JP7594487B2 - Manufacturing method of three-dimensional object - Google Patents

Description

The present invention relates to a method for manufacturing a three-dimensional object using the fused deposition modeling method.

3D printers are devices that use three-dimensional modeling data created by a computer to create three-dimensional objects by layering modeling materials in sequence, and several different methods are known. Among them, fused deposition modeling, in which a three-dimensional object is created by heating and melting thermoplastic resin and layering it, is becoming increasingly popular not only for industrial use but also for personal use, as the equipment that uses this method is low-cost.

The modeling materials generally used in the fused deposition modeling process are resin materials such as polylactic acid and ABS resin, but other resins would also be suitable if they could be used as modeling materials.
For example, polyacetal resin (hereinafter also referred to as "POM resin") has various excellent physical and mechanical properties, so it would be useful if it could be used as a modeling material and modeled by the fused deposition modeling method. However, since POM resin has a large shrinkage rate associated with a drop in temperature, there is a concern that warping may occur during modeling by the fused deposition modeling method. In addition, since POM resin has poor adhesion to other materials, there is a problem that if the above-mentioned warping occurs during modeling, the modeled object is likely to peel off from the modeling stage, making it difficult to continue modeling. For the above reasons, in the past, it was not easy to model by the fused deposition modeling method using POM resin or a modeling material containing it as a main component.

Various proposals have been made to solve the above-mentioned warping problem in modeling materials containing POM resin (see Patent Documents 1 and 2). Patent Document 1 describes a modeling material for 3D printers that uses a POM resin in combination with an inorganic filler and/or polylactic acid. Patent Document 2 describes a resin composition that contains a thermoplastic resin and inorganic fibers.

JP 2019-131762 A International Publication No. 2018/0432313

However, in both the modeling materials or resin compositions described in Patent Documents 1 and 2, it is necessary to add other additives such as inorganic fillers to suppress warping. In other words, it is difficult to form a three-dimensional object while suppressing the occurrence of warping using only POM resin (so-called neat resin) that does not contain additives. In addition, when using a modeling material containing inorganic fillers, there is a problem that the wear of the discharge nozzle that discharges the modeling material is accelerated. Furthermore, the disadvantage of POM resin, that is, poor adhesion to other materials, has not been overcome. Therefore, when modeling using POM resin by fused deposition modeling, there is a problem that additional material costs and labor are required, such as forming a special uneven shape on the modeling stage surface or attaching a material to the stage surface separately to improve adhesion. The above problems can occur not only with POM resin, but also with other crystalline thermoplastic resins that have a large shrinkage rate with a decrease in temperature.

The present invention has been made in consideration of the above-mentioned problems of the conventional art, and its objective is to provide a method for manufacturing a three-dimensional object by the fused deposition modeling method, which uses a modeling material containing a crystalline thermoplastic resin as a main component, yet suppresses the occurrence of warping during stacking, and during modeling, the formed three-dimensional object is firmly fixed onto the modeling stage, and the three-dimensional object can be easily peeled off from the modeling stage after formation.

One aspect of the present invention that solves the above problems is as follows.
(1) a first step of forming a three-dimensional object on a modeling stage by a fused deposition modeling method using a modeling material mainly composed of a crystalline thermoplastic resin under temperature conditions shown in the following formula 1;
Tm>Ts>Tc, and Tc>Ta>Tc-100 (Equation 1)
[In formula 1, Ts represents the temperature of the modeling stage (°C), Tc represents the crystallization temperature of the crystalline thermoplastic resin (°C), Tm represents the melting point of the crystalline thermoplastic resin (°C), and Ta represents the ambient temperature of the modeling area (°C).]
and a second step of peeling off the three-dimensional object formed in the first step from the surface of the modeling stage under a temperature condition represented by the following formula 2 after the first step,
Tc>Ts (Equation 2)
The method for producing a three-dimensional object, wherein the crystalline thermoplastic resin is one selected from the group consisting of polyacetal resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, and polyamide resin.

(2) The method for producing a three-dimensional object according to (1) above further includes, prior to the first step, forming a base layer between the modeling stage and the three-dimensional object by fused deposition modeling using the modeling material under the temperature conditions shown in formula 1.

(3) The method for manufacturing a three-dimensional object described in (1) above, in which in the second step, the three-dimensional object is peeled off and discharged from the surface of the modeling stage by a discharge mechanism that discharges the three-dimensional object outside the modeling stage, and then the method proceeds to the first step to form a new three-dimensional object.

(4) The method for manufacturing a three-dimensional object described in any one of (1) to (3), wherein the mass fraction of the crystalline thermoplastic resin in the modeling material is 99 mass% or more.

(5) The method for producing a three-dimensional object described in (1) to (4) above, characterized in that the melt flow rate of the crystalline thermoplastic resin is 20 g/10 min or less.

(6) The method for producing a three-dimensional object according to any one of (1) to (5), wherein the crystalline thermoplastic resin is a polyacetal resin.

The present invention provides a method for manufacturing a three-dimensional object by the fused deposition modeling method, which uses a modeling material containing a crystalline thermoplastic resin as a main component, while suppressing the occurrence of warping during stacking, and which allows the formed three-dimensional object to be firmly fixed onto the modeling stage during modeling, and can be easily peeled off from the modeling stage after formation.

4A to 4C are conceptual diagrams illustrating a flow of a method for manufacturing a three-dimensional object according to the present embodiment. FIG. 13 is a diagram showing a state in which a three-dimensional object on the modeling stage is removed by a robot arm. FIG. 2 is a perspective view showing a three-dimensional object formed in the example.

The method for producing a three-dimensional object according to the present embodiment includes a first step of forming a three-dimensional object on a modeling stage by a fused deposition modeling method using a modeling material mainly composed of a crystalline thermoplastic resin (hereinafter, also simply referred to as a "thermoplastic resin") under temperature conditions shown in the following formula 1:
Tm>Ts>Tc, and Tc>Ta>Tc-100 (Equation 1)
[In formula 1, Ts is the temperature of the modeling stage (°C), Tc is the crystallization temperature of the crystalline thermoplastic resin (°C), Tm is the melting point of the crystalline thermoplastic resin (°C), and Ta is the ambient temperature of the modeling area (°C).]
and a second step of peeling off the three-dimensional object formed in the first step from the surface of the modeling stage under a temperature condition represented by the following formula 2 after the first step,
Tc>Ts (Equation 2)
The crystalline thermoplastic resin is characterized in that it is one selected from the group consisting of polyacetal resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, and polyamide resin.

In the manufacturing method of a three-dimensional object according to the present embodiment, in the formation of a three-dimensional object by the fused deposition modeling method, the temperatures during lamination of the modeling materials are set within a predetermined range (first step), thereby suppressing the occurrence of warping of the laminated object due to a temperature drop during lamination, and the laminated object can be firmly fixed on the modeling stage. That is, even if the thermoplastic resin has a large shrinkage rate due to a temperature drop, the occurrence of warping is suppressed. Furthermore, even if the material has poor adhesion to other materials, the object can be firmly fixed to the modeling stage without special processing on the surface of the modeling stage during modeling. Similarly, after modeling, the atmospheric temperature of the modeling area is set within a predetermined range (second step), so that the formed three-dimensional object can be easily peeled off from the modeling stage. Furthermore, in each step, the respective effects are exerted without adding other additives.
In other words, even if the modeling material is a thermoplastic resin alone, it is possible to manufacture a three-dimensional object by the fused deposition modeling method. In addition, since no additives such as inorganic fillers are added, wear on the nozzle that discharges the modeling material is suppressed.
First, the overall flow of the method for producing a three-dimensional object according to the present embodiment will be described below with reference to the drawings. Note that, although the term "fused deposition modeling" is used below, it is synonymous with "fused deposition modeling."

Figure 1 conceptually shows the flow of the method for manufacturing a three-dimensional object of this embodiment. Figures 1(A) to 1(C) show the first step, and Figure 1(D) shows the second step. First, the temperature Ts of the modeling stage 1 and the ambient temperature Ta of the modeling area in the fused deposition modeling 3D printer are set so as to satisfy the above formula 1 (Figure 1(A)). Next, the discharge nozzle 2 that discharges the molten modeling material is discharged from the discharge nozzle 2 while scanning above the modeling stage 1 to form the base layer 4 (Figure 1(B)). After the base layer 4 is formed, the discharge nozzle 2 is further caused to scan above the base layer 4 while discharging the molten modeling material from the discharge nozzle 2 to form the structure 5 on the base layer 4 (Figure 1(C)). More specifically, based on the three-dimensional data of the structure 5 to be formed, shapes corresponding to the cross section of the structure 5 are sequentially stacked to form the structure 5. In the process of forming the structural part 5, air is sprayed from the air duct 3 located near the discharge nozzle 2 to cool and solidify the layered modeling material. After the formation of the structural part 5 is completed, the temperature of the modeling stage 1 is set to satisfy the above formula 2. That is, the temperature of the base layer, which was kept in a semi-molten state during modeling, is lowered below the crystallization temperature. Then, crystallization progresses in the base layer 4, and the adhesive strength of the base layer 4 to the modeling stage 1 decreases. In this state, the three-dimensional model 6 consisting of the base layer 4 and the structural part 5 is peeled off from the modeling stage 1 (FIG. 1(D)). Note that the base layer 4 shown in FIG. 1 is a layer that is formed as necessary and does not necessarily have to be formed. Details will be described later.

In addition, the 3D printer used in this embodiment is preferably one in which the modeling area is a chamber that forms an enclosed space in order to facilitate temperature control of the modeling area. In addition, in this embodiment, there are no particular limitations on the configuration of the modeling stage surface, but since the adhesion between the modeling stage and the three-dimensional object is maintained by keeping the modeling material near the modeling stage interface in a semi-molten state, a configuration in which a special structure such as large irregularities or numerous holes is formed on the surface of the modeling stage is not essential. On the other hand, if the modeling stage surface is an extremely smooth surface such as a polished glass surface, there is a risk that the adhesion with the modeling stage will be insufficient depending on the shape of the three-dimensional object, so in order to be more thorough, it is preferable for the surface to have a roughness similar to that of ground glass.

Here, the modeling stage temperature (Ts) described in this specification does not mean the temperature as a set value in the operation of a fused deposition modeling 3D printer, but means the actual measured value of the modeling stage temperature for a certain set condition. Although the temperature adjustment mechanism varies depending on the 3D printer, there is no guarantee that the modeling stage temperature as a set value necessarily matches the actual modeling stage surface temperature. In the 3D printer (FunmatHT Enhanced manufactured by INTAMSYS) actually used in the examples described below, there was a difference between the temperature as the set value of the 3D printer and the actual modeling stage surface temperature. Therefore, in the examples and comparative examples described below, the temperature of the modeling stage surface was actually measured by a thermocouple, and the temperature was taken as the modeling stage temperature (Ts).
The same applies to the ambient temperature (Ta) of the modeling area described in this specification, which means the actual measured value of the ambient temperature of the modeling area, not the temperature as a setting value of the 3D printer. In the examples and comparative examples described later, the temperature of the space about 5 cm above the surface of the center of the modeling stage was measured by a thermocouple, and this temperature was taken as the ambient temperature (Ta) of the modeling area.
From the above, in this embodiment, even if the temperature conditions as operational settings of the 3D printer are outside the range indicated by Equation 1 or Equation 2, it is sufficient that the actual temperature of the printing stage at that time and the actual measured values of the ambient temperature of the printing area are within the temperature range indicated by Equation 1 or Equation 2.
Each step will be described below.

[First step]
In the first step, a 3D object is formed on a modeling stage by a fused deposition modeling method using a modeling material mainly composed of a crystalline thermoplastic resin under the temperature conditions shown in the following formula 1.
Tm>Ts≧Tc (hereinafter referred to as "Formula 1A"), and Tc>Ta>Tc-100 (hereinafter referred to as "Formula 1B") (Formula 1)
[In formula 1, Ts is the temperature of the modeling stage (°C), Tc is the crystallization temperature of the crystalline thermoplastic resin (°C), Tm is the melting point of the crystalline thermoplastic resin (°C), and Ta is the ambient temperature of the modeling area (°C).]

Formula 1 specifies the temperature of the modeling stage (Formula 1A) and the ambient temperature of the modeling area (Formula 1B). In the first step, by satisfying Formula 1A, when the molten modeling material is layered on the modeling stage, the semi-molten modeling material is formed in layers. Therefore, the stress in the warping direction is suppressed against the occurrence of in-plane shrinkage at the beginning of the layering, and the occurrence of warping can be prevented. In addition, since the semi-molten modeling material exhibits strong adhesion to the modeling stage, the modeled object is firmly fixed on the modeling stage during modeling, and peeling from the stage can be suppressed. For example, when the melting point (Tm) of POM resin is 165°C and the crystallization temperature is 145°C, the temperature of the modeling stage (Ts) is set to 145°C or higher and lower than 165°C.

In formula 1A, if the temperature (Ts) of the modeling stage is equal to or higher than the melting point (Tm) of the thermoplastic resin, the thermoplastic resin (modeling material) near the interface of the modeling stage remains in a low-viscosity molten state during modeling. As a result, the structural part is dragged and moved when the discharge nozzle is operated during modeling, making it difficult to model the intended shape. Also, if the temperature (Ts) of the modeling stage is lower than the crystallization temperature (Tc) of the thermoplastic resin, the thermoplastic resin near the interface with the modeling stage does not enter a semi-molten state, and peels off without adhering to the modeling stage. The upper limit of the temperature (Ts) of the modeling stage is preferably Tm-2 (°C), and more preferably Tm-5 (°C). Also, the lower limit of the temperature (Ts) of the modeling stage is preferably Tc+2 (°C), and more preferably Tc+5 (°C).

In addition, in the first step, by satisfying formula 1B, i.e. by setting the ambient temperature (Ta) in the modeling area to less than the crystallization temperature (Tc) of the thermoplastic resin, the layered modeling material hardens easily. For example, when the crystallization temperature of POM resin is 145°C, the ambient temperature (Ta) in the modeling area is set to more than 45°C and less than 145°C. Here, the ambient temperature in the modeling area is the temperature to which the layered modeling material is exposed after being discharged from the discharge nozzle. In other words, the discharged and layered modeling material is exposed to a temperature that satisfies formula 1B, and the temperature drops and the material hardens. The modeling material hardens, allowing it to retain the intended three-dimensional shape.

In formula 1B, if the ambient temperature (Ta) of the modeling area exceeds the crystallization temperature (Tc) of the thermoplastic resin, the hardening of the laminated modeling material is significantly delayed, making it difficult to form the intended three-dimensional shape. If the ambient temperature (Ta) of the modeling area is less than the crystallization temperature (Tc) of the thermoplastic resin -100°C, the cooling rate during lamination is too fast, resulting in poor adhesion between the laminated layers, which may cause peeling or warping within the structure during modeling, making it impossible to form the intended three-dimensional shape. The upper limit of the ambient temperature (Ta) of the modeling area is preferably Tc-5 (°C), more preferably Tc-10 (°C). The lower limit of the ambient temperature (Ta) of the modeling area is preferably Tc-80 (°C), more preferably Tc-50 (°C).

In this embodiment, a three-dimensional object is formed on the modeling stage by the first step described above. Then, in the second step described below, the formed three-dimensional object is peeled off from the modeling stage.

[Second step]
After the first step, the three-dimensional object formed in the first step is peeled off from the surface of the modeling stage under the temperature condition shown in the following formula 2.
Tc>Ts (Equation 2)

Formula 2 specifies the temperature (Ts) of the modeling stage. That is, after the first step, by setting the temperature (Ts) of the modeling stage below the crystallization temperature (Tc), the crystallization and hardening of the thermoplastic resin (modeling material) near the modeling stage interface, which was kept in a semi-molten state during modeling, progresses, and the three-dimensional object can be naturally peeled off from the modeling stage. In this way, in the second step, the formed three-dimensional object can be peeled off from the modeling stage simply by lowering the temperature of the modeling stage. Note that, after the start of the second step, there is no particular limit to the rate of temperature reduction when the temperature of the modeling stage is set to the temperature shown in Formula 2. For example, it is also possible to stop heating the modeling stage, leave it, and simply return it to room temperature. In that case, when the heating of the modeling stage is stopped after the first step is completed, the second step will be automatically executed.

In the second step, if the temperature (Ts) of the modeling stage is equal to or higher than the crystallization temperature (Tc), the thermoplastic resin near the modeling stage interface remains in a semi-molten state, and the three-dimensional object cannot be easily peeled off. If an attempt is made to forcibly peel it off, there is a risk that the lower layer of the object will be damaged or the surface of the modeling stage will be scratched. In formula 2, the temperature (Ts) of the modeling stage is preferably equal to or lower than Tc - 5 (°C), and more preferably equal to or lower than Tc - 10 (°C). There is no particular lower limit for the temperature (Ts) of the modeling stage, and it can be set to, for example, about room temperature (20°C).

By the way, in the case of forming a three-dimensional object by a general fused deposition modeling 3D printer, after the formation is completed, the object is strongly adhered to the formation stage. Therefore, the object on the formation stage needs to be manually peeled off using a scraper (metal spatula) or the like. After the peeling, the adhered portion of the three-dimensional object may remain partially on the formation stage without peeling off, in which case the surface of the formation stage needs to be cleaned or the formation stage needs to be replaced. However, as described above, in this embodiment, in the second step, the three-dimensional object formed in the first step can be naturally peeled off from the formation stage. Therefore, the above-mentioned manual peeling using a scraper is not necessary, and the adhered portion of the three-dimensional object does not remain without peeling off, or if there is any, it is rare. Furthermore, it is possible to move on to the formation of the next new three-dimensional object without cleaning the formation stage or replacing the formation stage. Therefore, it is possible to automate the formation of three-dimensional objects.

In view of the above, in this embodiment, in the second step, the three-dimensional object is peeled off and discharged from the surface of the modeling stage by the discharge mechanism that discharges the three-dimensional object to the outside of the modeling stage, and then the process proceeds to the first step in succession to form a new three-dimensional object. Note that "proceeding to the first step in succession..." means that after the three-dimensional object that has been completely modeled is discharged, the process proceeds to the first step in a single flow, and there may be a short delay before proceeding to the first step.

After the second step is completed, the ejection mechanism for ejecting the three-dimensional object from the modeling stage without manual labor may be, for example, the following mechanism.
(1) Push-out mechanism This is a mechanism that moves a push-out member from the back to the front of the three-dimensional object on the modeling stage. The push-out mechanism can eject the three-dimensional object after the second step is completed. The shape of the push-out member can be a cylinder or a blade.
(2) Discharge nozzle mechanism The discharge nozzle that discharges the modeling material is also used to discharge the three-dimensional object. That is, the three-dimensional object is pushed from the back of the modeling stage to the front by scanning the discharge nozzle, and discharged. The discharge nozzle mechanism is useful because it uses the discharge nozzle provided in the 3D printer and can discharge the three-dimensional object without providing a separate discharge mechanism. Note that it is preferable to discharge the three-dimensional object by the discharge nozzle after the discharge nozzle has cooled.
(3) Air jetting mechanism: Air is blown onto the three-dimensional object, and the three-dimensional object is blown off and ejected from the modeling stage by the air pressure. Any known air jetting mechanism can be used as long as it can blow off the three-dimensional object.
(4) Robot Arm Mechanism This is a mechanism for removing a three-dimensional object from the modeling stage by using an external robot arm mechanism. The robot arm mechanism will be described later.
(5) Tilting Mechanism: A mechanism that ejects a three-dimensional object on the modeling stage by tilting the modeling stage or the 3D printer body.
Of the above mechanisms, (4) the robot arm will be described below with reference to FIG.

FIG. 2 shows how a three-dimensional object on the modeling stage is discharged by a robot arm. The 3D printer 20 shown in FIG. 2 includes a main body 22 and an electrically operated opening/closing door 25 attached to the main body 22. The modeling space 24 in the main body 22 includes a modeling stage 26 for modeling a three-dimensional object 36. Above the modeling stage 26, a discharge head 32 is provided, and the discharge head 32 can move freely in two dimensions by a guide rail 30 and a guide rail 34 perpendicular to the guide rail 30. In addition, a guide rail 28 is provided at the back of the modeling space 24, and the modeling stage 26 can move in the vertical direction. In the above configuration, during modeling, the modeling stage 26 is moved in the vertical direction along the guide rail 28 by a motor (not shown) and is controlled to be located near the discharge head 32. In addition, the discharge head 32 is moved freely in a two-dimensional plane above the modeling stage 26 via the guide rail 30 and the guide rail 34 by a motor (not shown), while discharging the modeling material. In addition, a robot arm 38 connected to a driving device (not shown) is provided outside the 3D printer 20.
When the modeling of the three-dimensional object is completed, the open/close door 25 is opened, and the robot arm 38 enters the modeling space 24 from the outside by a driving device (not shown) and grasps the three-dimensional object 36, and transports the three-dimensional object 36 in this state to a predetermined position outside. This operation can be performed by electrical control without human intervention. In this embodiment, in the second step, the three-dimensional object 36 naturally peels off from the modeling stage 26, so there is no need to cause the robot arm 38 to perform a special operation to peel off the three-dimensional object 36. Therefore, for example, after the modeling of one three-dimensional object is completed, the modeling of the next object can be performed continuously without human intervention.
Conventionally, a method for automatically discharging a three-dimensional object after modeling is known in which "modeling is performed with a thin film attached to the modeling stage, and the film is slid together with the film to cut and discharge the film." In this conventional technology, an extra film is required as a consumable. Furthermore, since a film is used, the heating temperature depends on the heat resistance of the film, and the temperature conditions are limited. In contrast, in this embodiment, since the three-dimensional object becomes naturally peelable from the modeling stage in the second step, consumables such as a film are not required, and only the three-dimensional object can be discharged. Furthermore, since a film is not required, the temperature conditions are not limited.

The above describes a mechanism that allows the removal of a three-dimensional object after the second step, but it goes without saying that in this embodiment, the three-dimensional object can also be removed manually.

On the other hand, in this embodiment, the method may further include a step of forming a base layer between the modeling stage and the three-dimensional object by the fused deposition modeling method using the same modeling material as the structure part under the temperature conditions shown in the above formula 1 before the first step. In this specification, the base layer refers to a base formed under the structure part. As described above, the base layer does not necessarily need to be provided, but for example, when the structure part 5 shown in FIG. 1 has a certain height, the modeling time is long, and as the structure part cools, the thermoplastic resin near the interface with the modeling stage directly below the structure part may also be gradually cooled and crystallization may progress. In this case, it is preferable to form the base layer 4 having a base area larger than the structure part 5 in order to maintain the adhesion between the three-dimensional object and the modeling stage. When forming the base layer, it is preferable to form it under conditions where the density is as close to 100% as possible so that no voids or gaps are formed in the base layer.
On the other hand, when a thin structure having a thickness of, for example, only a few layers is to be formed as the structural part 5, and when the desired shape can be formed without air cooling from the air duct 3, the formation of the base layer 4 is not necessarily required as long as the forming method of this embodiment, which satisfies the conditions of the above-mentioned formulas 1 and 2, is followed.

In this embodiment, when forming the base layer, the modeling material is discharged from the discharge nozzle onto the modeling stage under the temperature conditions shown in the above formula 1. The modeling material at this time is in a semi-molten state. That is, as described above, the semi-molten modeling material exhibits strong adhesion to the modeling stage, and is therefore firmly fixed onto the modeling stage during modeling. In addition, in order to further strengthen the adhesion between the base layer and the modeling stage, it is preferable to make the scanning speed of the nozzle when forming the base layer slower than the scanning speed of the nozzle when forming the structure portion.
On the other hand, in the present embodiment, the base layer is heated on the modeling stage and is kept in a semi-molten state during modeling, which tends to reduce voids and therefore makes the base layer denser than the structure.

In this embodiment, the base layer is firmly attached to the structural portion, and therefore the base layer cannot be easily removed. Therefore, it is preferable to remove the base layer by cutting, polishing, or the like.

Next, we will explain the modeling materials used in the manufacturing method of the three-dimensional object of this embodiment.

[Modeling materials]
The molding material used in this embodiment is mainly composed of a crystalline thermoplastic resin, and the shape is not particularly limited, and can be, for example, filament-like, pellet-like, etc., depending on the specifications of the 3D printer used in the fused deposition modeling method. As the crystalline thermoplastic resin, one selected from the group consisting of polyacetal resin (hereinafter also referred to as "POM resin"), polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, and polyamide resin is used.

In this embodiment, from the viewpoint of ensuring the retention of the structure on the modeling stage, the melt flow rate of the crystalline thermoplastic resin is preferably 20 g/10 min or less, and more preferably 2 to 15 g/10 min. The melt flow rate is measured by the measurement method specified in ISO 1133.

In this embodiment, the mass fraction of the crystalline thermoplastic resin in the modeling material can be 99% by mass or more. That is, in this embodiment, as described above, since the occurrence of warping during stacking and peeling from the modeling stage are suppressed, the additive manufacturing of a three-dimensional object can be carried out without adding inorganic fillers or the like, and the mass fraction of the crystalline thermoplastic resin can be 99% by mass or more. Furthermore, a three-dimensional object can be formed even if the mass fraction of the crystalline thermoplastic resin is 100% by mass, that is, as a neat resin. However, for the purpose of controlling the physical properties of the three-dimensional object, other additives such as inorganic fillers may be added as necessary.
Among the above crystalline thermoplastic resins, the POM resin will be particularly described in detail below.

(Polyacetal resin (POM resin))
POM resins are polymeric compounds whose main constituent unit is an oxymethylene unit (-CH ₂ O-), and include acetal homopolymers (e.g., trade name "Delrin" manufactured by DuPont USA) and acetal copolymers containing other comonomer units in addition to oxymethylene groups (e.g., trade name "Duracon" manufactured by Polyplastics Co., Ltd.).
As the POM resin used in this embodiment, an acetal copolymer is particularly preferable in terms of its thermal stability.

In the acetal copolymer, the comonomer unit contains an oxyalkylene unit having about 2 to 6 carbon atoms (preferably about 2 to 4 carbon atoms) (for example, an oxyethylene group (-CH ₂ CH ₂ O-), an oxypropylene group, an oxybutylene group, etc.).

The content of the comonomer units can be selected from the range of generally 0.01 to 20 mol%, preferably 0.03 to 10 mol%, and more preferably 0.1 to 7 mol%, as a proportion of the structural units of the polyacetal polymer, so long as the amount does not significantly impair the crystallinity of the resin.

The acetal copolymer may be a copolymer composed of two components, a terpolymer composed of three components, etc. The acetal copolymer may be a random copolymer, a block copolymer, a graft copolymer, etc.

There are also no particular restrictions on the degree of polymerization, branching, or crosslinking of such POM resins, as long as they are melt moldable.

(Other ingredients)
In the present embodiment, the modeling material may contain various known stabilizers selected as necessary, such as one or more of hindered phenol compounds, nitrogen-containing compounds, hydroxides of alkali or alkaline earth metals, inorganic salts, and carboxylates.

Furthermore, in this embodiment, one or more of typical additives for thermoplastic resins, such as weather (light) stabilizers, colorants such as dyes and pigments, lubricants, nucleating agents, mold release agents, antistatic agents, surfactants, organic polymer materials, inorganic or organic fibrous, powdery or plate-like fillers, etc., may be added as necessary, so long as the effect is not impaired.

The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

In the following examples and comparative examples, a three-dimensional object 10 was produced as shown in FIG. 3. The three-dimensional object 10 has a shape in which a cubic structural part 5 with a side length of 20 mm is joined to the center of a square sheet-like base layer 4 with a side length of 50 mm and a thickness of 0.5 mm. The area of the base layer 4 is larger than the area of one face of the structural part 5, and the base layer 4 protrudes from the joint with the structural part 5 by a margin width 7 of 15 mm.

[Example 1]
(First step)
As a molding material, a monofilament having a diameter of 1.75 mm and made of POM resin (manufactured by Polyplastics Co., Ltd., product name: DURACON (registered trademark) POM, grade name: M25-44, unreinforced, melt flow rate = 2.5 g/10 min, melting point: 165°C, crystallization temperature: 145°C) was prepared.
Next, the prepared modeling material was set in a fused deposition modeling 3D printer (manufactured by INTAMSYS, product name: FUNMAT HT Enhanced) to form a three-dimensional object. Specifically, a square sheet-shaped base layer of the above size was first formed under the temperature conditions shown in Table 1 below, and then a structure was formed under the same temperature conditions. The inner diameter of the nozzle that ejects the modeling material in the modeling device was 0.4 mm, the layer pitch was 0.2 mm, and the drawing speed of the structure was 30 mm/s.
In Example 1, with the object fixed on the modeling stage, the modeling material was layered without any problems until the end, and a three-dimensional object was formed.

(Second step)
After the first step was completed, the temperature of the modeling stage was lowered to 120° C., and the three-dimensional object was peeled off from the surface of the modeling stage. At that time, the entire base layer had turned white, and its adhesion to the surface of the modeling stage had decreased, so that the three-dimensional object naturally peeled off from the modeling stage without any special peeling operation.
The obtained three-dimensional object was separated into the structural portion and the base layer by cutting, and the density of each was measured by the Archimedes method using an electronic densitometer (SD-120L, manufactured by Mirage). The actual density of the structural portion was 1.36, while the actual density of the base layer was 1.41.

[Example 2]
As a molding material, a monofilament having a diameter of 1.75 mm and made of the same POM resin as in Example 1 was prepared.
Next, a three-dimensional object was formed in the same manner as in Example 1 under the temperature conditions shown in Table 1 above.
In Example 2, the modeling material was layered without any problems until the end with the model fixed on the modeling stage, and a three-dimensional model was formed. Moreover, by lowering the stage temperature after modeling, the three-dimensional model naturally peeled off from the modeling stage, as in Example 1.

[Example 3]
As a molding material, a monofilament having a diameter of 1.75 mm and made of the same POM resin as in Example 1 was prepared.
Next, a three-dimensional object was formed in the same manner as in Example 1 under the temperature conditions shown in Table 1 above.
In Example 3, the modeling material was layered without any problems until the end with the model fixed on the modeling stage, and a three-dimensional model was formed. Moreover, by lowering the stage temperature after modeling, the three-dimensional model naturally peeled off from the modeling stage, as in Example 1.

[Example 4]
(First step)
As a molding material, a monofilament having a diameter of 1.75 mm and made of the same POM resin as in Example 1 was prepared.
Next, a three-dimensional object was formed in the same manner as in Example 1 under the temperature conditions shown in Table 1 above.
In Example 4, although there were some areas that appeared to have poor adhesion at the interface of the layers in the laminated structure, the modeling material was layered to the end with the model fixed on the modeling stage, and a three-dimensional model with the intended shape was formed. Moreover, by lowering the stage temperature after modeling, the three-dimensional model naturally peeled off from the modeling stage, as in Example 1.

[Example 5]
As a molding material, a monofilament having a diameter of 1.75 mm and made of POM resin (manufactured by Polyplastics Co., Ltd., product name: DURACON (registered trademark) POM, grade name: M90-44, unreinforced, melt flow rate = 9.0 g/10 min, melting point: 165°C, crystallization temperature: 145°C) was prepared.
Next, a three-dimensional object was formed in the same manner as in Example 1 under the temperature conditions shown in Table 1 above.
In Example 5, the modeling material was layered without any problems until the end with the model fixed on the modeling stage, and a three-dimensional model was formed. Moreover, by lowering the stage temperature after modeling, the three-dimensional model naturally peeled off from the modeling stage, as in Example 1.

[Comparative Example 1]
The first step was carried out in the same manner as in Example 1, except that the temperature of the modeling stage in the first step was set to 144° C. However, the modeled object peeled off from the modeling stage at the stage of forming the base layer, and modeling in the first step could not be completed.

[Comparative Example 2]
The first step was carried out in the same manner as in Example 1, except that the temperature of the modeling stage in the first step was set to 165° C. However, the structure rotated without being fixed on the base layer, and the intended three-dimensional object was not obtained, and modeling in the first step could not be completed.

[Comparative Example 3]
The first step was carried out in the same manner as in Example 1, except that the ambient temperature in the modeling area in the first step was set to 28° C. However, peeling and large warping occurred due to insufficient adhesive strength between layers during modeling of the structure, and the intended shape could not be maintained, and the first step could not be completed.

[Comparative Example 4]
The first step was carried out in the same manner as in Example 1, except that the temperature of the modeling stage in the second step was set to 155° C. Then, when an attempt was made to peel off the three-dimensional object from the modeling stage while keeping the temperature of the modeling stage at 155° C., the base layer was firmly attached to the surface of the modeling stage in a semi-molten state, and the forceful peeling resulted in damage to the model.

As described above, in Examples 1 to 5, a three-dimensional object could be formed without any problems, and after formation, it could be easily peeled off from the modeling stage, whereas in Comparative Examples 1 to 3, which do not satisfy Formula 1, it was not even possible to form a three-dimensional object. Moreover, in Comparative Example 4, which does not satisfy Formula 2, although a three-dimensional object could be formed, it could not be easily peeled off after formation.

Claims (6)

a first step of forming a three-dimensional object on a modeling stage by a fused deposition modeling method using a modeling material mainly composed of a crystalline thermoplastic resin under temperature conditions shown in the following formula 1;
Tm>Ts>Tc, and Tc>Ta>Tc-100 (Equation 1)
[In formula 1, Ts represents the temperature of the modeling stage (°C), Tc represents the crystallization temperature of the crystalline thermoplastic resin (°C), Tm represents the melting point of the crystalline thermoplastic resin (°C), and Ta represents the ambient temperature of the modeling area (°C).]
and a second step of peeling off the three-dimensional object formed in the first step from the surface of the modeling stage under a temperature condition represented by the following formula 2 after the first step,
Tc>Ts (Equation 2)
The method for producing a three-dimensional object, wherein the crystalline thermoplastic resin is one selected from the group consisting of polyacetal resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, and polyamide resin. The method for manufacturing a three-dimensional object according to claim 1, further comprising, before the first step, forming a base layer between the modeling stage and the three-dimensional object by fused deposition modeling using the modeling material under the temperature conditions shown in formula 1. The method for manufacturing a three-dimensional object according to claim 1, wherein in the second step, the three-dimensional object is peeled off and discharged from the surface of the modeling stage by a discharge mechanism that discharges the three-dimensional object to the outside of the modeling stage, and then the method proceeds to the first step to form a new three-dimensional object. The method for manufacturing a three-dimensional object according to any one of claims 1 to 3, wherein the mass fraction of the crystalline thermoplastic resin in the modeling material is 99 mass% or more. The method for manufacturing a three-dimensional object according to any one of claims 1 to 4, characterized in that the melt flow rate of the crystalline thermoplastic resin is 20 g/10 min or less. The method for manufacturing a three-dimensional object according to any one of claims 1 to 5, wherein the crystalline thermoplastic resin is a polyacetal resin.

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