JPH0584788A - Injection molding method and injection molding machine - Google Patents

Abstract

PURPOSE:To reduce the number of traces of a gate flaw and the ejection flaw of an ejector pin on the surface of injection moldings by arranging the ejector pin on the axial line of a gate and utilizing the gate space as the ejection part of the moldings by the ejector pin. CONSTITUTION:A three plates mold is used in an injection molding machine. An ejector pin 19 is provided on the same axial line as the axial line of a cavity and also moved back and forth through the inside and outside of the cavity. In the case of taking out the moldings, while at least leaving the moldings in the cavity to the inside of the mold, one part of a runner stripper plate 3 is opened in such a gap that the runner moldings surely fall. Thereby the moldings in a runner 12 and a pin point gate 14 are taken out. After the runner moldings and the gate moldings are taken out, the mold is opened and also a movable mold 2 having the gate is moved to the runner stripper plate and allowed to abut thereon. The ejector pin 19 is actuated in the gate to eject the moldings to the outside of the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can minimize the number of gate traces and ejector traces due to ejector pins when taking out a molded product, and can make those traces inconspicuous and minimize the ejector pin diameter. Can be set,
At the same time, the present invention relates to an injection molding method and an injection molding machine that facilitate the removal of molded products of the runner and gate.

[0002]

2. Description of the Related Art In injection molding, various methods are adopted for taking out a molded product solidified in a mold.
In general, the mold is often opened and then ejector pins are actuated to protrude outside the mold.

By the way, since the protruding position of the ejector pin and the gate position in the cavity are different,
Inevitably, ejector pin protrusion marks and gate marks remain on the surface of the molded product taken out of the mold. For example, a pinpoint gate has been adopted to prevent these traces from remaining, but at least the ejector pin protrusion marks tend to remain clearly.Even if the protrusion operation is adjusted, the traces can be reduced. Even if it does, the ejector pin protrusion trace and the gate trace cannot be completely removed in any case. In addition, the protrusion mark by the ejector pin leaves a concave mark on the surface of the molded product, and the gate mark on one side leaves a protrusion mark on the surface of the molded product.

In order to eliminate these drawbacks as much as possible, the inventors of the present invention previously reduced the number of traces and at the same time made the traces less noticeable than in the past, and a molding machine therefor. (Japanese Patent Application No. 3-
168351).

In this injection molding method, a resin material which is kneaded and melted by an injection device is injected into a cavity formed in a three-piece metal mold through a sprue, a runner and a gate, and a molded product is produced by using an ejector pin. In the injection molding method of taking out from the mold, when taking out the molded product,
With at least the molded product in the cavity left in the mold, a step of opening the plate for supporting and guiding the guide pin and taking out the molded product in the runner and the gate, and after removing each of the molded products, open the mold and It comprises at least two steps of activating ejector pins in the gate to eject the molded product out of the mold.

The injection molding machine is equipped with an injection device and a three-piece assembly mold, and in the injection molding machine for taking out a molded product by an ejector pin, the three-piece assembly mold has two product cavities. Of the mold and a plate for supporting and guiding at least a guide pin disposed on the back side of the mold, the gate is parallel to the sprue and communicates at a right angle with the surface of the cavity, and the ejector pin is
It is guided by the plate on the same axis as the axis of the gate, and can move back and forth inside and outside the cavity.

[0007]

However, in the above-mentioned invention proposed above, when the buckling of the ejector pin is taken into consideration,
The length is naturally limited, and it is necessary to increase the pin diameter to make the ejector pin long.

In order to set the length of the ejector pin to be short, it is necessary to narrow the opening range of the plate due to the structure of the mold, and if the mold opening range is too narrow, the ejector pin is connected to the inside of the runner and the gate. The molded product to be molded is sandwiched between the mold and the plate, making it impossible to take out from the injection molding machine.

On the other hand, when trying to widen the mold opening range, the ejector pin diameter must be set large, and not only the gate trace becomes large but also the protrusion trace by the ejector pin becomes large, so that a good quality product can be obtained. Disappear.

The present invention has been developed to solve the above problems, and its purpose is to make it possible to reduce the number of traces and to make the traces less noticeable than before. An object of the present invention is to provide an injection molding method and an injection molding machine in which the ejector pin is short and the diameter thereof is set to the minimum, and there is no problem in taking out a molded product other than the molded product.

[0011]

In order to achieve the above object, the method according to the present invention uses a resin material which is kneaded and melted by an injection device into a cavity in a three-plate mold through a sprue, a runner and a pinpoint gate. In the injection molding method of injecting and taking out the molded product from the mold using the ejector pin, at the time of taking out the molded product, at least the molded product in the cavity is left in the mold and a part of the plate and the mold are opposed to each other. Opening the mold to separate each molded product in the runner and gate from the molded product in the cavity, and while holding each molded product in the plate, the plate and the mold may interfere with the fall of the molded product. A step of relatively moving to a range where it does not come and stopping, a step of separating the molded product from the plate at the stop position, and each molded product After the separation, the main constitution is provided with a step of opening one of the molds to abut against the plate, and a step of operating ejector pins in the gate to project the molded product out of the mold. The injection molding machine according to the present invention comprises an injection device and a three-piece mold,
In an injection molding machine for ejecting a molded product by an ejector pin, the gate is in communication with the sprue at a right angle to the inner surface of the cavity, the ejector pin is arranged on the same axis as the axis of the gate, and inside and outside the cavity. When the mold is opened, the two molds that make up the cavity are separated from the other plates until the molded products in the runner and gate fall enough to form the runner. After the product is removed from the mold, the control driving means that relatively moves the plate-side mold of the two molds until the plate again contacts, and the mold and the plate contact each other. After that, an operating means for operating the ejector pin so as to project into the cavity of the same mold through the gate, as a main configuration. That.

[0012]

For example, the die is composed of a moving die having a cavity for molding the product, a fixed die and a stripper plate for holding the runner molded article, and the stripper plate is attached to the back side of the moving die. The operation of the injection molding machine of the type described will be described.

After the movable mold moves toward the fixed mold and the mold is closed, the molten resin in the injection device is injected into the sprue from the injection nozzle and is filled into the cavity through the runner and the gate. It

When the resin is cooled and solidified, the mounting plate on the moving side starts to retreat, and the stripper plate is first retracted to form the runner and gate molded products held by the runner lock pin while leaving the molded product in the cavity. Separate from the mold.

Subsequently, the moving side mounting plate is retracted to move the stripper plate to a position where the distance between the die and the stripper plate does not hinder the fall of the molded product, and the runner lock pin is retracted there. The runner and gate are disengaged from the molded product, and the molded product is dropped outside the mold.

Subsequently, while the molded product is attached to the cavity of the movable mold, the movable mold is moved until it comes into contact with the above-mentioned stripper plate by a dedicated cylinder or the like, and at the same time, the ejector pin is operated to move. An ejector pin is inserted into the gate formed in the mold, and the tip of the ejector pin projects the molded product out of the mold.

Since the protruding portion of the molded product by the ejector pin coincides with the gate outlet, the gate mark left on the molded product is pressed by the tip of the ejector pin, and the trace becomes extremely small. .. Moreover, there are no other traces on the molded product, and it has an extremely good appearance.

[0018]

The present invention will be described in more detail below with reference to the illustrated embodiments. The drawings are all related to the present invention, and are operation explanatory views showing an outline of a mold device and an operation of the mold device in order in a four-hole button injection molding machine.

The parts of the injection molding machine other than those shown in the drawing, that is, the injection device, the mold opening / closing device, the details of the mold, etc., are the same as those of the conventional structure, and therefore the description thereof is omitted here.
The characteristic part of the present invention will be mainly described.

In FIG. 1, 1 is a fixed mold, 2 is a moving mold, 3 is a runner stripper plate, 4 is a receiving plate, 5
Is a spacer block, 6 is an ejector plate, 7 is a fixed side mounting plate, and 8 is a moving side mounting plate. The moving mold 2
A lock groove 32 of a cam link 30, which will be described later, is provided on a part of the side surface
A lock protrusion 2-1 that engages and disengages with the cam plate is provided on a side surface of the receiving plate 4, and a cam surface 4-1 that contacts the cam contact pin 33 of the cam link 30 is formed on the side surface of the receiving plate 4. .. A hot sprue bushing 9 is inserted through the fixed-side mounting plate 7 and the center of the fixed mold 1 and fixed by a locate ring 10.

The tip end outlet of the sprue 11 formed at the center of the hot sprue bushing 9 communicates with the runner 12 formed between the moving die 2 and the runner stripper plate 3. On the other hand, a cavity 13 which is a molding space for a four-hole button is formed on the mating surface of the fixed mold 1 and the movable mold 2, and the center of the cavity 13 and the runner 12 are pinpoint gates. They are connected at 14. In the molding of the four-hole button according to this embodiment, 16 buttons are simultaneously molded by one injection, that is, so-called 16 pieces are taken. However, one of them is shown in the drawing, and the others are omitted. ing.

The polyacetal resin, which is the raw material for the injection molding of the four-hole button according to this embodiment, has a small difference between the melting point (160 ° C.) and the crystallization temperature (145 ° C.), and the resin is not contained in the cavity during injection molding. When it is filled, the air and gas existing inside it are released from the mating surface of the mold while being compressed by the resin filling pressure.At this time, the surface layer of the resin is controlled by the mold temperature and naturally crystallizes. The temperature is lower than the oxidization temperature, the resistance of air and gas is transmitted to the resin surface,
This is because a so-called flow mark is likely to occur, and this tendency tends to occur remarkably because the polyacetal resin has a high crystallization speed. Furthermore, the polyacetal resin is liable to form a so-called paraform type precipitate (called a mold deposit), which has a low degree of polymerization of formaldehyde, which is the main raw material, and if the molding is continued for a long time, it is left on the cavity surface. Precipitates may adhere and deteriorate the appearance of the product. Therefore, although not shown, a part of the periphery of the cavity 13 may be communicated with an external intake source to positively release the gas of the mold deposit to the outside.

Reference numeral 17 is a runner lock pin, one end of which is fixed to the stepped hole of the receiving plate 4 and the other end of which is loosely inserted into an insertion hole formed in the runner stripper plate 3.
At the tip of the runner lock pin 17 that is loosely inserted into this insertion hole, an engaging portion 18 that engages with a molded product formed on the runner 12 is formed, and when the mold is closed, the engagement of the runner lock pin 17 is performed. The portion 18 projects into the runner 12 and becomes integral with the molding resin to be filled.

Reference numeral 19 denotes an ejector pin, which is one of the features of the present invention, the base end of which is fixed to the ejector plate 6, and the tip end of which is loosely inserted into the through holes of the receiving plate 4 and the runner stripper plate 3. When the mold is closed, the tip is attached so as to match the mating surfaces of the movable mold 2 and the runner stripper plate 3. This ejector pin 1
The installation position of 9 is set so that the axis of the pinpoint gate 14 and its axis coincide. That is, the pinpoint gate 14, the receiving plate 4, and the insertion holes of the ejector pins 19 of the runner stripper plate 3 are arranged in a straight line. In the present embodiment, the diameter of the tip of the ejector pin 19 is 0.8 mm, and the corresponding outlet diameter of the pin point gate 14 is designed to be 0.9 mm. These numerical values are not limited, and can be appropriately changed depending on the type of molding resin raw material, the type of molded product, other molding conditions, etc., but the four-hole button has a gate diameter of 1.1 mm. When it exceeds, it becomes difficult to separate the molded product in the gate from the molded product, and a part of the gate molded product remains on the surface of the product.

Numerals 20 and 21 are shoulder bolts, and one of the shoulder bolts 20 is set to have a predetermined length longer than the distance when the movable die 2 and the runner stripper plate 3 are most opened, and the tip thereof is a movable die. 2, the head 22 is larger than the head 22 formed on the receiving plate 4 and the spacer block 5 while penetrating through the through hole 23 having a smaller diameter than the head 22 formed on the runner stripper plate 3. Is loosely inserted in the through hole 24 of the diameter,
The other shoulder bolt 21 is set to have a predetermined length longer than the thickness when the runner stripper plate 3 and the receiving plate 4 are superposed, and the head 25 thereof has a large diameter portion of the stepped through hole 26 formed in the receiving plate 4. And is inserted into the runner stripper plate 3, and its tip is fixed to the runner stripper plate 3.

The above distance when the movable die 2 and the runner stripper plate 3 are opened most is such that the molded products of the runner and the gate fall freely without any interference by the movable die 2 and the runner stripper plate 3. That is a sufficient interval.

Reference numeral 30 is a cam link, one end of which is pivotally attached to the end of the fixed side mounting plate 7 so as to be rotatable, and which always presses the side surface of the mold by an elastic biasing means 31 such as a spring. And a lock groove 32 is formed in a portion of the cam link 30 that comes into contact with the moving mold 2 when the mold is closed, and a free end portion of the cam link 30 is provided with a receiving plate 4 of the receiving plate 4 when the mold is opened. A cam contact pin 33 that contacts the cam surface is projected.

In the present invention, reference numeral 40 designates a control drive unit of the die, which is the most important part together with the ejector pin 19 in the present invention when the die is opened. In this embodiment, the chain is interlocked with the movement of the moving side mounting plate 8. Mold 2 moving through 41
Also, the movement timing and movement range of the runner stripper plate 4 are drive-controlled.

That is, one end of one chain 41 is fixed to the side surface of the fixed mold 1 and the other end is fixed to the side surface of the movable mold 2, and the chain 41 is projected on the side surface of the spacer block 5. It is hung on the sprocket wheel 42. The length of the chain 41 is fixed mold 1 and movable mold 2
Is in the mold closed state, and the movable mounting plate 8 is in the final retracted position in the mold opening direction, the ends are fixed to the fixed mold 1 and the movable mold 2 while being wound around the sprocket wheel 42. The chain 41 is set to be in a tension state. Therefore, when the mold is completely closed, the chain 41 is in a state where the extra portion is slack.

An ejector rod 44 for actuating the ejector pin 19 is arranged below the central portion of the lower surface of the ejector plate 6.

Next, the molding method of the present invention using the above injection molding machine will be described with reference to FIGS. 1 to 6, in which the moving mold 2 is moved toward the fixed mold 1 by a driving device (not shown), After the mold was closed, the polyacetal resin kneaded and melted in the injection device (not shown) was injected into the hot sprue 11 in the sprue bush 9 from the injection nozzle (not shown), and passed through the runner 12 and the pinpoint gate 14. To fill the cavity 13. (See FIG. 1) At this time, a vacuum pump (not shown) may be operated to suck and exhaust the air and generated gas inside the cavity through the intake hole.

When the resin is cooled and solidified, the mold clamping device is actuated, the moving side mounting plate 8 starts to retreat, penetrates the runner stripper plate 3 and the receiving plate 4, and the tip fixed to the moving mold 2 is held. Until the bolt head 22 of the bolt 20 comes into contact with the back surface of the runner stripper plate 3, the runner stripper plate 3 and the receiving plate 4 are retracted as a unit, and the molded product remains in the cavity 13 as shown in FIG. The molded products in the runner 12 and the gate 14 held by the engaging portion 18 of the runner lock pin 17 are separated from the molds 1 and 2. At the position where the bolt head 22 of the shoulder bolt 20 comes into contact with the back surface of the runner stripper plate 3, the molded products in the runner 12 and the gate 14 do not receive any interference between the moving mold 2 and the runner stripper plate 3. It is a position with sufficient spacing to allow free fall. At this contact position, the cam link 30
The locking projection of the movable die 2 is engaged with the lock groove 32 of the movable die 2 and the movable die 2 is in close contact with the fixed die 1.

When the moving side mounting plate 8 is further retracted slightly from this state, the base end of the runner lock pin 17 is in contact with the stepped through hole of the receiving plate 4, so that the runner lock pin 17 is fixed to the receiving plate. Retreat with 4 and above runner 12
Also, the molded product of the gate 14 is disengaged from the tip end engaging portion 18 of the runner lock pin 17 and falls. At this time, the chain 41, which is wound around the sprocket wheel 42 and whose ends are fixed to the fixed mold 1 and the movable mold 2, is in a tensioned state, and at the same time, the cam surface 4-1 of the receiving plate 4 is of the cam link 30. It is at a position where it comes into contact with the cam contact pin 33 protruding at the tip. (See FIG. 3) Subsequently, when the moving side mounting plate 8 is retracted, the stripper plate 3 and the receiving plate 4 are retracted via a mold guide pin (not shown), and the cam link 30 causes the cam surface 4 of the receiving plate 4 to move. The movable die 2 is unlocked by rotating the movable die 2 in the direction away from the die against the urging means by 1 to rotate the sprocket wheel 42, and the chain 41
The movable mold 2 is separated from the fixed mold 1 with the molded product adhered to the cavity 13 via. (See FIG. 4) When the moving side mounting plate 8 continues to retract, the sprocket wheel 42 rotates as shown in FIG.
The moving die 2 is moved through the above until it comes into contact with the runner stripper plate 3.

When the moving die 2 comes into contact with the runner stripper plate 3, the moving side mounting plate 8 stops. After this stop, the ejector rod 43 is actuated to push the ejector plate 6 toward the fixed mold 1, and the ejector pin 17 is formed in the moving mold 2 through the through holes of the runner stripper plate 3 and the receiving plate 4. 1
4, and the molded product adhering to the cavity 13 is pushed out of the mold. (Refer to FIG. 6) Since the protruding portion of the molded product by the ejector pin 19 coincides with the gate outlet, the gate trace left on the molded product is pressed by the tip of the ejector pin 19, and the trace is extremely small. Will be things. Moreover, there is no other trace on the molded product, and a product having an extremely good appearance can be obtained.

It is obvious that the present invention is not limited to the above-mentioned examples, and therefore, the kind of resin as an injection molding raw material is not limited to the above polyacetal resin, either.
It is also possible to arrange the stripper plate 3 and the receiving plate 4 on the back side of the fixed mold 1, and to set the runner lock pin 17 and the ejector pin 19 on the fixed side mounting plate 7 side, and further to move the above Control drive unit 40 for mold 2
Also, instead of the chain 41, a hydraulic cylinder operated based on a control signal of an external control device (not shown) can be adopted, and the structure of the lock mechanism of the movable mold 2 and the mold is also of the present invention. Various changes can be made without departing from the spirit.

[0036]

As described above in detail, according to the present invention, the ejector pin is arranged on the axis of the gate, and the gate space is used as the protruding portion of the molded product by the ejector pin. The ejector pin and the gate trace overlap each other to form a single trace, and as a result of pressing the gate trace projecting on the molded product with the tip of the ejector pin, the trace is much larger than the conventional trace. It will be scarce. Furthermore, according to the present invention, the molded product in the runner or gate is removed from the runner lock pin in a sufficiently wide space, so that the molded product can be reliably discharged out of the mold. When ejecting a molded product from the mold that forms the cavity using the ejector pin, the ejector pin is operated while the mold with the gate is in contact with the plate that supports and guides the ejector pin. Can be set to be as short as possible, the ejector pin diameter can be minimized accordingly, and the protrusion mark by the ejector pin can be made small.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a mold part showing a resin filled state during injection molding according to the present invention.

FIG. 2 is a sectional view of an essential part showing a position where a molded product in a runner according to the present invention is separated from a mold.

FIG. 3 is a cross-sectional view of essential parts showing a mold open state when a molded product in the runner separates and falls from a mold.

FIG. 4 is a sectional view of an essential part showing a moving state of a moving die according to the present invention.

FIG. 5 is a cross-sectional view of essential parts showing a state in which the movable die is in contact with a runner stripper plate.

FIG. 6 is a cross-sectional view of essential parts showing an operating state of the ejector pin according to the present invention when the molded product according to the present invention is projected.

[Explanation of symbols]

 1 Fixed Mold 2 Moving Mold 2-1 Lock Protrusion 3 Runner Stripper Plate 4 Receiving Plate 5 Spacer Block 6 Ejector Plate 7 Fixed Side Mounting Plate 8 Moving Side Mounting Plate 9 Hot Sprue Bushing 10 Locate Ring 11 Sprue 12 Hot Runner 13 Cavity 14 pin point gate 15 seal ring 17 runner lock pin 18 engaging part 19 ejector pin 20,21 shoulder bolt 22,25 head 23,24 through hole 26 stepped through hole 30 cam link 31 biasing means 32 lock groove 33 cam Contact pin 40 Control drive unit 41 Chain 42 Sprocket wheel 43 Ejector rod

Claims (2)

[Claims] 1. A resin material which is kneaded and melted by an injection device is injected into a cavity in a three-piece mold through a sprue, a runner, and a pinpoint gate, and an ejector pin is used to take out a molded product from the mold. In the molding method, at the time of taking out the molded product, at least the molded product in the cavity is left in the mold and a part of the plate and the mold are relatively opened to form the molded product of the runner and the gate in the cavity. A step of separating from each other, and a step of relatively moving one of the plate and the mold to a range that does not hinder the fall of the molded product while holding each molded product on the plate and stopping the molded product. A step of separating the molded product from the plate at the stop position, and after separating each of the molded products, one of the molds is opened to contact the plate. That step and an injection molding method for the molded product by operating the ejector pin and a step projecting out mold, characterized in that it comprises a within the gate. 2. An injection molding machine comprising an injection device and a three-piece assembly die, wherein a molded product is taken out by an ejector pin, the gate is in communication with the sprue at a right angle to the inner surface of the cavity, and the ejector pin is It is arranged on the same axis as the gate axis and can move back and forth inside and outside of the cavity.When the mold is opened, first the cavity is moved until the runners and the molded articles in the gate fall to a sufficient distance. After separating the two molds and the other plate from each other to separate the runner molded product from the mold, the two molds are relatively moved until the plate-side mold and the plate come into contact again. Control drive means for moving the mold to the mold, and after the mold and the plate come into contact with each other, the ejector pin is operated so as to protrude through the gate into the cavity of the mold. Injection molding machine and characterized by having a motion means, a.