JP3687672B2 - Surface finishing method for powder sintered parts - Google Patents

Description

  The present invention relates to a surface finishing method for powder sintered parts, and more particularly to a surface finishing method for powder sintered parts by stereolithography.

  There is a method of manufacturing a powder sintered part known as an optical modeling method. The manufacturing method disclosed in Japanese Patent No. 2620353 (Patent Document 1) forms a sintered layer by irradiating a predetermined portion of a layer of a metal powder material with a light beam to sinter the powder at the corresponding portion. Then, a new layer of powder material is coated on the sintered layer, and a predetermined portion of the powder is irradiated with a light beam to sinter the powder at the corresponding location, so that a new sintered body integrated with the lower sintered layer is obtained. By repeating the formation of the bonding layer, a powder sintered part in which a plurality of sintered layers are laminated and integrated is created, and a model that is the design data (CAD data) of the part to be obtained is desired. By irradiating the light beam based on the cross-sectional shape data of each layer generated by slicing to the layer thickness, so-called powder-sintered parts of any shape can be easily obtained, and the manufacturing method by cutting or the like Compared to the desired shape quickly It is possible to obtain.

  By the way, unnecessary powder adheres to the periphery of the part that has been sintered and hardened by irradiating with a light beam, and the adhered powder adheres a surface layer having a low density to powder sintering. It will be formed into parts. In order to remove the low-density surface layer and obtain a smooth surface, the present applicant has disclosed in Japanese Patent Laid-Open No. 2002-115004 (Patent Document 2), powder sintering prepared so far after the formation of the sintered layer. It was proposed to insert the process of removing the surface part and / or unnecessary part of the part into the process of creating the sintered layer several times.

  That is, as shown in FIGS. 9 and 10, every time m layers of sintered layers are laminated, the excessively hardened portion A formed around is cut with a cutting tool C such as an end mill. In addition, since the excess hardened portion A may be drooped and may have a thickness nearly twice the thickness of the block B made of m layers of sintered layers, the cutting process cuts all of the excessive hardened portion A. The target range D is The reason why such cutting is performed in the middle of the lamination process of the sintered layer is to perform surface finishing without being restricted by the length of the cutting tool.

However, even when the above-described cutting process is performed, the surface roughness of the outer surface cannot be greatly improved. This is because the excessively hardened portion A that must be removed by cutting is larger than the cutting tool C (usually one having a diameter of about 2 to 3 mm), so that the cutting resistance is large, as shown in FIG. This is because there is a portion Z where the cutting tool is bent and cannot be cut.
Japanese Patent No. 2620353 JP 2002-115004 A

  The present invention has been invented in view of the above-described conventional problems, and it is an object to provide a surface finishing method for a powder sintered part capable of improving the surface roughness of a portion subjected to cutting. To do.

In order to solve the above-mentioned problems, the surface finishing method of a powder sintered part according to the present invention sinters the powder at a corresponding place by irradiating a predetermined portion of the layer of the metal powder material with a light beam to form a sintered layer. Then, a new layer of powder material is coated on this sintered layer, and a predetermined part is irradiated with a light beam to sinter the powder at the corresponding part, so that a new one integrated with the lower sintered layer is formed. When inserting a cutting process for cutting the outer surface of the laminate of the sintered layers created so far after forming any of the sintered layers, the side surface of the laminate is repeatedly formed. In the one-time cutting process, at least two times of cutting operations with different positions to be cut are performed on the laminate, and the first cutting is performed among a plurality of cutting processes in one cutting process. Cutting target position for cutting after machining It is characterized in that the shifting from a top view of a sintered layer produced so far in the deep position.

The part that could not be removed by the first cutting due to the bending of the cutting tool can be removed by the second and subsequent cuttings, and can have a good surface roughness, In particular, since the cutting target position of the cutting process after the first cutting process is shifted to a deep position when viewed from the top surface of the sintered layer that has been created so far, it is pushed by the tip of the cutting tool during the first cutting process. The bending of the excessively hardened portion can be reliably performed.

  At this time, the uppermost block of the laminated block delimited by the insertion of the cutting process is set as the processing target of the first cutting process among a plurality of cutting processes in one cutting process. If the lower block is the target of subsequent cutting of multiple cutting operations, that is, if multiple cutting operations on a block are performed in different cutting processes, efficient surface finishing is performed. be able to.

And the cutting speed of the cutting process when the cutting target position is deepened when viewed from the top surface of the sintered layer created so far, the cutting speed when the cutting target position is shallow when viewed from the top surface of the sintered layer created so far If the cutting speed is set lower than the cutting speed, it is possible to counter the increase in cutting resistance when the cutting range is widened because the cutting target position is deepened.

  In addition to performing the above first cutting process leaving the required finishing allowance and performing the above subsequent cutting process with zero finishing allowance, the above first cutting process is performed with no finishing allowance, and the above subsequent cutting process is performed. You may make it carry out by a zero cut process.

In the present invention, when the outer surface of the laminate of the sintered layers prepared so far is cut after the sintered layer is formed, the cutting is performed at least twice in one cutting process on the side surface of the laminate. The second and subsequent cuttings are performed by shifting the portion that could not be removed by the first cutting process due to bending of the cutting tool to a deep position as viewed from the top surface of the sintered layer created so far. It can be removed by processing, and a surface with good surface roughness can be obtained.

  Hereinafter, the present invention will be described based on an embodiment shown in the accompanying drawings. FIGS. 2 and 3 show an example of an apparatus for producing a sintered powder component by stereolithography, and a powder tank 26 provided with a lifting table 27. The metal powder material housed in 1 is supplied to the modeling tank 25 side by the squeezing blade 21 and the surface is smoothed to move up and down on the modeling stage, that is, in the space surrounded by the modeling tank 25 up and down. The powder layer forming means 2 for forming the powder layer 10 having a predetermined thickness on the lifting table 20 and the laser output from the laser oscillator 30 are irradiated to the powder layer 10 via a scanning optical system such as a galvano mirror 31. And a sintered layer forming means 3 for forming a sintered layer 11 by sintering powder, and an XY drive mechanism 40 is provided on the base portion of the powder layer forming means 2. And a cutting and removing device 4 provided with the over ring head 41.

  In the production of the sintered powder part, the powder material 10 is supplied to the surface of the modeling base 22 on the upper surface of the lifting table 20 and is smoothed by the blade 21 to form the first powder layer 10. The portion to be cured is irradiated with a light beam (laser) L to sinter the powder to form the sintered layer 11 integrated with the base 22.

Thereafter, the lifting table 20 is slightly lowered, the powder material is supplied again, and the blade 21 is used to form the second powder layer 10. A light beam (laser) is applied to the portion of the powder layer 10 to be cured. L is irradiated to sinter the powder to form the sintered layer 11 integrated with the lower sintered layer 11. The lifting table 20 is lowered to form a new powder layer 10. by repeating it is sintered layer 11 the required locations by irradiating, to produce a powder sintered component of interest.

  The irradiation path of the light beam is created in advance from the data of the three-dimensional CAD model of the powder sintered part to be obtained. That is, contour shape data of each cross section obtained by slicing STL data generated from a three-dimensional CAD model at an equal pitch (for example, 0.05 mm) is used. At this time, it is preferable to irradiate the light beam so that at least the outermost surface of the powder-sintered part can be sintered so as to have a high density (porosity of 5% or less).

  Then, the powder layer 10 is formed and the light beam is irradiated to form the sintered layer 11 repeatedly. The laminated thickness of the sintered layer 11 is, for example, the milling head in the cutting removal means 4. If the required value obtained from the cutting tool length 41 or the like is reached (after the lamination of the m layers is finished), the surface portion (including the side surface) of the powder sintered part formed so far by operating the cutting removal means 4 once. ).

  As described above, the excessively hardened portion A of the powder-sintered part is removed by cutting by the cutting and removing means 4, and the cutting path by the cutting and removing means 4 at this time is the same as the irradiation path of the light beam. Created in advance from three-dimensional CAD data. Then, after the cutting removal by the cutting removing means 4 is performed, the formation of the powder layer 10 and the formation of the sintered layer 11 are repeated again.

The above cutting process is executed many times until the sintering is completed. Here, the cutting target position is changed in one cutting process on the side surface of the laminate, and the cutting process is performed twice or more. It is supposed to be. That is, as shown in FIG. 1 (a), when the N-stage block B composed of m layers of sintered layers has been sintered and the cutting with the cutting tool (ball end mill) C is performed, first, the finishing allowance x Cutting is performed with the mark left. The cutting depth is suitably about the lower surface of the block B at the Nth stage + the cutting tool radius r. Once the cutting is performed, the cutting tool C is moved along the outer surface of the powder-sintered part to perform powder sintering. Cutting the entire circumference of the block B of the Nth stage of the part. In addition, the whole circumference here includes the inner circumference of this hole when the powder sintered part has a hole on its upper surface.

  When the above-described cutting is completed, as shown in FIG. 1B, cutting is performed in a state where the finishing allowance for the block B of the (N−1) -th stage is zero. For this purpose, the cutting depth is, for example, up to a position where the tip of the cutting tool 4 reaches a position lower than the lower surface of the (N-1) th stage by the tool radius r, and once cut, it follows the outer surface of the powder sintered part. By moving the cutting tool C, the entire circumference of the N-1 stage block of the powder sintered part is cut. At this time, the excessively hardened portion A that has been bent downward by being pushed by the cutting tool C when the N-th block B is cut is also removed.

  In addition, since the N-th stage block B and the N−1-th stage block B are cut at the side surface portion of the cutting tool 4 at the time of cutting in this cutting process, the load applied to the cutting tool 4 is large. Therefore, it is preferable that the second cutting process reduces the load on the cutting tool C at a lower processing speed than the first cutting process.

  Then, when the finish cutting of the N-1 stage block B of the powder sintered part is completed, the N + 1 stage block B is formed on the N stage block B by sintering, and then FIG. c) As shown in (d), the cutting process for sequentially performing the cutting of the side surface of the (N + 1) -th block B and the finishing cutting of the N-th block B with the cutting target position shifted to a deep position. Move on. A plurality of times of cutting for a certain block are divided into different cutting processes, and in this case, the removal of the excessively hardened portion A that has been bent downward by being pushed by the cutting tool C is efficiently performed. It can be carried out.

  In any case, at least two cutting operations are performed by shifting the cutting target position in one cutting process, and with respect to a certain block B, the first cutting process and the finishing after the next block B is stacked. The cutting tool C is to be cut twice, and by leaving the necessary finishing allowance in the first cutting, the cutting tool C is used in the final finishing cutting. Cutting under certain conditions can be performed, and the accuracy of the finished surface can be increased. Further, since the N-th stage block B is also cut at the time of cutting the next N + 1-th stage block B, the surface roughness is improved.

  As shown in FIG. 4, a cutting tool C having a root diameter φ0 sufficiently larger than the neck diameter φ1 and the blade diameter φ or having a large shank taper angle α has a strength capable of resisting the load. By making it a thing, the accuracy of the finished surface can be increased more reliably.

  In terms of further reducing the load applied to the cutting tool C, the cutting depth is made small, for example, about 0.02 to 0.1 mm, and the first cutting process with the finishing allowance x left is performed on the outer surface of the powder sintered part. As shown in FIG. 5, the cutting tool C is moved along the entire circumference to cut the entire circumference of the powder sintered part every time the cutting depth is increased and the finishing margin is zero. This cutting process may also be performed by a plurality of times of cutting with progressively deeper cutting depths.

  In the above example, the first cutting is performed with the finishing allowance x left, but as shown in FIG. 6, the first cutting is performed with the finishing allowance being zero, and then the finish is finished. You may make it perform the cutting process of the 2nd time by what is called zero cut finishing of the zero zero in the state where the cutting depth was deepened. Even if the cutting tool C bends as shown in the figure during the first cutting process and an uncut portion Z is generated in the excessively hardened portion A, the uncut portion x is left in the second cutting process with a deeper cutting depth. Can be removed at the side of the cutting tool C.

  Although it is not necessary to make the depth of cut for the first cutting process too large, at least the uppermost N-stage block B is cut with a blade Ca on the side surface of the cutting tool C as shown in FIG. It is preferable to set the cutting tool C at a position where the tip of the cutting tool C reaches the lower end of the portion where the excessively hardened portion A hangs down.

  The cutting depth of the second cutting in a certain cutting process (which may of course be the third) is that of the upper layer with the side of the lower block B as the main cutting object. Cutting and removing the drooping portion of the excessively hardened portion A of the block B and the portion bent downward by being pushed by the tip spherical portion Cb of the cutting tool C at the time of cutting. So that the depth of cut is larger than at the time of the first cutting. In addition, although FIG. 1 shows an example in which the cutting depth is increased by a depth corresponding to one step of the block B, as described above, when the drooping of the excessively cured portion A is smaller than the one step, The amount by which the cutting depth is shifted downward may be made smaller than the above-mentioned one stage. On the contrary, the amount by which the cutting depth is shifted downward may be larger than one stage of the block B.

  In addition, the processing target position of the first cutting process and the processing target position of the second cutting process in a plurality of cutting processes in one cutting process may be separated in the height direction. For example, the first cutting process is targeted at the Nth stage of the uppermost layer, and the second cutting process is positioned at the lower half and further lower layers of the N-1th stage block B located below the Nth stage block B. The upper half of the (N-2) -th stage block B may be targeted. It is possible to eliminate a possibility that a step is generated at the joint portion of the block B due to a core blur of the cutting tool C or the like.

By the way, shifting the cutting depth downward as viewed from the upper surface of the sintered layer created so far means that the cutting depth increases, and the N-1 stage block is formed by the second cutting process. When the cutting target is used, the N-th stage block B and the (N-1) -th stage block B may actually be the cutting target. In this case, the cutting load increases. In this regard, as shown in FIG. 8, as the cutting tool C, the blade length M of the side blade Ca is greater than the sum of the thickness of the Nth block B and the thickness of the N−1 block B. In order to shorten the length, it is preferable to use a portion having a long neck lower diameter φ1 so that the upper part of the N-th block B is removed from the object to be cut during the second cutting. When the first cutting process is not performed with a finishing allowance of zero, there is a portion that remains without being cut in the surplus hardened portion A of the N-th stage block B, but this part is the surplus of the next N + 1-th stage block B It will be cut by the cutting process for the hardened part A.

1 shows an example of an embodiment of the present invention, where (a) is a cross-sectional view at the first cutting, (b) is a cross-sectional view at the second cutting, and (c) is 1 for the next block. Sectional drawing at the time of the second cutting, (d) is a sectional view at the time of the second cutting. It is a schematic perspective view of an optical modeling apparatus same as the above. It is a schematic sectional drawing of an optical modeling apparatus same as the above. It is a side view of the other example of a cutting tool. It is sectional drawing which shows another example. Another example is shown, in which (a) is a cross-sectional view during the first cutting, and (b) is a cross-sectional view during the second cutting. Further, another example is shown, in which (a) is a sectional view at the time of the first cutting, and (b) is a sectional view at the time of the second cutting. It is sectional drawing which shows another example. It is sectional drawing which shows an excessive hardening part. It is sectional drawing which shows the problem at the time of the cutting of the excessive hardening part.

Explanation of symbols

A Excess hardening part B Block C Cutting tool

Claims (5)

By irradiating a predetermined portion of the metal powder material layer with a light beam, the powder at the corresponding portion is sintered to form a sintered layer, and a new layer of the powder material is coated on the sintered layer to form a predetermined layer. Repeatedly forming a new sintered layer that is integrated with the underlying sintered layer by irradiating the light beam to the location to sinter the powder at the relevant location, and after forming any sintered layer When inserting the cutting process for cutting the outer surface of the laminate of the sintered layers created so far, at least two cuttings in which the cutting target position is changed in one cutting process on the side surface of the laminate In addition to performing processing on the laminate, among the multiple cutting operations in one cutting process, the cutting target position of the cutting process after the first cutting process is the and wherein the shifted position deeper from a top view Surface finishing method of a powder sintered parts that.   The uppermost block of the laminated block delimited by the insertion of the cutting process is set as the processing target of the first cutting process among a plurality of cutting processes in one cutting process, and one block below the uppermost block. 2. The surface finishing method for a powder sintered part according to claim 1, wherein the block is set as a processing target of a subsequent cutting process among a plurality of cutting processes. Cutting when the cutting speed of the cutting when the cutting object position deeply as viewed from the upper surface of the sintered layer prepared so far, shallow when viewed from the upper surface of the sintered layer cutting target position has created so far 3. The method for surface finishing a powder sintered part according to claim 1, wherein the cutting speed is slower than the cutting speed.   4. The surface finishing method for powder sintered parts according to claim 1, wherein the first cutting is performed while leaving a required finishing allowance, and the subsequent cutting is performed with a finishing allowance of zero. .   4. The surface finishing method for a powder sintered part according to claim 1, wherein the first cutting is performed with a finishing allowance of zero, and the subsequent cutting is performed with a zero cut.

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