Three-dimensional object and method for forming three-dimensional object

Abstract

To provide a three-dimensional molded object with softness equivalent to that of the human body.SOLUTION: A three-dimensional molded object according to one aspect of the invention is the three-dimensional molded object molded by melting and laminating a thermoplastic resin or a composition thereof, including a repeating structure internally and having a Young's modulus in a range of 5 [kPa] or more and 20 [kPa] or less.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present application relates to a three-dimensional object and a method for forming a three-dimensional object. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as a representative example of a structure approximating human skin, an artificial breast is known as a prosthetic device that is attached to the position of a breast missing from a breast cancer.

[0003] To create an artificial breast with the same shape as an individual's breast, a mold is required to fit the shape, but molds are expensive and their production is labor-intensive. One method for creating molds is to use a three-dimensional modeling device such as a 3D printer, but the process of making the mold and then filling it with silicone rubber is a double effort.

[0004] Meanwhile, in recent years, three-dimensional modeling devices such as 3D printers are becoming more and more popular as devices for forming three-dimensional objects without using dies, etc. For example, 3D printers that form three-dimensional objects by the fused deposition modeling method tend to be cheaper than 3D printers that form three-dimensional objects by other methods, and some are even sold for personal use.

[0005] Also disclosed is a method for manufacturing a three-dimensional object using a multi-layer filament for three-dimensional modeling, which includes a step of obtaining a mixed resin by mixing a core layer portion and a sheath layer portion of the multi-layer filament for three-dimensional modeling in an extrusion section of a three-dimensional modeling device, and a step of extruding a molten mixed resin from the extrusion section (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0006] However, the configuration of Patent Document 1 leaves room for improvement in terms of forming a three-dimensional object that has the same softness as the human body, such as an object that resembles a human body part.

[0007] An object of the present invention is to provide a three-dimensional object having softness equivalent to that of the human body. [Means for solving the problem]

[0008] A three-dimensional object according to one aspect of the present invention is a three-dimensional object formed by melt lamination of a thermoplastic resin or a composition thereof, Has a void It has a repeating structure inside, Measured by softness measuring device Young's modulus is in the range of 5 kPa or more and 20 kPa or less. Effect of the Invention

[0009] According to the present invention, it is possible to provide a three-dimensional object having the same softness as the human body. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of a three-dimensional object forming apparatus according to an embodiment. [Diagram 2] 1A and 1B are diagrams illustrating the phenomenon in which a filament buckles. [Diagram 3] FIG. 13 is a diagram illustrating another example of the configuration of the three-dimensional object forming apparatus according to the embodiment. [Figure 4] FIG. 2 is a cross-sectional view of an example of the internal structure of an extrusion device when performing shaping using pellets. [Diagram 5] FIG. 2 is a block diagram illustrating an example of a hardware configuration of the three-dimensional object forming apparatus according to the embodiment. [Figure 6] FIG. 2 is a diagram illustrating Young's modulus. [Figure 7] 7A and 7B are diagrams of a honeycomb structure, where FIG. 7A is a top view and FIG. 7B is a perspective view. [Figure 8] 11 is a diagram illustrating an example of the relationship between the internal structure filling rate of a shaped object and Young's modulus when liquid paraffin is added to change the Young's modulus; FIG. [Figure 9] FIG. 2 is a diagram illustrating the relationship between Asker hardness and Young's modulus. [Figure 10] FIG. 2 is a diagram illustrating an elasticity sensor and an indenter of a softness measuring instrument. [Figure 11] FIG. 13 is a diagram illustrating the relationship between the softness measurement results and the compression test results. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and duplicated explanations may be omitted.

[0012] The following embodiments are illustrative of a three-dimensional object and a three-dimensional modeling method for embodying the technical concept of the present invention, and the present invention is not limited to the following embodiments. The dimensions, materials, shapes, and relative positions of the components described below are intended to be illustrative, and not to limit the scope of the present invention, unless otherwise specified. In addition, the sizes and positional relationships of the components shown in the drawings may be exaggerated to clarify the explanation.

[0013] [Overall configuration example] As an embodiment of a three-dimensional modeling apparatus having a modeling unit that forms modeling layers on a modeling stage with a modeling material, a three-dimensional modeling apparatus 1 that forms a three-dimensional object by a fused deposition modeling method using a thermoplastic resin will be described.

[0014] 1 is a diagram showing an example of the configuration of a three-dimensional modeling apparatus 1 according to an embodiment. The three-dimensional modeling apparatus 1 is an FDM (fused deposition modeling) type that melts and applies resin in a filament state wound around a reel 4. The three-dimensional modeling apparatus 1 also includes at least a layer modeling means that ejects resin, which is a modeling material, to form modeling layers.

[0015] As shown in FIG. 1, the three-dimensional object modeling apparatus 1 includes a housing 2, a modeling stage 3, a reel 4 around which a filament F is wound, and a discharge module 10.

[0016] The three-dimensional modeling apparatus 1 includes a cooling block and a heating block. The cooling block may be provided above the heating block. The cooling block includes a cooling source and cools the filament F. This prevents the molten filament F from flowing back toward the upper part of the discharge module 10, an increase in resistance to extruding the molten filament F, or clogging of the transport path due to solidification of the molten filament F.

[0017] The heating block includes a heater as a heat source and a temperature sensor (not shown) (e.g., a thermocouple) for detecting the temperature to control the heater. The resin supplied to the discharge module 10 through the transfer path is heated and melted, and is supplied to the discharge nozzle.

[0018] The discharge nozzle provided at the lower end of the discharge module 10 discharges molten or semi-molten resin supplied from the heating block through the extruder 11 in a linear shape onto the modeling stage 3. The discharged resin is cooled and solidified, and layers of a predetermined shape are stacked. Furthermore, the discharge nozzle repeats the operation of discharging molten or semi-molten resin in a linear shape onto the stacked layers, thereby piling up and stacking new layers. In this way, the 3D modeling apparatus 1 forms a 3D object MO on the woven fabric or net-like sheet.

[0019] The discharge module 10 and the heating module are movably held via a connecting member on an X-axis drive shaft 31 extending in the left-right direction (X-axis direction) of the 3D modeling apparatus 1. The discharge module 10 can move in the left-right direction (X-axis direction) of the 3D modeling apparatus 1 by the driving force of an X-axis drive motor 32.

[0020] The X-axis drive motor 32 is held movably along the Y-axis drive shaft extending in the front-rear direction (Y-axis direction) of the 3D modeling apparatus 1. The X-axis drive shaft 31 moves along the Y-axis direction together with the X-axis drive motor 32 by the driving force of the Y-axis drive motor 33, whereby the discharge module 10 and the heating module move in the Y-axis direction.

[0021] A Z-axis drive shaft 34 and a guide shaft 35 penetrate the modeling stage 3, and the modeling stage 3 is held movably along the Z-axis drive shaft 34 extending in the up-down direction (Z-axis direction) of the 3D modeling apparatus 1. The modeling stage 3 moves in the up-down direction (Z-axis direction) of the 3D modeling apparatus 1 by the driving force of a Z-axis drive motor 36.

[0022] Furthermore, if the melting and discharging of the resin continues over time, the periphery of the discharge nozzle may become dirty with molten resin, etc. Therefore, by periodically performing a cleaning operation on the periphery of the discharge nozzle using the cleaning brush 37 provided in the 3D modeling device 101, it is possible to prevent the filament from adhering to the tip of the discharge nozzle.

[0023] In order to prevent adhesion, it is preferable that the cleaning operation be performed before the temperature of the molten resin has completely dropped. In this case, it is preferable that the cleaning brush is made of a heat-resistant material.

[0024] Furthermore, the abrasive powder generated during the cleaning operation may be collected in a dust box 38 provided in the 3D modeling apparatus and periodically discarded, or may be discharged to the outside of the 3D modeling apparatus 1 through a suction path.

[0025] 1, when modeling using a filament, a long filament F, which is used to model a three-dimensional object MO and is made of a resin composition with a thermoplastic resin as a matrix, is placed in a pullable wound state on a reel 4. Here, the filament F is a solid material in the shape of a long, thin wire.

[0026] The extrusion module 10 includes an extruder, a cooling block, a filament guide, a heating block, and an extrusion nozzle.

[0027] In this configuration, the filament F wound around the reel 4 is pulled by the rotation of the extruder (drive means for the filament F) constituting the discharge module 10, and rotates without exerting a large resistance force, thereby supplying the filament F. That is, the filament F is supplied to the discharge module 10 of the three-dimensional modeling apparatus 1 by being drawn in by the extruder.

[0028] When using a soft filament F such as a human body part in the FDM method, during the process of feeding the filament F to the extrusion module 10, for example, the filament F may become entangled in the gear, and the filament F may buckle between the gear and the extrusion module 10.

[0029] Here, buckling refers to a state in which, when a load applied to a structure is gradually increased, the deformation pattern suddenly changes at a certain load, resulting in a large deflection.

[0030] 2 is a diagram for explaining the phenomenon in which the filament F buckles. FIG. 2 shows how the filament F passes through the extruder 11 and is sent to the discharge module 10. Buckling occurs at a portion 111.

[0031] When buckling occurs, the unmelted parts of the filament F cannot push the molten parts out of the nozzle, causing ejection problems. When the Young's modulus of the filament F becomes 25 MPa or less, buckling becomes noticeable. This makes it difficult to create three-dimensional objects with the same softness as human body part models, especially breasts.

[0032] 1 is a diagram showing another example of the configuration of a 3D modeling apparatus according to an embodiment, illustrating the configuration of the 3D modeling apparatus 1a. The 3D modeling apparatus 1a is a type that extrudes pellet-shaped resin with a screw in a cylinder.

[0033] As shown in FIG. 3, the three-dimensional modeling apparatus 1a includes a housing 2a, a modeling stage 3a, an extrusion device 5 that extrudes resin with a screw in a cylinder, and a heater unit 6.

[0034] The modeling stage 3a has a surface as flat as possible and can be set horizontally to model the material on it. The material of the modeling stage 3a can be anything that achieves the above-mentioned purpose, such as metals such as aluminum (Al) and stainless steel, resin, glass, etc., and the modeling stage 3a may have a heater.

[0035] Fig. 4 is a cross-sectional view showing an example of the internal structure of the extrusion device 5. As shown in Fig. 4, the extrusion device 5 has a nozzle 52 at the lower end side of a cylinder 51 arranged perpendicular to the modeling stage 3a, and a screw 54 is arranged inside the cylinder 51, the rotation of which is controlled by a screw motor 53, for melting pellets and supplying them to the nozzle 52 side.

[0036] The figure shows a case where a gear pump 56 is disposed on the tip side of the screw 54. A heater 57 for heating the inside of the cylinder 51 is provided on the peripheral wall surface of the cylinder 51, and a hopper 58 for supplying a resin material to the inside of the cylinder 51 is provided on the upper side of the cylinder 51.

[0037] Fig. 5 is a block diagram showing an example of a hardware configuration of the 3D modeling apparatus 1. As shown in Fig. 5, the 3D modeling apparatus 1 has a control unit 100. The control unit 100 is configured as a so-called microcomputer having an MPU, a memory, various circuits, etc., and is electrically connected to each unit as shown in Fig. 5.

[0038] The three-dimensional modeling apparatus 1 is provided with an X-axis coordinate detection mechanism that detects the X-axis position of the discharging module 10. The detection result of the X-axis coordinate detection mechanism is sent to the control unit 100. The control unit 100 controls the driving of the X-axis drive motor 32 based on the detection result, and moves the discharging module 10 to a target position in the X-axis direction.

[0039] The three-dimensional modeling apparatus 1 is also provided with a Y-axis coordinate detection mechanism that detects the Y-axis position of the discharging module 10. The detection result of the Y-axis coordinate detection mechanism is sent to the control unit 100. The control unit 100 controls the driving of the Y-axis drive motor 33 based on the detection result, and moves the discharging module 10 to a target position in the Y-axis direction.

[0040] The 3D modeling apparatus 1 is provided with a Z-axis coordinate detection mechanism that detects the Z-axis position of the modeling stage 3. The detection result of the Z-axis coordinate detection mechanism is sent to the control unit 100. The control unit 100 controls the driving of the Z-axis drive motor 36 based on the detection result, and moves the modeling stage 3 to a target position in the Z-axis direction.

[0041] In this manner, the control unit 100 controls the movement of the discharging module 10 and the modeling stage 3, thereby moving the relative positions of the discharging module 10 and the modeling stage 3 to the target positions.

[0042] Furthermore, the control unit 100 outputs control signals to the respective driving units of the extruder 11, the cooling block 22, the discharge nozzle 25, and the cleaning brush 37, thereby controlling the driving of these units.

[0043] [3D modeling method using FDM] The FDM-based 3D modeling device 1 has a simple mechanism and a relatively short modeling time, making it suitable for modeling objects of a certain size, such as human body parts. When using the FDM method to obtain a 3D object with a soft texture like a human body part, for example when modeling a particularly soft human body part such as a breast, modeling with a very soft resin is required.

[0044] However, since the FDM method involves extruding a hard filament F through an extruder 11 to a nozzle, it is difficult to extrude a material that is too soft.

[0045] Although there are soft resin products (such as PolyMaker PolyFlex TPU95) that are filaments made from elastomers with a longitudinal Young's modulus of about 19 MPa, there is room for improvement in terms of filamentization and extrusion of soft resins with a longitudinal Young's modulus of 5 MPa or less.

[0046] This is because it is difficult to create soft filaments with a longitudinal Young's modulus of 5 MPa or less, and furthermore, when trying to extrude them using a gear, phenomena such as buckling occur.

[0047] The inventors have succeeded in using a 3D modeling device 1 with a screw pump to melt-layer and mold a thermoplastic resin with a Young's modulus of 100 kPa or less, and further creating a structure with a repeating structure inside, thereby obtaining a very soft 3D object MO with a Young's modulus in the range of 5 kPa or more and 20 kPa or less when pressed from the surface to the inside of the 3D object.

[0048] Incidentally, the problem with evaluating soft three-dimensional objects such as human body parts is that there is no established method to quantitatively indicate their texture. For industrial materials, the Vickers hardness test (JIS Z 2244), Rockwell hardness test (JIS Z 2245), tensile test (JIS K7161 / JIS Z 2241), etc. are often used to determine the strength up to the limit of deformation or breakage, but it is not realistic to use these evaluations on the human body. This is because the force applied when measuring is too strong, making it difficult to measure soft objects accurately. Above all, it is dangerous to measure the actual human body using these methods.

[0049] In the embodiment, we consider whether there are any evaluation items that can be quantitatively expressed for "softness," which is considered to be one of the major factors that determine the texture when providing human body parts, and if such items exist, we indicate a preferred range as an alternative characteristic value.

[0050] We consider "Shore hardness," "Asker hardness," and "Young's modulus" as methods for quantitatively expressing the softness of living organisms.

[0051] (I) Shore hardness There is a device called a durometer that measures the hardness of a material. There are several types, some for soft materials and some for hard materials, but the Shore hardness, which is an index of hardness for soft materials, is often used to measure the hardness of rubber and urethane elastomers. This measurement method involves pressing a terminal against the surface of the sample and measuring the amount of pressure applied when the repulsive force reaches equilibrium. This method is not dangerous when used on living organisms, but the repulsive force obtained is very small for soft materials such as organs, making it difficult to obtain accurate measurement results. In this measurement, the higher the number, the harder the material is, and the lower the number, the softer it is.

[0052] However, even the softest rubber Shore hardness material is still hard compared to the softness required by doctors. Therefore, the Shore hardness indicating the softness of organs is 2 or less, and even if taken broadly, it is 5 or less, which is not suitable as a method to quantitatively express the softness of living organisms.

[0053] (II) Asker hardness Compared to the Shore hardness used to measure the hardness of general rubber, the Asker hardness is an index used to measure softer materials (soft rubber, foam type, etc.). The name comes from the Asker rubber hardness meter, a durometer developed by Kobunshi Keiki Co., Ltd. There are also various types, and among them, the Asker rubber hardness meter type C is a hardness meter that is also adopted by JIS K 7312. This is also suitable for measuring very soft materials, as the larger the number, the harder the material, and the smaller the number, the softer the material. In the embodiment, CSC2, an index that is even softer than the Asker C hardness, is used to evaluate very soft materials.

[0054] (III) Young's modulus Young's modulus, also known as the modulus of elasticity in elongation or the modulus of longitudinal elasticity, indicates the ratio of stress to strain when a material or object behaves elastically. In other words, it is an index of the rigidity of a resin; a higher value indicates a higher rigidity, and a lower value indicates a higher flexibility.

[0055] Young's modulus is a proportional coefficient that indicates the proportional relationship between stress and strain in the elastic range, and the initial gradient of the stress-strain curve (SS curve) obtained in a uniaxial tensile test is expressed as Young's modulus. Here, Figure 6 is a diagram explaining Young's modulus.

[0056] There are many ways to measure Young's modulus, including static testing such as tensile testing, compression testing, and torsion testing, as well as dynamic testing such as resonance testing, ultrasonic pulse testing, and pendulum testing. If the amount of displacement (strain) can be measured accurately, it is possible to express subtle differences in softness.

[0057] It is known that this Young's modulus can be evaluated by Hertz's elastic contact theory in the contact mechanics of materials, and is already used in a wide range of industrial fields. In Hertz's elastic contact theory, when a sufficiently hard spherical indenter is pressed into a semi-infinite specimen, the relationship between the indentation load and indentation amount δ can be expressed by the following equation (1) using the diameter φ of the spherical indenter, Young's modulus E, and Poisson's ratio ν.

number

[0058] However, when the sample to be indented has a finite thickness and there is something harder than the sample underneath, the load F obtained will be higher than the load F expressed by equation (1). This increase in load F also leads to an increase in Young's modulus E evaluated by equation (1), but since the increase becomes more significant as the indentation depth δ increases, we consider the evaluation using the following equation (2) using coefficient B as the relationship that represents this.

number

[0059] In this case, the apparent Young's modulus E1 deduced from the coefficient A in equation (2) by comparing it with the coefficient A in equation (1), and the intrinsic Young's modulus E of the sample satisfy the following relationship in equation (3).

number

[0060] In equation (3), E1 = E when the indentation amount δ = 0. Furthermore, from equation (3), the situation in which the apparent Young's modulus E1 changes with an increase in the indentation amount δ changes depending on the size of the indentation amount, so the coefficient B has the property of expressing the influence of the sample thickness, and equations (2) and (3) represent the overlap ratio when the indentation deformation of a finite thickness sample is considered to be the sum of the contact deformation of a semi-infinite sample and the compressive deformation of a finite thickness sample.

[0061] In order to measure and quantify the softness of the sample, the inventors measured Young's modulus using the Yawasa Softness Meter, an apparatus that uses the Hertz elastic contact theory to determine Young's modulus from the ball indenter diameter, indentation load, and indentation amount.

[0062] A more specific example will be described below.

[0063] [Example 1] The olefin-based thermoplastic elastomer (hereinafter referred to as TPO) used in Example 1 is a thermoplastic elastomer in which ethylene propylene rubber (EPDM, EPM) is finely dispersed in polypropylene (PP).

[0064] TPO is an elastomer (elastic body) at room temperature, and is a unique synthetic resin that has rubber-like properties but can be molded in the same way as general plastics. In Example 1, the plasticizer was appropriately adjusted and mixed into the TPO to adjust the hardness to each level.

[0065] A plasticizer is a material that permeates between polymer molecules to weaken the intermolecular forces of the polymer and make each molecular chain easier to move, thereby lowering the glass transition point of the polymer and imparting flexibility to the polymer.

[0066] Since plasticizers are mixed in large quantities into resins, they must be compatible with the resin. In addition, they must have many other properties, such as low volatility, excellent heat resistance, and excellent weather resistance, and various plasticizers that meet these requirements have been developed.

[0067] Ester-based plasticizers are often used, but in particular, in order to obtain a softness that is close to that of living tissue, in Example 1, liquid paraffin, hardened oil, hardened castor oil, higher alcohols such as octyldodecanol, squalane, squalene, castor oil, liquid rubber (polybutene), and fatty acid esters such as isopropyl myristate were considered.

[0068] Among these, it was found that liquid paraffin, hardened oil, and hardened castor oil are preferable. It was found that the content of the plasticizer is preferably 20% by mass to 80% by mass with respect to the total resin.

[0069] If the plasticizer content is too low, the resin will become too hard and will not have the soft texture of human body parts, while if the amount of plasticizer is too high, the resin will become excessively sticky and oily, and will become unstable due to excessive softening, making it impossible to produce with consistent quality.

[0070] The content of the plasticizer is more preferably 40% by mass or more and 75% by mass or less, and even more preferably 50% by mass or more and 70% by mass or less.

[0071] In Example 1, liquid paraffin was used, which has high compatibility with human body parts and has particularly favorable characteristics in terms of softness and texture. It was found that liquid paraffin is non-volatile, has very high biocompatibility, and can stably mold soft resin.

[0072] Liquid paraffin (Hicoll M, manufactured by Kaneda Co., Ltd.) was added to TPO (Mitsui Chemicals' Milastomer) to adjust the Young's modulus to each softness. The TPO was put into a twin-screw extruder (Henschel Mixer, manufactured by Mitsui Mining Co., Ltd.) and heated and melted at 240°C (melt kneading temperature is preferably 160°C or higher and 300°C or lower), while adding a plasticizer at an arbitrary ratio to adjust the softness. The adjusted resin was pelletized using a pelletizer (Tanaka's TSS100), a soft pellet processing machine.

[0073] Each resin pelletized in this way was molded using a screw pump type 3D modeling device 1a (e.g., manufactured by Eslabo) shown in Figure 3. The test piece size was 40 [mm] x 40 [mm] x 40 [mm]. The Young's modulus was measured by compressing at a speed of 3.0 [mm / sec] using a Yawasa softness measuring instrument YWS series HG MSES (manufactured by Tech Gihan Co., Ltd.).

[0074] For measurements using the softness measuring device, the maximum load was 1.0 [N], the indentation speed was 3.0 [mm / sec], and the indenter diameter was 30 [mm], and the center position of the test piece surface (40 x 40 [mm]) was measured.

[0075] Generally, a compression test is used to measure the Young's modulus of a material. However, since the compression test is a test method in which a large surface is crushed, it was determined that this softness measuring device is suitable for measuring the Young's modulus, which is the softness of a human body part, as in this embodiment, and the results of the above measuring device were used as the Young's modulus.

[0076] The softness of the resin adjusted by the above method was approximately 200 [kPa], 120 [kPa], 100 [kPa] (actual measured value 97 [kPa]), and 80 [kPa].

[0077] Resins adjusted to various Young's moduli were molded into the above test piece sizes, and the Young's moduli were measured. In Example 1, voids were created inside the test piece by a repeating structure, and the softness was measured as the Young's modulus. The shape of the repeating structure may be a honeycomb, a triangle, a square, a grid structure, etc., but since there was no significant difference in the Young's modulus if the internal structure filling rate was basically the same, the honeycomb repeating structure was standardized for molding and evaluation. The outer shell of the test piece was four layers each.

[0078] Figure 7 illustrates an example of a honeycomb structure 70, where Figure 7(a) is a top view and Figure 7(b) is a perspective view. As shown in Figure 7, the honeycomb structure 70 includes a repeating structure.

[0079] In addition, in parallel with Example 1, the type of plasticizer added was changed. In addition to liquid paraffin, the plasticizers tried were hydrogenated oil, hydrogenated castor oil, higher alcohols such as octyldodecanol, squalane, squalene, castor oil, liquid rubber (polybutene), and fatty acid esters such as isopropyl myristate. All of them were found to have the effect of softening the material. However, it was hydrogenated oil and hydrogenated castor oil that had characteristics closest to those of liquid paraffin.

[0080] The Young's modulus of breast adipose tissue, one of the softest parts of the human body, was 3.25 kPa (reference: Elastic moduli of normal and pathological human breast tissues: an inversion-technique-based investigation of 169 samples Abbas Samani1, Judit Zubovits2 and Donald Plewes3 Published 16 February 2007 · 2007 IOP Publishing Ltd Physics in Medicine & Biology, Volume 52, Number 6 Citation Abbas Samani et al 2007 Phys. Med. Biol. 52 1565). For the entire breast, the measured softness using the softness measuring device is between 5 kPa and 20 kPa.

[0081] The Young's modulus was set to the same value as that of the breast. Organs such as the kidneys and liver have a similar softness. By achieving this goal, it is possible to model particularly soft human body parts, which can be ideally used for pre-operative simulations and surgical practice.

[0082] The goal was to directly model the softest human body parts, and as an indicator of softness, we aimed for a range of measurement values ​​on a softness meter between 5 kPa and 20 kPa.

[0083] Here, Fig. 8 is a diagram illustrating the relationship between the internal structure filling rate of a three-dimensional object and Young's modulus when the Young's modulus is changed by adding liquid paraffin. As shown in Fig. 8, when a resin adjusted to have a Young's modulus of 199 kPa or less is used, a softness suitable for human body parts can be achieved with an internal structure filling rate of 20% or more and 50% or less.

[0084] When the internal structure filling rate was less than 20%, the resin became too sparse and the upper part of the internal repeating structure could not be filled with resin, resulting in a 3D object with holes. When the internal structure filling rate was more than 50%, the material was not soft enough for use as a human body part, and it was not possible to add plasticizer to the material to make it softer.

[0085] The internal structure filling rate here is the ratio of the internal structure expressed by the formula {(volume of resin) / (volume of space including resin inside)} x 100, and does not include the outer shell structure.

[0086] [Example 2] Although there has been a high demand for a three-dimensional object having almost the same softness as a patient's body parts, especially breasts, it has been difficult to realize this, but this embodiment makes it possible to create a three-dimensional object having the same size and shape as a patient's body parts, especially breasts, using the three-dimensional printing apparatus 1 or 1a. This makes it possible to reproduce a breast of the same size and shape as a patient who has lost a breast through surgery, for example, and attach it to the chest.

[0087] In addition, the softness of the breasts varies from person to person, and if the shaped breasts are different from one's natural softness, it can lead to an uncomfortable feeling when wearing them.

[0088] It would be ideal if the softness of the patient's actual breasts could be measured using Young's modulus, but measuring the softness of a patient's breasts using Young's modulus requires a somewhat large-scale device, such as a softness measuring device, so in practice it was difficult to create a three-dimensional object that corresponded to the softness of a patient's breasts.

[0089] Therefore, in order to explore the possibility of using a simpler device for measurement, an Asker rubber hardness tester CSC2 type manufactured by Kobunshi Keiki Co., Ltd. was used to measure the Asker CSC2 hardness. In Example 2, the Asker CSC2 hardness was measured for samples having various internal structure filling rates in a resin having a Young's modulus of 97 [kPa] shown in FIG. 8 using this CSC2 type hardness tester.

[0090] Here, Fig. 9 is a diagram illustrating the relationship between the Asker hardness and the Young's modulus. Fig. 9 shows the correspondence relationship between the Asker CSC2 hardness and the Young's modulus of each sample having various internal structure filling rates in the resin having the Young's modulus of 97 [kPa] shown in Fig. 8.

[0091] The percentages in Fig. 9 indicate the internal structure filling rate of the three-dimensional object at each measurement point. As shown in Fig. 9, a correspondence was found between the Asker CSC2 hardness and the Young's modulus measured by the softness meter. In addition, a clear correspondence was obtained between these softnesses within the range of 5 kPa to 20 kPa, which is the range of softness of the human breast defined in this embodiment (hatched area in Fig. 9).

[0092] This shows that the use of an Asker rubber hardness tester, which is a simple measurement method, makes it possible to correlate with Young's modulus, and furthermore, to calculate back the internal structural filling rate of a 3D object from that Young's modulus. In other words, it was found that the hardness of an individual patient's breast can be measured relatively cheaply and easily in the medical field, and reflected in the softness of a 3D object.

[0093] In this way, by obtaining data showing the correspondence in advance, the softness of a human body part measured using the Asker hardness scale can be immediately converted into Young's modulus, and in order to realize that Young's modulus, it is possible to determine the internal structural filling rate of a three-dimensional object that has a repeating structure inside it.

[0094] It was also found that the three-dimensional object formed by the repeated internal structure filling rate has a softness almost equivalent to the softness of the measured patient's breast. In this way, when considering an application in which a breast of the same size and shape as that of a patient who has lost a breast through surgery is reproduced and attached to the chest, it is possible to form a breast that matches the softness of the breast of each individual patient. With this embodiment, the attached breast becomes equivalent to the softness of one's own breast, greatly improving the discomfort of wearing it.

[0095] In Example 2, a measuring device called Yawasa Softness Measuring Instrument HG MSES (manufactured by Tech Gihan Co., Ltd.) was used. The reason for defining Young's modulus using this measuring device is that the surfaces of soft human organs and breasts are curved, and a measuring method that presses the surface is not appropriate for measuring their softness.

[0096] For example, when it is desired to form a three-dimensional object having the same size and shape as a patient's breast and measure its softness, measurement by pressing an indenter into a relatively small area is suitable. Figure 10 is a diagram showing an example of an elasticity sensor and an indenter of a softness measuring device. The area surrounded by a dashed line in Figure 10 corresponds to the elasticity sensor 200.

[0097] However, generally, when determining Young's modulus in a compression test of a resin, a precision universal testing machine is used as specified in JIS-K7181. It is preferable to be aware of the approximate correspondence with the Young's modulus obtained using a universal testing machine.

[0098] The compression test was performed using a precision universal testing machine (Shimadzu Corporation) at a test speed of 1 mm / sec. The test piece dimensions were 40 x 40 x 40 mm, and the thickness of the outer circumference was approximately 2 mm. Young's modulus is the value obtained by dividing the difference in compressive stress (σ2-σ1) by the difference in compressive strain (ε2-ε1), assuming that the compressive stresses corresponding to compressive strains ε1=0.01 and ε2=0.02 are σ1 and σ2, respectively.

[0099] Fig. 11 is a diagram illustrating the relationship between the results of softness measurements and the results of compression tests. It was found that the Young's modulus in the compression test was approximately 1.8 times that of the Young's modulus in the softness measurements. This makes it possible to make the Young's modulus in the softness measurements correspond to that in the compression tests.

[0100] In this way, the internal structure filling rate of the three-dimensional object MO according to this embodiment is determined based on the results of measuring the softness of the human body parts of the wearer of the human body part approximation object.

[0101] [Effects] As described above, the three-dimensional object MO according to this embodiment has a repeating structure inside and a Young's modulus in the range of 5 kPa to 20 kPa, which makes it possible to provide a three-dimensional object having the same softness as the human body.

[0102] Furthermore, in the three-dimensional object MO according to this embodiment, the thermoplastic resin or the composition thereof has a Young's modulus of 100 kPa or less, which makes it possible to obtain a very soft three-dimensional object having a Young's modulus in the range of 5 kPa to 20 kPa when pressed from the surface to the inside of the three-dimensional object.

[0103] Moreover, the three-dimensional object MO according to this embodiment has an internal structure filling rate of 20% or more and 50% or less, which makes it possible to provide a three-dimensional object with a softness suitable for human body parts.

[0104] Furthermore, the resin of the three-dimensional object MO according to this embodiment is an elastomer material containing any one of liquid paraffin, hardened oil, and hardened castor oil, which makes the material of the three-dimensional modeling part softer and allows for the creation of a soft three-dimensional object suitable for human body parts.

[0105] Moreover, the three-dimensional object MO according to this embodiment is a hollow human body part approximation. For example, artificial breasts are mainly classified into solid and hollow types. Solid types are made by pouring hardening silicone rubber into a mold and hardening it into the shape of a breast, but have the disadvantage of being heavy. On the other hand, conventionally, hollow types are made by forming the outer frame of a breast with a silicone rubber film and injecting air into the inside, which is light in weight but has the disadvantage of feeling like rubber and different from the feel of human skin.

[0106] In this embodiment, it is possible to form a soft three-dimensional object suitable for human body parts, so that it is possible to obtain an approximation of a human body part, such as a hollow artificial breast, which is light in weight and has a feel similar to human skin.

[0107] Furthermore, the internal structure filling rate of the three-dimensional object MO according to this embodiment is determined based on the results of measuring the softness of the human body parts of the wearer of the human body part approximation object, making it possible to provide a three-dimensional object that can more faithfully reproduce the softness of the human body parts of the wearer.

[0108] Although the embodiments have been described above, the present invention is not limited to the above specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0109] The embodiment also includes a method for forming a three-dimensional object, for example, a method for forming a three-dimensional object by melt lamination of a thermoplastic resin or a composition thereof, which includes a step of determining a filling rate of an internal structure based on a result of measuring the softness of a part of a human body part held by a wearer of the human body part approximation object. By using such a method for forming a three-dimensional object, it is possible to provide a three-dimensional object having the above-mentioned effects. [Explanation of symbols]

[0110] 1 Three-dimensional modeling device 2. Chassis 3. Modeling Stage 4 Reels 5. Extrusion Equipment 51 Cylinder 52 Nozzle 53 Screw motor 54 Screw 56 Gear Pump 6 Heater unit 10 Dispensing module 11 Extruder 70 Honeycomb structure F filament MO 3D object [Prior art documents] [Patent documents]

[0111] [Patent Document 1] JP 2018-167405 A

Claims

1. In a three-dimensional object produced by melt lamination of a thermoplastic resin or a composition thereof, The structure has a repeating structure having voids therein, A three-dimensional object having a Young's modulus measured by a softness measuring device in the range of 5 kPa or more and 20 kPa or less.

2. A three-dimensional object as described in claim 1, characterized in that the Young's modulus of the thermoplastic resin or its composition is 100 kPa or less.

3. A three-dimensional object as described in claim 1 or 2, characterized in that the internal structure filling rate due to the repeating structure is 20% or more and 50% or less.

4. A three-dimensional object described in any one of claims 1 to 3, characterized in that the thermoplastic resin is an elastomer material containing any one of liquid paraffin, hardened oil, or hardened castor oil.

5. 5. The three-dimensional object according to claim 1, which is a hollow object resembling a human body part.

6. 6. The three-dimensional object according to claim 5, wherein the internal structure filling rate is determined so as to provide the corresponding Young's modulus based on a result of softness measurement, performed with an Asker hardness tester, of a part of the human body part held by a wearer of the human body part approximation object.

7. A three-dimensional object described in any one of claims 1 to 6, wherein the Young's modulus is the Young's modulus obtained when the three-dimensional object is pressed from its surface toward its inside.

8. A method for forming a three-dimensional object by melt laminating a thermoplastic resin or a composition thereof, comprising the steps of: a step of melting the thermoplastic resin pellets in a cylinder, and extruding and laminating the molten thermoplastic resin with a screw in the cylinder, thereby forming a three-dimensional object having a repeating structure with voids therein; and determining an internal structure filling rate of a repeating structure having voids based on the results of softness measurement, using an Asker hardness tester, of a portion of a human body part held by a wearer of the human body part approximation, so as to provide a corresponding Young's modulus measured by a softness measuring device.

9. The molding method described in Claim 8, characterized in that the internal structure filling rate is determined so that the Young's modulus is in the range of 5 kPa or more and 20 kPa or less.

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