WO2005011955A1

WO2005011955A1 - Metal mold, and formed body molding method by the metal mold

Info

Publication number: WO2005011955A1
Application number: PCT/JP2003/009906
Authority: WO
Inventors: Akira Yotsutsuji
Original assignee: Coki Engineering Inc.
Priority date: 2003-08-04
Filing date: 2003-08-04
Publication date: 2005-02-10
Also published as: AU2003252392A1

Abstract

A metal mold having a special valve pin, characterized in that a communication hole (13) opened to the cavity side end face (11) of the valve pin (7) and allowing a molding material filling passages (12) to communicate with a cavity (6) is drilled into the valve pin (7) at the tip part, whereby since the molding material (9a) not allowed to escape can be escaped into the molding material filling route (12) through the communication hole (13) when the valve pin (7) is operated to cut off a gate, even such a thin-walled member that the wall thickness of a formed body (10) is 2 mm at the gate (8) portion thereof can surely cut off the gate, and the molding material filling route (12) can be directly connected to the cavity (6) without providing a runner.

Description

Mold and molding method of molded body by the mold

In the present invention, it is possible to form a molding material such as a mixture of a powder for sintering and a resin pinda (in particular, a thick molded article) as well as a resin, and in addition, it is not clear.

The present invention relates to a resource-saving type mold suitable for forming a cylinder such as a syringe cylinder, which always requires a high degree of cleanliness and precision, and a method of forming a molded body using the mold. Background art

The mold (101) for forming a conventional cylinder forms a cold runner (108) at a right angle from a hot runner (107) disposed at the center of the female mold (102) as shown in FIG. The measuring resin (109) was high-pressure filled into the cavity (106) from the heel portion (110c) of the (110). In such a method, when the measuring resin (109) is injected at high pressure into the cavity (106) from the ridge (110c) of the cylinder (110), as shown in FIG. 10, the gate of the ridge (110c) is From the part close to (111), the measuring resin (109) is gradually filled.

At this time, as shown in Fig. 9, in the method of injecting the measuring resin (109) into the cavity (106) from the flange (110c) of the cylinder (110), the generation of the cold runner (108) is avoided. In this case, the resin (109) of the cold runner (108) is discarded each time, and there is a problem that the waste of the resin (109) is large. (This point is the same for the molding of metal powder, which will be described later.)

In addition, the molded product cylinder (110) is removed from the mold (101) together with the cold runner (108), and the cold runner (108) will be cut off from the gate (111) in a later step. However, if the target product does not particularly like the inclusion of foreign matter like the cylinder (110), the molding material particles generated in the cutting process will be regarded as defective if they adhere to the inside of the cylinder (110). And the product yield is also bad.

In the case of products that require supercleanliness, such as a cylinder (110), it is not possible to manually intervene in the process described above; There is also the problem of bringing about. The above explained the problem centering on the case of using the resin as the molding material (109), but the case of using the molding material (109) such as the mixture of the powder for sintering and the resin pineda is different. There is a problem with

That is, when a molding material (109) such as a mixture of a powder for sintering and a kneaded product of a resinous pinda is injected and filled by the above-described cord runner method, after filling, the inside of the cavity (106) is filled via the gate (111). Holding pressure to molding material (109) “The molding material (109) in the cavity (106) reduces its volume as it cools. This reduced volume is pressured from the molding material supply side via the soot (111). It is necessary to supply it, and this is the pressure to prevent shrinkage of the molding in the cavity (106). ”The thin gate (111) is a cold mold ( Since it is provided in 101), it is easy to cool and solidify this part in a state in which the molding material (109) after injection filling does not move, and thereafter the molding material (109) in the cavity (106) is retained. It won't come under pressure. As a result, in the case of a thin wall of about 2 mm, there is a problem that if the thickness is larger than that, a shrinkage occurs in the molded product, which causes a defect. In other words, in the case of using a molding material (109) such as a mixture of a powder for sintering and a resin binder, it is impossible to mold a material having a thickness of about 2 mm or more by the conventional cold runner method.

Therefore, it is conceivable to use the hot runner method, but in the case of the hot runner method (not shown), if the area near the gout portion of the molded product is 2 mm or less, half of the cavity in the cavity at the gut cut after the holding process is completed. There is a problem that there is no room for excess molding material to escape from the solidified molding gate cut bin and gate cutting can not be performed (US Pat. Nos. 6, 2 8 7 6 and 5 4 B 1).

The present invention addresses the problems of conventional molds using such cold runners. In the first place, it is possible to save materials and simplify the process by eliminating cold runners, and secondly, it is possible to finish the injection molding without any foreign matter such as particles of molding material. Even if it is possible to form a product, and thirdly, if the molding material is a mixture of a powder for sintering and a resin binder, it goes without saying that the gate cut in a thin-walled product is 2 mm or more. However, the problem is to develop a mold that can obtain a complete molded product and a molding method of the molded product using the mold. Disclosure of the invention

According to the basic idea of the present invention, the mold (1) according to "Claim 1" has "a cavity (6) having a predetermined shape inside and a cavity (6) communicating with the cavity (6) via a gate (8)". A molding material injection passage (12) for supplying a fluid-form-measured molding material (9) to the cavity (6); and a gate (8) capable of being released into the molding material injection passage (12) In a mold (1) provided with pulp pins (7) arranged,

A communication hole (13), which opens at the cavity side end face (11) of the valve pin (7) and communicates the molding material injection path (12) and the cavity (6), is drilled at the tip of the valve pin (7). "It is characterized by things.

In this way, after holding pressure, when the valve pin (7) is operated and gate cutting is performed, the tip of the bulb pin (7) is inserted into the gate (8) in the final scene of the gate cut. The molding material which is pinched between the cavity end face (11) of the valve pin (7) and the tip of the core (5) in the gate (8) part and there is no escape place (9a) "in case of Fig. 5" Molded material (9 a) which exists in the gate (8) when the tip of the valve pin (7) is fitted inside (8), and is pushed excessively into the cavity (6) by the valve pin (7) (9 a) The case of FIG. 7 can escape to the molding material injection path (12) through the communication hole (13), and the thickness of the molding (10) at the gate (8) portion is 2 mm and so on. Even thin-walled members can be gate-cut reliably. As a result, it becomes possible to connect the molding material injection path (12) and the cavity (6) directly without setting a runner. As for the molding method using the mold (1),

(a) Injection filling the molding material (9) measured from the molding material supply side (12) through the gate (8) into the cavity (6),

(b) After filling, hold pressure to apply a predetermined pressure to the filling material in the cavity;

(c) Return the excess molding material (9a) accumulated in the gut (8) portion to the molding material supply side (12) when the gate is cut after completion of the pressure holding step.

(d) Subsequently, the molded material (9) in the cavity (6) is cooled to solidify it into a molded body (10), and then the molded body (10) is taken out.

As described above, “after holding pressure, when the gate (8) is gate-cut, the excess molding material (9a) accumulated in the gout (8) portion is returned to the molding material supply side (12). As described above, and in particular, even when the molding material (9) is a special one such as a mixture of a powder for sintering and a resin binder, gate cutting can be reliably performed. Brief description of the drawings

FIG. 1 is a cross-sectional view showing a mold clamping state of a mold according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of a state in which gate cutting with pulp pins is performed in FIG. 3 is a cross-sectional view showing the mold opening state of the mold of the first embodiment of the present invention, and FIG. 4 is a cross-sectional view showing the product adjustment state of the mold of the first embodiment of the present invention. 5 is an enlarged cross-sectional view of a mold state of a mold according to the first embodiment of the present invention, and FIG. 6 is an enlarged cross-sectional view of a gate open state of the mold according to the first embodiment of the present invention. 7 is an enlarged cross-sectional view of the mold of the second embodiment of the present invention, FIG. 8 is an enlarged cross-sectional view of the gate of the second embodiment of the present invention, and FIG. FIG. 10 is a cross-sectional view of the prior art example, and FIG. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail according to the illustrated embodiments. The present invention can be applied to all runnerless moldings “when using a core and when not using a core”. First, as the first embodiment, a columnar core (5) and a cylindrical fossa (4 ) In the case of using a core in this case, for example, a representative example of a thin-walled cylindrical molded body (10) having a wall thickness of 2 mm or less (FIGS. The cylinder (10 ') was adopted as 6). General shape as the second embodiment "Thin ring shaped body (10") with a wall thickness of 2 mm or less in the case of no core in this case, in the case of no core in this case, "2 of course, 2 mm The above is also acceptable. Explain the case. Also, although the above _three explanations will be mainly focused on the case where normal resin is used as a molding material, it is also possible to use a mixture of a powder for sintering and a resin binder as another material. Examples of such materials include the following. In the description of the second embodiment (FIGS. 7 and 8), members of the same application are indicated by the same numbers to avoid complicated explanation, and in principle, the explanation thereof is omitted, focusing on the differences. I will explain. As described above, the cylinder which is the lower concept of the compact (10) is represented by (10 '), and the ring-shaped compact is represented by (10 ").

The molding material (9) is composed of a powder for sintering and a binder resin mainly composed of two kinds of resins composed of a uniform mixture of a solvent-soluble resin and a solvent-insoluble resin. The powder for sintering is composed of a metal material as a main material to be sintered, an oxide, a nitride, quartz, a glass, and a pinder for bonding these.

As the sintering main material that can be sintered, metal materials (stainless steel powder, Ni, W, Mo, Fe), carbides (WC, TiC, carbon carbide), nitrides (nitrides) For example, boron, silicon nitride, alumina nitride), oxides (quartz, alumina, glass, zirconia), etc. are mentioned as examples, and as the pinders for bonding these sintering main materials, Co, Ni are mentioned. Be In the case of oxide (quartz, alumina, glass, zircon), it may be sintered without a pinder. As these sintered products, cemented carbide members, cermet members, ceramic members, quartz glass members, tungsten members, stainless steel members, nickel members, molybdenum members Ribden members, glass members or composites thereof may be mentioned. Also, the average grain size of the main sintering material may be optimum depending on the application, but for example, in the case of a cemented carbide member, the one having an average grain size of about 0.2 to 0.5 μm is an edge (blade) It is preferable in securing the durability of the part. The general grade is an average particle size of about 2 μm.

The pine resin carrying the sintering powder is mainly composed of a solvent-soluble resin which is soluble in the solvent 1 and a solvent-insoluble resin which is not soluble in the solvent, and is composed of necessary additives such as a plasticizer and a mold release material. . It is more preferable that the solvent-soluble resin and the solvent-insoluble resin be completely mixed and coexist at the operating temperature, and in the present embodiment, both melt in the solvent at the melting temperature (high temperature) and be uniform at the operating temperature. Resin is used which separates in a mixed state.

Furthermore, when the solvent-soluble resin and the solvent-insoluble resin are merely mixed, the solvent-insoluble resin may be in the form of fibers or feathers in order to enhance the shape retention after degreasing and the uniform dispersion of the sintering powder. It is desirable to use That is, in the case of a resin in which the solvent-insoluble resin is in the form of fibers or feathers, it melts together completely uniformly in the solvent-soluble resin at high temperature (melting temperature of both). When this is cooled, the solvent-insoluble resin is gradually precipitated in the form of fibers, and the solvent-soluble resin and the powder for sintering become present in a entangled state between the fibers, and the solvent-soluble resin and the baking are extremely finely and uniformly. The binder powder is in a state of being dispersed between the fibrous solvent insoluble resins.

Examples of such solvent soluble resins are polystyrene, acrylic resin, vinyl chloride, cyclic polyolefin resin, polycarbonate and transition plastic. Also, examples of solvent insoluble resins include polypropylene, polyethylene, polyacetal, etc., and these are dissolved at high temperature (and solvent insoluble resins are precipitated at room temperature). Examples of solvents include xylene, toluene, benzene, etc. There are aromatic solvents and chlorinated solvents such as dichlormethane and dichlorethane. Other plasticizers such as dibutyl phthalate and dibutyl phthalate Examples of such materials include zinc stearate and stearic acid amide. The mixing ratio of the solvent-insoluble resin to the solvent-soluble resin is 1: 0.5 to 4.0 in volume ratio. In addition, the volume ratio of the binder resin to the powder for sintering is 40:60 to 65:35. These are formed into a conventional pellet shape and used in the same manner as conventional resins. .

First, (Figures 1 to 6) will be described. The mold (1) is composed of a female die (2) and a male die (3), and the female die (2) and the male die (3) are fixed to the fixed die plate (15) and the movable die plate (16). Each is attached and the male die (3) can be clamped to the female die (2). (Of course, although not shown, it is needless to say that the reverse is also possible.)

The female mold (2) is a first female member (2a) having a parting surface (P2), a cavity member attached to the first female member (2a) and having a mold cavity (4) recessed therein. (30), a second female member (2b) provided on the back of the first female member (2a), a hot runner bush (20) attached to the second female member (2b), and A hydraulic or pneumatic pin drive (25) for advancing and retracting the pulp pin (7) through a lube pin operating lever (25a), a sprue attached to the back of the second female member (2b) Mounting block (27), Back side of female die (2), third female member (2d) to attach female die (2) to fixed die plate (15), second female member (2b) A spacer member (28) disposed between the second female member (2d) and the third female member (2d) to form a storage space (28) of the sprue mounting block (27) between the members (2b) and (2d) 2c), the third female member (2d) and the valve operating lever ( 25a), and comprises an auxiliary panel (25d) and a valve pin (7) for pressing the valve pin (7) in the gate cutting direction and assisting the gate cutting operation of the pin drive section (25). There is.

In the first female member (2a), one or more recesses (18) are formed from the parting surface (P2) to the back surface of the first female member (2a) and open on the parting surface (P2) side A cavity member (30) in which 4) is formed is stored in the recess (18). Here, the mold cavity (4) is recessed in conformity with the outer diameter shape of the cylinder (10 ').

Details of the mold cavity (4) of the cavity member (30) will be described according to FIGS. Ru. A thin gate (8) communicating with the molding material injection path (12) of the horizontal bush (20) is drilled in the portion of the cavity member (30) facing the horizontal bush (20). Following the gut (8), the outer diameter of the small diameter tip (10a) of the cylinder (10 '), which is slightly larger in diameter than the gut (8), is formed, followed by the cylinder body. The outer portion of (10b) is formed, and the outer portion of the largest-diameter flange portion (10c) is formed on the parting surface side.

The gate (8) is formed in a straight cylindrical shape with a portion (8a) extending from the small diameter front end (10a) to the rear [the molding material supply side (1)] as can be seen from the gate partial enlarged view of FIG. And a trumpet-shaped portion (8b) opened in a trumpet shape from the cylindrical portion (8a) to the rear, and the tip portion of the valve pin (7) described later is precisely It is supposed to fit into the The tip of the pulp pin (7) described later is removed from the gate (8) to open and close the gate (8).

A molding material injection passage (12) is drilled in the hot runner bush (20), into which the valve pin (7) is inserted and connected to the molding material communication passage (24), and the tip portion thereof is the gate It is connected to (8) and formed with the same taper as the trumpet-like portion (8b) of the gate (8). For example, the heater (29) is disposed on the hot runner bush (20), and the molding material (9) in the molding material injection path (12) of the hot runner bush (20) is transferred to the gate (8). It is heated all the way to keep it molten. Note that (19) is the storage hole for hot runner bush (20).

The sprue mounting block (27) is mounted with the sprue bush (22) as described above, and is communicated with the sprue bush (22), and is branched into a plurality of parts along the 1st line, A molding material communication passage (24) connected to the injection passage (12) is drilled from the sprue hook (22) to the sprue mounting block (27). In addition, a guide hole (21) for guiding a valve pin (7) described later is drilled in the sprue mounting block (27).

Pulp pin Γ7) is a rod-like one whose tip is partially tapered The rear end is fixed to the valve pin actuating rod (25a), and is slidably inserted in the guide hole (21), and the portion projecting from the sprue mounting block (27) is a hot runner bush It is inserted into the molding material injection path (12) of (20). The tip portion of the pulp pin (7) is formed so as to be precisely fitted into the goat (8). That is, as shown in the enlarged cross sectional view of FIG. 6, the tip portion of the pulp pin (7) extends straight from the cavity side end face (11) to the rear along the cylindrical portion (8a) of the gate (8). It comprises an elongated portion (7a) and a tapered portion (7b) whose diameter gradually increases rearward from the elongated portion (7a) to the rear. The taper angle of the tapered portion (7b) is slightly smaller than that of the flange portion (8b). As a result, when the tip portion is inserted into the gate (8), the tip portion is guided by the trumpet shaped portion (8b), and the portion (7a) extended to the straight portion of the tip portion is the gate (8). It fits snugly into the cylindrical part (8a) of the car and a reliable gate cut is made. In other words, the diameter of the elongated portion (7a) and the inner diameter of the cylindrical portion (8a) of the goat (8) are formed so as to be close to zero error.

Furthermore, the cavity side end face (11) is formed with a conical recess (7c) into which a conical portion (5e) of the tip of the core (5) described later fits precisely. The diameter of this conical recess (7c) of the cavity side end face (11) (and the maximum diameter (d) of the conical portion (5e) at the tip of the core (5) are formed to be equal but the cylindrical portion (8a Smaller than the inner diameter (D) of), and a gap (K) is formed between the cylindrical portion (8a) and the conical portion (5e) as shown in Fig. 5. The tip portion of the valve pin (7) is a gate ( When it is separated from 8), as shown in FIG. 5, the molding material (9) flows from the gap (K) into the cavity (6), and conversely, the tip portion of the pulp pin (7) is the gate (8) The gap (K) is closed by the end ring portion (11a) of the cavity side end face (11) when it is fitted in. Of course, at this time, the cylinder of the gate (8) Since the part (7a) extending straight is fitted into the part (8a) without any gap, the molding material (9) does not enter into the cylindrical part (8a). The end ring portion (11a) refers to a flat ring surface between the outer periphery of the cavity side end face (11) and the largest inner periphery of the conical recess (7c). Furthermore, at the tip portion of the valve pin (7), the tip pore (13a) axially drilled from the ceiling portion of the conical recess (7c) and the tip pore (13a) and the valve pin (at right angles thereto). A right angle pore (13b) connecting the outer surface of 7) is formed, and a communication hole (13) is formed by the tip end pore (13a) and the right angle pore (13b).

The pin drive portion (25) is composed of a cylinder hole (25b) formed in the second female member (2b) and a biston member (25c), and a pulp pin operating lever (25a) is formed on the biston member (25c). And the valve pin (7) is made to slide through the valve pin operating lever (25a) by operating the biston member (25c). (M) and (N) are inlets and outlets for hydraulic oil or compressed air for operating the piston member (25c). The size of the piston drive portion (25) can be reduced by the action of the auxiliary panel (25d), whereby the overall shape of the mold (1) can be reduced.

The male mold (3) has a male body (3a) attached to the movable die plate (16), and one or more attached to the mold cavity (4) on the inner side of the male body (3a). The core (5), which is disposed on the inside of the male main body (3a) so as to be in contact with and separated from the core (5), and the mold (3b) and the mold after And an extrusion member (26) for releasing the molded cylinder (10 ') by extruding 3b) in the separation direction.

The embedded end (5d) of the core (5) is embedded in the male body (3a), and the core (5) is a base (5c) projecting from the inside of the male body (3a); 5c) is more similar to the inner peripheral shape of the cylindrical portion of the mold cavity (4) on the end side, and constitutes the inner peripheral shape of the flange portion (10c) and the cylinder portion (10b) of the cylinder (10 ') A cylindrical portion (5b), and a projection (5a) protruding from the center of the tip of the cylindrical portion (5b) and forming an inner peripheral surface of the injection needle attaching portion (10a) of the cylinder (10 '). The tip of the projection (5a) is conical as described above, and the diameter of the conical portion (5e) is (d).

Next, the operation of the mold (1) according to the present invention will be described. First, move the moving die plate (16) to press and clamp the male die (3) to the female die (2). At this time, the gate (8) is closed at the tip of the valve pin (7) and the pulp pin is The conic section (5e) at the tip of the core (5) fits tightly into the conical recess (7c) of (7), as shown in Fig.1.

Subsequently, as shown in Fig. 2, the pin drive unit (25) operates to pull back the valve pin (7) and open the gate (8). In this state, the injection molding machine is operated to inject the measured molding material (9) from the nozzle (23). The injected metering molding material (9) passes through the sprue plug (22), the molding material passage (24), the molding material injection passage (12), and the high pressure (into the cavity (6)) from the gate (8). For example, it is pressed by 1, 0 0 0~ 2, 0 0 0 kg / cm 2). The state is shown in the enlarged detail of FIG. As can be seen from the figure, since the gate (8) is formed on the central axis (CL) of the core (5), the cylindrical portion (8a) of the gut (8) and the projection (5a) of the core (5) The gap (K) composed of and has the same width [(D− d) Z 2] over the entire circumference, and the material for molding and molding material (9) flowing from the gut (8) into the cavity (6) has a cavity (6) The force applied to the outer peripheral surface of the core (5) is evenly distributed over the entire circumference, and the core (5) is inclined in one direction by winding the core (5) as in the prior art. There is no Therefore, the cavity (6) does not generate uneven thickness from the beginning to the end of the injection molding, and does not generate uneven thickness in the thickness of the molded cylinder (10 ').

In this way, when the filling of the measurement molding material (9) to the cavity (6) is completed, the process proceeds to the pressure holding step, and the pressure from the nozzle (23) of the injection molding machine is filled with the molding material in the cavity (6) (9) Keep on The filling and molding material (9) solidifies with cooling and shrinks at the same time, but the above-mentioned pressure replenishes the molding material (9) from the gate (8) and prevents the generation of a sink in the cylinder (10 '). . After the cylinder (10 ') has cooled to some extent and has not shrunk, the pressure holding process is finished, and the pin drive section (25) is reversely operated to advance the pulp pin (7), as shown in FIG. Close the gate (8) at the tip of the valve pin (7) as shown in the detailed drawing.

At this time, in the gate (8) part, the excess molding material (9a) which is sandwiched between the cavity side end face (11) of the pulp pin (7) and the tip (14) of the core (5) It is possible to escape to the molding material injection path (12) through the hole (13) The conical portion (5e) of the tip of the pulp pin (7) fits closely in the conical recess (7c) of the cavity side end face (11) of the valve pin (7) to close the tip pore (13a), and The portion (7a) of the pulp pin (7) extending in the straight portion of the pulp pin (7) is fitted into the cylindrical portion (8a) of the gate (8) with substantially zero fitting to close the got (8) and at the same time The tip ring part (11a) of the outer peripheral part of the cavity side end face (11) of the valve pin (7) is closed by the gap (K), and the gate cut is surely done with a small force. This ensures that the cavity (6) is shut off from the molding material injection path (12). Subsequently, the filling molding material (9) in the cavity (6) gradually cools and solidifies through the cooling step. When the molding material (9) is solidified, move the moving die plate (16) as shown in Fig. 3 to separate the male die (3) from the female die (2) and open the die. The molded article (10) is attached to the core (5) and pulled out of the mold cavity (4) of the female mold (2).

At this time, as can be seen from the enlarged detail view of FIG. 6, the tip of the injection needle attaching portion (10a) of the cylinder (10 ') is surely shut off from the molding material injection passage (12). Since the molding material (9) in (12) is held in a molten state by the hot runner bush (20), the cylinder (10 ') which is a molded article is not adhered with a cold runner as in the prior art It is removed from the mold cavity (4) in a fully molded condition without waste. As a result, cold runners, which are conventionally wasted, will not occur.

Finally, the push-out member (26) is operated to separate the intermediate mold (3b) from the male mold body (3a), and the collar (10c) of the cylinder (10 ') is engaged and pushed out. ) Release the cylinder (10,). When the removal of the cylinder (10 ') is completed, the parting surface is cleaned, and then the clamping process is started again and the above-mentioned work is repeated.

Next, referring to FIGS. 7 and 8, the case where the core (5) is not used will be described. The structure of the mold (1) is basically as described above, and the difference is that the molded body (10) is not a hollow cylinder like a cylinder (10 ') but a ring-shaped molded body (10 ") That is, in this case, there is no projection (5a) of the core (5), and this does not abut the tip of the valve pin (7). The tip of the pin (7) is formed flat, and the communication hole (13) formed at the tip of the valve pin (7) is closed when the gate (8) is closed by the valve pin (7). 4) It will be open to the side (see Figure 8).

The gate (8) is also the same as in Example 1, and as can be seen from the enlarged gate parts in FIGS. 7 and 8, the portion (8a) opened in the mold cavity (4) is formed in a straight cylindrical shape. And the rib-like portion (8b) opened in a trumpet shape from the cylindrical portion (8a) to the rear, and the tip portion of the valve pin (7) to be described later is precisely It is supposed to fit in. The tip of a valve pin (7), which will be described later, is inserted into and removed from the goth (8) to open and close the goth (8).

The tip portion of the valve pin (7) comprises a tip pore (13a) drilled in the direction of the central axis of the flat cavity side end face (11) and a tip pore (13a) and valve pin (7) at right angles thereto. A right angle pore (13b) connecting the outer surface is formed, and a communication hole (13) is formed by the tip end hole (13a) and the right angle pore (13b).

The difference from the first embodiment is that the core (5) does not exist in the second embodiment, and the conical portion (5e) of the tip of the core (5) and the tip end face (11) of the pulp pin (7) Since the front end side end face (11) is formed into a flat surface because it does not contact, when the gate is closed, the outlet of the gut (8) and the front end side end face (11) of the valve pin (7) are aligned. There is. Therefore, even when the tip of the valve pin (7) is fitted into the gate (8) during gate cutting, the mold cavity (4) and the molding material injection passage (12) can be inserted via the communication hole (13) at the tip. And are slightly connected.

Next, the difference in the operation of the second embodiment will be described. The injection molding machine is operated as described above, and the molding material (9) measured from the nozzle (23) is injected to measure the molding material (9 )) In the cavity (6) as described above under high pressure. When filling of the measurement molding material (9) into the cavity (6) is completed, the process proceeds to the pressure holding step, and the pressure from the nozzle (23) of the injection molding machine is applied to the filling material (9) in the cavity (6). to continue. The filling and molding material (9) gradually shrinks as it cools and shrinks at the same time, but the above-mentioned pressure refuels the molding material (9) from the goth (8) and causes the ring-shaped molding (10 ") To prevent. • When the ring-shaped compact (10 ") cools to a certain extent and the shrinkage hardly occurs, the pressure holding process is finished, the pin drive section (25) is reversely operated, and the pulp pin (7) is advanced. As shown in the enlarged detail drawing, the gate (8) is closed by the tip of the valve pin (7) At this time, the cavity side end face (11) of the valve pin (7) in the gate (8) 10 "), and the excess molding material (9a) with no escape space can escape to the molding material injection path (12) through the communication hole (13), and the gate cut can be performed with a small force. You can do it smoothly. (Especially, when the thickness of the compact (10 ") around the gate (8) is as thin as 2 mm or less, the gate can not be cut.)

At this time, the portion (7a) of the valve pin (7) extending to the straight portion is fitted into the cylindrical portion (8a) of the gate (8) with almost zero fitting to close the gate (8). . However, the difference from Example 1 is that the tip pore (13a) of the communication hole (13) is not blocked by the projection (5a) of the core (5), and the cavity (6) and the molding material injection path ( 12) is in communication with the communication hole (13), but closing the gate (8) at the tip of the pulp pin (7) will cause the tip of the valve pin (7) to Heat is taken in contact with the lower gate (8), and the temperature drops, and only a very small amount of molding material (9) in the communication hole (13) solidifies and blocks the communication hole (13). No, it will complete the gate cut. The molding material (9) in the solidified communication hole (13) is reheated when the valve pin (7) is pulled back and enters the high temperature molding material injection path (12), and the original flow Return to the body.

Subsequently, the filling molding material (9) in the cavity (6) gradually cools and solidifies through the cooling step. When the molding material (9) is solidified, move the moving die plate (16) as shown in Fig. 3 to separate the male mold (3) from the female mold (2) and open the mold. The ring shaped body (10 ") is mounted on the core (5), withdrawn from the mold cavity (4) of the female die (2) and finally taken out by activating the pusher member (26).

At this time, as can be seen from the enlarged detail view of FIG. 8, the ring-shaped body (10 ′ ′) is in the form-free state without any waste attached with the cold runner as in the prior art as described above. Therefore, cold runners, which were previously wasted, will not occur. When a mixture of a powder sintered material and a binder resin is used as the molding material (9), the ring-shaped molded body (10 ′ ′) is a green body for powder sintering [solvent-soluble resin component and solvent-insoluble A powder for sintering (= powder to be sintered + binder) is molecularly dispersed in a binder resin mainly composed of a resin component], and apparently it is the same as an ordinary thermoplastic resin molded member, After the subsequent degreasing and sintering steps, it becomes a sintered member.

As described above, according to the present invention, the valve pin is operated to perform gate cutting by opening the communicating hole connecting the cavity with the molding material injection path by opening the end of the valve pin to the end surface of the goat side. When it is pinched between the gate side end face of the pulp pin and the tip of the core, the molding material with no space can escape to the molding material injection path through the communication hole, and the operating force of the valve pin is greatly increased. It is possible to reduce to

Also, since the gate cut is carried out at the tip of the molded product in this way, it is possible to save a great deal of the material cost that conventional cold runners generate. Furthermore, if cold runners do not occur, there is no process for cutting cold runners from molded articles, and equipment costs and other costs can be reduced accordingly, and the finished products are molded as molding is completed. Not only is it possible to fully automate the line, but the particles of molding material particles generated at the time of cutting are not attached to the molded product, particularly to a medical member such as a cylinder, and this portion However, they have very good effects, such as the elimination of defective products.

Claims

One j claims

1. A molding material injection passage which internally communicates with the cavity of a predetermined shape and the cavity through the gate and supplies the molding material in a fluid state to the cavity, and the gate in the molding material injection passage In a mold provided with a valve pin arranged to be removable.

A mold characterized in that a communication hole opened at the gate side end face of the pulp pin and communicating the molding material injection path and the cavity is formed at the tip of the valve pin.

2. The mold according to claim 1, wherein the molding material is a mixture of a powder for sintering and a resin binder.

3 (a) Injection filling of the molding material measured from the molding material supply side through the gate to the cavity,

(c) When the gate is cut after completion of the pressure holding process, excess molding material accumulated in the gate portion is returned to the molding material supply side.

(c) Subsequently, cooling is performed to solidify the molding material in the cavity into a molded product,

(d) After that, a method of molding a molded body characterized by taking out the molded body.

4. The method of molding a molded article according to claim 3, wherein the molding material is a mixture of a powder for sintering and a resin binder.