JP5836852B2 - Manufacturing method of mold parts - Google Patents

Description

The present invention relates to a mold part manufacturing method for forming a product space in a mold used for molding synthetic resin products and tablets.

  For example, when a synthetic resin product is injection-molded, a process of injecting synthetic resin into a product space formed between a mold cavity and a core and opening the mold after cooling the synthetic resin is performed. In this mold opening process, the molded product may lose its shape.

  Give more specific examples. Case 1. When a cylindrical container with an elongated bottom is molded from soft resin by injection molding, the inner surface of the container-shaped product space is formed with a cylindrical movable mold (core), and the outer surface of the product space is fixed. There is a structure formed by a mold (cavity). FIG. 5 shows the core. In this case, in the mold opening process, the core is moved so as to be pulled out in the longitudinal direction of the cylinder with respect to the cylindrical molded product. At this time, as shown in FIG. 6, the mouth of the molded product was deformed so as to bend, and a defective product was produced.

  Moreover, when press-molding a tablet from powder (tablet molding), a step of putting the powder into a product space of a mold and opening the mold after tableting is performed. In this mold opening process, the tablet may lose its shape.

  Give more specific examples. Case 2. In the case of press-molding the powder into a fixed shape, for example, a tablet that is solidified into a small meteorite shape, the upper and lower sides of the product space with this meteorite shape are cylindrical upper and lower punches (movable mold). There is a structure in which the outer peripheral surface of the product space is formed with a mortar (fixed mold). In this case, at the time of molding, the upper part of the lower punch is placed in the lower part of the die, and the powder put into the die is compressed by lowering the upper punch from the top, and the upper punch is moved upward Then, a process of pushing up the lower eyelid and taking out the tablet is performed. A part of the tablet taken out in this manner may be chipped as if it is peeled off, and a defective product may be produced. When such a defect occurs, powder is applied to the product space forming surface (surface forming the product space) of the upper eyelid or the lower eyelid, for example, as shown in FIG. Was stuck.

  The cause of the occurrence of such a defective product is considered to be due to the poor mold releasability of the mold part (core or ridge). This is because the product space forming surfaces of these mold parts are all mirror-finished. For this reason, when the material is solidified, it is assumed that the molded product is in close contact with the entire mirror surface (the entire smooth surface) that is the product space forming surface. When the mold is opened, the mold parts are about to peel off from the molded product at once, and a vacuum is generated between the molded product and the mold parts, and a uniform force is applied to the entire surface of the product space, and the reaction As a result, it is considered that a large force is applied to the molded product, and as a result, the molded product loses its shape and the material adheres to the product space forming surface of the mold part.

  From the above estimation, it is usually considered as one of the countermeasures to improve the releasability that the product space forming surface of the mold part is roughened by using, for example, polishing paper. By making the surface rough, for example, when the mold is opened, a non-uniform force is applied to the entire surface of the product space forming the core, and the force applied to the molded product is reduced as a reaction. As a result, the molded product loses its shape. It is thought that etc. can be prevented. However, since the mold has a shape transfer function, if the product space forming surface is roughened, the rough surface is easily reflected in the product as it is. In addition, it is assumed that the following problems 1) and 2) occur.

1) For example, when it is molded with a mirror-finished mold part, the product is a smooth surface without a pattern, and may be glossy depending on how light strikes. However, if the mirror surface is rough, it is assumed that the rough surface becomes a pattern and is clearly transferred to the product, or that the gloss is lost.
In addition, when molded with mirror-finished mold parts, by using a transparent resin, the container as a product may be transparent so that the contents filled therein can be seen from the outside of the container. is there. However, when the mirror surface is rough, it is also assumed that the transparency of the container is lowered or becomes opaque.
If such loss of gloss or opacity of the container occurs, the commercial value is reduced.

  2) When forming the product space forming surface into a rough surface (unevenness), if the unevenness is large, there is a risk that the surface of the molded product will bite into the unevenness. Then, it is assumed that the unevenness becomes resistance at the time of mold opening, making it difficult to open the mold, scratching the product, and wearing the mold parts.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method of manufacturing a mold part that can prevent at least as much as possible from deforming a molded product.

The present invention relates to a method of manufacturing a mold part used for forming a product space, and a linear concave groove having a depth of 1 μm or less is spirally formed with respect to a product space forming surface of the mold part by electron beam irradiation. And extending the groove in the substantially perpendicular direction with respect to one direction selected from the direction in which the material moves on the product space forming surface and the mold opening direction. Concave grooves are formed at intervals along the selected one.

When the extending direction of the groove is parallel to the direction, it is assumed that the following problems occur. For example, when the extending direction of the groove is formed parallel to the direction in which the material moves on the product space forming surface, the material easily enters the groove as the material moves. The material that has entered the concave groove becomes a factor that increases the contact area between the molded product and the mold part, and becomes a mold release resistance when the mold is opened. As the material enters the recessed groove, the contact area between the molded product and the mold part increases, and it becomes difficult to move the mold part when the mold is opened, and as a result, the molded product is liable to lose its shape.
Therefore, by making the extension direction of the concave groove as large as possible with respect to the direction in which the gap of the concave groove is provided, and making it a substantially vertical direction, it becomes difficult for the material to enter the concave groove, and the product mold It is assumed that collapse can be prevented as much as possible.

When irradiating with an electron beam, it may be possible to irradiate the electron beam intermittently (at a predetermined pitch) in the form of dots. In this case, the groove formed in a linear shape has innumerable dots ( The shape is such that the circular depressions are continuous. In such a form , the seam is formed continuously, which is not desirable. Therefore, it is preferable to do the following.
That is, the concave groove is formed in a seamless state by electron beam irradiation.

Further, as a more specific example of a method for manufacturing a mold part, there is the following.
That is, in the method of manufacturing a mold part including a core for injection molding, the extending direction of the concave groove is a direction substantially perpendicular to the mold opening direction. In the injection molding, the product is fixed to the cavity when the mold is opened, and the product is released from the cavity by the ejecting pin. Therefore, the product needs to be separated from the core when the mold is opened. Therefore, the releasability is desired for the core rather than the cavity.
In addition, in the method of manufacturing a die part for press molding, the extending direction of the groove is a direction substantially perpendicular to the direction in which the material moves on the product space forming surface during pressing. As a more specific example, there is a method of manufacturing a mold part including a press-molding punch for compressing a material powder into a tablet.

According to the mold part obtained by the present invention, it was proved from the experimental results that the molded product can be prevented from being deformed. Moreover, the groove on the product space forming surface is difficult to be transferred to the product (only thinly transferred), and the product has excellent appearance in that it has few scratches.

  The reason why such an experimental result was obtained is presumed to be as follows. In the groove, which is the region that has been irradiated with the electron beam, a re-quenched layer is formed by rapid solidification after melt processing, and the crystal is further refined, so that the hardness and smoothness are improved. That is, the product space forming surface is not roughened by conventional polishing paper, but a smooth surface with less irregularities is formed in the product space surface. Therefore, the hardness and smoothness of the product space forming surface are improved, and the mold is easily opened. In addition, when the material hardens on the product space forming surface, voids are formed in the groove formed on the product space forming surface, and the product hardened in the product space contacts the product space forming surface of the mold part. The area (contact area) is reduced, and as a result, the mold is easily opened. Further, since the concave groove is linear, voids are continuously formed in the concave groove, and it is difficult for the material to enter the concave groove as compared with the configuration in which the dot-like depressions are scattered. In addition, since the concave grooves are formed at intervals in the direction in which the material or the like moves, the contact area is reduced over a wide region of the product space forming surface, and the mold is easily opened. In addition, since the extending direction of the grooves is a direction substantially perpendicular to the direction in which the grooves are spaced, the other direction (for example, a direction parallel to or oblique to the direction in which the grooves are spaced) In comparison with the direction of the material), it becomes difficult for the material to enter the groove, and as a result, the mold is easily opened. In addition, since the groove is 1 μm or less in depth, even if material enters the groove and hardens, it does not hinder the mold opening, and is formed between the grooves. Since the smoothness of the recessed groove region is improved as compared with the region not subjected to the electron beam irradiation, the mold release resistance is reduced and the mold is easily opened. From the above, it is estimated that the product is less likely to lose its shape.

Further, since grooves are formed in a spiral shape, as compared to those provided an annular groove large number, at a moving distance in a direction such that the material has no joint portion of the groove, is product appearance Are better. In addition, if a ditch | groove is formed in the continuous state which is seamless by electron beam irradiation, it will have a specific surface form.

Furthermore, in a method for manufacturing a mold part including a core for injection molding, where the extending direction of the groove is a direction substantially perpendicular to the mold opening direction, the mold obtained by this manufacturing method is used. When molded with parts, it was easy to open the mold and proved to be excellent in appearance.

Further, in the method of manufacturing a mold part for press molding, when the extending direction of the concave groove is substantially perpendicular to the direction in which the material moves during pressurization, the material adheres to the mold part. It was proved that the appearance of the product was excellent. Specifically, the effect in the case of a mold part composed of press-molding ridges for compressing material powder into tablets was proved.

It is a graph which shows the result of the friction abrasion test leading to the present invention. It is a table | surface with a photograph which shows the state of the test piece external appearance, etc. of the friction abrasion test leading to this invention. It is a photograph which shows the molded article manufactured by injection molding. It is a table | surface with a photograph which shows the product space formation surface of the ridge used for press molding. It is a photograph which shows the movable metal mold | die used for injection molding. It is a photograph which shows the inferior goods manufactured by injection molding. It is the photograph which shows the ridge used for press molding, and its product space formation surface.

  In order to evaluate how rough the surface of the mold part should be, a frictional wear test was conducted. The frictional wear test is performed by rotating the mating material (POM ball) against the surface of the test piece in a circular shape while pressing it with a predetermined pressure.

  SKD61 was used as the material of the test piece, and a sample having a pattern (hereinafter referred to as “texture”) formed with an electron beam on the mirror-finished surface of SKD61 and an untreated sample were prepared. As the untreated test piece, the one whose surface was mirror-finished and the one whose surface was rougher than the mirror surface (# 220 polished surface) were used.

  In addition, four types of test pieces with different textures were prepared. The first is a small circular recess formed at predetermined pitches in the vertical and horizontal directions with respect to the surface of the SKD 61 (hereinafter referred to as “dot texture”). When the surface of the test piece is irradiated with an electron beam to form a texture, the irradiated portion is instantaneously melted and solidified, and is finally slightly depressed (depth 1 μm or less). Become. Second, a plurality of linear concave grooves are formed in parallel to the surface of the SKD 61 at predetermined pitches (hereinafter referred to as “line texture”). The third is a structure in which straight grooves are formed at predetermined pitches in the vertical and horizontal directions on the surface of the SKD 61 (hereinafter referred to as “lattice texture”). The fourth is that linear concave grooves are formed radially at equal angles with respect to the surface of the SKD 61 (hereinafter referred to as “radiation texture”). Moreover, what changed the irradiation conditions of the electron beam about each texture was prepared. Table 1 below shows an outline of the test, and Table 2 shows electron beam processing conditions (EB processing conditions) for forming a texture.

As a test result, the friction coefficient and the amount of wear of the POM ball are shown in Table 3 below and FIG.

From Table 3 and FIG. 1, the following contents 1) to 3) were confirmed.
1) Regarding the coefficient of friction, the untreated (mirror surface) is the highest, and the textured test piece is lower than the untreated test piece.
2) Regarding the amount of wear of the POM ball, the radiation texture tends to be the lowest.
3) There is no correlation between the surface roughness, the coefficient of friction, and the wear amount of the POM ball.
From the above 1) to 3), it is presumed that the friction coefficient and the amount of wear of the POM ball are different due to the unique shape of the texture. In addition, the coefficient of friction has a correlation with the mold releasability of the mold parts, and the ball wear amount has a correlation with the scratches in the product shape of the molded product molded by the mold and the wear of the mold parts. From the estimated results of Table 3 and FIG. 1, it is estimated that a radiation texture is formed on the surface of the mold part, which shows good performance in both the coefficient of friction and the amount of wear of the POM ball. Seems desirable.

Furthermore, as a result of the test, the state of the wear scar due to the appearance of the test piece (TP appearance) is shown in FIG. From FIG. 2, the following contents 1) and 2) were confirmed.
1) The amount of POM adhering that can be judged from the state of wear marks by microscopic observation is most untreated (mirror surface).
2) As for the state of wear marks that can be judged from the appearance of TP, there are wear marks at 0.1 mm of the dot texture and twice irradiation, 0.3 mm of the line texture, 0.3 mm of the lattice texture, and 11.25 ° of the radiation texture. In the radial texture, it is 11.25 °, and there is an abrasion mark that is continuous in an arc shape similar to that of no treatment (mirror surface). This is probably because the radial texture of 11.25 ° is closest to the mirror surface of the texture. However, in the case of no treatment (mirror surface), in addition to the linear wear trace that continues in an arc shape, the radiation texture has this kind of trace, even though there is a trace of the trace that some areas have peeled off. There are almost no signs of wear.
From the above 1) and 2), it can be seen from FIG. 2 that wear marks are reduced by applying some texture rather than no processing (mirror surface).

  Based on the test results in Table 3, FIG. 1 and FIG. 2, it can be expected that the radiation texture is the best. In the frictional wear test with the radiation texture, the POM ball is moving in a direction perpendicular to the extending direction of the groove. Therefore, if the groove is formed in a direction perpendicular to the moving direction of the material or the mold part, the wear resistance of the mold part can be improved and the mold part can be released from the molded product. I can expect.

Under the above assumption, a test equivalent to the injection molding of Example 1 described in the background art column was performed, and the release property and the surface properties (transfer and scratches) of the product were evaluated. As described in case 1, the molded product manufactured by injection molding from a soft resin is a cylindrical container having an elongated bottom (see FIG. 3). The inner surface side of the product space forming surface of the same shape as this container is formed with a cylindrical movable mold (core) (see FIG. 5), and the outer surface side is formed with a cylindrical fixed mold (cavity) with a bottom. To do. Then, several kinds of textures are applied to the core, which is a movable mold, and it is evaluated which texture is superior in terms of releasability and product surface shape. The texture to be evaluated corresponds to the dots, lines, radiations, and lattices, and any one of the textures was formed on the cores of No. 1 to No. 7. Each No. core is described in detail below.
The No. 1 core is formed by spirally forming a single linear groove on the outer peripheral surface which is the main part of the product space forming surface. The spiral groove is formed in a continuous and continuous state along the cylindrical outer peripheral surface of the core by electron beam irradiation. By the way, the columnar core reciprocates along its longitudinal direction, and moves backward (retreats) along the longitudinal direction when the mold is opened. In addition, resin is injected into the product space from the back of the core toward the tip (from the opening side of the container toward the bottom). The direction in which the resin is injected is the direction in which the material moves on the product space forming surface in the longitudinal direction of the core, and the extending direction of the groove is substantially perpendicular to this direction (longitudinal direction of the core) (90 Degree). Moreover, the spiral grooves are formed at regular intervals with respect to the longitudinal direction of the core, and an electron beam is irradiated between the adjacent concave grooves at intervals in the longitudinal direction of the core. There is no mirror surface left. The texture applied to the No. 1 core corresponds to the radiation texture.
The No. 2 core differs from the No. 1 core in that the concave grooves are formed at an angle of 45 degrees with respect to the longitudinal direction of the core (the moving direction of the material). Further, the concave grooves are formed every 3.6 ° along the circumferential direction of the cylindrical core, and a total of 100 concave grooves are formed in parallel along the outer peripheral surface of the core. The texture applied to the No. 2 core corresponds to the line texture.
The No. 3 core differs from the No. 1 core in that the concave grooves are formed in a lattice shape at an angle of +45 degrees and an angle of -45 degrees with respect to the direction in which the resin is injected. The texture applied to the No. 3 core corresponds to the lattice texture.
The No. 4 core is formed by forming substantially circular depressions at predetermined pitches in the vertical and horizontal directions over the entire cylindrical outer peripheral surface of the core. The electron beam is irradiated intermittently at a predetermined pitch so that such a depression is formed. The texture applied to the No. 4 core corresponds to the dot texture.
The core of No. 5 has the same dot texture as the core of No. 4, and the difference is that the pitch for forming the depressions is rougher than that of the core of No. 4.
The No. 6 core has the same dot texture as the No. 4 core. The difference is that the pitch is fine (half the pitch of No. 4) and the current value when irradiating the electron beam is lowered. It is the point which made each hollow small by this.
The No. 7 core is such that an electron beam is applied to the entire outer peripheral surface of the cylinder without any gap so that there is no mirror surface in the entire longitudinal direction of the core subjected to the electron beam. More specifically, the spiral groove is formed on the outer peripheral surface of the cylinder by an electron beam like the No. 1 core, but the groove is not substantially spaced from the longitudinal direction of the core. By forming, an electron beam is applied to the entire outer peripheral surface of the cylinder.

In the following Tables 4 to 6, for each of No.1 to No.7, the core appearance photograph, the core magnified photograph, the magnified photograph of the product (molded product), the electronic for forming the texture A beam processing condition (EB processing condition), a result, and a texture image (a diagram representing a texture) are shown.

表７での「NG（％）」は、所定突出圧力で行われた型開きの総回数に対して、成形品からコアが正常に抜き外れなかった回数を％で表したものである。また、「製品への転写」は、テクスチャが製品に転写された状態を表す。製品傷は、コア抜き取り時に成形品に形成された引き抜き傷の状態を表す。そして、以下の評価基準を用いた。
「NG（％）」については、最も低い不良率を○、最も高い不良率を×、その中間を△の評価とする。
「製品への転写」については、転写が無いものを○、転写状態が濃いものを×、薄いものを△、の評価とする。
「製品傷」については、傷の無いものを○、多いものを×、少ないものを△の評価とする。 The evaluation results for Tables 4 to 6 are shown in Table 7 below.

“NG (%)” in Table 7 represents the number of times that the core has not been normally removed from the molded product with respect to the total number of times of mold opening performed at a predetermined protrusion pressure. “Transfer to product” represents a state in which the texture is transferred to the product. The product scratch represents the state of a pull-out scratch formed on the molded product when the core is removed. And the following evaluation criteria were used.
For “NG (%)”, the lowest defective rate is evaluated as “◯”, the highest defective rate is “×”, and the middle is evaluated as “Δ”.
Regarding “transfer to product”, the evaluation is “◯” when there is no transfer, “×” when the transfer is dark, and “△” when it is thin.
As for “product scratches”, the evaluation is ○ when there is no scratch, × when there are many, and Δ when there are few.

  Using the above evaluation criteria, the final evaluation was determined according to the number of x. As a result, it can be determined that the texture formed on the No. 1 core with the smallest number of x is ideal. As described above, this texture is a spiral linear concave groove formed in a continuous state by electron beam irradiation, and is spaced in the direction in which the material moves on the product space forming surface. In addition, it is formed at intervals in the mold opening direction. Further, the extending direction of the concave groove is a direction of approximately 90 degrees with respect to the mold opening direction.

  Moreover, the test using the press molding of Example 2 described in the background art column was performed, and the release properties and the surface properties (transfer and scratches) of the product were evaluated. Here, two types of textures were evaluated. In this press molding, the product space forming surface of the upper punch is a portion that forms the upper surface of a small garnet-like tablet. More specifically, the specific shape of the product space forming surface is a circular shape, and has a dome shape in which a dent gradually swells in an arc shape toward the center of the circle. In this press molding, the upper part of the lower iron is arranged in the lower part of the mortar, and the powder is put into the mortar in this state. Then, the upper punch is lowered to the upper part of the die and the lower part of the upper punch is plunged into the upper part of the die, whereby the powder is compressed into a tablet. When compressed, the powder is assumed to move anti-radially from the outer periphery of the product space forming surface of the upper bowl toward the center. Then, after raising the upper eyelid, the tablet is taken out by raising the lower eyelid.

  With respect to such a product space forming surface, No. 11 upper collar in which concave grooves are radially formed from the center of the dome and No. 12 in which concave grooves are spirally formed from the center of the dome toward the outer periphery. Prepared the upper arm. As described above, since the traveling direction of the material is anti-radial, the No. 12 type has a groove formed in a direction substantially perpendicular to the traveling direction of the material. In the No. 11 type, a groove is formed in parallel with the moving direction of the material. These two types of upper punches were press-molded (tablet) many times, and it was confirmed whether or not the powder adhered to the product space forming surface. The test results are shown in FIG.

  From FIG. 4, it was confirmed that in the No. 11 type, the powder adhered to the center of the product space forming surface. On the other hand, it was confirmed that no powder adhered to the No. 12 type. From the above, it was confirmed that when the extending direction of the concave groove is a direction substantially perpendicular to the direction in which the material moves on the product space forming surface during pressurization, the molded product can be prevented from being deformed.

The present invention is not limited to the above embodiment. For example, the manufacturing method of a mold part used for forming the product space forming surface can be applied even when the product space forming surface has another shape. Moreover, it is applicable also to the manufacturing method of the metal mold components used for shaping | molding other than injection molding or press molding. Furthermore, the material of the mold part is not limited to SKD61, and may be other material, for example, a mold material such as tool steel. Note that the line width of the groove and the distance between the mirror-finished regions formed between the grooves are optimal depending on the viscosity or particle size of the material, the pressure during pressing, etc. I think that the.

Claims (5)

A method of manufacturing a mold part used to form a product space,
A linear concave groove having a depth of 1 μm or less is formed spirally with respect to the product space forming surface of the mold part by electron beam irradiation ,
The extending direction of the recessed groove is set to a direction substantially perpendicular to one direction selected from the direction in which the material moves on the product space forming surface and the mold opening direction, and the recessed groove extending in the substantially perpendicular direction, A method of manufacturing a mold part, wherein the mold part is formed at intervals along the selected one. Method for producing a mold part according to claim 1, wherein the forming in a state where electron beam irradiation continuously without the groove seamless by the. A method of manufacturing a mold part comprising a core for injection molding, groove mold component according to claim 1, wherein that a direction substantially perpendicular to the extending direction with respect to the mold opening direction Manufacturing method . 2. A method of manufacturing a die part for press molding, wherein an extending direction of the groove is a direction substantially perpendicular to a direction in which a material moves on a product space forming surface during pressurization. Or the manufacturing method of the metal mold components of 2. Method for producing a mold part according to claim 4, wherein the compressing the powder material is a manufacturing method of a mold part comprising a punch for press molding for the tablets.

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