JPH10225939A - Molding die and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the life of a molding die by making either of a cavity plate or a core plate of the die of metal and the other of resin. SOLUTION: A cavity plate 1 and a core plate 2 are of the injection molding die for molding a cover for a mouse to be used for computer operation. The cavity plate 1 is manufactured by cutting a metal block, while the core plate 2 is manufactured with a resin. In the center of the core plate 2, a core 25 for molding the inner face of the cover for the mouse is formed protruding. The surface 26 of the core plate 2 corresponds to the surface 16 of the cavity plate 1. Further, on both right/left sides of the core plate 2, guide protrusion 27 which fit into the guide recessed parts 20 of the cavity plate 1 are formed. Thus it is possible to prolong the life of the molding die while maintaining the same manhours of manufacturing this molding die as those for a resin mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding a polymer material such as synthetic resin or rubber into a predetermined shape, and more particularly to molding a resin molded product (model) necessary for confirming product design. The present invention relates to a molding die useful for a trial production die for producing a small number of products and a production die for molding a small number of products. The present invention also relates to a technology of manufacturing those molds by an optical shaping technology of curing a photocurable resin while controlling an ultraviolet laser based on three-dimensional data.

[0002]

2. Description of the Related Art The stereolithography technique is disclosed in Japanese Patent Application Laid-Open No. 56-1444.
No. 78, Japanese Unexamined Patent Publication No. 60-247515, and the like, and have been put to practical use in the creation of a model for confirming the design of a product or a product. In addition, in 1994
Nikkei Mechanical Separate Volume, published on March 22, 1995
NIKKEI MECHANIC issued on February 20, 2008
"AL" introduces injection molding dies made by stereolithography and molded products. The present invention relates to these molding dies and methods for producing them, and also to improvements in those techniques.

A procedure for manufacturing an injection mold by a currently known stereolithography method will be described with reference to FIG. First, a target resin product is designed using three-dimensional CAD (step S
-1). Pro-ENGINEER (Pro
-E), CATIA, IDEAS, etc. are commercially available, and what is called a workstation level computer is used. Next, 3 of this resin molded product
Adds know-how of resin injection molding such as draft angle and shrinkage ratio during molding to dimensional CAD (product) data. Then, by setting a parting line surface and performing a data inversion operation, CAD data of the mold is obtained (step S).
-3). By this operation, two types of data, that is, a mold type and a core type are obtained. Further, by adding data such as a pin hole of an eject pin to a gate port, a runner, and a core mold required at the time of injection molding, CAD data of a mold mold and a core mold are completed (step S-4). The above steps S-1 to S-4 are all performed on a computer.

Based on the CAD data of the mold and the core, a resin mold faithful to the CAD data is manufactured by an optical molding technique (step S-5). As the optical shaping apparatus that can be used for this purpose, for example, there are commercially available products sold by Teijin Seiki Co., Ltd., Demec Corporation, Seamet Corporation and the like.

[0005] Photocurable resins that can be used for this purpose include, for example, those filled with solid fine particles disclosed in JP-A-7-26060. Is commercially available in a state containing, and can be easily obtained.

After molding, the resin mold is subjected to post-curing and surface treatment after washing, and in some cases, post-treatment such as polishing the inner surface to eliminate the laminating step peculiar to the article manufactured by optical molding. After that, as in the case of a general metal mold, it is incorporated into a mold base (step S-6), attached to an injection molding machine, and injection molded with a designated resin, for example, an ABS resin or a polycarbonate resin (step S-6). S
-7).

As a resin mold other than the optical molding method, for example, “Plastic Molding Technology” No. 10 published in July 1993
A model inversion method described in Vol. 7 using a metal resin composite material obtained by mixing an aluminum fine powder and an epoxy resin is known. For this, a master model is created in advance, a mold is placed around the master model, a metal resin material in a flowing state is poured into the mold, a core mold is formed, and then the core is turned upside down. This is a manufacturing method for molding a mold. This manufacturing method is also used mainly as a mold for injection molding because it can be manufactured in a shorter time than a metal mold.

[0008]

Injection molding of a resin mold by the above-described stereolithography has an advantage that a target molded product can be obtained in a very short time if three-dimensional CAD data is available. There are many disadvantages. The first point is that the life of the mold is short, that is, the number of products that can be formed before the mold is broken is as small as about 50 to 100 pieces. This short life is considered to be an inevitable drawback for resin molds, and resin molds are used for small-scale production of prototypes, and when the final product shape is solidified, metal for mass production is used. It is a general form of use to make a mold.

The second point is that it is difficult to remove a stacking step unique to stereolithography in a mold state, and this step is transferred to a molded product. In particular, since the cavity surface is generally a surface expressing a design of a product, that is, a design surface in most cases, the transfer of the laminated steps is not preferable.

The mold for molding using the metal resin as described above has a life of about 500 to 1000 pieces, which is longer than that of the mold by stereolithography. However, it is desirable to further extend the life so that it is suitable for medium volume production.

The present invention solves the above problem, that is, while maintaining the advantages of a resin mold as much as possible.
It is a first object of the present invention to provide a molding die capable of prolonging the life of the die and sufficiently responding to some medium-volume production. Further, the present invention provides a molding die that reduces the lamination step of its design surface while maintaining the advantages of the optical molding method as much as possible, and provides a molding die for smoothing the surface of a molded product, and provides a manufacturing method thereof. Is a second task.

[0012]

Means for Solving the Problems In order to solve the above first object, a mold for molding of the present invention is a mold for molding a polymer material comprising a mold mold and a core mold, One of the mold type and the core type is made of metal, and the other is made of a resin type. As the resin mold, one manufactured by a stereolithography method is preferable.

When employing a resin mold manufactured by stereolithography, the mold corresponding to the surface expressing the design of the product to be molded is made of metal, and the other mold is made of metal. It is preferable to use the resin type, whereby the second object is achieved. Further, in the present invention, it is preferable that the mold is made of metal.

[0014] The method for producing a molding die of the present invention comprises the steps of:
Create three-dimensional CAD data, create three-dimensional CAD data of a mold type and a core type based on the data, convert the three-dimensional CAD data of either type into NC data, and make a metal While the mold is created, a resin mold is created by stereolithography based on the three-dimensional data of the other mold, and the mold mold and the core mold are combined.

[0015]

When one of the mold and the core is made of metal and the other is made of resin, it takes more time and effort to manufacture both than resin, but both are made of metal. Compared to the case, the labor and efficiency of manufacturing the mold are greatly improved. In other words, in addition to the merits of simply using one of the molds as a resin mold, the simplification of the structure of the metal mold and the reduction in the number of trial molding and mold correction work synergistically, so that both are metal molds In comparison with the above, the man-hours required for the production of the mold, including test punching and correction, are greatly reduced.

Further, by using one of the metal molds, there is an advantage that the life of the other resin mold is greatly extended. Although the reason is not clear, it is considered that the temperature rise of the mold is small, thereby lowering the heat load. That is, the resin mold has a low thermal conductivity, and heat is stored in the mold to shorten the life of the mold. However, when a metal mold is used for one side, heat brought into the mold by a material such as resin melted through the metal mold is quickly discharged to the outside of the system, and a rise in the temperature of the resin mold is suppressed. It is presumed that the life is extended. That is, it is considered that the metal mold also functions as a heat exchanger simultaneously with the function of the molding die. Therefore, it is considered that the heat load of the other resin mold is reduced, and as a result, the life of the mold is extended.

In particular, when a resin mold for stereolithography is employed as the resin mold, the material constituting the mold is made of a photo-curable resin containing inorganic solid fine particles, so that the heat conductivity is low and, therefore, The effect of extending the service life of the mold made by the mold is remarkable. When using a stereolithography mold as the resin mold,
It is preferable that the mold corresponding to the surface expressing the design is a metal mold, whereby a step pattern peculiar to stereolithography is not transferred to the design surface of the product, and the design of the product is improved.
Further, depending on the product, a polishing operation for removing a step pattern on the product surface, which has been conventionally performed, becomes unnecessary.

It is more effective to use a metal mold for the mold mold. That is, generally, in the case of a resin molded product, the cavity surface has few bosses and ribs, and often has a smooth design surface. In such a case, as described above, by making the mold mold a metal mold, the laminated steps are not transferred to the design surface of the product, and the design of the product is improved.

A second advantage is that the manufacturing and repair time for relatively complex core molds is greatly reduced. That is, the metal mold is processed and manufactured by cutting using a milling machine or NC machine, processing using an electric discharge machine, cutting using a wire cutting machine, or the like. Such machines are generally operated automatically by computer control, but cannot be controlled by three-dimensional CAD data, and so-called NC data must be created through several steps. Therefore, when the molding surface is complicated, it takes time to create the data, and the entire time required for manufacturing the metal mold becomes extremely long. In particular, generally, a core surface having a complicated shape such as a boss or a rib does not allow a cutting tool to enter a narrow groove or the like, and must rely on electric discharge machining. Therefore, it is necessary to manufacture from the discharge electrode corresponding to the shape of the groove for electric discharge machining, and the production time is further increased. Therefore, by making the core mold a resin mold by stereolithography, the manufacturing time of the mold for molding can be greatly reduced.

On the other hand, since the mold surface is a design surface and is constituted by a relatively simple smooth surface, conversion from CAD data to NC data is easy, and the time required for cutting is short. Therefore, even if the mold is a metal mold, the manufacturing time of the entire mold does not increase so much.

According to the method of manufacturing a molding die of the present invention, it is possible to efficiently produce a molding die in which one of the above-mentioned members is made of metal and the other is made of resin.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of a molding die according to the present invention will be described with reference to the drawings. FIG.
FIG. 1B is a perspective view showing a mold mold and a core mold showing one embodiment of the molding die of the present invention. Note that this figure and FIGS. 2, 3a, 3b, 3c, and 4 all show the output of three-dimensional CAD data of the type described later.
The mold mold 1 and the core mold 2 are molds for injection molding, and are for molding the cover 3 of the mouse for computer operation shown in FIG. The material of the cover 3 is assumed to be, for example, ABS resin. The cover 3 has a form in which a box having a rectangular planar shape is turned down.

FIGS. 3a, 3b and 3c are a plan view, a side view and a front view of the cover 3, respectively. As shown in FIG. 3b, the front half of the cover 3 is somewhat inclined so as to become lower toward the front. The inclined surface 4 is provided with a through hole 5 for incorporating a push button. Further, a chamfer 6 is provided on the near side and the left and right ridge lines, and a shallow concave portion 8 is provided on the left corner of the flat portion 7 on the near side. The front end of the cover 1 is provided with a half-square cylindrical projection 9 for taking out the cord to the outside. As can be seen from FIGS. 3a to 3c, the surface of the cover, that is, the cavity 15 of the mold 1 corresponding to the design surface has no protrusions and is smooth.

FIG. 4 is a bottom view showing the inside of the cover 3. A thin rib 10 protrudes from the inner surface of the inclined surface 4 so as to surround the through hole 5. Further, five thin ribs 11 protrude from the inner surface of the flat portion so as to be parallel to each other. Further, screw bosses 12 for fixing the cover 3 to the body of the mouse project from the left and right sides of the front end and the central part of the rear end.

The mold 1 shown in FIG. 1A is manufactured by cutting a metal block. The material of the metal block is
What is generally used as a mold material for injection molding, for example, SK materials such as JIS SKD and SKH materials are used. Each of these has a thermal conductivity of 0.1 cal / cm · sec ℃
And the coefficient of thermal expansion is about 11 × 10 ⁻⁶ / ° C. A cavity 15 corresponding to the surface of the cover is recessed at the center of the mold 1. Surface 16 of mold 1
Is the parting surface.

On the inner surface of the cavity 15, a projection 17 corresponding to the above-described shallow recess (reference numeral 8 in FIG. 2) is formed, and a front end corresponding to the surface of a half-tubular projection (reference numeral 9 in FIG. 2). A rectangular column-shaped concave portion 18 is formed. Also mold type 1
Is provided with a spool for introducing the molten resin and a runner 19. Guide recesses 2 for alignment with the core mold 2 are provided on the left and right of the surface 16 of the mold 1.
0 is formed. In addition, notched step portions 21 are provided at the four corners.
Is formed, and a bolt hole 22 for attaching to a mold base is formed in the cutout step.

Since there are few irregularities on the surface of the cover 3, the cavity 15 of the mold 1 and its periphery are also smooth. Therefore, there is almost no electric discharge machining or wire cutting, and even if it is a metal mold which is manufactured by cutting out an integrated metal block, the production is relatively easy. In addition, since a portion of the inner surface of the cavity 15 corresponding to the inclined surface (reference numeral 4 in FIG. 2) of the cover is inclined, a coarse laminating step occurs when manufacturing by stereolithography. Since it is a mold, there is no such stacking step, and there is only a small step due to NC processing. However, since it is a metal type, the minute steps can be easily removed by polishing or the like.

On the other hand, the core mold 2 shown in FIG. 1B is a resin mold, and is manufactured by a stereolithography method in this embodiment. As the material, a known material that is commercially available as a resin material for stereolithography can be used. For example, "TSR752" manufactured by Teijin Seiki Co., Ltd. can be preferably used. The material can be formed into the shape shown in FIG. 1B by laminating and shaping while curing with an ultraviolet laser into a shape based on CAD data, as described later. The thermal conductivity of such a resin mold is usually 1.17 × 10 ⁻³ cal / cm ·
sec · ° C., and the coefficient of linear expansion is 2.8 to 8.2 × 10
^-5 cm / cm / ° C.

At the center of the core mold 2, a core 25 for forming the inner surface of the mouse cover protrudes. Core type 2
Surface 26 is a surface opposite to the mold-type surface 16,
Guide protrusions 27 are provided on the left and right to be fitted with the cavity-shaped guide recesses 20. In addition, cutout steps 2 at the four corners
8 and bolt holes 29 are formed.

A step 30 corresponding to the end face of the cover, which is a product, is provided around the core 25. Further core 2
5 is provided with a projection 31 for forming a through hole (reference numeral 5 in FIG. 2) of the product, and an annular groove 32 for forming a rib (reference numeral 10 in FIG. 4) around the protrusion 31. Are formed. On the front side, five thin grooves 33 for forming parallel ribs (reference numeral 11 in FIG. 4) are formed. Further, on the front end side, a prismatic projection 34 for forming the inner surface of the projection at the front end (reference numeral 9 in FIG. 2) and penetrating the front end wall is provided. Further, concave portions 3 for forming screw bosses are provided at the left and right sides of the front end and at the center of the rear end.
5 are provided. A large number of small through holes 36 formed in the core 25 are holes for passing ejector pins for extracting a molded product.

As can be understood from the above, the design surface of the product such as the cover 3 is relatively flat, so that the mold 1 is relatively simple, whereas the core 2 forming the inner surface of the cover 3 is not. , And are relatively complicated due to ribs and holes. In addition, since the projections for forming the through holes 5 penetrating the cover 3 and the like are also provided on the core mold 2, it can be understood that the core mold 2 is further complicated. Therefore, when the mold for forming such a product is a metal mold for the mold mold and a resin mold for the core mold, it is possible to extend the life of the mold while maintaining the number of manufacturing steps at the same level as the resin mold.

Next, referring to the block diagram of FIG.
A description will be given of the manufacturing steps of the above-described mold and core molds for molding and up to injection molding using those molds. This manufacturing method is one embodiment of the manufacturing method of the present invention.

As is clear from FIG. 5, the three-dimensional CAD product data creation step (S-1) starts with the mold type and core type CA.
The process up to the D data creation step (S-4) is the same as the method of manufacturing a molding die by the conventional stereolithography described with reference to FIG.
That is, a step of creating three-dimensional CAD product data of a product (S-1), and a step of adding know-how of resin injection molding such as draft angle and shrinkage ratio during molding to the three-dimensional CAD data (S-). 2), set the parting line surface,
By performing the data inversion operation, a step (S-3) of creating CAD data of the mold is performed, and then a mold for adding data such as a gate hole, a runner, and a pin hole of a protruding pin required at the time of injection molding. A core type CAD data creation step (S-4) is performed. The above steps S-1 to S-4 are all performed on a computer.

From the next step, the steps are divided into a mold type and a core type. However, for the production of core molds,
Since it is manufactured by the stereolithography method, as in the case of FIG. 6, the CAD is performed by the stereolithography technology based on the core type CAD data.
The step of manufacturing a resin mold faithful to the data (S-5), the post-processing step, and the step of assembling into a mold base (S-6) are performed in this order.

On the other hand, the mold mold is processed from the metal block by the above-described processing machine, and therefore, differs from the stereolithography process. That is, first, CL data (cutting location data) indicating a cutting path of a cutting tool or a wire of a wire cutting machine is generated using the CAD data of the mold (step S-8). The CL data includes data such as the type of the tool and the feed pitch of the tool in the X, Y, and Z directions. All of these operations are performed on a computer.

Next, the CL data is converted into NC data for actually controlling the NC machine (step S-9). This data conversion can be carried out by conventionally used conversion software such as CADTHIAS manufactured by Nihon Unisys or PPM Corporation. Using the NC data, an NC machine is operated to cut an accurate mold from the metal block (step S-10).

The NC machine may be selected depending on the size of the mold and the type of processing. For example, an NC machining center, an NC lathe, an NC boring machine,
General-purpose machines such as NC milling machines, or commercially available N
Use a dedicated machine for C mold processing. The mold 1 manufactured as described above is incorporated into a known mold base (step S-11), and is used for injection molding in combination with the core mold described above (step S-7).

In the above embodiment, the resin mold by the optical molding method is adopted as the core mold. However, the resin mold by the optical molding method may be adopted as the mold mold, and the metal mold may be adopted as the core mold. The resin mold can be molded by a method other than the optical molding method, for example, a model inversion method. In that case, for example, a mold having a relatively high thermal conductivity such as a mold made of a metal resin can be used.

In the above embodiment, the cover of a computer mouse is described as an example. However, a resin molded product smaller than a mouse, such as push buttons and gears used for the cover, a keyboard cover, Large resin moldings such as cabinets for personal computers, mobile phones, housings for small liquid crystal televisions, and the like can also be manufactured using the mold for molding of the present invention or by the method for producing the mold of the present invention. Further, the resin mold can be manufactured by a stereolithography method or a manufacturing method such as an inversion method from the above-described model.

[0040]

Next, a description will be given of an injection molding mold actually manufactured and the result of molding by the mold. As previously mentioned,
FIG. 3A is a plan view of the output of a product design CAD of a mouse for a computer as viewed from a design surface (a surface on the front side of the product). FIG. 4 is a bottom view of the output of the same product design CAD as viewed from the inner surface in which electric parts and the like are incorporated. FIG. 2 is a perspective view of the design surface.

The CAD data already contains information necessary for a molding die. That is, the correction of the shrinkage ratio of 4/1000 is performed on the assumption that the draft taper is 0.5 degree and the ABS resin is used as the molding material. FIGS. 1A and 1B show the results obtained by performing an inversion operation from the CAD data shown in FIGS. 3 and 4, and further adding bolt holes and ejector pin holes for assembling into a mold base.
Such an inversion operation can be easily performed by commercially available mold design support software.

As described above, FIG. 1A shows the CA of FIG.
FIG. 1B shows the output of the core type CAD data created by inverting the CAD data of FIG. 4 and the output of the mold type CAD data created by inverting the D data.

Next, the core type CAD data shown in FIG.
It was converted to TL (Stereo Lightgraphy) data, and a resin mold was created using an optical shaping apparatus Soriform manufactured by Teijin Seiki Co., Ltd. The photocurable resin used was TSR752 (TRS is a trademark of Teijin Machinery Co., Ltd.) containing inorganic and organic solid fine particles. The lamination pitch of the modeling was 50 μm. The shaped product after the shaping was washed, subjected to post-processing such as surface treatment, and incorporated into a separately prepared mold base. When the main part of this resin mold was measured, CAD
It turned out that the data was finished to within ± 100 μm.

On the other hand, cutting path data (CL data) of a tool used in the NC machine was generated based on the mold CAD data of FIG. 1A. The tool used is to use 8mm, 5mm, 4mm and 2mm ball end mills.
The pitch in the X, Y and Z directions was selected according to the size of the tool. The CL data was converted to NC data, and the number of revolutions and the feed speed of the tool were selected.

The NC data was sent to a cutting machine made by Makino Seiki, and a block of carbon steel S50C was cut to produce a mold 1 shown in FIG. 1A. When the main part of the mold 1 was inspected, it was found that the accuracy was within ± 50 μm with respect to the CAD drawing. The mold 1 was combined with the core 2 manufactured by the above-mentioned stereolithography apparatus, but there was no problem in fitting the mold even though the material and manufacturing method of the mold differ from those of the mold. This is a groundbreaking finding that overturns the expectation that considerable rework is required because the materials and manufacturing methods are completely different. The coefficient of linear expansion of the mold-type metal material is 11.6 × 10 ⁻⁶ cm / cm / ° C., the thermal conductivity is 0.110 cal / cm · ° C., and TSR-752
The coefficient of thermal expansion after molding is 1.17 × 10 ⁻³ ca.
l / cm · ° C. This metal mold was assembled into a separately prepared mold base and attached to an injection molding machine (FN-2000) manufactured by Nissei Plastics Industry Co., Ltd.

Subsequently, injection molding was performed using this composite mold using ABS resin (GA-501) manufactured by Sumika ABS Latex Co., Ltd. The molding was performed at a resin temperature of 240 ° C. and an injection pressure of 471 kg / cm ² for ABS resin. The pressure holding time was 10 to 15 seconds. After molding 30 shots with ABS resin, raise the temperature to 20 with PC resin.
Shot molding was performed, but there was no abnormality in the mold. Also,
All of the molded products had no deformation such as warpage, and the design surface was finished smoothly. Note that the outer dimensions of the X axis and Y axis are AB
0.4% to 1% shrinkage with S resin, 0.1 ~ with PC resin
The shrinkage was 0.2%.

As is clear from the above, the molding die having one of the metal mold and the other of the resin mold has a slightly larger number of manufacturing steps than the resin mold. It can be seen that the life is greatly increased.

[Brief description of the drawings]

FIGS. 1a and 1b are perspective views each showing an embodiment of a molding die of the present invention.

FIG. 2 is a perspective view of a product to be molded using the molding die.

3a, 3b and 3c are a plan view, a side view and a front view of the product.

FIG. 4 is a bottom view of the product.

FIG. 5 is a block diagram showing one embodiment of a method for manufacturing a molding die of the present invention.

FIG. 6 is a block diagram showing an example of a method for manufacturing a molding die by a conventional stereolithography method.

[Explanation of symbols]

 1 Mold type 2 Core type 3 Cover (product)

Claims (5)

[Claims] 1. A mold for molding a polymer material, comprising a mold mold and a core mold, wherein one of the mold mold and the core mold is made of metal, and the other is a resin mold. A mold for molding. 2. The molding die according to claim 1, wherein the resin die is manufactured by a stereolithography method. 3. The molding die according to claim 2, wherein a mold corresponding to a surface expressing a design of a product to be molded is made of a metal, and the other is a resin mold. 4. The mold according to claim 2, wherein said mold is made of metal. 5. Creating three-dimensional CAD data of a molded product,
Based on the data, mold-type and core-type three-dimensional CAD data are created, and either one of the three-dimensional CAD data is created.
The D data is converted to NC data, and a metal mold is created based on the D data. On the other hand, a resin mold is created by stereolithography based on the three-dimensional data of the other mold, and their mold and core molds are formed. A method of manufacturing a mold for molding by combining