JP2020059051A - Sand-lamination molding machine - Google Patents

Abstract

To provide a sand-lamination molding machine that is inexpensive but improved in the accuracy of molding, and adapted to irradiate a laser beam for curing resin to a layer of a resin-coated sand.SOLUTION: The sand-lamination molding machine comprises: a container unit 30 that receives resin-coated sand rs; layer forming means 20 that forms a layer SL of the resin-coated sand rs received in the container unit 30; and irradiation units 40, 50, 60 that irradiate a laser beam for curing resin to the layer SL. When the irradiation of the laser beam to the layer SL is completed, the layer forming means 20 forms the new layer SL of resin-coated sand on the layer SL. The container unit 30 receives the resin-coated sand rs in which the surface of a sand particle is coated with a resin having an ortho ratio of 55% or higher and 75% or lower. The irradiation units 40, 50, 60 irradiate a laser beam at an output of 10 W or higher and 80 W or lower.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sand laminating machine for irradiating a layer of resin coated sand with laser light for curing a resin.

  The casting mold is composed of a main mold and a core, and the main mold is made of sand mold or metal mold, but the core is generally made of sand mold that maintains the strength with an organic binder (binder). Is. The core is for forming the hollow portion of the casting, and the core that has formed the hollow after casting also causes the binder to burn, so that the core can be easily separated from the casting. Especially in the case of complicated shapes and narrow groove shapes, use the "Coated Sand", which is a thermosetting resin such as phenolic resin as a binder coated on sand, and blow it into a heating mold for molding. Is often used. Also, in the case of a core that forms a small hole shape inside the casting, gas defects due to the gas pressure generated from the resin occur, and as a countermeasure against this, a hollow core is used to ensure air permeability of the core It is known that gas defects can be evacuated to avoid gas defects. On the other hand, in the case of a non-thermosetting binder, it hardens by adding a curing agent or a gas curing reaction, so it can be molded at room temperature and can be molded even if it is not a mold, and there is no need to heat the mold. On the other hand, since hollow core molding is not possible, gas escape is insufficient and gas defects are likely to occur.

  The shell mold method has an advantage that a hollow core can be molded by discharging the uncured portion inside the core (reversal sand removal) by reversing the mold when the surface layer is blown into the mold and cured by heat. However, it is not a general-purpose machine that is widespread, but a dedicated molding machine is required.Moreover, if you want to arrange small holes and hollow parts in each part of the core more efficiently to escape the generated core gas during casting. Has a limited hollow shape, and sand can be discharged only from the blowing port, and a complicated hollow shape is difficult. Furthermore, in the case of prototypes and non-mass production products, the mold is expensive, so core molding is difficult, and it is financially difficult to examine the shape of the core using multiple molds. There are also problems.

  In order to solve these problems, it has been proposed in recent years to mold a mold using a layered molding technique (see, for example, Patent Document 1). In the layered manufacturing technique described in Patent Document 1, a layer of coated sand is formed, and a curing agent is selectively dispersed in the layer, so that the portion where the curing agent is dispersed becomes a curing portion. When the application of the curing agent is completed, a new coated sand layer is formed on the layer having the cured portion, and the curing agent is selectively applied again to provide the cured portion on the new coated sand layer. . After that, the layer formation and the selective spraying of the curing agent are repeated to obtain a three-dimensional mold in which the cured portions are laminated.

  However, in order to realize the additive manufacturing technology using a curing agent described in Patent Document 1, a very expensive investment is required.

  By the way, by using the additive manufacturing technique, various three-dimensional molded objects can be obtained without being limited to the mold. In addition to the additive manufacturing technology using the curing agent described above, additive manufacturing technology using laser light has also been developed (see, for example, Patent Document 2). In the layered manufacturing technique described in Patent Document 2, a layer of resin coated sand is irradiated with laser light for curing a resin, and a portion of the layer of resin coated sand irradiated with laser light serves as a cured portion. When the irradiation of the laser light is completed, a new resin coated sand layer is formed on the layer having the cured portion, and the laser light is irradiated again to provide the cured portion on the new resin coated sand layer. After that, the layer formation and the laser light irradiation are repeated to obtain a three-dimensional structure in which the hardened portions are laminated.

International Publication No. 2015/29935 JP, 2005-169434, A

  However, the additive manufacturing technology using laser light described in Patent Document 2 irradiates a high-output laser light of 5 kW, so that the cost of the device inevitably increases. In addition, when high-power laser light is used, the heat of the laser light may be transmitted to the outer region and lower region adjacent to the cured part, and the shape and dimensional accuracy of the finished model may not be as designed. is there.

  In view of the above circumstances, it is an object of the present invention to provide a sand additive molding machine that is inexpensive and has improved molding accuracy.

The sand additive molding machine that solves the above object,
A storage part that stores the resin coated sand,
Layer forming means for forming a layer of resin coated sand stored in the storage section,
An irradiation unit that irradiates the layer with laser light for curing the resin,
The layer forming means, when the irradiation of the laser beam to the layer is completed, to form a new resin coated sand layer on the layer,
The storage section stores a resin coated sand in which the surface of the sand particles has an ortho rate of 55% or more and 75% or less and is coated with resin.
It is characterized in that the irradiation unit irradiates the laser light with an output of 10 W or more and 80 W or less.

  Here, the layer is laminated on a base, and the base descends at a predetermined pitch when the irradiation of the laser beam onto the layer is completed. A new layer of resin coated sand may be formed after the platform descends at the predetermined pitch. In addition, an elevating means for elevating the base at a predetermined pitch may be provided. Alternatively, the layers are stacked on a base placed in a frame, and the frame rises at a predetermined pitch when irradiation of the laser light onto the layers is completed. May form a new layer of resin coated sand after the frame rises at the predetermined pitch. In addition, an elevating means for elevating and lowering the frame at a predetermined pitch may be provided.

  Further, the layer is laminated on a base, and the layer forming means rises at a predetermined pitch when the irradiation of the laser beam onto the layer is completed, and rises at the predetermined pitch. After that, a new layer of resin coated sand may be formed. Further, an elevating means for elevating the layer forming means at a predetermined pitch may be provided.

  Further, the resin coated sand stored in the storage portion may be provided on the base, and the layer forming means may supply the resin coated sand stored in the storage portion. The layer may be formed on the base while being supplied onto the base.

  According to the sand laminating machine, the sand particles whose surface is coated with a resin having an ortho ratio showing an ortho-bonding ratio of 55% or more and 75% or less (hereinafter referred to as high ortho resin) are used. With a general resin that emphasizes strength, it is possible to obtain extremely high strength only by heating it up to around 250 ° C, but with high ortho resin, curing progresses while heating up to around 150 ° C, and The strength of is secured. The irradiation unit can output only the laser light of 10 W or more and 80 W or less, so that the low cost of the device is realized. Even with such a low output, as described above, the high orthoresin is cured while being heated up to about 150 ° C. and a certain degree of strength is secured, so that the high orthoresin is irradiated with laser light to be cured. The three-dimensional modeled object in which the advanced hardening portion is laminated has at least strength enough to be taken out from the sand laminating machine. Furthermore, by suppressing the output of the laser light to a low output, the heat of the laser light is prevented from being transmitted to the outer region and the lower region adjacent to the cured portion, and the molding accuracy is improved.

Further, in the irradiation section, the laser light output is P [W], the laser scanning speed is v [mm / s], the laser scanning pitch is w [mm], and the stacking pitch in the layer forming means is h [mm]. In such a case, the energy density (E [J / mm ³ ]) is expressed as P / (vwh) [ws / mm ³ ] = E [J / mm ³ ]. In the sand laminating machine, the energy density is preferably 1.3 J / mm ³ or more under the condition that the output (P) of the laser light is 10 W or more and 80 W or less.

  Moreover, the storage part may be such that the sand particles of the resin coated sand stored in the storage part are ceramic artificial sand. That is, the ceramic-based artificial sand may be 100% by mass. Ceramic-based artificial sand has a lower thermal conductivity than commonly used silica sand, and the heat of laser light is less likely to diffuse to the outer and lower layers, further improving molding accuracy. To be

Also, in the above sand laminating machine,
The irradiating unit may irradiate the entire shape with laser light by scanning, and then irradiate the laser light so as to trace the contour of the shape.

Also, in the above sand laminating machine,
The output of the laser light when the irradiation unit irradiates the entire shape with the laser light and the output of the laser light when tracing the contour of the shape may be the same output.

  Further, the irradiating unit may irradiate the laser light by lowering the output of the laser light when tracing the contour of the shape than the output of the laser light when irradiating the entire shape with the laser light. It may be a feature.

Also, in the above sand laminating machine,
The irradiation unit irradiates the entire desired shape with laser light by scanning, and then irradiates the laser light so as to trace the outermost peripheral edge that is in contact with the contour of the shape and outside the contour. It may be characterized.

Also, in the above sand laminating machine,
The irradiation unit irradiates a laser beam over a plurality of stacked resin-coated sand layers to cure a plurality of support portions that become thinner toward the upper portion at dispersed positions, and then, onto the plurality of support portions. A mode may be characterized in that the product portion connected to each of the plurality of supporting portions is cured by irradiating the laminated resin coated sand layers with laser light.

  The term "dispersion" as used herein means that the product portion is supported at a plurality of points so as not to bend.

  According to the above aspect, the deformation of the product portion can be suppressed. Further, when the product part is taken out from the sand laminating machine, the support part is thinner toward the upper part, so that the product part is easily broken at the boundary, and the product part is easily taken out. be able to.

  When the support portion is solid, the diameter of the upper end surface may be 2 mm or more and 7 mm or less. If it is less than 2 mm, it becomes difficult to support the product part, and the product part may be deformed. On the other hand, if the finishing area of the product portion after folding near the boundary between the product portion and the support portion (near the upper end surface) exceeds 7 mm, not only the work becomes difficult but also the finishing work. There is a risk that the dimensional accuracy will be changed. The supporting part may be hollow, and in this case, the thickness which is the difference between the outer diameter and the inner diameter is 0.5 mm or more and 3.5 mm or less, and the outer diameter of the upper end is the lower limit. The value is 2 mm as in the case of a solid one, whereas the upper limit value exceeds 20 mm and becomes 20 mm.

Also, in the above sand laminating machine,
The resin coated sand stored in the storage section is supplied, and a storage section for temporarily storing the resin coated sand in a lump form is provided,
The layer forming means may be characterized by scraping a lump of resin coated sand temporarily stored in the storage portion into a layer to form a layer of the resin coated sand.

  By doing so, a layer having a uniform structure and a uniform thickness can be formed.

  It should be noted that the base may be provided on which the layers are laminated, and the storage unit may be provided on the base, or may be provided on the upstream side of the base. The layer forming means may scrape and spread a lump of resin coated sand temporarily stored in the storage section on the base.

  According to the present invention, it is possible to provide a sand additive molding machine that is inexpensive and has improved molding accuracy.

It is a sectional view of a sand layered modeling machine which is one embodiment of the present invention. It is sectional drawing which shows a mode that the laser beam is irradiated in the sand laminating machine shown in FIG. It is a figure which shows typically the mode that the laser beam was irradiated to the resin coated sand. It is a figure which shows an example of the relationship between the cross-sectional pattern on a computer, and an actual irradiation area. It is a figure which shows another example of the relationship between the cross-sectional pattern on a computer, and an actual irradiation area. It is a figure which shows an example of the molded article shape | molded by the sand laminating machine of this embodiment.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a cross-sectional view of a sand additive molding machine that is an embodiment of the present invention.

  The sand laminating machine 1 shown in FIG. 1 has a modeling frame 10, a leveling member 20, and a supply device 30. The modeling frame 10 is a rectangular frame member, and a laminated plate 11 and a lifting mechanism 12 are provided inside. The laminated plate 11 is moved up and down by the lifting mechanism 12. A value of the descending pitch can be set in the elevating mechanism 12, and the laminated plate 11 descends stepwise for each descending pitch set in the elevating mechanism 12. In the present embodiment, the descent pitch can be set in the range of 0.1 mm or more and 0.7 mm or less, but it can be set to a length greater than 1 time and less than 3 times the particle size of the resin coated sand described later. preferable. The initial state of the laminated plate 11 is a state in which the height position of the surface 11a of the laminated plate 11 matches the height position of the upper edge 10t of the shaping frame 10. Flange portions 101 and 102 are provided on one end side (the left side in FIG. 1) of the molding frame 10 and the other end side (the right side in FIG. 1) on the opposite side, respectively, and above the flange portion 101 on the one end side. The supply device 30 is arranged.

  The leveling member 20 is a blade extending in the width direction of the modeling frame 10 (direction perpendicular to the paper surface in FIG. 1), and the initial position is a position on the flange portion 101 on one end side of the modeling frame 10. Become. The leveling member 20 travels from one end side where the supply device 30 is arranged to the other end side on the opposite side with the position of the lower end 20b aligned with the height position of the upper edge 10t of the shaping frame 10 (FIG. 1). (Refer to the outline arrow shown in (b)).

  The supply device 30 stores the resin coated sand rs, and supplies a fixed amount of the resin coated sand rs from the supply port 301 onto the flange portion 101 on one end side of the molding frame 10. The supply port 301 is a slit-shaped opening extending in the width direction of the modeling frame 10 (direction perpendicular to the paper surface in FIG. 1), and the flange portion 101 on the one end side extends across the width direction of the modeling frame 10. A lump of resin coated sand rs is temporarily stored. The supply device 30 corresponds to an example of a storage section, and the flange portion 101 on the one end side corresponds to an example of a storage section.

  The resin coated sand rs housed in the supply device 30 is obtained by coating the surface of ceramic artificial spherical sand with a resin having an ortho rate of 55% or more and 75% or less.

The ceramic system as used herein refers to one having a mullite crystal structure or one containing one or more of alumina, kaolin, silica and the like as a main component. The artificial spherical sand is produced by a sintering method or a melting method, has a high sphericity, and has a maximum particle size distribution peak in the range of 0.05 mm or more and 0.45 mm or less. It is more preferable that the diameter falls within the range of 0.25 mm or less. The sphericity is determined based on the value obtained from the formula (perimeter of sand particle) ² ÷ (4π × projected area of sand particle) as a value representing the degree of unevenness. If the value indicating the degree of unevenness is 1, it is a perfect circle, and the larger the value, the greater the degree of unevenness. The artificial spherical sand has a value representing the degree of unevenness of 1.15 or less. When the value representing the degree of unevenness is 1.15 or less, the filling rate of the resin coated sand rs is increased, the contact area between the resin coated sands rs is widened, and the bonding strength is strengthened. As the sand, silica sand, or natural sand such as zircon sand or chromite sand may be blended, but since the thermal conductivity of ceramic artificial sand is lower than that of natural sand, the heat of laser light In order to suppress unnecessary diffusion, it is preferable to use only ceramic-based artificial sand. However, when setting the output of the laser light as low as possible, intentionally mix a large amount of natural sand (for example, silica sand) having a high thermal conductivity (for example, 50% or more) to efficiently transfer a small amount of heat energy. May be prioritized.

  The resin in the present embodiment is a high ortho novolac type phenol resin, and when reacting phenol and formaldehyde, phenol is added to formaldehyde in excess and a divalent metal salt is used as a catalyst, whereby phenol is methylene at the ortho position. A thermosetting resin represented by the following formula (1) bonded by

  The high ortho novolac type phenol resin has a pH of 4 or more and 5 or less, an ortho rate of 55% or more and 75% or less, has a large number of para positions, and has a property of rapid curing.

  The laminated plate 11 shown in FIG. 1A is in a state of being lowered by one step, and the laminated space sp having a thickness of the above-described descending pitch is higher than the height position of the upper edge 10t of the shaping frame 10 (FIG. 1A). (See) is provided. The resin coated sand rs supplied onto the flange portion 101 is leveled by the leveling member 20 that travels toward the other end side, and the laminated space sp is filled with the resin coated sand rs from one end side. That is, the leveling member 20 scrapes the mass of the resin coated sand rs temporarily stored in the flange portion 101 on the one end side in the width direction of the modeling frame 10 into the stacking space sp in a layered manner, and the stacking space sp contains the resin. A layer of the coated sand rs having a thickness of the descending pitch is formed. The leveling member 20 corresponds to an example of a layer forming means. In FIG. 1, a plurality of layers SL are formed on the surface 11a of the laminated plate 11, and in FIG. 1 (b), more than half of the plurality of layers SL from one end side to the other end side is exceeded. The leveling member 20 has moved up to the point where a new layer is being formed. According to the sand additive molding machine 1 of the present embodiment, it is possible to form the layer SL having a uniform structure and a uniform thickness. Further, the supply port 301 may be worn by the resin coated sand rs, and the opening area may be increased. As the opening area increases, the amount of resin coated sand rs temporarily stored in the flange portion 101 on the one end side increases. However, according to the sand laminate molding machine 1 of the present embodiment, the thickness of the layer SL is determined by the height position of the leveling member 20 that scrapes and spreads the lump of the resin coated sand rs in a layered manner, and thus the resin coated sand to be temporarily stored. Even if the amount of rs increases, the thickness of the layer SL does not increase. Even if the leveling member 20 is worn by the resin coated sand rs, the leveling member 20 can be replaced much more easily than the supply device 30.

  FIG. 2 is a cross-sectional view showing how the sand laminating machine shown in FIG. 1 is radiating laser light. In FIG. 2, the layer SL that has been formed up to more than half as shown in FIG. 1B is formed on the entire surface inside the shaping frame 10 (the entire surface of the laminated plate 11).

  The sand laminating machine 1 also has a laser oscillator 40, a scanner 50, and a control unit 60. The laser oscillator 40 oscillates a semiconductor laser beam, and the output value can be set in the range of 10 W or more and 80 W or less. If it is less than 10 W, the thermal energy supplied from the laser beam is insufficient, the temperature of the resin coated sand does not rise sufficiently, and it becomes difficult to thermally cure, and the cost of the apparatus is reduced by suppressing the temperature to 80 W. Further, it is more preferable to use a laser oscillator whose output value can be set in the range of 25 W or more and 50 W or less. When the output value is 25 W or more, the molding time is shortened, the molding efficiency is improved, and by suppressing the output value to 50 W, the apparatus becomes much lower in price.

  The scanner 50 is provided with a condenser lens 501 that condenses the laser light oscillated by the laser oscillator 40, and a rotating mirror 502 that continuously changes the irradiation angle of the laser light. In FIG. 2, the laser light is shown by a gray arrow line.

  In order to form a molded article having a desired three-dimensional structure with this sand laminating machine 1, first, the molded article to be formed is three-dimensionally expressed on a computer, and the molded article is made parallel to a plurality of layers at the descending pitch. Data representing a cross-sectional pattern for each layer when sliced is created in advance. Then, this data is input to the control unit 60. The control unit 60 causes the laser oscillator 40 to oscillate a laser beam or rotate the rotating mirror 502 based on the input data. That is, the control unit 60 controls the laser oscillator 40 and the rotating mirror 502 so that the portion corresponding to the sectional pattern is irradiated with the laser light and the portion not corresponding to the sectional pattern is not irradiated with the laser light.

  In the region of each layer SL irradiated with the laser beam, the resin of the resin coated sand rs is heated to about 150 ° C. to be melted and undergo a curing reaction, so that the artificial spherical sands of the adjacent resin coated sand rs are bonded to each other. It is bound through the cured resin and becomes a cured part. In FIGS. 1 and 2, the black portion of each layer SL is the cured portion. In FIG. 2, the hardened part is being formed in the uppermost layer SL.

  FIG. 3 is a diagram schematically showing how the resin coated sand is irradiated with laser light. In this example, the diameter of one particle of the resin-coated sand is such that the maximum peak of the particle size distribution is 0.1 mm, and in this FIG. 3, all the resin-coated sand particles are represented by a diameter of 0.1 mm. There is. Further, the descending pitch is 0.2 mm. Therefore, the thickness of one layer of the resin-coated sand layer SL is 0.2 mm, which corresponds to two particles of the resin-coated sand, and one layer has a two-row configuration. In FIG. 3, three layers SL are shown. ing. Hereinafter, when distinguishing these three layers, they are referred to as a lower layer SL1, an intermediate layer SL2, and an upper layer SL3. In the uncured resin coated sand rsp, the artificial spherical sand cs and the high ortho novolac type phenol resin hof covering the surface thereof are shown separately. On the other hand, the cured resin coated sand obtained by melting and hardening the high ortho novolac type phenolic resin hof is not distinguished, and is denoted by the symbol rsh.

  FIG. 3A is a diagram schematically showing a state in which the layer SL of the resin coated sand is irradiated with the laser beam B5k of 5 kW.

  Since the laser beam B5k of 5 kW has a high output, it passes through the upper layer SL3 and reaches the intermediate layer SL2 below it. Further, since the thermal energy supplied from the laser beam B5k of 5 kW is large, the cured resin coated sand rsh is widely spread. Further, in FIG. 3A, even a part of the uncured resin coated sand constituting the middle layer SL2, which has been cured by the previous laser light irradiation, has been cured by the laser light B5k irradiated on the upper layer SL3. It has become resin coated sand rsh.

  FIG. 3B is a diagram schematically showing an example of the present embodiment, in which the layer SL of the resin coated sand rs is irradiated with the laser beam B25 of 25 W.

  Since the laser beam B25 of 25 W has a relatively low output, it stops in the upper layer SL3 and does not reach the intermediate layer SL2 below it. That is, the laser beam B25 is irradiated up to the upper row forming the upper layer SL3 shown in FIG. More specifically, not all of the upper row of resin-coated sand that constitutes the upper layer SL3 is irradiated, but about 5/6 from the top. In addition, since the thermal energy supplied from the 25 W laser light B25 is relatively small, the cured resin coated sand rsh does not greatly spread in the lateral direction as shown in FIG. It stays in SL3. That is, as described above, the laser beam B25 is irradiated only up to about 5/6 from above the resin coated sand in the upper row constituting the upper layer SL3, but due to heat conduction, the laser beam B25 in the lower row constituting the upper layer SL3 is irradiated. The resin coated sand rsh has been cured to the resin coated sand. It should be noted that the resin coated sand forming the middle layer SL2 is not the cured resin coated sand rsh. Therefore, in the example of the present embodiment shown in FIG. 3B, the shape and dimensional accuracy of the finished modeled product are as designed, and high molding accuracy is guaranteed.

The cured resin coated sand rsh shown in FIG. 3 (b) is heated to about 150 ° C., and as a result, melts and undergoes a curing reaction, and a bending strength of about 300 N / cm ² is secured.

  FIG. 4 is a diagram showing an example of the relationship between the cross-sectional pattern on the computer and the actual irradiation area.

  In FIG. 4, the actual irradiation region is viewed from directly above, and the rectangle of the two-dot chain line in the drawing represents the outer edge (outline) of the cross-sectional pattern on the computer. As shown in FIG. 4A, the rectangular cross-section pattern includes a left side edge p1, a right side edge p2, a front side edge p3, and a back side edge p4. Further, the X direction shown in FIG. 4A is the left-right direction in FIGS. 1 and 2, and the Y direction is the width direction of the modeling frame 10 (direction perpendicular to the paper surface in FIGS. 1 and 2). Become.

  Further, in FIG. 4, the irradiated area is shown in black. Here, the laser spot diameter of this embodiment is 0.1 mm in diameter, and the laser scanning pitch, which is the interval in the X direction with respect to the scanning in the Y direction, is 0.15 mm. For this reason, the laser irradiation areas in the adjacent scanning lines in the Y direction do not overlap with each other, and a gap of 0.5 mm is generated. Strictly speaking, it is represented by white in FIG. It is omitted in the drawing and is shown in black.

  FIG. 4B is a diagram showing a state in which a little time has passed after the start of scanning, the scanning in the X direction has been completed 5 times, and the scanning in the Y direction is being performed for the sixth time. In the first scanning in the Y direction, the right side edge p2 of the sectional pattern on the computer is scanned from the front side edge p3 to the rear side edge p4 of the sectional pattern.

  FIG. 4C is a diagram showing a state in which the scanning in the X direction is all completed and the final scanning in the Y direction is being performed, and FIG. 4D is the final scanning in the Y direction. It is a figure which shows a mode. In the final scanning in the Y direction, the left side edge p1 of the sectional pattern on the computer is scanned from the front side edge p3 to the rear side edge p4 of the sectional pattern. As shown in FIG. 4D, in this example, laser light is emitted over the entire area of the cross-sectional pattern on the computer.

  Then, the outer peripheral edge (contour) of the sectional pattern on the computer is irradiated again with laser light. That is, the laser light is irradiated so as to trace the contour of the cross-sectional pattern. In FIG. 4E and FIG. 4F, the laser light applied to the outer peripheral edges (p1 to p4) of the cross-sectional pattern is shown in gray. The example shown in FIG. 4 (e) is an example in which the output of the laser light that is irradiated again to the outer peripheral edge of the cross-section pattern is the same as the output of the laser light when it is irradiated over the entire cross-section pattern (for example, 50 W). is there. In the example shown in FIG. 4 (e), the outer surface of the modeled object is more firmly bound and the surface stability is improved, as compared with the example shown in FIG. 4 (d). On the other hand, in the example shown in FIG. 4F, the output of the laser light that is irradiated again to the outer peripheral edge of the cross-sectional pattern is weaker than the output of the laser light when it is irradiated over the entire area of the cross-sectional pattern (for example, 30 W). This is an example of dropping. The gray line showing the irradiated laser light is shown thinner if the output of the laser light is weak, and the gray line in FIG. 4 (f) is shown thinner than the gray line in FIG. 4 (e). There is. In the example shown in FIG. 4 (f), the surface stability may be slightly inferior to the example shown in FIG. 4 (e), but the molding accuracy is maintained at a high level. That is, in the example shown in FIG. 4E, when the thermal energy from the previous irradiation remains in the resin coated sand, the same amount of thermal energy as the previous irradiation is added by the re-irradiation, and the cured resin While the area of the coated sand may expand compared to the state shown in FIG. 4D, in the example shown in FIG. 4F, the thermal energy due to re-irradiation is reduced by lowering the output of the laser light. Can be expected to balance the surface stability and the molding precision at a high level.

  FIG. 5 is a diagram showing another example of the relationship between the cross-sectional pattern on the computer and the actual irradiation area. Hereinafter, differences from the example shown in FIG. 4 will be mainly described.

  Similar to FIG. 4, this FIG. 5 is also a view of the actual irradiation area as viewed from directly above, and the two-dot chain line rectangle in the drawing represents the outer edge (outline) of the cross-sectional pattern on the computer. . Also in FIG. 5, the irradiated area is shown in black. In FIG. 5 as well, similarly to FIG. 4, the space between the irradiation regions in the scanning lines in the Y direction is strictly represented by white, but is omitted from the drawing and represented by black.

  Similar to FIG. 4A, FIG. 5A is a stage in which a little time has passed after the start of scanning, the scanning in the X direction is completed five times, and the sixth scanning in the Y direction is performed. It is a figure which shows a mode. In the example shown in FIG. 5A, in the first scanning in the Y direction, one scan is left inward in the X direction from the right side edge p2 of the sectional pattern on the computer, and the front side edge p3 of the sectional pattern is moved in the Y direction. Scanning is performed in the Y direction from a position vacant inward by the laser spot diameter to a position vacant inward in the Y direction from the inner side edge p4 of the cross-sectional pattern.

  FIG. 5B is a diagram showing a state in which all the scans in the X direction are completed, one scan is left inward in the X direction from the left side edge p1 of the sectional pattern on the computer, and the last scan is performed in the Y direction. FIG. 5C is a diagram showing a state in which the final scanning in the Y direction is completed. In the final scanning in the Y direction, one scan is left inward in the X direction from the left edge p1 of the cross-sectional pattern on the computer, and a section is opened from the front side edge p3 of the cross-sectional pattern inward in the Y direction by the laser spot diameter. Scanning is also performed in the Y direction from the back side edge p4 of the pattern to a position spaced inward in the Y direction by the laser spot diameter. As shown in FIG. 5C, in this example, the laser beam is applied to a region slightly smaller than the sectional pattern on the computer. That is, thereafter, as shown in FIG. 5D, since the outer peripheral edge of the cross-sectional pattern on the computer is scanned once, the laser light is applied to the entire inner region with one cycle left. In FIG. 5D, the outer peripheral edge (outline) of the sectional pattern on the computer is irradiated with laser light. That is, the laser light is irradiated so as to trace the contour of the cross-sectional pattern. In other words, after irradiating the entire desired shape (here, the entire rectangular area that is one size smaller than the cross-sectional pattern on the computer) with laser light, the outermost portion outside the contour that touches the contour of the shape Laser light is irradiated so as to trace the peripheral edge (here, the outer peripheral edge of the cross-sectional pattern). Also in FIG. 5D, the laser light applied to the outer peripheral edges (p1 to p4) of the cross-sectional pattern is shown in gray. In the example shown in FIG. 5D, the output of the laser light applied to the outer peripheral edge of the cross-section pattern is the same as the output of the laser light when the area slightly smaller than the cross-section pattern is irradiated (for example, 50 W). It is an example. However, by slightly increasing the size of the area smaller than the cross-sectional pattern, the output of the laser light with which the outer peripheral edge of the cross-sectional pattern is irradiated can be set low (for example, 30 W). In the example shown in FIG. 5 described above, the scanning in the Y direction is repeated along the X direction to irradiate a region smaller than the cross-sectional pattern on the computer with laser light, and then contact the contour of the region. This is an example of irradiating the laser light to the outermost peripheral edge outside the contour to irradiate the entire area of the sectional pattern on the computer with the laser light.

  FIG. 6 is a diagram showing an example of a modeled object molded by the sand laminating machine of this embodiment.

  The modeled object shown in FIG. 6 is a hollow core C supported by a plurality of support portions F provided upright from the base plate B. 1 and 2 show a state in which the modeled object shown in FIG. 6 is being modeled. The hollow core C corresponds to the product part. The base plate B is formed on the surface 11a of the laminated plate 11 and has an area larger than the projected area of the hollow core C. The support portions F are dispersedly arranged on the base plate B, and become thinner toward the top, and the upper end surface is connected to the hollow core C. That is, the support portion F connects the base plate B and the hollow core C. The base plate B is prevented from warping due to its area and thickness, and the supporting portion F supports the hollow core C at a plurality of points so that the hollow core C does not warp or distort. According to the sand laminating machine 1 of the present embodiment, after curing the plurality of supporting portions F at dispersed positions, the laser is spread over the plurality of resin coated sand layers SL laminated on the plurality of supporting portions F. By irradiating with light, the hollow core C connected to each of the plurality of supporting portions F is cured.

  When the hollow core C is taken out of the sand additive molding machine 1, the supporting part F becomes thinner toward the upper part, so that the hollow core C easily breaks at the boundary between the supporting part F and the hollow core C. It can be taken out easily. The support portion F has an upper end surface having a diameter of 2 mm or more and 15 mm or less. If it is less than 2 mm, it becomes difficult to support the hollow core C, and the hollow core C may be deformed. On the other hand, if the finishing area of the hollow core C after folding near the boundary between the hollow core C and the supporting portion F (near the upper end surface) exceeds 15 mm, not only the work becomes too large but also the finishing is difficult. There is a risk that the dimensional accuracy will change due to the work.

  As described above, according to the sand laminate molding machine 1 of the present embodiment, by making it possible to output only a low output laser beam, a low price of the device is realized. Even if the output is low, the high ortho novolac type phenolic resin is cured while being heated up to about 150 ° C. and a certain degree of strength is ensured. Therefore, the cured portion irradiated with laser light and cured is advanced. The hollow core C in which the is laminated has at least a strength that can be taken out from the sand laminating machine 1.

  The hollow core C taken out from the sand additive molding machine 1 is subjected to secondary firing after finishing the root portion of the support portion F. In this secondary firing, the hollow core C is heated while being filled with particles. For example, it is heated in a microwave oven at 250 ° C. for about 6 hours. The particles filled in the secondary firing are for preventing the deformation of the hollow core C, that is, a shape maintaining member, and the surface of which is not covered with a range, for example, glass beads, graphite particles, or alumina particles. And silica particles are used.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, when the irradiation of the laser beam to the layer SL of the resin coated sand formed (laminated) on the laminated plate 11 is completed, the laminated plate 11 is raised at a predetermined pitch, and the leveling member 20 is A new resin-coated sand layer SL may be formed (laminated) on the laminated plate 11 after the laminated plate 11 has risen at a predetermined pitch.

  Further, the mode in which the leveling member 20 moves up and down instead of the leveling up and down of the laminated plate 11 may be adopted, or the mode in which the lifting and lowering of the layered plate 11 and the leveling member 20 are combined may be adopted.

  Further, the leveling member 20 also serves as a supply means for supplying the resin coated sand rs stored in the supply device 30 or the resin coated sand rs temporarily stored in the flange portion 101 on the one end side onto the laminated plate 11. However, the supply device 30 may supply the resin coated sand rs onto the laminated plate 11 while moving from the one end side to the other end side like the leveling member 20.

  Further, instead of temporarily storing the mass of the resin coated sand rs on the flange portion 101 on the one end side, it may be temporarily stored on the laminated plate 11 and spread by the leveling member 20 as in the present embodiment. .

  Next, the present invention will be described more specifically by way of examples, but the present invention is not limited to the examples described below. In each of the examples and comparative examples, a hollow core having the shape shown in FIG. 6 was formed as a formed object.

(Example 1)
Cera beads (registered trademark) # 1450 manufactured by ITOCHU CERATECH CORPORATION was used as the artificial spherical sand. The particle size distribution has a single peak, and the maximum peak is 0.106 mm.

As the resin, a fast curing type high ortho novolac type phenol resin (ortho ratio of 55% or more and 75% or less) was used. The ortho rate can be calculated by the following formula by measuring the absorbance by the KBr method using an infrared spectrophotometer.
Ortho rate (%) = D760 ÷ (D760 + 1.44 × D820) × 100
In this case, it refers to the absorbance at 760cm ^-1 and D760, refers to the absorbance at 820cm ^-1 and D820.

  The descending pitch (stacking pitch) was 0.30 mm. The laser output was 25 W, the laser spot diameter was 0.1 mm, the laser scanning speed was 300 mm / sec, and the laser scanning pitch was 0.15 mm. The laser scanning pitch is an interval in the X direction with respect to the scanning in the Y direction shown in FIGS. 4 and 5, and in the first embodiment, since the laser spot diameter is 0.1 mm, the adjacent scanning lines in the Y direction. The laser irradiation areas in 2 do not overlap with each other, and a gap of 0.5 mm is generated.

When the output of laser light is P [W], the laser scanning speed is v [mm / s], the laser scanning pitch is w [mm], and the stacking pitch is h [mm], P / (vwh) [ws / ^mm 3] = E [when obtaining the J / mm ^3] as the energy density ^{(E [J / mm 3]} ), in the case of example 1, the energy density becomes 1.85J / mm ^3.

The bending strength of the core in Example 1 before the secondary firing was 300 N / cm ² .

  Table 1 shows each condition, energy density, and bending strength.

Table 1 also shows each condition, the energy density, and the bending strength of each of Examples 2 and 3 and Comparative Examples.

(Example 2)
The same conditions as in Example 1 were used except that the laser output was set to 30 W. The energy density of this Example 2 is 2.22 J / mm ³ . The bending strength of the core in Example 2 before the secondary firing was 639 N / cm ² .

(Example 3)
The conditions were the same as in Example 1 except that the laser output was 50 W and the laser scanning speed was 500 mm / sec. The energy density of this Example 3 is 2.22 J / mm ³ . The bending strength of the core in Example 3 before the secondary firing was 684 N / cm ² .

(Example 4)
The conditions were the same as in Example 3 except that the laser scanning speed was 750 mm / sec. The energy density of this Example 4 is 1.48 J / mm ³ . The bending strength of the core in Example 4 before the secondary firing was 234 N / cm ² .

(Example 5)
The conditions were the same as in Example 3 except that the descending pitch (stacking pitch) was 0.35 mm. The energy density of this Example 5 is 1.90 J / mm ³ . The bending strength of the core in Example 5 before the secondary firing was 720 N / cm ² .

(Example 6)
The same conditions as in Example 3 were used except that the stacking pitch was 0.40 mm. The energy density of this Example 6 is 1.67 J / mm ³ . The bending strength of the core in Example 6 before the secondary firing was 700 N / cm ² .

(Example 7)
The conditions were the same as in Example 3 except that the stacking pitch was 0.45 mm. The energy density of this Example 7 is 1.48 J / mm ³ . The bending strength of the core in Example 7 before the secondary firing was 733 N / cm ² .

(Example 8)
The same conditions as in Example 3 were used except that the stacking pitch was 0.50 mm. The energy density of this Example 8 is 1.33 J / mm ³ . The bending strength of the core in Example 8 before the secondary firing was 597 N / cm ² .

(Example 9)
The conditions were the same as in Example 3 except that the laser scanning pitch was 0.16 mm. The energy density of this Example 9 is 2.08 J / mm ³ . The bending strength of the core in Example 9 before the secondary firing was 642 N / cm ² .

(Example 10)
The conditions were the same as in Example 3 except that the laser scanning pitch was 0.17 mm. The energy density of this Example 10 is 1.96 J / mm ³ . The bending strength of the core in Example 10 before the secondary firing was 728 N / cm ² .

(Example 11)
The conditions were the same as in Example 3 except that the laser scanning pitch was 0.18 mm. The energy density of this Example 11 is 1.85 J / mm ³ . The bending strength of the core in Example 11 before the secondary firing was 609 N / cm ² .

(Example 12)
The conditions were the same as in Example 3 except that the laser scanning pitch was 0.19 mm. The energy density of this Example 12 is 1.75 J / mm ³ . The bending strength of the core in Example 12 before the secondary firing was 600 N / cm ² .

(Example 13)
The conditions were the same as in Example 3 except that the laser scanning pitch was 0.20 mm. The energy density of this Example 13 is 1.67 J / mm ³ . The bending strength of the core in Example 13 before the secondary firing was 374 N / cm ² .

(Comparative example)
The same conditions as in Example 1 were used except that a random novolac type phenolic resin was used as the resin for coating the surface of the artificial spherical sand. The random novolac type phenolic resin has an ortho rate of 40% or more and 50% or less and a pH of 1 or less.

In the comparative example, the core was broken when the core (product part) was taken out from the sand additive molding machine. When the bending strength was measured using the broken pieces of the core, it was only 83 N / cm ² .

In Example 4 as well, when the core (product part) was taken out from the sand additive molding machine, it could be taken out without breaking it, but the core was about to break. On the other hand, in Example 1, the core (product part) could be taken out from the sand laminating machine without any problem. From these results, when the product part before the secondary firing is taken out from the sand laminating machine, the bending strength is 250 N / cm ² or more in order to maintain the shape of the product part without losing its shape. And guess that it is safe.

  The core in each of the examples taken out from the sand laminating machine did not have the supporting portion shown in FIG. 6, and the supporting portion remained inside the molding frame while being buried in the resin coated sand.

  The core in each example taken out from the sand laminating machine was subjected to secondary firing after finishing the root of the supporting portion. In the secondary firing, the core was filled with glass beads and heated in a microwave oven at 250 ° C. for 6 hours. The broken pieces of the core in the comparative example were also heated in the microwave oven at 250 ° C. for 6 hours.

The bending strength of the core after the secondary firing in each example was 1000 N / cm ² or more and 1500 N / cm ² or less, and the bending strength was significantly improved compared to before the secondary firing. On the other hand, the bending strength of the shards after the secondary firing in the comparative example was 1750 N / cm ² , and the bending strength was dramatically improved as compared with the respective examples before the secondary firing.

  The bending strength of the core after the secondary firing in each example is equal to or higher than the bending strength of the commonly used shell core, and it was confirmed that the core can be used in place of the shell core. .

Further, it has been found that the bending strength that allows the core to function without breaking in actual casting is 600 N / cm ² . In the conventional shell core, it can be said that it is over-spec, but considering the disintegration property of the core after casting, the bending strength does not need to be 1750 N / cm ² , and Examples 2, 3, 5 to 7, 9 In Nos. 12 to 12, the core as taken out from the sand laminating machine can be used for casting without performing secondary firing.

Furthermore, in Examples 1 to 13, it can be seen that the energy density is 1.3 J / mm ³ or more. Further, comparing Example 2 and Example 3, the energy densities are the same, and the bending strengths of both are over 600 N / cm ² . As for the molding conditions of the core, since the molding time becomes shorter as the laser scanning speed becomes faster, it can be said that the working example 3 is more preferable than the working example 2. Moreover, the bending strength value of Example 3 is higher than that of Example 2.

Regarding the stacking pitch, the laser output was made uniform to 50 W, the stacking pitch was 0.30 mm in Example 3, 0.35 mm in Example 5, 0.40 mm in Example 6, and 0.45 mm in Example 7. In each case, the bending strength far exceeds 600 N / cm ² , but in Example 8 in which the stacking pitch is expanded to 0.50 mm, the bending strength is less than 600 N / cm ² . Since the maximum peak in the particle size distribution of the artificial spherical sand is 0.106 mm, the layer pitch, that is, the thickness of one layer of the resin coated sand is 2-3 times the maximum peak, which is 2 to 3 times in Example 3. It can be said that it is about 3 times in Example 5, about 3 to 4 times in Example 6, about 4 times in Example 7, and 4 to 5 times in Example 8. When the laser output is 50 W, the lamination pitch (thickness of one layer of resin coated sand) is preferably less than 5 times the maximum peak in the particle size distribution of the sand particles used. When it is 5 times or more, the thermal energy supplied from the laser beam is insufficient, the temperature of the lower resin coated sand in one layer of the resin coated sand does not rise sufficiently, and it becomes difficult to thermally cure, Bending strength decreases. As a result of investigating the case where the laser output is 25 W, the stacking pitch (thickness of one layer of the resin coated sand) is less than 3 times the maximum peak in the particle size distribution of the sand particles used in this case. Was found to be preferable. In summary, the lamination pitch is preferably set to a length that is larger than 1 time and smaller than 3 times the particle size of the resin coated sand. When it is 1 time, the heating efficiency is poor, the number of laminations increases, and the modeling time is prolonged. On the other hand, when the amount is 3 times, the heat of the laser beam is not completely transmitted to the bottom, and insufficient curing or insufficient binding may be a problem.

As for the laser scanning pitch, the laser output was set to 50 W, the laser scanning pitch was 0.16 mm in Example 9, 0.17 mm in Example 10, 0.18 mm in Example 11, and 0.19 mm. In each of Example 12, the bending strength is 600 N / cm ² or more, but in Example 13 in which the laser scanning pitch is expanded to 0.20 mm, the bending strength is far below 600 N / cm ² . Since the diameter of the laser spot is 0.1 mm, in Example 13 in which the laser scanning pitch is expanded to 0.20 mm, a gap of 0.1 mm is provided between the laser irradiation areas in the adjacent scanning lines in the Y direction. It's happening. Here, since the maximum peak in the particle size distribution of the artificial spherical sand is 0.106 mm, the interval between the laser irradiation regions on the adjacent scanning lines is about the particle size of the sand particles or less when the laser output is 50 W. It would be preferable to have. In addition, as a result of investigating the case where the laser output is 25 W, it is found that the interval between the laser irradiation regions on the adjacent scanning lines is preferably about 1/2 or less of the particle diameter of the sand particles in this case. It was In addition, regardless of whether the laser output is 50 W or 25 W, if the laser irradiation areas in adjacent scanning lines overlap, thermal energy becomes too large in the overlapped portion. Preferably not.

1 Sand Laminating Machine 10 Forming Frame 11 Laminating Plate 12 Elevating Mechanism 20 Leveling Member 30 Feeding Device 40 Laser Oscillator 50 Scanner 60 Control Unit cs Artificial Spherical Sand hof High Orthonovolak Phenolic Resin rs Resin Coated Sand sp Laminating Space SL Layer B Base plate C Hollow core F Support

Claims (7)

A storage part that stores the resin coated sand,
Layer forming means for forming a layer of resin coated sand stored in the storage section,
An irradiation unit that irradiates the layer with laser light for curing the resin,
The layer forming means, when the irradiation of the laser beam to the layer is completed, to form a new resin coated sand layer on the layer,
The storage section stores a resin coated sand in which the surface of the sand particles has an ortho rate of 55% or more and 75% or less and is coated with resin.
A sand additive molding machine, wherein the irradiation unit irradiates a laser beam with an output of 10 W or more and 80 W or less.   2. The sand laminate molding according to claim 1, wherein the irradiation unit irradiates the entire shape with laser light by scanning and then irradiates the laser light so as to trace the contour of the shape. Machine.   3. The sand according to claim 2, wherein the output of the laser light when the irradiation unit irradiates the entire shape with laser light and the output of the laser light when tracing the contour of the shape are the same. Additive modeling machine.   The irradiation unit lowers the output of the laser light when tracing the contour of the shape below the output of the laser light when irradiating the entire shape with the laser light, and irradiates the laser light. The sand laminate molding machine according to claim 2.   The irradiation unit irradiates the entire desired shape with laser light by scanning, and then irradiates the laser light so as to trace the outermost peripheral edge that is in contact with the contour of the shape and outside the contour. The sand additive molding machine according to claim 1, wherein   The irradiation unit irradiates a laser beam over a plurality of stacked resin-coated sand layers to cure a plurality of support portions that become thinner toward the upper portion at dispersed positions, and then, onto the plurality of support portions. 6. The product portion connected to each of the plurality of supporting portions is cured by irradiating the laminated resin coated sand layers with laser light. A sand additive molding machine according to item 1. The resin coated sand stored in the storage section is supplied, and a storage section for temporarily storing the resin coated sand in a lump form is provided,
7. The layer forming means scrapes and spreads a lump of resin coated sand temporarily stored in the storage portion into a layer to form a layer of the resin coated sand. The sand additive molding machine according to item 1.