JP2000246770A - Mold for molding resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To combine both a mold body and an insert core by regulating materials and hardnesses of the body and the core and allowing simultaneous machinability and wear resistance to be compatible at a high level. SOLUTION: A mold body and an insert core are both manufactured of the same material of a free cutting steel containing 0.80 to 2.50 of wt.% of Si and having a surface hardness Hv of 165 to 210, and molded by cutting in the state that the both are combined. After molding, only the core is hardened to a surface hardness Hv of 500 to 950, to create a gap in the hardness, thereby improving its wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin molding die, and more particularly, to a composite type resin molding die in which an insert core for molding an undercut portion of a resin product is slidably combined with a mold body. About.

[0002]

2. Description of the Related Art Resin products are generally manufactured by injection molding in which a resin material heated and softened is pressed into a mold. The mold has a basic configuration in which a pair of cavities into which a resin is press-fitted in a mold-clamped state is a basic configuration. However, depending on the shape of the resin product, these two dies, that is, the mold body is used. An undercut portion that prevents the mold opening occurs. Therefore, the undercut portion is formed in the mold body by an insert core which is slid in a direction intersecting with the mold opening direction of the mold body and combined so as to be released. Examples of the type of the insert core include a pin, a bush, and an insert. The mold by the combination of the mold body and the insert core,
In order to prevent the occurrence of mold displacement, burrs, and the like, simultaneous machining is usually performed in which both are combined and machined simultaneously to form an inner surface.

[0003] Incidentally, it is naturally required that the shape of the cavity of the mold and the inner surface thereof be machined in accordance with the shape and surface condition of the product with high accuracy. For the purpose, etc., it is also required to improve the secondary processing properties such as polishing and polishing properties and graining properties for obtaining a surface having a satin pattern. Therefore, the conditions required for the material of the mold are becoming more sophisticated, and a prerequisite for satisfying the requirements is that the machinability is high. By the way, in the case of the mold using the combination of the mold body and the insert core as described above, the sliding of the insert core with respect to the mold body causes abrasion and galling, which shortens the life of the mold. . Therefore, conventionally, carbon steel such as S55C is used for the mold main body, while SK material, SCM material, SKS material, etc. are used for the insert core, and further heat treatment such as quenching is performed to harden, and the hardness and hardness of both are increased. By creating a gap in the material, the slidability of the insert core is improved, and the occurrence of wear and galling is suppressed. As a technique for improving the surface hardness, in addition to the above-described heat treatment, a different material having a high hardness may be incorporated into the surface portion, or a nitriding treatment disclosed in Japanese Patent Application Laid-Open No. Hei 10-235653.

[0004]

However, when the surface is hardened as described above, there arises a problem that the manufacturing cost of the mold is increased. As a solution to this problem, we have developed steel with improved machinability and applied it to the mold body,
Attempts have been made to reduce the cost and time required for machining, but if the machinability is further improved, the wear resistance will be reduced. Also, when molding the mold body and the insert core by the above simultaneous processing, since the gap between the hardness of both becomes remarkable, when processing the insert core, the tool is quickly worn or damaged or broken. The processing time is prolonged, and the productivity is deteriorated.
Accordingly, an object of the present invention is to provide a resin molding die that enables simultaneous processing of a mold main body and an insert core without a reduction in tool life and improves wear resistance.

[0005]

Means for Solving the Problems In the conventional mold, the material and hardness of the mold body and the insert core are made different in order to improve the abrasion resistance. That is, there is an adverse effect that it is difficult to simultaneously process the two. The inventor of the present invention has examined what means can achieve the conflicting characteristics.First, the two materials must be of the same material, have free cutting properties, and have the same hardness and appropriate hardness. Was made an essential requirement because simultaneous processing was most easily performed. Then, the requirement of adding wear resistance by making the hardness different after the simultaneous processing was cleared. Therefore, the present invention provides a resin molding die including a mold body and an insert core slidably combined with the mold body, wherein the mold body and the insert core are made of the same material, and Si:
0.80 to 2.50% by weight, and has a surface hardness H
v: Free-cutting steel of 165 to 210, both are formed by cutting in a combined state, and after forming, only the insert core is hardened to a surface hardness Hv: 500 to 950. And

According to the present invention, the same material, ie, S
i: 0.80 to 2.50% by weight and surface hardness Hv: 165 to 210 (HRC 3.0 to 17.0) Free-cutting steel is used to produce a material for the mold body and the insert core, Simultaneous processing is performed by cutting in a state where these materials are combined, and the inner surface of the cavity is formed into a shape according to the product. Since they are free-cutting steels of the same material and hardness, simultaneous machining is extremely easy to perform, shortening the machining time and suppressing a reduction in the life of the cutting tool. Next, a hardening treatment is performed only on the insert core to reduce its surface hardness to H.
v: Finish to 500 to 950 (HRC 49.0 to 69.0). By performing the surface hardening treatment in this manner, the gap between the hardness of the mold body and the hardness of the insert core is optimized for improving wear resistance.

The composition of the free-cutting steel is as follows: Si: 0.8
0 to 2.50% by weight is essential. S in this range
The effect of containing i is a moderate increase in the _Acl transformation point of steel,
Even if the surface temperature during cutting increases, austenite transformation hardly occurs, so that machinability is improved and machining distortion after cutting is suppressed. In addition to Si, C: 0.05-
It is desirable to contain 0.55% by weight and Mn: 0.10 to 2.50% by weight. C is an element effective for increasing the strength of steel. If it is less than 0.05% by weight, it is difficult to secure strength, and if it exceeds 0.55% by weight, toughness and machinability are deteriorated. Mn is an element effective for improving hot workability and hardenability of steel. If the content is less than 0.10% by weight, the effect is hardly obtained. If the content is more than 2.50% by weight, the low-melting-point SiO ₂ —FeO-based oxide generated on the surface of the cutting chips becomes a high-melting-point SiO ₂ —MnO-based oxide. It turns into harmful machinability.

In order to harden the insert core after the simultaneous processing of the mold body and the insert core, the insert core is heated to about 520 to 580 ° C. for 3 to 180 minutes in a stream of anhydrous NH ₃ after heat treatment of quenching and tempering. A nitridation treatment for generating a nitrogen compound on the surface is used. This nitriding treatment is preferable because it is not necessary to perform heat treatment such as quenching after the treatment, unlike the carburizing treatment, so that deformation can be suppressed. From the viewpoint of further suppressing deformation, a low-temperature nitriding treatment at a treatment temperature as low as possible is preferable. After nitriding,
When the surface is subjected to a sulfurizing treatment for generating sulfides, the sulfides improve the sliding property and shorten the initial adaptation time to the mold body, and as a result, the quality of the resin product is stabilized from the initial operation, which is preferable. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is a front sectional view showing a state where a resin product is molded by a mold to which the present invention is applied. In the mold, a mold body 1 is constituted by an upper mold 1a and a lower mold 1b, and a resin material heated and softened is located in a cavity 2 formed between upper and lower molds 1a and 1b. And press-fitting, the dish-shaped resin product P is formed. After the molding, the upper and lower dies 1a and 1b are relatively vertically separated from each other and opened, and the extrusion pin 4 is raised to take out the resin product P from the die 1. FIG. 2B is a sectional view taken along the line II-II in FIG.
As shown in the figure, a convex piece P1 having an L-shaped cross section is formed at a predetermined position on the lower surface of the resin product P as shown in the figure. The convex piece P1 is an undercut portion that prevents the mold body 1 from opening, and is formed by an insert core 5 inserted into the mold body 1 from a lateral direction.

The insert core 5 is mounted on the lower mold 1b so as to be slidable in the horizontal direction as shown in FIG. 3 showing the mold open state, and as shown in FIGS. 2 (a) and 2 (b), the upper mold It is held at the mold clamping position by the locking block 6 set at 1a. In the mold-clamped state, the inclined pin 7 is attached to the locking block 6 so as to be inclined rightward in FIG.
Is inserted into the insert core 5. And the mold body 1
When the mold is opened, the insert core 5 is moved to the left by the inclined pin 7 which comes out upward, and separates from the resin product P. Thereby, the resin product P can be taken out. The insert core 5 is prevented from dropping from the lower mold 1b by the stopper 8 fixed to the lower mold 1b.

The mold body (upper die 1a and lower die 1b) 1 and insert core 5 are composed of 0.80 to 2.50% by weight of Si, 0.05 to 0.55% by weight of C, and 0. 10
2.50% by weight, surface hardness Hv: 165-21
No. 0 (HRC 3.0 to 17.0). And insert core 5
Only is finally cured and has a surface hardness of Hv: 500
To 950 (HRC 49.0 to 69.0).

The mold body 1 and the insert core 5
First, a raw material is manufactured using free-cutting steel made of the same material. Next, simultaneous processing is performed by cutting in a state where these materials are combined, and the inner surface of the cavity 2 is formed into a shape corresponding to the product. Then
Only the insert core 5 is subjected to nitriding treatment, and its surface hardness is set to Hv: 500 to 950 (HRC 49.0 to 69.0).
To finish. As a preferable nitriding treatment, the insert core 5 that has been subjected to the heat treatment of quenching and tempering is heated to about 520 to 580 ° C. for 3 to 180 minutes in a stream of anhydrous NH ₃ to generate a nitrogen compound on the surface. Next, after this nitriding treatment, the surface of the insert core 5 is subjected to a sulfurizing treatment.

According to the mold of the present embodiment, the mold body 1 and the insert core 5 are made of free-cutting steel of the same material, and have the same hardness in the simultaneous machining stage. The processing time can be shortened easily, and the reduction in the life of the cutting tool can be suppressed. Then, by performing surface hardening only on the insert core 5 after the simultaneous processing, the gap between the hardness of the mold main body 1 and the hardness of the insert core 5 is optimized for improving wear resistance. In addition, since the insert core 5 is subjected to the sulfurizing treatment, the sulphide generated on the surface improves the slidability, and the mold body (in this case,
The initial run-in time for the lower mold 1b) 1 is reduced, and as a result, the quality of the resin product P is stabilized from the initial operation.

[0014]

EXAMPLE Next, an example will be described in which the material according to the present invention is examined for wear resistance, cutting workability, and the like. (1) Abrasion resistance test by the pin-on-disk method A disk 10 having a diameter of 100 mm as shown in FIG. 4A was tested using a free-cutting steel having a hardness Hv of 180 made of the material of the mold body of the present invention. The required number of pieces were prepared, and this was used as a test piece corresponding to the mold body. On the other hand, hardness H shown in Table 1 below
v: Pin 2 of ten kinds of hardness in the range of 320 to 1260
No. 0 was prepared for each of the five test pieces to obtain test pieces corresponding to these insert cores. As shown in FIG.
The test portion (wear portion) 20b protruding from the axis of the reference surface 20a is 1 mm / 10 mm in length. Hv:
For the pins of 320 and Hv: 430, hard Fe-based materials were used as they were. Also, pins with Hv 510 to 950 were obtained by subjecting a hard Fe-based material to a nitriding treatment so as to have respective surface hardnesses. Also, Hv: 1020, Hv: 1090,
The pins of Hv: 1260 were subjected to nitriding treatment and hard chromium plating treatment on a hard Fe-based material to finish each surface hardness.

[0015]

[Table 1]

As shown in FIG. 4 (a), while rotating the disk around the axis at 500 rpm, the radius
The test portion of the pin was vertically pressed against a portion corresponding to 0 mm at a constant pressure, and the amount of wear of both at the time when the sliding distance reached 50 km was measured. An oil-based cutting agent was supplied as a lubricant to the surface of the disk. The amount of wear of the disk was the depth from the surface of the portion where the pin was pressed, and the amount of wear of the pin was the reduced length of the height of the test portion. The average values of the test results for five pins having the same hardness were calculated, and are shown in Table 1 and graphed in FIG.

As is apparent from FIG. 5, the wear amount of the disk is approximately 120 to 1 until the hardness of the pin is about Hv: 950.
Although it is constant at 30 μm, it can be seen that the wear amount sharply increases when Hv: 950 is exceeded. Further, it can be seen that the wear amount of the pin changes substantially constant at 50 μm or less when Hv: 500 or more. Therefore, when the hardness of the mold body is Hv: 180, the hardness of the insert core is Hv.
v: 500 to 950 is effective, and within such a range, the hardness of the insert core is preferably Hv: 600 to 800.

(2) Machining Efficiency Test Each steel of Examples of the present invention and Comparative Examples to the present invention composed of the components shown in Table 2 below was used with a cutting tool having a cutting tool radius of 31.5 mm, using a tool rotation speed and feed rate. The cutting was performed at a speed of 100 m as the allowable cutting limit, and the time required was measured. As is evident from the results in Table 3 below, the embodiment can increase the rotation speed and the feed rate of the cutting tool as compared with the comparative example, and the machining efficiency based on the feed rate is the case where the comparative example is regarded as 1. It can be seen that the example is about 1.5 times.

[0019]

[Table 2]

[0020]

[Table 3]

(3) Tool life test As shown in Table 4 below, under the same conditions as the cutting conditions for the comparative example of the above-mentioned machining efficiency test, the steels of the examples and comparative examples shown in Table 2 were cut, and cutting tools were cut. The cutting distance at the time when the cutting edge was worn to the same level was measured. As shown in Table 4, while the example could cut 518 m, the cutting distance of the comparative example was 100 m, and the tool life of the example was about 5.2 times longer than that of the comparative example.

[0022]

[Table 4]

(4) Relationship between Nitriding Treatment Conditions and Hardness The nitriding treatment conditions for the steels of the examples shown in Table 2 were set to A to F as shown in Table 5 below.
The surface and inner depths of F were measured. FIG. 6 is a graph of the results, and it was confirmed that the temperature of the nitriding treatment conforming to the present invention was approximately 520 to 580 ° C.

[0024]

[Table 5]

[0025]

As described above, according to the present invention,
Since the mold body and the insert core are made of the same material and have the same hardness in the simultaneous machining stage, the simultaneous machining is extremely easy to perform, the machining time is shortened, and the shortening of the life of the cutting tool is suppressed. Then, by hardening only the insert core than the mold body after the simultaneous processing, the gap between the hardness of the two becomes optimal in improving the wear resistance. That is, it is very promising as a combination of a mold main body and an insert core, which has both high simultaneous workability and high wear resistance.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a mold according to an embodiment of the present invention.

2A is a view in the direction of arrow A in FIG. 2B, and FIG.
FIG. 2 is a sectional view taken along line II-II in FIG. 1.

FIG. 3 is a side sectional view showing a mold opening state of a mold according to an embodiment of the present invention.

FIG. 4A is a perspective view showing a method of a wear resistance test by a pin-on-disk method performed in an embodiment of the present invention,
(B) is an enlarged side view of the tip of the pin used for it.

FIG. 5 is a diagram showing a result of a wear resistance test by a pin-on-disk method performed in an example of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Die main body, 1a ... Upper mold, 1b ... Lower mold, 2 ... Cavity, 5 ... Insert core, P ... Resin product, P1 ... Undercut part.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 38/02 C22C 38/02 (72) Inventor Kuniki Suzuki 1-4-1, Chuo, Wako-shi, Saitama Stock Inside Honda R & D Co., Ltd. (72) Inventor Junzo Nakazawa 1-4-1 Chuo, Wako-shi, Saitama F-Term Co., Ltd. Honda R & D Co., Ltd. 4F202 AJ14 CA11 CB01 CD22 CK32 CK54

Claims (1)

[Claims] 1. A resin molding mold comprising a mold body and an insert core slidably combined with the mold body, wherein the mold body and the insert core are made of the same material. , Si: 0.80 to 2.50% by weight, and made of free-cutting steel having a surface hardness Hv: 165 to 210, and both are formed by cutting in a combined state. Only the core has a surface hardness Hv:
A resin molding die, which has been subjected to a curing treatment at 500 to 950.