JP2010255057A - Apparatus for forming shaped article with electron beam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for forming a shaped article with an electron beam, which can form the shaped article having a smoother surface than that of a conventional one even when a metal powder having a large particle size is used. <P>SOLUTION: This forming apparatus forms the shaped article by the steps of: melting the metal powder (primary melting); subsequently elevating a base plate by just H1 with an elevator so that the top surface of a melt 14 is positioned at a focusing point 61; and remelting the melt (secondary melting) on the base plate by scanning the melt with the electron beam. Thereby, the forming apparatus can perform secondary-melting of the melt with the electron beam which has the same focusing diameter as in the first melting, without adjusting the focus point of the electron beam, and accordingly can form the shaped article having the smoother surface than that of the conventional one even when the metal powder having the large particle size is used. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is based on data obtained by slicing three-dimensional CAD data to a certain thickness (pitch), and irradiates and melts an electron beam on metal powder, and repeats this to melt the powder and form a shaped article having a desired shape. The present invention relates to an electron beam modeling technique that can reduce the unevenness of the surface of a modeled object in an electron beam modeling apparatus.

  The 3D modeling method is a rapid molding method called rapid prototyping, which is a method for rapidly producing parts using polymers without using molds or cutting. The stereolithography method, which is a method of layering three-dimensional CAD data and repeating molding for each layer using an ultraviolet laser, visible light laser, or near-infrared light flash lamp, using a curing resin, is the beginning.

  After that, a powder lamination method was developed in which plastic was sintered with a laser instead of a photo-curing resin. As an application of this method, it became possible to manufacture inorganic materials and metal parts by coating resin on foundry sand and metal powder and melting and sintering, but the mechanical strength is obtained by metal processing. Compared with weakness, the range of use is limited.

  In order to solve this problem, a metal modeling method has been developed in which a metal is melted with a laser and three-dimensional modeling is performed. This makes it possible to perform molding in the atmosphere by taking advantage of the advantage of the laser, but has a problem that it is inevitable to mix impurities (oxides).

  The three-dimensional modeling method using an electron beam was developed in this background, preventing contamination by impurities for modeling in vacuum, and the metal characteristics of laminated metal due to its energy efficiency compared to lasers. However, it is close to the characteristics of forged products, has little oxide in the composition, and can form refractory metals or difficult-to-weld metals.

  Non-Patent Document 1 describes the outline of an electron beam shaping apparatus to which this patent is applied. In the text, "This apparatus produces titanium parts based on data designed by 3D CAD. Inside the vacuum chamber. Then, the titanium powder is sprinkled with an average thickness of about 100 microns, and then the part where the electron beam is needed is scanned and the titanium powder irradiated with the electron beam melts into a thin titanium layer. The layers are stacked vertically, and the electron beam has a deep depth of focus, so the titanium layers are completely fused together. ”However, there is no mention of means for smoothing the molten surface. Not.

Tsuneo Akano, “Introduction of new processing equipment for titanium”, Titanium, vol.56, No4 (2008), P49, left column, lines 17 to 24.

  As described above, even in the electron beam modeling technique that is superior among many three-dimensional modeling methods, there is still a need to solve problems in order to make use of the advantages.

  The first problem is that the surface roughness of the product is about the same as the particle size, and is not suitable for applications that require microparts or smoothness. This is because the particle size of the metal powder used in the electron beam modeling apparatus is large, and the unevenness of the surface of the modeled object generated by lowering the elevator on which the modeled object is mounted in a step that matches this particle size, It has the problem of becoming coarser to the particle size of the powder. In order to solve this problem, if the elevator descent step is simply made fine, the melting surface will be higher than the reference level, and there will be a problem that powder supply and reiki operation as the next process can not be done. To do.

  The second problem is to solve the problem by melting the metal powder with the electron beam in the first step and then irradiating the same position as the first step with the electron beam to smooth the molten surface. When the electron beam is irradiated at the same focal position, the focused spot diameter of the electron beam becomes large, and there is a problem that the focused density of the electron beam at that position is lowered and the metal surface cannot be brought to an appropriate temperature.

  The third problem is that the definition of the modeled object is limited to several times the particle size of the metal powder. It is well known that the smaller the particle size of the metal powder, the greater the risk of dust explosion. For this reason, the electron beam modeling apparatus prohibits the use of fine metal powder and uses metal powder having a particle size with a low risk of dust explosion. For this reason, there is a problem that the fineness of the modeled object becomes several hundred microns, which is not suitable for the production of fine parts.

  The present invention has been made based on such a background, and an object of the present invention is to provide an electron beam modeling apparatus capable of producing a modeled object having a smoother surface than that of a conventional metal powder having a large particle size. Is to provide.

  The present invention adopts the following means in order to solve the above problems. Note that the reference numerals used in the description and drawings of the embodiments for carrying out the invention to be described later are added in parentheses for reference, but the constituent elements of the present invention are not limited to those added.

First, an electron beam modeling apparatus according to the present invention is as follows.
A vacuum chamber (7) whose inside is evacuated by a vacuum pump, an electron beam generator (filament 1, grid cup 2, anode 3) for generating an electron beam (6) to be irradiated into the vacuum chamber, A focus coil (4) for focusing the electron beam generated by the electron beam generator, and a deflection coil (5) for deflecting the electron beam focused by the focus coil and scanning it to an arbitrary position And a powder container (9) for storing a metal powder (11) for modeling a modeled object, and a base plate in which the upper surface is exposed in the vacuum chamber and the metal powder is supplied from the powder container to the upper surface. (15), Reiki (10) for scraping and leveling the metal powder supplied on the base plate, and raising and lowering the base plate Including the order of the elevator (8), and,
A descent step of lowering the base plate by the elevator so that the upper surface of the base plate is positioned below the focusing point (61) of the electron beam by the particle size of the metal powder; A supply step of supplying the metal powder on the plate, a scraping step of scraping the metal powder supplied on the base plate with the reiki (FIG. 3 above), and scraping on the base plate A preheating step of preheating the metal powder by scanning the electron beam with the averaged metal powder (FIG. 4), and layered two-dimensional data obtained by slicing the three-dimensional CAD data of the modeled object to a predetermined thickness And scanning the electron beam onto a metal powder preheated on the base plate. It is assumed that the modeling object is modeled by stacking layers of the melted metal powder (14) on the base plate by performing a modeling process of repeating the melting step of melting (FIG. 6) ( FIG. 5).

And the electron beam modeling apparatus according to claim 1
The shaping process includes a step of raising the base plate (only H1) by the elevator so that the upper surface of the melt (14) is positioned at the converging point (61) after the melting step; FIG. 8), a remelting step of scanning the electron beam (6) on the melt on the base plate based on the layered two-dimensional data to melt the melt (referred to as a remelt 141). (FIGS. 8 to 9).

An electron beam modeling apparatus according to claim 2
In the shaping process, after the melting step, the focusing point (61) is positioned on the upper surface of the melt (141) (that is, the focusing point 61 is positioned below the surface of the table 12 by H1). ) An adjustment step for adjusting the electron beam (6), and remelting for melting the melt by scanning the melt on the base plate with the adjusted electron beam based on the two-dimensional layered data And a step (above, FIG. 10).

Furthermore, the electron beam modeling apparatus according to claim 3 is the electron beam modeling apparatus according to claim 2,
After the melting step, the melt on the base plate is scanned with the electron beam to pre-heat the melt, and the pre-heating is observed so that the focused diameter of the electron beam is optimized. An observation step is performed (FIG. 11: spot size and luminance are observed), and the adjustment step is performed based on the observation result.

  According to the electron beam shaping apparatus according to claim 1, after the melting step (primary melting), the base plate is raised by the elevator so that the upper surface of the melt is located at the converging point, and on the base plate. By scanning the melt with an electron beam and remelting the melt (secondary melting), the secondary melting by the electron beam is performed with the same focusing diameter as the primary melting without adjusting the focusing point of the electron beam. Therefore, even if metal powder having a large particle diameter is used, it is possible to produce a shaped article having a smoother surface than before.

  According to the electron beam shaping apparatus according to claim 2, after the melting step (primary melting), the electron beam is adjusted so that the focal point is located on the upper surface of the melt, and the adjustment is performed on the melt on the base plate. The secondary melting by the electron beam is performed with the same focused diameter as the primary melting without raising the base plate by the elevator by scanning the electron beam thus remelted (secondary melting). Therefore, even if metal powder having a large particle size is used, it is possible to produce a shaped article having a smoother surface than before.

  Further, according to the electron beam shaping apparatus according to claim 3, after the primary melting and before the secondary melting, the melt on the base plate is scanned with the electron beam to preheat the melt, and the preheating is performed. In this case, the electron beam is observed so as to have an optimum focusing diameter (for example, spot size and brightness), and based on the observation results, the electrons are positioned so that the focusing point is located on the upper surface of the melt. Since the beam is adjusted, the optimum focusing point of the electron beam can be obtained by adjustment.

FIG. 1 is a diagram showing a configuration of an electron beam modeling apparatus currently used. FIG. 2 is an enlarged schematic view of the vicinity of the table 12 and the elevator 8, and is a view for explaining preheating. FIG. 3 is a view showing a state in which the powder 11 is supplied from the powder container 9 and leveled by the reiki 10. FIG. 4 is a view showing a state in which the powder 14 on the base plate 15 is irradiated with the electron beam 6. FIG. 5 is a view showing that the powder melt 14 is present on the base plate 15 and the powder 11 supplied thereon is in a state of being leveled by the reiki 10. FIG. 6A is a schematic diagram in which the electron beam 6 is scanned on the powder 11, and FIG. 6B is a diagram illustrating a state in which the powder 11 is melted into a melt 141. FIG. 7 is a diagram showing the positional relationship between the focusing point 61 and the melt 14 when the focusing point of the electron beam 6 is not changed when remelting. FIG. 8 is a diagram showing a measure for solving the problem of FIG. FIG. 9 is a diagram showing the relationship between the remelted body 141 having an improved smooth surface and the table 12. FIG. 10 is a view showing an example in which the elevator 14 is not raised when the melt 14 is remelted. FIG. 11 is a graph showing one example for obtaining the focusing point 61 of the electron beam.

  FIG. 1 shows the structure of an electron beam forming apparatus that melts metal powder with an electron beam along with two-dimensional layered data obtained by slicing three-dimensional CAD data, and directly produces a three-dimensional metal model from CAD data. Is. In FIG. 1, when an electric current is passed through the filament 1 of an electron gun installed in a vacuum chamber 7 that is evacuated by a vacuum pump (not shown), an electron beam 6 is generated therefrom and accelerated by the grid cup 2 and the anode 3. Radiated forward (downward in the figure). The electron beam 6 spreads with propagation, and the electron beam 6 is focused forward by the action of an electron lens obtained by passing a current through the focus coil 4. Next, by applying a sawtooth wave current to the deflection coil 5 to deflect the electron beam 6, the electron beam 6 can be irradiated or scanned at an arbitrary position. The vacuum chamber 7 is provided with a powder container 9, a table 12 having an elevator 8, and a rake 10 for leveling metal powder (hereinafter simply referred to as “powder”) 11. The elevator 8 moves by a predetermined amount. The powder container 9 supplies a certain amount of powder 11, and the Reiki 10 levels the powder 11 on the processed surface to be uniform. In this state, the electron beam 6 is focused and scanned on the surface of the powder 11 by the focus coil 4 and the deflection coil 5 to melt the powder 11. This situation is described in detail in FIG.

    The powder 11 used here is made of, for example, titanium and has a particle size of 40 to 100 μm (that is, an average particle size of 70 μm), but the material may be titanium / aluminum / vanadium alloy, cobalt / chromium alloy, etc. The particle size may be 25-80 μm.

  FIG. 2 is an enlarged schematic view of the vicinity of the table 12 and the elevator 8. In the figure, a base plate 15 is placed on the elevator 8, and the temperature of the base plate 15 is increased by preheating the electron beam 6 on the entire surface of the base plate 15 by scanning and irradiation.

  FIG. 3 shows a state in which the powder 8 is supplied from the powder container 9 of FIG.

  FIG. 4 shows a state where the powder 14 on the base plate 15 is irradiated with the electron beam 6. The electron beam 6 is adjusted so that its focusing point 61 is on the upper surface of the powder 14. First, the electron beam 6 is scanned over the entire surface to preheat the powder, and then the necessary portions are melted based on the two-dimensional layered data obtained by slicing the three-dimensional CAD data of the modeled object to a predetermined thickness.

  FIG. 5 shows a state after repeating FIG. 3 and FIG. 4, and there is a molten powder melt 14 corresponding to the number of repetitions on the base plate 15, and the powder supplied thereon 11 is in a state leveled by Reiki 10.

  FIG. 6A is a schematic diagram in which the electron beam 6 is irradiated on the powder 11, and the powder 11 before melting is placed on the melt 14. FIG. 6B shows a state in which the powder 11 is melted to form a melt 14. When the metal melts and becomes liquid, the gap between the powders 11 is filled, and thus the bulk of the melt 14 is reduced.

  In the normal process, after the elevator is lowered by a certain amount in the state of FIG. 6B, the powder 11 is supplied from the powder container 9, the leveling by the rake 10 is obtained, and the state returns to the state of FIG. This repetition is a conventional process. In this process, it is difficult for the roughness of the surface of the melt 14 to completely smooth the irregularities of the particles of the powder 11.

  In the present invention, after the normal process in FIGS. 6 (a) and 6 (b), the melt 14 is irradiated and melted with an electron beam to smooth the surface of the melt 14. FIG. When the electron beam 6 is irradiated on the surface of the melt 14 that is below the distance H1 from the surface of the table 12 as described above, the focusing point 61 of the electron beam 6 is located at a distance approximately H1 higher than the surface of the melt 14 and Since the diameter 62 of the electron beam 6 on the surface 14 is larger than the focusing diameter 61, not only a sufficient melting effect is not obtained, but also the surface irregularities may be increased.

  FIG. 8 is a diagram showing a measure for eliminating the above-described drawbacks, and after the first irradiation and melting process, the elevator 8 is moved up by a distance H1 so that the surface of the melt 14 is aligned with the focusing point 61 of the electron beam 6. After that, the electron beam 6 is irradiated to effectively remelt the melt 14.

FIG. 9 shows the relationship between the remelted body 141 having the improved smooth surface thus obtained and the table 12.
When the thickness of the conventional powder supply layer is D, the thickness d of each layer of the conventional melt is expressed by the following equation. d = D-H1
On the other hand, according to the process of the present invention, it can be seen that the thickness of each layer is d = D− (H1 + H2), which is finer. This indicates that not only the surface of the three-dimensional model but also the side surface becomes smoother.

As shown in FIG. 10, in order to remelt the melt 14, it is also effective as a method for realizing the effect of the present invention to connect the focusing point 61 of the electron beam 6 below the table 12 by a distance H1. In this case, the distance d between the surface of the melt 141 after remelting and the surface of the table 12 is expressed by the following equation. That is, d = H1 + H2
As this method, it is possible to control the current supply to the focus coil 4 so as to obtain a long focusing length H1.
In this case, the descending amount of the elevator 8 for the next layer needs to be reduced by H2.

  FIG. 11 is a graph showing one example for obtaining the electron beam focusing point 61 in FIG. 10 and shows the relationship between the spot size of the electron beam 6 and the temperature of the melting point by electron beam irradiation. The temperature of the melting point is observed with a commercially available infrared thermography. Here, the relative luminance of the melting point due to the irradiation of the electron beam 6 indicates a point object whose center is the irradiation point. The spot size is defined as the diameter of the contour line where the relative luminance is one half of the maximum luminance at the melting point.

DESCRIPTION OF SYMBOLS 1 ... Filament 2 ... Grid cup 3 ... Anode 4 ... Focus coil 5 ... Deflection coil 6 ... Electron beam 7 ... Vacuum chamber 8 ... Elevator 9 ... Powder container 10 ... Reiki 11 ... Powder 12 ... Table 14 ... Melt body 15 ... Plate 61 ... focusing point 62 (electron beam) spot size 141 (electron beam on the melt) ... remelt H1 height difference between the melt 14 and the table 12 surface H2 ... remelt material 141 and the table 12 surface Difference in height

Claims (3)

A vacuum chamber whose inside is evacuated by a vacuum pump, an electron beam generator for generating an electron beam irradiated in the vacuum chamber, and a beam for focusing the electron beam generated by the electron beam generator A focus coil, a deflection coil for deflecting and scanning an electron beam focused by the focus coil to an arbitrary position, a powder container for storing metal powder for modeling a model, and an upper surface of the vacuum coil A base plate exposed in the chamber and supplied with the metal powder from the powder container on the upper surface, a rake for scraping the metal powder supplied on the base plate, and for raising and lowering the base plate And an elevator,
A descent step of lowering the base plate by the elevator so that the upper surface of the base plate is positioned below the focal point of the electron beam by the particle size of the metal powder; and from the powder container onto the base plate A supply step of supplying the metal powder; a scraping step of scraping the metal powder supplied on the base plate with the reiki; and the electron added to the metal powder scraped on the base plate. A preheating step of scanning the beam to preheat the metal powder, and preheating on the base plate based on layered two-dimensional data obtained by slicing the three-dimensional CAD data of the modeled object to a predetermined thickness. A melting step in which the metal powder is scanned with the electron beam to melt the metal powder. By performing the molding process of returning an electronic beam shaping device to shape the shaped article on the base play preparative stacked layers of melt said metal powder,
The modeling process is based on the ascending step of raising the base plate by the elevator and the layered two-dimensional data so that the upper surface of the melt is located at the converging point after the melting step, An electron beam shaping apparatus further comprising: a remelting step of scanning the electron beam onto the melt on the base plate to melt the melt. A vacuum chamber whose inside is evacuated by a vacuum pump, an electron beam generator for generating an electron beam irradiated in the vacuum chamber, and a beam for focusing the electron beam generated by the electron beam generator A focus coil, a deflection coil for deflecting and scanning an electron beam focused by the focus coil to an arbitrary position, a powder container for storing metal powder for modeling a model, and an upper surface of the vacuum coil A base plate exposed in the chamber and supplied with the metal powder from the powder container on the upper surface, a rake for scraping the metal powder supplied on the base plate, and for raising and lowering the base plate And an elevator,
A descent step of lowering the base plate by the elevator so that the upper surface of the base plate is positioned below the focal point of the electron beam by the particle size of the metal powder; and from the powder container onto the base plate A supply step of supplying the metal powder; a scraping step of scraping the metal powder supplied on the base plate with the reiki; and the electron added to the metal powder scraped on the base plate. A preheating step of scanning the beam to preheat the metal powder, and preheating on the base plate based on layered two-dimensional data obtained by slicing the three-dimensional CAD data of the modeled object to a predetermined thickness. A melting step in which the metal powder is scanned with the electron beam to melt the metal powder. By performing the molding process of returning an electronic beam shaping device to shape the shaped article on the base play preparative stacked layers of melt said metal powder,
After the melting step, the modeling process is performed on the base plate based on the adjustment step of adjusting the electron beam so that the focusing point is located on the upper surface of the melt, and the two-dimensional stratified data. An electron beam shaping apparatus further comprising a remelting step of scanning the melt with the adjusted electron beam to melt the melt. The electron beam shaping apparatus according to claim 2,
After the melting step, the melt on the base plate is scanned with the electron beam to pre-heat the melt, and the pre-heating is observed so that the focused diameter of the electron beam is optimized. An electron beam shaping apparatus characterized by performing an observation step and performing the adjustment step based on the observation result.

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