JP4537823B2 - Powder molding method - Google Patents

Description

The present invention, flour powder molding process for the manufacture of high mass productivity of sintered parts with stable quality, specifically, be formed efficiently with a simple powder molding apparatus with less powder compact density difference about powder powder molding method that enables.

  The sintered part is made by sintering a powder compact. An example of the sintered part is shown in FIG. The illustrated sintered component 20 is a vane for a compressor, and has a recess 21 at one end. Since the concave portion 21 has curved side surfaces 21a and 21a, when the concave portion 21 is formed by molding with a mold of a powder molding apparatus, the raw material powder is compressed by the mold for die cutting after molding. It needs to be done in the Z-axis direction in the figure.

  When receiving the regulation, as shown in FIG. 7, the lower punch 2 is divided into the lower first punch 2a and the lower second punch 2b by using a powder molding apparatus, and the concave portion 21 is formed by the lower first punch 2a. A method of forming the end faces 22 on both sides with the lower second punch 2b is usually employed.

  Feeding of the raw material powder into the cavity 5 is performed using a powder feeding apparatus as disclosed in Patent Document 1 below. When the powder supply device finishes powder supply and returns to the initial position from the cavity 5, so-called chopping is performed by a powder supply box (not shown), and the ground powder remains in the cavity 5. . At this time, when the raw material powder is molded using a punch in which the recessed portion forming portion and the end surface forming portion are integrally formed, a compact having a uniform density due to a difference in compression density between the region having the recessed portion 21 and the region without the recessed portion 21. Cannot be obtained. Therefore, a molding method using the apparatus shown in FIG. 7 is employed as a method for eliminating the problem.

The powder molding apparatus of FIG. 7 can adjust the relative position (upper end position) of the lower first punch 2a and the lower second punch 2b to reduce the density difference of each part of the powder molded body. However, when the divided punch is used, the labor for adjusting the position of the punch increases and the productivity is adversely affected. Moreover, a burr | flash generate | occur | produces in a powder molded object in the position which combined the division | segmentation punch. Further, depending on the shape of the sintered part, the lower first punch and the lower second punch may have sharp edges, and the punch strength is likely to decrease.
JP-A-6-210495

If it is possible to produce a powder molded body with a recess having a small density difference between the respective parts without adjusting the position of the punch, it becomes possible to improve the molding efficiency of the molded body and increase the productivity of the sintered part. Also,
Since it is not necessary to divide the punch, it is possible to produce a powder molded body without burrs, and the problem of punch strength reduction that occurs when using a divided punch can be solved. This invention has an object to provide a powdery powder molding method responded to the request.

  In order to solve the above-mentioned problems, in the present invention, in powder molding obtained by compressing a raw material powder filled in a cavity, a powder molded body having a concave portion formed by an upper punch on the upper surface is provided. A groove across the cavity is provided at the top of the die, and further, a powder scraper having a shape corresponding to the groove is provided in a powder feeding box for feeding raw material powder into the cavity, and the powder box is fed onto the die after the powder feeding. And moved along the groove to scrape off a part of the raw material powder filled in the cavity with the powder scraper.

  This powder feeding method is preferably carried out by inclining the both side surfaces of the groove provided in the die and the both side edges of the powder scraper corresponding to the surface at an angle not exceeding the repose angle of the raw material powder charged into the cavity.

  Moreover, it is preferable that the raw material powder is introduced into the cavity by using a suction powder feeding method. The suction powder feeding method is a method in which raw material powder is introduced into a cavity while relatively moving a die and a lower punch inserted in the die in a direction in which the volume of the cavity is enlarged. It is more preferable that the raw material input by the suction powder feeding is carried out while sucking air into the powder feeding box from an intake hole provided in the powder feeding box.

The present invention provides a powder molding method in which a plurality of powder molded bodies having the same shape and the same size are simultaneously molded in one shot by feeding with the above-mentioned powder feeding method. In this method, a powder molding machine die having a plurality of cavities is provided with a groove that crosses the top of each cavity, and a powder scraper that corresponds to the shape of each groove in a powder feeding box that feeds raw powder into each cavity. And using a powder feeding device in which the difference in the gap size between each groove and the powder shaving stored in each groove is smaller than the average particle diameter of the raw material powder charged into the cavity, After the powder feeding box is fed, it is moved along the groove on the die to scrape a part of the raw powder filled in each cavity with the powder scraper, and then compress the raw powder in each cavity. Mold. In addition, the average particle diameter of the raw material powder as used herein refers to the particle diameter of particles whose sum of masses reaches 50% of the total mass from the smaller particle diameter in the histogram of the particle diameter measured by the sieving method.

In the powder molding method of the present invention, powder scraping is provided in a powder feeding box, and a portion of the raw material powder filled in the cavity is scraped off so that a groove is formed in the upper portion of the filling area. The scraping can make a difference for adjusting the density difference between the powder filling amounts of the end face forming part and the recessed part forming part, and the density is obtained using the stepped upper punch in which the end face forming part and the recessed part forming part are integrally formed. It becomes possible to form a powder compact with a recess having a small difference.

  In addition, since the density difference can be adjusted without using the divided punch, problems such as a decrease in productivity, a generation of burrs on the powder compact, and a decrease in punch strength can be solved.

  In addition, if the both sides of the groove provided on the die and both side edges of the powder shaving are inclined at an angle not exceeding the angle of repose of the raw material powder put into the cavity, the shape of the groove formed in the raw powder with the powder shaving will not collapse. Therefore, the density of the molded body is less likely to vary.

  In addition, when the raw material powder is charged into the cavity by the suction powder feeding method, the air can be prevented from being trapped and the charging can be performed quickly and reliably. If suction powder feeding is carried out while sucking air into the powder feeding box from the suction hole provided in the powder feeding box, the density variation during powder feeding of the raw material powder due to negative pressure in the powder feeding box can be reduced.

  In addition, in the powder molding method of the present invention, the average particle size of the raw material powder charged into the cavities is the difference in gap size between each groove and the powder scraper housed in each groove. Since it uses a smaller powder feeder, there is almost no difference in the scraping amount of the raw material powder by each powder scraping. Can be increased.

Hereinafter, embodiments of the powder molding method of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a mold of a powder molding apparatus used when manufacturing the sintered part 20 of FIG. In the figure, 1 is a die, 2 is a lower punch held by a base plate (not shown), 3 is an upper punch driven by an upper ram of a press machine, and 4 is a powder feeding box of a powder feeding device. The lower punch 2 is a simple punch having a rectangular cross section and a flat upper end. The upper punch 3 has a convex portion 3b that hangs downward from the lower surface 3a. The lower surface 3a forms the end surface 22 of the powder molded body for the sintered component 20, and the convex portion 3b forms the concave portion 21.

  The powder feeding box 4 slides on the die 1 and moves from the initial position (standby point) onto the cavity 5, and feeds the raw material powder A fed from a hopper (not shown) through the hose 6 into the cavity 5. The charging is preferably performed using a suction powder feeding method.

In the powder molding method of the present invention, the upper punch 3 is formed into a stepped punch with a convex portion 3b, and the end surface on one side of the powder molded body is molded with the upper punch 3 including the concave portion formed on the surface. Moreover, the groove | channel 7 which crosses the upper part of the cavity 5 is provided in the die | dye 1 of a powder shaping | molding apparatus, and the powder scraper 8 matched with the groove | channel 7 is provided in the powder supply box 4. FIG. The powder scraper 8 to be inserted into the groove 7 is provided at least at the front end (right side of FIGS. 1 to 3 and 5) of the powder feeding box 4. As shown in FIG. 1 to FIG. 3 or FIG. 5, this powder scraper 8 is preferably provided also on the rear side of the powder feeding box 4 (left side in FIG. 1 to FIG. 3 and FIG. 5). This rear-side powder scraper 8 prevents the raw material powder A from leaking out of the groove 7. Therefore, although it is not essential, it can be said that it is extremely preferable in practice.

  The groove 7 is preferably a groove approximated to the shape of the concave portion 21 provided in the powder molded body because variation in the compression amount at the time of powder molding is suppressed to be small. Further, both side surfaces 7a of the groove 7 and both side edges of the powder scraper 8 are preferably inclined at an angle α equal to or less than the repose angle of the raw material powder A. If it carries out like this, the shape of the groove | channel formed in raw material powder by scraping will become difficult to collapse. If the shape of the groove collapses, there will be a part that will become insufficiently powdered and a part that will be excessively powdered, and the density of each part of the molded product will vary, but if the shape of the formed groove is maintained, it will be due to the collapse of the groove shape There is no variation in density.

  Here, when the shape of the groove 7 is made equal to the shape of the concave portion provided in the powder compact, the angle α may be set to an angle less than the repose angle even when the angle α exceeds the repose angle of the raw material powder A.

  The powder shaving 8 is attached to the lower edge of the front wall of the powder feeding box 4 in a suspended manner. The powder scraper 8 having a shape similar to the groove 7 is moved together with the powder feeding box 4, and a part of the upper part of the raw material powder A put into the cavity 5 is scraped off by the powder scraper 8.

  FIG. 2 shows the operation of the dropping powder feeding method, and FIG. 3 shows the operation of the suction powder feeding method. In the dropping powder feeding method of FIG. 2, the die 1 is raised with respect to the lower punch 2 in advance, and the powder feeding box 4 is slid onto the cavity 5 from the initial position on the die 1. In the process, the raw material powder A in the powder feeding box 4 falls into the cavity 5 while pushing out the air in the cavity 5.

  On the other hand, in the suction powder feeding method of FIG. 3, the powder feeding box 4 is slid from the initial position on the die 1, and when the powder feeding box 4 reaches the powder feeding start point, the lower punch 2 and the die 1 are moved to the volume of the cavity 5. The raw material powder A is sucked into the cavity 5 created by the die 1 and the lower punch 2 by continuing relative movement in the direction in which the material expands. In this method, the raw material powder A can be filled smoothly and reliably, and a powder compact having a more stable weight and size than the dropping powder feeding method can be obtained. In addition, when air is introduced into the powder supply box 4 from the intake hole 9 provided in the powder supply box 4 during powder supply by this method, the internal pressure of the powder supply box 4 does not become negative, and the raw powder A Deterioration of fluidity is prevented and variation in filling amount is suppressed.

  In both the drop powder feeding shown in FIG. 2 and the suction powder feeding shown in FIG. 3, when the powder feeding box 4 is returned from the cavity 5 to the initial position, so-called chopping is performed in the powder feeding box 4 to recover surplus powder. To do. At the same time, a part of the raw material powder A filled in the cavity 5 is scraped off by the powder scraper 8 moving in the groove 7 at the same time, and a groove in the shape of extending the groove 7 is formed above the raw material powder A. . When the depth of the groove is changed, the compression ratio of the recessed portion forming region of the molded body changes, and therefore, the compression ratio of the recessed portion forming region can be made substantially equal to the compression ratio of the other regions without using a divided punch. No problems when using split punches.

  FIG. 4 shows an embodiment of the powder molding method of the present invention. In the illustrated method, two cavities 5 are provided in the die 1 of the powder forming apparatus to be used, and the raw material powder A charged in each cavity 5 is compressed by the lower punch 2 and the upper punch 3 respectively, and the same specification (the same shape, Mold two vane powder compacts of the same dimensions at the same time.

  The cavities 5 and 5 are provided side by side in a direction perpendicular to the direction in which the powder supply box 4 advances and retreats. Then, two sets of grooves 7 crossing the upper part of each cavity 5 are provided in the die 1, and the inside of each groove 7 is moved to the powder feeding box 4 when the powder feeding box 4 returns from the powder charging position. A powder scraper 8 that scrapes a part of the raw material powder A filled in the cavity 5 into a shape corresponding to the shape of the groove 7 and a powder that prevents leakage of the raw material powder from the groove 7 on the rear side of the powder feeding box 4. Two sets of shavings 8 are provided (FIG. 4 discloses only the powder shaving on the front side of the powder feeding box).

  The powder feeding box 4 is divided into two rooms, and the raw material powder A is fed from the hopper via the independent hose 6 (see FIG. 4) and the branch pipe 10 as shown in FIG. If the raw material powder that has flowed into is separately put into two cavities partitioned from each other, uneven distribution of the raw material powder can be suppressed.

The two sets of grooves 7, 7 provided in the die 1 and the powder scrapers 8, 8 inserted in each groove 7 are basically made to have the same dimensions, and the tolerance is 0.05 mm, for example. In the following, the difference (L ₁ -L ₂ ) between the gap dimensions L ₁ and L ₂ between the powder scraper 8 inserted into each groove 7 and the bottom of the groove 7 is made smaller than the average particle diameter of the raw material powder A. The remaining raw material powder after cutting in the two powder feeding portions is the same, and the amount of powder filled in each cavity 5 is uniform.

  For this reason, there is no great difference in the weight and height of the obtained powder compact, and it is possible to efficiently mold a plurality of powder compacts that meet the standards. In addition, if powder feeding is performed by the suction powder feeding method of FIG. 3, the difference in weight and height between the powder compacts obtained by simultaneous molding is sufficiently small.

  For example, as a result of examining the weight distribution of each part of the powder molded body made by supplying powder by the dropping powder feeding method of FIG. 2 and the powder molded body made by feeding powder by the suction powder feeding method of FIG. About 40% of the samples using the drop powdering method deviated from the median weight ± 0.15 g, whereas those using the suction powdering method were 30 samples. All were within the median weight ± 0.15 g.

  Moreover, when the difference of the average value (average value of 30 pieces) of two powder compacts (target weight 15 g) formed simultaneously in the left and right cavities was examined, the drop powder feeding method was adopted. While the difference was 0.29 g, the difference when the suction powder feeding method was adopted was 0.032 g, and the difference was extremely small.

  Furthermore, when the difference in height (overall length) of the powder compacts formed simultaneously in the left and right cavities was examined, those using the drop powder feeding method are the target lengths among those formed in the right cavities. There are those that exceed the value ± 0.07 mm, and those that are formed with the cavity on the left side that are less than the target value ± 0.07 mm, and the length of the powder molded body formed with the left and right cavities. The difference in average value was 0.06 mm. On the other hand, those using the suction powder feeding method do not have any powder molded body formed with the left and right cavities exceeding the target length of ± 0.07 mm, and the powder formed with the left and right cavities. The difference in the average value of the lengths of the molded bodies was also as small as 0.01 mm.

(A) Cross-sectional view of mold of powder molding apparatus used in this invention, (b) Cross-sectional view along line XX in FIG. 1 (a), (c) Enlarged front view of groove and powder shaving Diagram showing the operation of the drop dusting method Diagram showing the operation of the suction powdering method (A) The figure which shows embodiment of the powder shaping | molding method of this invention, (b) The enlarged view of the principal part (A) Top view which shows an example of the powdering box used by the method of FIG. 4, (b) Sectional drawing of the powdering box The perspective view which shows an example of the sintered component manufactured by applying this invention Sectional drawing of the metal mold | die of the conventional powder molding apparatus which shape | molds the sintered part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Die 2 Lower punch 3 Upper punch 3a Lower surface 3b Convex part 4 Powder supply box 5 Cavity 6 Hose 7 Groove 7a Side face 8 Powder scraper 9 Intake hole 10 Branch pipe 20 Sintered part 21 Recessed part 22 End face A Raw material powder

Claims (1)

A powder molding method for simultaneously molding a plurality of powder molded bodies having recesses formed by an upper punch on an upper surface thereof, wherein a die for a powder molding apparatus having a plurality of cavities is provided with a groove crossing the upper part of each cavity, The powder feed box that puts the raw material powder into each cavity is provided with powder shaving corresponding to the shape of each groove, and the gap size difference between each groove and the powder shaving stored in each groove is thrown into the cavity Powdering is performed using a powdering device smaller than the average particle size of the raw material powder, and the powdering box is moved along the groove on the die after powdering to each cavity with the powder scraper. A powder molding method characterized by scraping a part of the filled raw material powder and then compressing the raw material powder in each cavity.

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