JP2970300B2 - 3D modeling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional forming method for forming a three-dimensional shape by curing a photocurable resin by irradiating a laser beam.

[0002]

2. Description of the Related Art In recent years, as a method of forming various three-dimensional shapes, a liquid photocurable resin is scanned with a laser beam to form a cured layer of the resin, and a plurality of the cured layers are laminated to form a desired layer. A three-dimensional forming method for forming a three-dimensional shape has been widely used.

A conventional three-dimensional printing method will be described below. FIG. 2 shows a schematic configuration of a three-dimensional printing apparatus to which the principle of the three-dimensional printing method is applied.

[0004] The three-dimensional printing apparatus includes a part for processing three-dimensional shape data and a device for forming a three-dimensional shape based on the data.

[0005] The data processing part includes a three-dimensional CAD system 1 for creating a three-dimensional shape, and an EWS (Engineering Workstation) for calculating data for a molding apparatus based on the three-dimensional shape created by the three-dimensional CAD system 1. 2).

On the other hand, an apparatus for forming a three-dimensional shape comprises a resin tank 10 containing a liquid photocurable resin 7, and a forming table 13 which can be moved up and down by an elevating device 6 is provided in the resin tank 10. I have. As photocurable resin,
Various resins that can be cured by light irradiation can be used. For example, epoxy resins such as epoxy acrylate and modified polyurethane methacrylate are used.

Above the resin tank 10, a laser XY scanning device 4 for irradiating a laser beam generated by a laser generator 5 via an optical fiber 9 while freely scanning the liquid surface of the photocurable resin 7 in the XY directions. Is provided. In addition,
The laser generator 5, the laser XY scanner 4, and the lift 6 are controlled by the NC controller 3 based on the data of the EWS 2.

Next, the operation of the above apparatus will be described. First, a desired three-dimensional shape is created in the three-dimensional CAD system 1, and the three-dimensional shape data is converted into an STL (storage list) format and transmitted to the EWS 2. Can be The EWS2 converts the data expressed in the STL format of the three-dimensional shape into the XY plane at equal intervals ΔZ on the Z axis.
And the desired three-dimensional shape is represented as an aggregate of data of each cross-sectional shape. The value of ΔZ is determined by the type of the photocurable resin and the power of the laser beam.

Next, the forming table 13 is positioned below the liquid level of the photo-curable resin 7 by a space ΔZ in cross section.
Is covered with a liquid photocurable resin layer having a thickness of ΔZ. The laser XY scanning device 4 scans the surface of the photocurable resin 7 with laser light in a shape corresponding to the lowermost cross-sectional shape, cures the surface resin layer, and forms the lowermost cross-sectional layer on the forming table 13.

At this time, as shown in FIG. 3, the laser beam is emitted in the X-axis direction at an interval 19 based on the diameter of the laser beam.
Scanning is performed from one end of the cross-sectional shape 17 to the other end in parallel with the Y-axis as shown by an arrow 18 while shifting each time.

When the one-section layer is formed, the forming table 13 is further immersed in the uncured photocurable resin by the elevating device 6 by the interval of the section ΔZ, and the upper portion of the previously formed resin cured layer is re-formed. Cover with a liquid photocurable resin layer having a thickness of ΔZ. Thereafter, similarly to the above, the laser XY scanning device 4 scans the surface of the photocurable resin 7 with laser light in a shape corresponding to the second cross-sectional shape following the lowermost cross-sectional layer, and places a laser beam on the upper surface of the lowermost cross-sectional layer. The two cross-section layers are cured and shaped.

By repeating this process up to the highest part of the three-dimensional shape, a three-dimensional shape is formed by laminating a plurality of cured layers of the photocurable resin.

[0013]

The photocurable resin used in the three-dimensional printing apparatus shrinks by about 2 to 5% by volume when irradiated with a laser beam and cured. Therefore, when the uncured photocurable resin is irradiated with the laser beam, the uncured photocurable resin 43 exists around the area 41 to be irradiated with the laser beam as shown in FIG. Is irradiated with a laser beam to the area 41, and the resin cures and shrinks to form 42. In order to compensate for the curing shrinkage, the surrounding uncured resin is cured while being supplied as indicated by an arrow 44. Due to the progress, stress due to shrinkage at the time of curing hardly occurs.

However, as shown in FIG. 4B, the cured resin 4
When 5 is present, when the uncured photocurable resin is irradiated with laser light, the resin in the region 47 is cured and tries to shrink, but since there is no supply of uncured resin from the surroundings, The cured part 45 is drawn by the curing resin,
A tension 46 is generated. That is, internal stress is generated in a direction from a previously cured portion to a later cured portion due to shrinkage accompanying the curing of the resin.

Further, when the photocurable resin is irradiated with the laser beam, only about 98% of the irradiated portion is cured, and it takes a considerable time to completely cure the photocurable resin. Therefore, once cured, the curing proceeds further, the resin shrinks inside the molded product, and further stress is generated.

Therefore, when the laser beam is scanned in the direction parallel to the X-axis or the Y-axis on the photo-curable resin as in the prior art, for example, when the laser beam is linearly scanned in the direction of arrow 59 as shown in FIG. And the irradiation area of the laser beam is 53, 54, 55, 5
The light-curing resin also gradually cures in the same direction as the scanning direction of the laser light as the laser light is scanned. Therefore, the internal stress 58 is generated and accumulated such that the previously cured portion 51 is pulled by the later cured portion 52 as shown by an arrow 58 due to shrinkage accompanying the curing of the resin.

That is, in the conventional scanning method, the internal stress 58 is generally biased in the same direction, that is, in a direction parallel to the X axis or the Y axis, and as a result, there is a possibility that the molded product is deformed such as warping.

The present invention provides a method for preventing a bias in internal stress and preventing deformation of a molded product in three-dimensional molding.

[0019]

According to the present invention, in order to attain the above object, a laser beam is scanned in a ring shape, concentric polygonal shape or spiral shape from the approximate center of gravity of each cross section outward. The conductive resin is cured so as to spread outward from the approximate center of gravity of each cross-sectional shape, and a cured cross-sectional layer of the resin is formed.

[0020]

According to the method of the present invention, the resin is hardened from the center of gravity to the outside by scanning the laser beam outward from the center of gravity of each cross-sectional shape, and the stress due to shrinkage during hardening is reduced. The stress is generated outward from the approximate center of gravity, and the stress is dispersed as a whole.

[0021]

Embodiments of the present invention will be described below. Since the configuration of the three-dimensional printing apparatus is the same as that of the conventional example shown in FIG. 2, the description of each part will be omitted.

In the configuration shown in FIG. 2, a desired three-dimensional shape is created in the three-dimensional CAD system 1, the three-dimensional shape data is converted into the STL format by the three-dimensional CAD system 1, and the data is sent to the EWS 2. EWS
Numeral 2 cuts the data expressed in the STL format of the three-dimensional shape at equal intervals ΔZ along the Z-axis, and expresses the desired three-dimensional shape as an aggregate of data of each cross-sectional shape.

Next, the forming table 13 is positioned below the liquid level of the photo-curable resin 7 by a space ΔZ in cross section.
Is covered with a liquid photocurable resin layer having a thickness of ΔZ. The laser XY scanning device 4 scans the surface of the photocurable resin 7 with laser light in a shape corresponding to the lowermost cross-sectional shape, and cures the surface resin layer on the forming table 13 to form the lowermost cross-sectional layer.

At this time, in the present embodiment, as shown in FIG. 1, the radius of the laser light is enlarged by a constant value based on the diameter of the laser light with the center of the approximate center of gravity 16 of the sectional shape 14 as the center, ie, the scanning start point. While scanning, scanning is performed in a ring shape, concentric polygonal shape or spiral shape.

When the one cross section layer is formed, the forming table 13 is further immersed in the uncured photocurable resin by the cross section interval ΔZ by the elevating device 6, and the upper portion of the previously formed resin cured layer is again formed. It is covered with a photocurable resin layer on the liquid having a thickness ΔZ. Then, the laser XY scanning device 4 scans the surface of the photocurable resin 7 with laser light in a shape corresponding to the second cross-sectional shape following the lowermost cross-sectional layer in the same manner as described above. The cross-section layer is cured and shaped.

By repeating this process up to the highest part of the three-dimensional shape, a three-dimensional shape is formed by laminating a plurality of cured layers of the photocurable resin.

As a result, the photocurable resin is irradiated with the laser beam, and the resin is cured outward from the approximate center of gravity of each section, and stress due to shrinkage at the time of curing is generated in an outward direction from the approximate center of gravity. For this reason, the stress of the molded product is radially distributed in each cross section and is not biased in a certain direction, so that deformation such as warping of the molded product can be prevented.

[0028]

As described above, according to the present invention, the resin is hardened from the substantially center of gravity by scanning the laser beam outward from the substantially center of gravity of the cross section in a ring shape, concentric polygonal shape, or spiral shape. By proceeding outward and dispersing the internal stress due to the shrinkage due to the curing of the resin as a whole and eliminating the bias in a certain direction, the deformation of the molded product can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view showing a laser beam scanning pattern in the method of the present invention.

FIG. 2 is a schematic configuration diagram of a three-dimensional printing apparatus.

FIG. 3 is a plan view showing a laser beam scanning pattern according to a conventional method.

FIG. 4 is a plan view showing a curing pattern of a photocurable resin.

FIG. 5 is a conceptual diagram illustrating the principle of generation of internal stress.

[Explanation of symbols]

 Reference Signs List 1 3D CAD system 2 EWS 3 NC controller 4 Laser XY scanner 5 Laser generator 6 Lifting device 7 Photocurable resin 8 Modeling object 9 Optical fiber 10 Resin tank 13 Forming table 14 Cross section 15 Laser scanning path 16 Approximate center of gravity 17 Cross-sectional shape 18 Laser scanning path 19 Laser scanning interval

Claims (1)

(57) [Claims] 1. A desired three-dimensional shape is represented as an aggregate of data on cross-sectional shapes cut at equal intervals, and the following steps (1) and (2) are repeated based on the data to form a plurality of layers of light. In a three-dimensional forming method of forming a three-dimensional shape by laminating a curable resin layer, a laser beam is scanned in a ring shape, a concentric polygonal shape, or a spiral shape outward from a substantially center of gravity of the cross-sectional shape. 3D modeling method. (1) A laser beam is scanned from above a water tank filled with an uncured liquid photocurable resin to cure a surface resin layer having a shape corresponding to a cross-sectional shape. (2) The cured resin layer is settled in the uncured liquid photocurable resin by the interval of the cross section.