylactic acid, the diameter of the extrusion head is 0.4mm, the layer thickness is 0.3mm, and the temperature of the forming bin is 40 ℃. The heating temperature was 90 ℃ and the heating time was 10 minutes.

The three-dimensional structure of the printed planar part after heat treatment is shown in fig. 11, which corresponds to fig. 10, where in fig. 11 the upper layer printing speed is higher than the lower layer printing speed in the bottom area 17 of the chair back, resulting in a bending of this area towards the upper layer, resulting in a planar shape to the chair back. The upper layer of the four legs of the chair, zone 13, zone 14, zone 15 and zone 16, prints at a lower rate than the lower layer, causing the material to bend (bend down) towards the lower layer, bending the original planar shape at right angles to form the legs of the chair.

Compared with the prior art, the invention has the beneficial effects that:

1. the controllable selective deposition is carried out on the active layer material and the passive layer material by adopting a melt extrusion deposition method, and the principle of deformation is realized by utilizing the strain generated when the thermoplastic polymer is higher than the glass transition temperature and the printing speed difference of the active layer material and the passive layer material, so that the driving force is generated. The spatial positions of the materials of the active layer and the passive layer of the required model are designed, so that the 3D printing forming method for converting the plane shape into the three-dimensional structure is realized, and the method has the advantages of simple process, low cost and the like;

2. A3D printing forming method for converting a plane shape into a three-dimensional structure is designed, and shape change from one-dimensional to two-dimensional and two-dimensional to three-dimensional space is realized. Compared with the traditional 3D printing method, the method has the advantages that the printed sample piece is only required to be printed in a planar shape, does not need to support materials, can be completed in a short time, and has the advantages of material saving, high efficiency, time saving and the like;

3. energy is saved, the fused deposition molding needs to heat and melt the material to consume electric energy, the method has short processing time and consumes less energy, and although the printed piece needs to be heated, the time is short and the energy consumption is little;

4. the strength of the printed product is high, the direct printing three-dimensional structure is formed by layer-by-layer accumulation, the strength of the direct printing three-dimensional structure depends on the bonding strength between layers, the invention converts a two-dimensional shape into a three-dimensional structure, the three-dimensional structure is formed by continuous wires, two dimensions are bent into three dimensions, and the strength of the three-dimensional structure is higher than that of the direct printing three-dimensional structure accumulated layer by layer.

While embodiments of the invention have been disclosed above, it is not intended to be limited to the uses set forth in the specification and examples. It can be applied to all kinds of fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. It is therefore intended that the invention not be limited to the exact details and illustrations described and illustrated herein, but fall within the scope of the appended claims and equivalents thereof.

Claims

1. A3D printing forming method for converting a plane shape into a three-dimensional structure is characterized by comprising the following steps:

2. The 3D printing forming method of converting a planar shape into a three-dimensional structure according to claim 1, wherein the thermoplastic is one selected from polylactic acid, ABS, polycaprolactone and polypropylene materials.

3. A 3D print forming method for transforming a plane shape into a three-dimensional structure as claimed in claim 1, wherein the thermoplastic filament is 1.75 mm or 3mm filament.

4. A 3D printing forming method of converting a plane shape into a three-dimensional structure according to claim 1, wherein the printing speed is abrupt or gradual in different areas of the same layer or different layers, and the printing speed is in a range of 30-250 mm/s.

5. The 3D printing forming method of converting a plane shape into a three-dimensional structure according to claim 1, wherein the printing path is composed of straight lines of different angles, or different curved lines, or a combination of the straight lines and the curved lines in different regions of the same layer or different layers.

6. The 3D printing molding method for converting a planar shape into a three-dimensional structure according to claim 1, wherein the step S1 is characterized in that the model is composed of two thermoplastic plastic layers, including a model active layer and a model passive layer.

7. The 3D printing forming method of converting the planar shape into the three-dimensional structure according to claim 6, wherein the printing speed V1 of the model active layer material of the step S1 is in the range of 30-250mm/S, and the printing speed V2 of the model passive layer material is in the range of 30-250 mm/S.

8. The 3D printing and forming method for converting the planar shape into the three-dimensional structure according to claim 6, wherein the printing temperature of step S2 is set to 195 ℃ -210 ℃, the inner diameter of the extrusion head is 0.4mm, each time one layer of printing is completed, the printing platform descends by one printing layer height, and then the deposition is performed according to the deposition path of the next printing layer, and the cycle is repeated until the required printing of the sample piece is completed.

9. The 3D printing molding method of converting a planar shape into a three-dimensional structure according to claim 6, wherein the step S4 is heating with 60-120 ℃.

10. The 3D printing molding method of converting a planar shape into a three-dimensional structure according to claim 9, wherein the heating time of step S4 is 5 to 60 minutes.