JP2023032629A - Thermal-melting type three-dimensional printer - Google Patents

Abstract

To provide a thermal-melting type three-dimensional printer capable of suppressing molding defects.SOLUTION: There is provided a thermal-melting type three-dimensional printer that comprises an extruder and a pushing mechanism. The extruder includes a hopper, a cylinder and a nozzle. The hopper is configured to be able to supply pellets into the cylinder through a raw material supply port provided in the cylinder. The extruder is configured to melt and knead the pellets supplied into the cylinder to form a molten resin in the cylinder, and to extrude the molten resin through the nozzle to form a strand. The pushing mechanism is configured to push the pellets placed on a placement surface of the hopper into the cylinder through the raw material supply port.SELECTED DRAWING: Figure 1

Description

The present invention relates to a hot-melt three-dimensional printer.

Patent Document 1 discloses a method of forming a strand by melting pellets made of a thermoplastic elastomer using a screw extruder and extruding them from a nozzle, and scanning the strand to manufacture a model. disclosed.

Japanese Patent Application Laid-Open No. 2020-146988

When the pellets are fed into the cylinder of the extruder through the hopper, if the surface of the pellets is sticky, a so-called bridging phenomenon may occur in which the pellets stick together on the hopper. If the bridging phenomenon occurs, the pellets will not be sufficiently supplied into the cylinder, leading to molding defects.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a hot-melt three-dimensional printer capable of suppressing molding defects.

According to the present invention, a hot-melt three-dimensional printer comprising an extruder and a pushing mechanism, the extruder comprising a hopper, a cylinder and a nozzle, the hopper being mounted on the cylinder Through the raw material supply port, pellets can be supplied into the cylinder, and the extruder melts and kneads the pellets supplied into the cylinder to form a molten resin in the cylinder, and the molten resin is passed through the nozzle. The tertiary resin is configured to extrude resin to form a strand, and the pushing mechanism is configured to push the pellets placed on the placement surface of the hopper into the cylinder through the raw material supply port. A source printer is provided.

In the three-dimensional printer of the present invention, the pushing mechanism configured as described above pushes the pellets into the cylinder.

Various embodiments of the present invention are illustrated below. The embodiments shown below can be combined with each other.

Preferably, in the three-dimensional printer described above, the pushing mechanism includes a rod that contacts the pellet, and a drive mechanism that drives the rod, and the tip of the rod pushes the pellet to the raw material. It is a three-dimensional printer that is driven to press in the direction of the supply port.
Preferably, in the three-dimensional printer described above, the rod includes a flexible portion, and the rod is bent at the flexible portion so that the tip of the rod extends in the direction of the raw material supply port. A three-dimensional printer that is driven to move toward.
Preferably, in the three-dimensional printer described above, the drive mechanism is configured to rotate the root of the rod about a rotation axis extending in a non-vertical direction.

FIG. 1A is a front view (cylinder 2b is a sectional view) showing a hot-melt three-dimensional printer 1 according to one embodiment of the present invention, and FIG. 1B is a right side view of the pushing mechanism 3 in FIG. 1A. FIG. 2 shows the state after the rod 3a has been lowered from the state of FIG. 1, and FIGS. 2A and 2B are diagrams corresponding to FIGS. 1A and 1B, respectively. FIG. 3 shows the state after the rod 3a is further lowered from the state of FIG. 2, and FIGS. 3A and 3B are diagrams corresponding to FIGS. 1A and 1B, respectively.

Embodiments of the present invention will be described below. Various features shown in the embodiments shown below can be combined with each other. In addition, the invention is established independently for each feature.

As shown in FIG. 1, a hot-melt three-dimensional printer 1 according to one embodiment of the present invention includes an extruder 2 and a pushing mechanism 3. As shown in FIG.

<Extruder 2>
The extruder 2 comprises a hopper 2a, a cylinder 2b and a nozzle 2c. The hopper 2a is configured to be able to supply the pellets 4 into the cylinder 2b through a raw material supply port 2b1 provided in the cylinder 2b. The raw material supply port 2b1 is preferably provided on the side surface of the cylinder 2b. The hopper 2a is preferably attached to the cylinder 2b, and more preferably attached to the side surface of the cylinder 2b.

The extruder 2 is configured to melt-knead the pellets 4 supplied into the cylinder 2b in the cylinder 2b to form the molten resin 4a, and to form the strand 5 by extruding the molten resin 4a through the nozzle 2c. . A screw 2d is arranged in the cylinder 2b, and by rotating the screw 2d with a motor 2e, the pellets 4 are melted and kneaded to form a molten resin 4a, and the molten resin 4a is directed toward the tip of the cylinder 2b. It can be transported and pushed out through the nozzle 2c.

The diameter of the screw 2d is, for example, 5-80 mm, preferably 10-60 mm. Specifically, this diameter is, for example, 5, 10, 20, 30, 40, 50, 60, 70, 80 mm, and may be within a range between any two of the values exemplified here.

The strand 5 is linear and has a diameter of, for example, 0.5 to 6.0 mm, preferably 1.0 to 4.0 mm. Specifically, this diameter is, for example, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 mm, and may be in the range between any two of the values exemplified here.

The pellets 4 are placed on the placement surface 2a1 of the hopper 2a. The angle of the mounting surface 2a1 with respect to the horizontal plane is preferably 0 to 80 degrees, more preferably 15 to 60 degrees. Specifically, this angle is, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 degrees. It may be in a range between any two of the numbers given.

The width (length in the depth direction in FIG. 1A) and height of the raw material supply port 2b1 are, for example, 1 to 10 cm, preferably 2 to 8 cm. Specifically, the width and height are, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 cm, and are within the range between any two of the numerical values exemplified here. There may be.

The extruder 2 can be moved three-dimensionally (moved in the XYZ directions) by a drive mechanism (not shown). A single-layer structure can be formed by two-dimensionally scanning the extruder 2 while discharging the strand 5 from the nozzle 2c, and a desired shaped object can be formed by stacking the single-layer structures. .

<Pushing mechanism 3>
The pushing mechanism 3 is configured to push the pellets 4 placed on the placement surface 2a1 of the hopper 2a into the cylinder 2b through the raw material supply port 2b1. The mounting surface 2a1 is normally an inclined surface that becomes lower toward the raw material supply port 2b1, and it is expected that the pellets 4 will be supplied into the cylinder 2b by their own weight. If the pellets 4 stick together on the hopper 2a, a so-called bridging phenomenon may occur. supply becomes insufficient, leading to molding defects. On the other hand, in the present embodiment, the pushing mechanism 3 pushes the pellets 4 into the cylinder 2b, so even if the surface of the pellets 4 is sticky, the pellets 4 can be sufficiently supplied into the cylinder 2b. , and molding defects caused by insufficient supply of the pellets 4 are suppressed.

In this embodiment, the pushing mechanism 3 includes a rod 3a that contacts the pellet 4 and a drive mechanism 3b that drives the rod 3a. The pushing mechanism 3 is preferably attached to the extruder 2 , and more preferably attached to the upper portion of the extruder 2 .

The rod 3a is driven such that the tip 3a1 of the rod 3a presses the pellet 4 in the direction of the raw material supply port 2b1. In order to eliminate the bridging phenomenon of the pellet 4, it is conceivable to break the bridge of the pellet 4 with a piston that moves in the vertical direction. In some cases, the lack of supply of the pellets 4 may not be resolved sufficiently due to sticking together. On the other hand, in the pushing mechanism 3 of the present embodiment, the tip 3a1 of the rod 3a does not simply move vertically, but pushes the pellet 4 toward the raw material supply port 2b1 as shown in FIGS. driven as According to such a configuration, the bridge of the pellet 4 is broken by pressing by the tip 3a1, and the pellet 4 is moved in the direction of the raw material supply port 2b1. The supply of pellets 4 inside is facilitated.

The diameter of the tip 3a1 of the rod 3a is, for example, 1 to 20 mm, preferably 3 to 15 mm. This diameter is specifically for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30 mm, and may be in the range between any two of the values exemplified here.

The rod 3a preferably has a soft portion 3a2. The soft portion 3a2 is a portion that is curved when the rod 3a is pressed against the mounting surface 2a1, and is made of a soft material such as rubber. The bending elastic modulus of the soft portion 3a2 is preferably 70 to 700 MPa, for example. Specifically, this bending elastic modulus is, for example, 70, 80, 90, 100, 250, 400, 550, 700 MPa, and may be within a range between any two of the numerical values exemplified here. The rod 3a may be composed only of the soft portion 3a2, and preferably composed of the soft portion 3a2 and the hard portion 3a3 made of a material having a higher flexural modulus than the soft portion 3a2. The hard portion 3a3 is preferably arranged at a position farther from the tip 3a1 than the soft portion 3a2. Moreover, it is preferable that the tip 3a1 is provided in the soft portion 3a2. The bending elastic modulus can be measured according to JIS K7171.

The length of the soft portion 3a2 (the length in the longitudinal direction when the soft portion 3a2 is straightened) is preferably 2 cm or longer, more preferably 3 cm or longer. The length of the soft portion 3a2 is, for example, 2 to 30 cm, specifically, for example, 2, 3, 4, 5, 10, 15, 20, 25, 30 cm. It may be in the range between the two or any more. The soft portion 3a2 may have a constant cross-sectional shape over the entire length, and may taper toward the tip 3a1, for example.

Rod 3a is preferably driven such that tip 3a1 of rod 3a moves toward raw material supply port 2b1 while rod 3a is curved at soft portion 3a2. With such a configuration, when the root 3a4 of the rod 3a is moved downward, the tip 3a1 of the rod moves toward the raw material supply port 2b1, and when the root 3a4 of the rod 3a is moved upward. , the tip 3a1 of the rod moves away from the raw material supply port 2b1. In other words, the vertical movement of the base 3a4 of the rod 3a is converted into the movement of the tip 3a1 of the rod 3a toward and away from the raw material supply port 2b1.

Any mechanism capable of operating the rod 3a as described above can be adopted as the drive mechanism 3b, and examples thereof include a cylinder mechanism and a rotation mechanism. As the cylinder mechanism, there is a mechanism for vertically reciprocating the base 3a4 of the rod 3a. Examples of the rotating mechanism include a mechanism capable of converting rotating motion into reciprocating motion in the vertical direction of the base 3a4 of the rod 3a.

The driving mechanism 3b of this embodiment is a rotating mechanism, and includes a motor 3b1, a motor shaft 3b2, a disc 3b3, and a bracket 3b4.

The motor shaft 3b2 is rotated by being driven by the motor 3b1. The rotation direction of the motor shaft 3b2 is, for example, counterclockwise when viewed from the disk 3b3 side, as shown in FIG. 1B. Disk 3b3 is fixed to motor shaft 3b2, and bracket 3b4 is fixed to disk 3b3. A base 3a4 of the rod 3a is fixed to the bracket 3b4. Therefore, as shown in FIGS. 2 and 3, the disk 3b3, the bracket 3b4, and the base 3a4 also rotate with the rotation of the motor shaft 3b2. The direction of the motor shaft 3b2 coincides with the rotation axis of the member that rotates with the rotation of the motor shaft 3b2.

Since the motor shaft 3b2 is oriented in a non-vertical direction, its vertical position changes periodically when the base 3a4 rotates. Therefore, by rotating the motor shaft 3b2, the base 3a4 can be vertically reciprocated. The angle between the motor shaft 3b2 and the horizontal plane is preferably 45 degrees or less, more preferably 30 degrees or less. This angle is, for example, 0 to 45 degrees, specifically, for example, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45 degrees. It may be in a range between the two or less than whichever.

As the motor shaft 3b2 rotates, the root 3a4 reciprocates not only in the vertical direction, but also in the left-right direction in FIG. reciprocate. When the root 3a4 reciprocates in the left-right direction, the tip 3a1 and its neighboring portion also reciprocate in the left-right direction, so the bridge is more likely to collapse.

The amplitude of the tip 3a1 in the reciprocating motion (the length between the position closest to the raw material supply port 2b1 and the position farthest from the raw material supply port 2b1) is, for example, 0.5 cm or more, preferably 1 cm or more. This amplitude is, for example, 0.5 to 10 cm, specifically, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 cm, as illustrated here It may be in a range between any two of the numbers or in any or more.

During the reciprocating motion, the tip 3a1 may or may not enter the outer peripheral surface of the cylinder 2b. When the tip 3a1 comes closest to the cylinder 2b, the distance from the tip 3a1 to the outer peripheral surface of the cylinder 2b is preferably 10 cm or less, more preferably 5 cm or less. This distance is, for example, -2 cm to 10 cm, specifically for example -2, -1, -0.5, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 cm, and may be in the range between any two of the values exemplified herein, or any less. A negative value means the distance that the tip 3a1 has entered the inside of the outer peripheral surface of the cylinder 2b.

<Pellet 4>
Pellets 4 are not particularly limited, but thermoplastic elastomer is preferable.

The pellets 4 are in the form of granules that can be fed into the extruder 2 . The shape of the pellet 4 is not particularly limited, but may be, for example, spherical, spheroidal, or the like. Let L be the length of the longest part of the pellet 4 (the length in the major axis direction in the case of a spheroid), and the diameter of the surface perpendicular to the longest part (the length in the minor axis direction in the case of a spheroid) Assuming D, L/D is, for example, 1 to 10, preferably 1 to 5. L is, for example, 0.5 to 10 mm, preferably 2 to 8 mm. Specifically, L/D is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and is within the range between any two of the numerical values exemplified here. good too. Specifically, L is, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 mm, and within the range between any two of the numerical values exemplified here There may be.

Examples of thermoplastic elastomers include styrene elastomers, olefin elastomers, acrylic elastomers, and the like. The thermoplastic elastomer preferably contains a styrenic elastomer. Since a styrene-based elastomer is highly flexible, the inclusion of a styrene-based elastomer in the thermoplastic elastomer increases the flexibility of the thermoplastic elastomer. The proportion of the styrene-based elastomer in the thermoplastic elastomer is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, specifically, for example, 50, 60, 70, 80, 90, 100% by mass. , within a range between any two of the numerical values exemplified herein.

Styrene-based elastomers are thermoplastic elastomers having styrene units, and styrene-based copolymers (for example, styrene-ethylene-styrene block copolymer (SES), styrene-butadiene-styrene block copolymer (SBS), Styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene rubber (SBR), etc.), hydrogenated styrenic copolymers (e.g., styrene-ethylene/propylene-styrene block copolymer (SEPS), styrene- Ethylene-butylene-styrene block copolymer (SEBS), styrene-butylene-butadiene-styrene block copolymer (SBBS), hydrogenated styrene-butadiene rubber (HSBR), etc.) A blended product can be mentioned.

The Shore A hardness of the thermoplastic elastomer is preferably 0-10, more preferably 0-2. Since the surface of the pellet 4 having such physical properties is likely to be sticky, the technical significance of modeling using the three-dimensional printer 1 of this embodiment is significant. Shore A hardness is specifically, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, within the range between any two of the numerical values illustrated here There may be. When the Shore A hardness is within this range, a model having excellent flexibility can be obtained. Shore A hardness is measured based on JIS K6253.

The melt flow rate (hereinafter “MFR”) of the thermoplastic elastomer is preferably 10-200 g/10 minutes, more preferably 60-140 g/10 minutes. In this case, it is easy to increase the molding accuracy. Specifically, the MFR is, for example, minutes and may be in the range between any two of the numbers exemplified herein. MFR is measured according to JIS K-7210 at a measurement temperature of 150° C. and a test load of 2.16 kg.

The angle of repose of the pellets 4 is preferably 35 degrees or more. With such a pellet 4, the bridging phenomenon is likely to occur, so the technical significance of modeling using the three-dimensional printer 1 of the present embodiment is significant. This angle of repose is, for example, 35 to 80 degrees, and specifically, for example, , 75, 80 degrees, and may be in the range between any two of the values exemplified herein, or any greater. The angle of repose can be measured by the following method.
(1) First, a pile of pellets 4 is formed by injecting pellets 4 vertically onto a horizontal measuring table (10.5 cm in diameter). Pellets 4 are injected until the pellets 4 overflow the measuring table.
(2) Next, at the edge of the upper surface of the measuring table, the angle of inclination of the pile of pellets 4 from the horizontal plane is measured with a protractor, and the obtained measured value is defined as the angle of repose.

1. Example 1
A modeled object was modeled using the three-dimensional printer 1 shown in FIG. As the soft portion 3a2, one having a diameter of 0.6 cm, a length of 4 cm, and a bending elastic modulus of 300 MPa was used. The rod 3a was driven such that the base 3a4 of the rod 3a made a circular motion with a diameter of 2.4 cm. The cycle of circular motion was set to 3 seconds. As a result, the tip 3a1 of the rod 3a reciprocates toward and away from the raw material supply port 2b1.

Pellets 4 (styrene-based elastomer, AR-SC-0, manufactured by Aron Kasei Co., Ltd., long sphere, length in major axis direction is about 4.5 mm, length in minor axis direction is about 4.5 mm) about 2.5 mm, repose angle of 40 degrees, Shore A hardness: 0, MFR at 150 ° C.: 127.52 g / 10 minutes), and while operating the pushing mechanism 3, the extruder 2 is run at 150 ° C. It was made to operate and molded. As the molding progressed, the pellet 4 was pushed into the cylinder 2b to obtain a desired shaped object.

2. Comparative example 1
Modeling was performed in the same manner as in Example 1, except that the pushing mechanism 3 was not provided. A bridging phenomenon occurred in the pellet 4, and the pellet 4 was not sufficiently supplied into the cylinder 2b, resulting in poor molding.

3. Comparative example 2
Modeling was performed in the same manner as in Example 1, except that a cylinder mechanism that reciprocated in the vertical direction was used instead of the pushing mechanism 3 . Although the bridge of the pellet 4 was broken by the cylinder mechanism, the pellet 4 was not sufficiently supplied into the cylinder 2b, resulting in poor molding.

1: Hot-melt three-dimensional printer 2: Extruder 2a: Hopper 2a1: Mounting surface 2b: Cylinder 2b1: Raw material supply port 2c: Nozzle 2d: Screw 2e: Motor 3: Pushing mechanism 3a: Rod 3a1: Tip 3a2: Soft Portion 3a3: Hard portion 3a4: Base 3b: Drive mechanism 3b1: Motor 3b2: Motor shaft 3b3: Disk 3b4: Bracket 4: Pellets 4a: Molten resin 5: Strand

Claims (4)

A hot-melt three-dimensional printer,
Equipped with an extruder and a pushing mechanism,
The extruder comprises a hopper, a cylinder and a nozzle,
The hopper is configured to be able to supply pellets into the cylinder through a raw material supply port provided in the cylinder,
The extruder is configured to melt-knead the pellets supplied into the cylinder to form a molten resin in the cylinder, and extrude the molten resin through the nozzle to form a strand,
The three-dimensional printer, wherein the pushing mechanism pushes the pellet placed on the placement surface of the hopper into the cylinder through the raw material supply port. The three-dimensional printer according to claim 1,
The pushing mechanism includes a rod that contacts the pellet and a drive mechanism that drives the rod,
The three-dimensional printer, wherein the rod is driven such that the tip of the rod presses the pellet toward the raw material supply port. The three-dimensional printer according to claim 2,
the rod comprises a soft portion,
The three-dimensional printer, wherein the rod is driven such that the tip of the rod moves toward the raw material supply port while the rod is curved at the soft portion. The three-dimensional printer according to claim 2 or claim 3,
The three-dimensional printer, wherein the drive mechanism is configured to rotate the base of the rod about a rotation axis extending in a non-vertical direction.

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