JP3920728B2 - Mold and molding method of molded body using the mold - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In the present invention, molding of molding materials such as a kneaded product of a sintering powder and a resin binder as well as a resin (particularly molding of a thick molded product) is also possible.Is possible, plusThe present invention relates to a resource-saving mold that is optimal for molding a cylinder such as a syringe that requires extremely high cleanliness and precision, and a molding method using the mold.
[0002]
[Prior art]
As shown in FIG. 9, a conventional cylinder molding die (101) forms a cold runner (108) at a right angle from a hot runner (107) disposed in the central portion of a female die (102). The weighing resin (109) was filled into the cavity (106) with high pressure from the flange portion (110c) of (110). In such a system, when the weighing resin (109) is injected into the cavity (106) from the flange (110c) of the cylinder (110) at a high pressure, the gate (111) of the flange (110c) as shown in FIG. The metering resin (109) is gradually filled from the portion close to).
[0003]
At this time, as can be seen from FIG. (110) No buttocks (110c) From weighing resin (109) The cavity (106) Injecting into the cold runner (108) The cold runner is inevitable every time (108) Part of resin (109) Will be discarded, resin (109) There is a problem of wastefulness. ( This point is the same as the metal powder molding described later. )
[0004]
In addition, cylinders that are molded products (110) Is a cold runner (108) With mold (101) Removed from the gate in a later process (111) Cold runner from the part (108) Will be cut off, but the target product is a cylinder. (110) If you don't like foreign materials like (110) If it adheres to the inside, it must be discarded as a defective product, and the product yield is also poor.
[0005]
Molded product is a cylinder (110) In the case of a product that requires ultra-cleanliness, there is a problem in that the cutting process cannot be performed manually, and an automatic machine must be put into the cutting process, resulting in high costs. The above is a resin molding material (109) Although the problem was explained mainly in the case of the molding material, a molding material such as a kneaded product of a sintering powder and a resin binder (109) There is another problem when using.
[0006]
That is, a molding material such as a kneaded product of a sintering powder and a resin binder (109) When injection filling is performed using the cord runner method described above, the gate is filled after filling. (111) Through Cavity (106) Inside molding material (109) Hold pressure on “cavity” (106) Inside molding material (109) Decreases its volume with cooling.
[0007]
Gate (111) This reduced volumetric volume is supplied under pressure from the molding material supply side, and thereby the cavity (106) The holding pressure is to prevent the sink of the molded body inside. ”, But it ’s a thin gate (111) Cold mold (101) Molded material after injection filling because it is provided inside (109) This part is easy to cool and solidify when it does not move. (106) Inside molding material (109) The holding pressure is no longer applied. As a result, in the case of a thin wall of about 2 mm, there is a problem that if the wall is thicker than that, the molded body will be sinked, resulting in a defect. In other words, a molding material such as a kneaded product of a sintering powder and a resin binder. (109) In the case of using the conventional cold runner method, although it has a thickness of about 2 mm or more, it cannot be molded.
[0008]
Therefore, the hot runner method can be adopted. However, in the case of the hot runner method (not shown), if the thickness of the molded part near the gate is 2 mm or less, the semi-solidified state in the cavity when the gate is cut after the pressure holding process is completed. There was a problem that the gate could not be cut because there was no escape space for the excess molding material between the molded body and the gate cut pin.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the problems of the conventional mold using such a cold runner.Eliminating the cold runner can save material and simplify the process.The final product can be formed only by injection molding without the generation of foreign substances such as molding material particles.ThirdEven if the molding material is a kneaded product of a powder for sintering and a resin binder, a mold that can obtain a complete molded product even when the thickness is 2 mm or more, as well as a gate cut in a thin one, and Development of a molding method of a molded body using the mold is an issue to be solved.
[0010]
[Means for Solving the Problems]
  As described in “Claim 1”For syringe moldingThe mold (1) is based on the basic idea of the present invention.Cavity member (30) Mold cavity formed inside (Four) As well as mold cavity (Four) Core inserted and removed (Five) Consisted ofA cavity (6) of a predetermined shape;Cavity member (30) Provided inCommunicating with the cavity (6) through the gate (8) and supplying the fluid metered molding material (9) to the cavity (6)And heater (29) Hot runner bush with (20) Formed inA molding material injection path (12) and a valve pin (7) disposed in the molding material injection path (12) so as to be insertable into and removable from the gate (8) are provided.For syringe moldingIn mold (1),
  On the gate side end face (11) of the valve pin (7)ProvidedOpeningWhenMolding material injection path (12)AndA communicating hole (13) that communicates is drilled at the tip of the valve pin (7).And
  Gate (8) In the cavity (6) From molding material injection path (12) Cylindrical part toward (8a) Is provided,
  Valve pin (7) Tip of (7a) Is the cylindrical part (8a) Fit into the gate (8) It is formed in a cylindrical shape so as to close
  core (Five) The tip of the valve pin (7) The gate (8) Valve pin when inserted into (7) Gate side end face (11) Formed in close contact withIt is characterized by.
[0011]
In this way, after holding the pressure, when the valve pin (7) is operated to perform the gate cut, in the final scene of the gate cut, the tip of the valve pin (7) is fitted into the gate (8), The molding material (9a) “in the case of FIG. 5” or the gate (8) sandwiched between the cavity side end face (11) of the valve pin (7) and the tip of the core (5) in the gate (8) portion and having no escape space. ) When the tip of the valve pin (7) is fitted in the molding material (9a) that is present in the gate (8) portion and excessively pushed into the cavity (6) by the valve pin (7) "in the case of FIG. 7" Can escape to the molding material injection path (12) through the communication hole (13), and the gate cut can be reliably performed even with a thin member having a thickness of the molded body (10) at the gate (8) portion of 2 mm. become able to. As a result, the molding material injection path (12) and the cavity (6) can be directly connected without providing a runner.
[0012]
  "Claim2”Used the mold (1)SyringeA molding method,
  "(A)Cavity member (30) Mold cavity formed inside (Four) And the mold cavity (Four) Core inserted and removed (Five) And cavity composed of (6) Weighed molding material (9) The heater (29) Hot runner bush with (20) Formed inMolding materialInjection pathFrom (12), Cavity member (30) Gate provided in (8) ThroughInjection filling,
  (B) After filling, a predetermined pressure is applied in the cavity (6).MoldingHold the pressure applied to the material (9),
  (C) After completion of the pressure holding step,Gate (8) Valve pin that is detachably mounted on (7) The gate (8) Insert into the gate cut and core (Five) Tip and valve pin (7) Gate side end face (11) And close the valve pin (7) Gate side end face (11) And molding material injection path (12) Communication hole that communicates with (13) Through gate (8) Excess molding material accumulated in the part (9a) The molding material injection path (12)Back to,
  (D)Subsequently, it is cooled to solidify the molding material (9) in the cavity (6) to form a molded body (10).
  (E)Thereafter, the molded body (10) is taken out.In the method of molding a syringe, characterized by
  Gate (8) In the cavity (6) From molding material injection path (12) Cylindrical part toward (8a) Is provided,
  Valve pin (7) The tip of the cylindrical part (8a) Fit into the gate (8) It is formed in a cylindrical shape so as to closeIt is characterized by
[0013]
Thus, “after holding the pressure, the gate (8) When the gate is cut, the gate (8) Excess molding material accumulated in the part (9a) The molding material supply side (12) And so on, as mentioned above, and in particular, the molding material (9) However, even in the case of a special product such as a kneaded product of a sintering powder and a resin binder, the gate cut can be performed reliably.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail according to illustrated embodiments. The present invention can be applied to all runnerless molding `` when a core is used and when a core is not used ''. First, as a first embodiment, a columnar core (5) and a cylindrical mold cavity (4) When a cylindrical molded product (10) is manufactured using a “in this case, a core is used. For example, as a representative example (FIGS. 1 to 6) of a thin cylindrical molded product (10) having a thickness of 2 mm or less. A cylinder (10 ') was adopted. "In this case, without a core, a thin ring-shaped molded product (10") with a thickness of 2 mm or less near the gate (8) "Of course, 2 mm or more It may be ". The case will be explained. In addition, the above explanation will focus on the case where ordinary resin is used as a molding material, but as other materials, a kneaded product of a sintering powder and a resin binder can also be used. The following are mentioned. In the description of the second embodiment (FIGS. 7 and 8), the members having the same application are indicated by the same reference numerals in order to avoid the complexity of the description, and the description thereof is omitted in principle, and the description will focus on the differences. I will do it. In addition, as described above, the cylinder, which is a subordinate concept of the molded body (10), is represented by (10 ′), and the ring-shaped molded body is represented by (10 ″).
[0016]
This molding material (9) is composed of a sintering powder and a binder resin mainly composed of two kinds of resins composed of a homogeneous mixture of a solvent-soluble resin and a solvent-insoluble resin. The powder for sintering is composed of a metal material, oxide or nitride, quartz, glass, which is a main material to be sintered, and a binder that couples them.
[0017]
As the sintering main material capable of being sintered, metal materials (stainless powder, Ni, W, Mo, Fe), carbides (WC, TiC, chromium carbide), nitrides (boron nitride, silicon nitride, alumina nitride) Examples thereof include oxides (quartz, alumina, glass, zirconia), and examples of the binder include Co and Ni as binders for bonding these sintered main materials. In the case of an oxide (quartz, alumina, glass, zirconia), it may be sintered without a binder. Examples of these sintered products include cemented carbide members, cermet members, ceramic members, quartz glass members, tungsten members, stainless steel members, nickel members, molybdenum members, glass members, and composite materials thereof. Depending on the application, the average particle size of the sintered main material may be optimum. For example, in the case of a cemented carbide member, the average particle size of about 0.2 to 0.5 μm is the edge (blade) portion. It is preferable for ensuring the durability. A general grade has an average particle diameter of about 2 μm.
[0018]
The binder resin carrying the sintering powder is mainly composed of a solvent-soluble resin that is soluble in one solvent and a solvent-insoluble resin that is insoluble in the solvent, and is composed of necessary additives such as a plasticizer and a release material. It is more preferable that the solvent-soluble resin and the solvent-insoluble resin are completely mixed and co-existing at the use temperature. In this embodiment, both the solvent-soluble resin and the solvent-insoluble resin are soluble in one solvent at the melting temperature (high temperature) and are uniform at the use temperature. Resins that are separated in a mixed state are used.
[0019]
Furthermore, in order to improve the shape retention after degreasing and the uniform dispersibility of the powder for sintering than when the solvent-soluble resin and the solvent-insoluble resin are merely mixed, the solvent-insoluble resin has a fibrous or feather shape. It is desirable to use a resin. That is, in the case where the solvent-insoluble resin is a fiber-like or feather-like resin, the resin is completely and uniformly dissolved in the solvent-soluble resin at a high temperature (= the melting temperature of both). When this is cooled, the solvent-insoluble resin gradually precipitates in the form of fibers, and the solvent-soluble resin and the powder for sintering are entangled between the fibers. The powder for use is dispersed between the fibrous solvent-insoluble resins.
[0020]
Examples of such solvent-soluble resins include polystyrene, acrylic resin, vinyl chloride, cyclic polyolefin resin, polycarbonate, and transition plastic. Examples of solvent-insoluble resins include polypropylene, polyethylene, and polyacetal. Solvents that dissolve these at high temperatures (however, solvent-insoluble resins precipitate at room temperature) are aromatic solvents such as xylene, toluene, and benzene. And chlorinated solvents such as dichloromethane and dichloroethane. In addition, examples of the plasticizer include dioctyl phthalate and dibutyl phthalate, and examples of the release material include zinc stearate and stearic acid amide. The mixing ratio of these solvent-insoluble resins and solvent-soluble resins is 1: 0.5 to 4.0 in volume ratio. The volume ratio of the binder resin to the sintering powder is 40:60 to 65:35. These are formed into ordinary pellets and used in the same manner as conventional resins.
[0021]
First, (FIGS. 1 to 6) will be described. The mold (1) is composed of a female mold (2) and a male mold (3) .The female mold (2) and the male mold (3) are fixed to the fixed die plate (15) and the movable die plate (16). The male mold (3) can be opened and clamped with respect to the female mold (2). (Of course, although not shown, the reverse is also possible.)
[0022]
The female mold (2) includes a first female mold member (2a) having a parting surface (P2), a cavity member that is attached to the first female mold member (2a) and in which the mold cavity (4) is recessed. (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 valve pin operating rod A hydraulically or pneumatically driven pin drive unit (25) for moving the valve pin (7) forward and backward via (25a), a sprue mounting block (27) attached to the back of the second female member (2b), A third female member (2d), a second female member (2b), and a third female member that constitute the back of the female die (2) and attach the female die (2) to the fixed die plate (15) A spacer member (2c) disposed between the member (2d) and the housing (28) of the sprue mounting block (27) between the members (2b) and (2d), a third female member ( 2d) and the valve operating rod (25a). To press the valve pin (7) is constructed out an auxiliary spring which assists the gate cut operation of the pin driving portion (25) (25d) and the valve pin (7).
[0023]
The first female member (2a) has one or more recesses (18) formed from the parting surface (P2) to the back surface, and the mold cavity (4) opening to the parting surface (P2) side. ) Is formed in the recess (18). Here, the mold cavity (4) is recessed according to the outer diameter shape of the cylinder (10 ′).
[0024]
Details of the cavity (4) of the cavity member (30) will be described with reference to FIGS. A narrow gate (8) communicating with the molding material injection path (12) of the hot runner bush (20) is formed in a portion of the cavity member (30) facing the hot runner bush (20). ) Followed by the outer portion of the narrow tip (10a) of the cylinder (10 ') to which the injection needle is attached, which is slightly larger in diameter than the gate (8), followed by the cylinder body (10b) An outer shape portion is formed, and the outer shape portion of the flange portion (10c) having the largest diameter is formed on the parting surface side.
[0025]
As can be seen from the enlarged view of the gate portion of FIG. 5, the gate (8) is formed in a straight cylindrical shape with a portion (8a) directed from the narrow tip (10a) to the rear [molding material supply side (1)]. A trumpet-shaped portion (8b) that opens in a trumpet shape from the cylindrical portion (8a) to the rear, and a tip portion of a valve pin (7), which will be described later, fits precisely in the gate (8) portion. It comes to include. A tip of a valve pin (7), which will be described later, is inserted into and removed from the gate (8) so that the gate (8) can be opened and closed.
[0026]
The hot runner bush (20) is provided with a molding material injection path (12) into which the valve pin (7) is inserted and connected to the molding material communication path (24). And the same taper as the trumpet-shaped portion (8b) of the gate (8). The hot runner bush (20) is provided with, for example, a heater (29), and the molding material (9) in the molding material injection passage (12) of the hot runner bush (20) reaches the gate (8). It is heated to keep it molten. Reference numeral (19) denotes a storage hole of the hot runner bush (20).
[0027]
As described above, the sprue bushing (22) is attached to the sprue mounting block (27). The sprue bushing (22) communicates with the sprue bushing (22). A molding material communication path (24) connected to (12) is drilled from the sprue bush (22) to the sprue mounting block (27). In addition, a guide hole (21) for guiding a later-described valve pin (7) is formed in the sprue mounting block (27).
[0028]
The valve pin (7) is a rod with a part of the tip tapered, and its rear end is fixed to the valve pin operating rod (25a) and is slidably inserted into the guide hole (21). The portion protruding from the sprue mounting block (27) is inserted into the molding material injection path (12) of the hot runner bush (20). The distal end portion of the valve pin (7) is formed so as to fit precisely into the gate (8). That is, as shown in the enlarged sectional view of FIG. 6, the tip of the valve pin (7) is a portion extending straight from the cavity side end surface (11) to the rear in accordance with the cylindrical portion (8a) of the gate (8). (7a) and a taper portion (7b) whose diameter gradually increases rearward from the straight portion (7a). The taper angle of the taper portion (7b) is slightly smaller and smaller than that of the trumpet-shaped portion (8b). Thus, when the tip portion is inserted into the gate (8), the tip portion is guided by the trumpet-like portion (8b), and the straight portion (7a) of the tip portion is the cylindrical portion of the gate (8) ( It fits snugly into 8a) and a reliable gate cut is made. In other words, the diameter of the straight portion (7a) and the inner diameter of the cylindrical portion (8a) of the gate (8) are formed so as to fit close to zero error.
[0029]
Further, the cavity side end face (11) is formed with a conical recess (7c) into which a conical portion (5e) at the tip of the core (5) described later is fitted precisely. The diameter (d) of the conical recess (7c) on the cavity side end surface (11) and the maximum diameter (d) of the conical portion (5e) at the tip of the core (5) are formed to be equal to the cylindrical portion ( As shown in FIG. 5, a gap (K) is formed between the cylindrical portion (8a) and the conical portion (5e), which is smaller than the inner diameter (D) of 8a). When the tip of the valve pin (7) is detached from the gate (8), the molding material (9) flows into the cavity (6) from the gap (K) as shown in FIG. When the tip portion of 7) is fitted in the gate (8), the gap (K) is closed by the tip ring portion (11a) of the cavity side end surface (11). Of course, at this time, since the straight portion (7a) is fitted into the cylindrical portion (8a) of the gate (8) without any gap, the molding material (9) is placed in the cylindrical portion (8a). Never get in. The tip ring portion (11a) is a flat ring surface between the outer periphery of the cavity side end surface (11) and the maximum inner periphery of the conical recess (7c).
[0030]
Further, the tip portion of the valve pin (7) has a tip pore (13a) drilled in the axial direction from the ceiling portion of the conical recess (7c) and a tip pore (13a) and a valve pin (7 ) Are formed with the right-angled pores (13b), and the communication holes (13) are formed by the tip-shaped pores (13a) and the right-angled pores (13b).
[0031]
The pin drive unit (25) is composed of a cylinder hole (25b) formed in the second female member (2b) and a piston member (25c), and a valve pin actuating rod (25a) is provided on the piston member (25c). The valve pin (7) is slid through the valve pin operating rod (25a) by operating the piston member (25c). (M) and (N) are pressure oil or compressed air inlets and outlets for operating the piston member (25c). Note that the dimensions of the piston drive section (25) can be reduced by the action of the auxiliary spring (25d), whereby the overall shape of the mold (1) can be reduced.
[0032]
The male mold (3) has a male main body (3a) attached to the movable die plate (16), and one or more attached to the mold cavity (4) inside the male main body (3a). The core (5) is disposed so as to be able to contact and separate from the inside of the male mold body (3a), and the intermediate mold (3b) into which the core (5) is inserted and removed, and after the mold is opened, the intermediate mold (3b) And an extruding member (26) for releasing the molded cylinder (10 ') in the separating direction.
[0033]
The embedded end (5d) of the core (5) is embedded in the male main body (3a), and the core (5) protrudes from the inside of the male main body (3a) (5c), the base ( 5c) A circle that is similar to the inner peripheral shape of the cylindrical portion of the mold cavity (4) on the tip side and that forms the inner peripheral shape of the flange portion (10c) of the cylinder (10 ') and the cylinder portion (10b) The columnar part (5b) and the columnar part (5b) have a protruding part (5a) that projects from the center of the tip and forms the inner peripheral surface of the injection needle mounting part (10a) of the cylinder (10 ′). The tip portion of the protrusion (5a) has a conical shape as described above, and the diameter of the conical portion (5e) is (d).
[0034]
Next, the operation of the mold (1) according to the present invention will be described. First, the movable die plate (16) is operated to press and clamp the male mold (3) to the female mold (2). At this time, the gate (8) is closed at the tip portion of the valve pin (7), and the cone portion (5e) at the tip of the core (5) is closely fitted in the conical recess (7c) of the valve pin (7) in FIG. It becomes a state.
[0035]
Subsequently, as shown in FIG. 2, the pin driving section (25) is operated 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 bush (22), the molding material passage (24), the molding material injection channel (12), and enters the cavity (6) from the gate (8) with a high pressure (for example, 1,000-2,000kg / cm²). The state is shown in the enlarged detail view of FIG.
[0036]
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 gate (8) and the protrusion (5a) of the core (5) Is the same width [(D−d) / 2] over the entire circumference, and the metering molding material (9) flowing into the cavity (6) from the gate (8) at high pressure is the cavity (6 ) Flows evenly over the entire circumference, the force applied to the outer peripheral surface of the core (5) is even over the entire circumference, and the core (5) can be bent and tilted in one direction as in the conventional example. Absent. Therefore, the cavity (6) does not cause uneven thickness from the beginning to the end of the injection molding, and the thickness of the molded cylinder (10 ′) does not vary.
[0037]
Thus, when the filling of the metering molding material (9) into the cavity (6) is completed, the pressure holding process is started, and the pressure from the nozzle (23) of the injection molding machine is changed to the filling molding material (9) in the cavity (6). Continue to hang. The filling molding material (9) gradually solidifies with cooling and shrinks at the same time, but the molding material (9) is replenished from the gate (8) by the pressure, and the occurrence of sink marks in the cylinder (10 ′) is prevented. When the cylinder (10 ') has cooled to some extent and has hardly contracted, the pressure holding process is completed, the pin driving unit (25) is reversely operated to advance the valve pin (7), and the enlarged detail view of FIG. As shown, the gate (8) is closed at the tip of the valve pin (7).
[0038]
At this time, in the gate (8) portion, the excess molding material (9a) sandwiched between the cavity side end surface (11) of the valve pin (7) and the tip (14) of the core (5) and having no escape space is communicated. It can escape to the molding material injection path (12) through the hole (13), and the conical recess (7c) on the cavity side end surface (11) of the valve pin (7) has a conical portion (5e ) Tightly closes and closes the tip fine hole (13a), and the straight part (7a) of the valve pin (7) is fitted to the cylindrical part (8a) of the gate (8) with almost zero fitting. As a result, the gate (8) is closed, and at the same time, the gap (K) is closed by the tip ring portion (11a) of the outer peripheral portion of the cavity side end surface (11) of the valve pin (7), and the gate cut is reliably performed with a small force. As a result, the cavity (6) is surely cut off from the molding material injection path (12).
[0039]
Subsequently, the filling molding material (9) in the cavity (6) is gradually cooled and solidified through a cooling process. When the molding material (9) is solidified, as shown in FIG. 3, the movable die plate (16) is actuated to separate the male mold (3) from the female mold (2) and perform mold opening. The molded article (10) is attached to the core (5) and pulled out from the mold cavity (4) of the female mold (2).
[0040]
At this time, as can be seen from the enlarged detailed view of FIG. 6, the tip of the injection needle mounting portion (10a) of the cylinder (10 ′) is securely cut off from the molding material injection path (12). In (12), since the molding material (9) is held in a molten state by the hot runner bush (20), the cylinder (10 ') which is the molded product has no cold runner as in the past. It is removed from the mold cavity (4) in a completely molded state without waste. Therefore, the cold runner which has been conventionally wasted is not generated.
[0041]
Finally, the pushing member (26) is actuated to separate the intermediate die (3b) from the male die main body (3a), and the flange (10c) of the cylinder (10 ′) is engaged and pushed out, and the core (5) Remove the cylinder (10 ') from. When the removal of the cylinder (10 ′) is completed, the parting surface is cleaned, and then the mold clamping process is started again, and the above operations are repeated.
[0042]
Next, a case where the core (5) is not used will be described with reference to FIGS. The structure of the mold (1) is basically as described above. The difference is that the molded body (10) is not a hollow cylindrical body like a cylinder (10 ') but a ring-shaped molded body (10' '). It is a point that accompanies certain things. That is, in this case, the protrusion (5a) of the core (5) does not exist and this does not come into contact with the tip of the valve pin (7), so the tip of the valve pin (7) is formed flat, and the valve pin The communication hole (13) formed at the tip of (7) opens to the mold cavity (4) side when the gate (8) is closed by the valve pin (7) (see FIG. 8). ).
[0043]
The gate (8) is the same as in Example 1, and as can be seen from the enlarged views of the gate part in FIGS. 7 and 8, the part (8a) opening in the mold cavity (4) is formed in a straight cylindrical shape, It consists of a trumpet-shaped portion (8b) that opens from the cylindrical portion (8a) toward the rear, and the tip of the valve pin (7), which will be described later, fits precisely into this gate (8) portion. It is like that. A tip of a valve pin (7), which will be described later, is inserted into and removed from the gate (8) so that the gate (8) can be opened and closed.
[0044]
The tip of the valve pin (7) has a tip pore (13a) drilled in the direction of the central axis of the flat cavity side end surface (11), and the tip pore (13a) and the outer surface of the valve pin (7) perpendicular to this. And right-angled pores (13b) are formed, and the communicating pores (13) are formed by the tip-shaped pores (13a) and the right-angled pores (13b).
[0045]
The difference from the first embodiment is that the core (5) does not exist in the second embodiment, and the conical portion (5e) at the tip of the core (5) and the tip end surface (11) of the valve pin (7) are in contact with each other. Since the tip end surface (11) is flat, the outlet of the gate (8) and the tip end surface (11) of the valve pin (7) coincide with each other when the gate is closed. Yes. Therefore, when the gate is cut, even when the tip of the valve pin (7) is fitted into the gate (8), the mold cavity (4) and the molding material injection path (12) are connected via the communication hole (13) of the tip. Slightly connected.
[0046]
Next, only the differences in the operation of the second embodiment will be described. The injection molding machine is operated as described above, and the measured molding material (9) is injected from the nozzle (23) to measure the molding material (9 ) Into the cavity (6) at the same high pressure as described above. When the filling of the metering molding material (9) into the cavity (6) is completed, the pressure holding process is started, and the pressure from the nozzle (23) of the injection molding machine is continuously applied to the filling molding material (9) in the cavity (6). . The filling molding material (9) gradually solidifies with cooling and shrinks at the same time, but the molding material (9) is replenished from the gate (8) by the pressure described above, and sinking of the ring-shaped molding (10 '') occurs. To prevent.
[0047]
When the ring-shaped molded body (10 ″) has cooled to some extent and hardly contracted, the pressure holding process is completed, and the pin driving portion (25) is reversely operated to advance the valve pin (7). As shown in the enlarged detail view, the gate (8) is closed at the tip of the valve pin (7). At this time, the surplus molding material (9a) sandwiched between the cavity-side end surface (11) of the valve pin (7) in the gate (8) and the ring-shaped molded body (10 '') is free from the escape space. It is possible to escape to the molding material injection path (12) through (13), and the gate cut can be smoothly performed with a small force. (Especially, when the thickness of the molded body (10 ″) around the gate (8) is as thin as 2 mm or less, gate cutting is impossible.)
[0048]
At this time, the straight portion (7a) of the valve pin (7) extending into the cylindrical portion (8a) of the gate (8) is fitted with almost zero fitting to close the gate (8). However, the difference from the first embodiment 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 when the gate (8) is closed at the tip of the valve pin (7), the tip of the valve pin (7) has a low temperature. Heat is removed from contact with the gate (8), the temperature drops, and a very small amount of the molding material (9) in the communication hole (13) is solidified to block the communication hole (13). The cut will be completed. 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 fluid Return to.
[0049]
Subsequently, the filling molding material (9) in the cavity (6) is gradually cooled and solidified through a cooling process. When the molding material (9) is solidified, as shown in FIG. 3, the movable die plate (16) is actuated to separate the male mold (3) from the female mold (2) and perform mold opening. The ring-shaped molded body (10 ″) is attached to the core (5), pulled out from the mold cavity (4) of the female mold (2), and finally, the pushing member (26) is operated and taken out.
[0050]
At this time, as can be seen from the enlarged detailed view of FIG. 8, the ring-shaped molded body (10 '') is the mold cavity in a completely molded state without waste as in the conventional case where the cold runner is not attached. Taken from 4). Therefore, the cold runner which has been conventionally wasted is not generated.
[0051]
When a kneaded product of a powder sintered material and a binder resin is used as the molding material (9), this ring-shaped molded body (10 '') is a green body for powder sintering [solvent soluble resin component and solvent insoluble. Sintering powder (= sintering target powder + binder) is molecularly dispersed in a binder resin mainly composed of a resin component], and is apparently the same as a normal thermoplastic resin molded member, It becomes a sintered member through the subsequent degreasing and sintering steps.
[0052]
【The invention's effect】
more than,According to the present invention, the tip of the valve pinOpening the gate side end face, and making a communication hole that connects the cavity and the molding material injection path, when the gate cut is performed by operating the valve pin, the gate side end face of the valve pin and the tip of the core The molding material sandwiched between the two and having no escape field can escape to the molding material injection path through the communication hole, and the operating force of the valve pin can be greatly reduced and the gate can be cut reliably.
[0053]
In addition, since the gate cut is performed at the tip portion of the molded product in this way, the material cost of the conventional cold runner can be greatly saved. In addition, the fact that no cold runner is generated means that there is no need to cut the cold runner from the molded product, and that the cost can be reduced, including the equipment cost, and the finished product is molded and removed when the molding is completed. Therefore, not only can the line be fully automated, but the molding material particle particles generated at the time of excision will not adhere to the molded product, especially medical parts such as cylinders, and defective products will also occur in this part. It is possible to eliminate the problem and to achieve extremely excellent effects.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a mold clamping state of a mold according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a state where a gate cut by a valve pin is performed in FIG.
FIG. 3 is a cross-sectional view showing the mold open state of the mold of the first embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a product ejecting state of the mold according to the first embodiment of the present invention.
FIG. 5 is an enlarged cross-sectional view showing a gate cut state of the mold according to the first embodiment of the present invention.
FIG. 6 is an enlarged cross-sectional view of the mold of the first embodiment of the present invention in the gate open state.
FIG. 7 is an enlarged cross-sectional view showing a gate cut state of a mold according to a second embodiment of the present invention.
FIG. 8 is an enlarged cross-sectional view of a mold according to a second embodiment of the present invention in a gate open state.
FIG. 9 is a sectional view of a conventional example.
FIG. 10 is an enlarged cross-sectional view of a conventional example of a filling state of a molding material
[Explanation of symbols]
(1) Mold
(2) Female type
(3) Male type
(4) Mold cavity
(5) Core
(6) Cylindrical cavity
(7) Valve pin
(8) Gate
(CL) Core axis

Claims (2)

Type fossa which is formed in the cavity member, and a cavity of a predetermined shape made of a core that is inserted into and removed from the mold fossa, through a gate provided in the cavity member communicating with said cavity, said cavity in a fluidized metered molding material supplied, it is and heater and the molding material injection path formed in the hot runner bush is provided, removably disposed on the gate in the molding material injection path In a mold for syringe molding provided with a valve pin,
An opening formed in the gate-side end face of the valve pin, communicating holes communicating with said molding material injection path are formed in the distal end portion of the valve pin,
The gate is provided with a cylindrical portion from the cavity toward the molding material injection path,
A tip portion of the valve pin is formed in a columnar shape so as to fit into the cylindrical portion and close the gate,
A die for molding a syringe , wherein the tip end surface of the core is formed at a position in close contact with a gate side end surface of the valve pin when the valve pin is inserted into the gate . (A) In a cavity constituted by a mold cavity formed inside the cavity member and a core inserted into and removed from the mold cavity, a measured molding material is formed on a hot runner bush provided with a heater. From the molding material injection path, injection filling through the gate provided in the cavity member,
  (B) After filling, a holding pressure is applied to apply a predetermined pressure to the molding material in the cavity,
  (C) After completion of the pressure holding step, a valve pin disposed so as to be detachable from the gate is inserted into the gate, the gate is cut and the end surface of the core and the gate side end surface of the valve pin are brought into close contact with each other. Returning the excess molding material accumulated in the gate portion through the communication hole communicating the gate side end surface of the valve pin and the molding material injection path to the molding material injection path,
  (D) Subsequently cooling to solidify the molding material in the cavity to form a molded body,
  (E) Then, in the method for molding a syringe, the molded body is taken out,
  The gate is provided with a cylindrical portion from the cavity toward the molding material injection path,
  A method for molding a syringe, wherein a tip portion of the valve pin is formed in a columnar shape so as to be fitted into the cylindrical portion and close the gate.

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