JPH01114408A - Process and device for synthetic resin injection molding - Google Patents

Abstract

PURPOSE:To enable high precision molding, and improve cutting-off at the gate, by a method wherein a heat molten resin is cooled and solidified at the gate after injection molding, and the gate is closed, then the resin is remolten to open the gate, and another injection molding is effected. CONSTITUTION:A molten resin passes through a runner 7, and a gate 4 into a cavity 3. In the injection process by the injection mechanism 9, since the resin in the conical gate 4 is in the cooling region, it solidifies very soon at a narrow tip 4a of an extremely small volume, to make a state of so called 'gate closed', a proper amount of molten resin is surely cast in the cavity 3 to effect a high precision molding. The heat molten resin dwelled in the gate 4 is sucked up according to the stroke amount of a suction piston rod 12, which enable the next molding operation to be effected at high speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for controlling a gate leading to a mold cavity by using a so-called
A cold gate or a configuration similar to a cold gate,
In connection with the molding operation, a small amount of hot molten resin that approaches this gate is solidified by the gate or sucked from the gate to the runner side to open and close the gate, thereby ensuring high precision moldability. This invention relates to a new synthetic resin injection molding method and apparatus.

(Prior art) In general, as a means of controlling a small amount of hot molten resin in a narrow space called a gate each time a molding operation is performed, the gate is constantly kept in a heated area and kept in the molten state "open" for molding. There are known methods and devices for molding by intermittently heating the material to melt and solidify the material and opening and closing the gate.

In the former, since the resin in the gate is always in a molten state, there are problems with moldability and it is unsuitable for high precision molding, so it is used exclusively for molded products that do not require much precision. In the latter case, since the resin of the gate is locally solidified each time the molding operation is performed, it has the advantage of good moldability and is suitable for high-precision molding.

[Problem that the invention seeks to solve]

By the way, in the above-mentioned injection molding method and apparatus,
In the latter method, in which the resin in the gate is locally cooled and solidified, it is necessary to open the gate by heating and melting it, rather than by cooling it in a narrow place called the gate. thermal control measures are required.

However, the runner side across the gate requires a thermal environment consisting mainly of heating, while the cavity side requires a thermal environment consisting mainly of cooling. The problem lies in the fact that it is located right at the boundary of the environment and thermal control at this boundary has a sensitive effect on the runner section and cavity.

In addition, internal heating methods and external heating methods are known as means for heating the runner section, but in the latter external heating method in particular, the runner section is linear and the storage space for the hot molten resin is small. However, there are positional constraints and problems in that the means for thermally controlling the gate must be provided in a narrow position on the outer periphery of the gate.

By the way, in the case of the former type of injection molding machine in which the gate is kept open at all times, during the molding operation, especially when the mold is opened, the molten resin exposed to the gate may drip, string, etc. To prevent resin leakage, for example, a suck-back body is placed between the nozzle of an injection molding machine and the nozzle contact part of the mold so that it can move back and forth, and when the mold is opened, this suck-back body is moved and prevents the melting in the runner. A resin vacuum suction mechanism is known that sucks resin under reduced pressure to prevent leakage of molten resin from a gate.

However, this resin decompression suction mechanism sucks the amount of suction according to the movement of the suckback body throughout the runner process, and is only intended to leak resin from the gate, so it does not have high precision moldability. There was a point.

[Means for solving problems]

This invention was made by focusing on the stacking point, and a molten resin suction means is provided in the runner including the runner section, and a conical resin suction means is provided in the runner, which is located in the cooling area outside the heating area, at the same time as the injection operation is completed. The hot molten resin is cooled and solidified at the gate, and the gate is closed.
Immediately, the cooled and solidified resin is sucked together with the hot molten resin in the opposite direction of the injection operation, and the gate is opened.
The above-mentioned problems are solved by heating and melting the material in the heating region of the runner section and performing the next injection molding operation.

[Effect]

First, the resin injected into the cavity by the injection operation is immediately cooled and solidified. At the same time, since the conical gate is located in the cooling region, the molten resin within the gate immediately begins to solidify, resulting in a so-called "gate open" state, which improves high-precision moldability in the cavity. Immediately, the molten resin suction mechanism pulls the solidified resin inside the gate into the runner along with the hot molten resin, and the gate opens.
becomes. The solidified resin that has been drawn in is heated in the heating region of the runner section, and becomes a thermally molten state again.

On the other hand, the molded product inside the cavity is discharged by opening the mold. Then, after the mold is clamped again, the hot molten resin is filled into the cavity from the runner section through the gate by the injection operation and the return movement of the molten resin suction mechanism, and the above-described molding operation is repeated.

〔Example〕

Next, one embodiment of the present invention will be described based on sectional views of main parts of the apparatus shown in FIGS. 1 to 4.

In each figure, 1 is a movable mold equipped with a male mold, 2 is a fixed mold equipped with a female mold, and a desired cavity 3 can be formed by both molds 1.2. Reference numeral 4 denotes a conical gate that opens toward the cavity 3 and is located in the cooling area, and has a configuration similar to a so-called cold gate or a cold gate.

A runner (flow path) 7 including the runner portion 5 is bored between the gate 4 and the nozzle touch portion 6.

The illustrated runner section 5 has an external heating type configuration, and a heater 8 wound in a tubular shape is arranged around the outer periphery so that the linear runner section 5 can be centripetally heated with respect to the gate 4. It has become. (The heater 8 can be a high-frequency electromagnetic induction heating means or the like.) 9 is an injection mechanism connected to the nozzle touch part 6, and 10 is a molten resin connected to the runner 7. It is a suction mechanism.

The configuration of the molten resin suction mechanism 10 will be shown below.

Reference numeral 11 denotes a suction runner that communicates with the runner 7, in which a suction piston rod 12 is disposed so as to be freely movable backwards.
It is constructed so that it can be slid in an airtight manner. Reference numeral 13 denotes a cylinder for operating the suction piston rod 12, which is operated by fluid pressure supplied in the forward and reverse directions through fluid pressure inlets and outlets 15 and 16 that are open in the cylinder chamber 14 in the front and back.
The suction piston rod 12 can be moved back and forth via the piston 17.

In the figure, 18 is the hole for the cartridge heater, and 19 is the hole for the cartridge heater.
indicates cooling holes.

The effect will be explained based on the stacked structure.

First, a desired molten resin is injected from the nozzle touch part 6 by the injection mechanism 9 in the same manner as in a normal injection molding operation, and the molten resin is injected into the cavity 3 through the runner 7 and the gate 4. (Refer to Fig. 1) Due to the injection operation by this injection mechanism 9, the resin located in the conical gate 4 is in the cooling region, so it immediately solidifies at the narrow tip 4a with an extremely small volume, and the so-called r-gate opens. Thus, just the right amount of molten resin is reliably injected into the cavity 3 and molded with high precision.

At the same time as this injection molding operation is completed, the molten resin suction mechanism lO
By applying this function, the solidified resin at the narrow tip 4a of the conical gate 4 is separated from the molded product A in the cavity 4, and the gate 4 is separated from the molded product A in the cavity 4 due to the suction action of the adjacent unsolidified hot melt resin. It moves smoothly along the conical shape and is sucked up to the runner portion 5. In this state, the molded product A can be taken out by moving the movable mold 1 and performing a mold opening operation.

Next, the operation of the above-mentioned molten resin suction mechanism 10 will be explained.

That is, when a desired gas or liquid is caused to flow in through the fluid pressure inlet/outlet 15 and the piston 17 is moved to the suction side, the suction piston rod 12 is driven to effectively suction the molten resin in the lifter 7, and the suction piston rod 12 The amount of suction corresponding to the stroke amount is sucked into the suction runner 11. Therefore, the hot molten resin stored in the gate 4 is drawn in, and when the gate 4 is in the open state, that is, the "gate open" state, it is sucked up to the state shown in FIG. 2, that is, the tip of the runner part 5, and in that state Under the heating action of the heater 8, the solidified resin returns to a thermally molten state and is maintained therein.

Next, the same operation can be repeated by performing the mold clamping operation as shown in FIG. 4 and then performing the next injection molding operation.

In synchronization with the operation of the injection mechanism 9, the molten resin suction mechanism 1
If gas or liquid is injected from the fluid pressure inlet/outlet 16 in the direction opposite to the above operation and the piston 17 is moved in the opposite direction, the hot molten resin temporarily stored in the suction runner 11 will be removed. , flows into the runner 7, becomes a molding resin, and is supplied to the cavity 4.

Moreover, the amount of molten resin in the portion of the gate 4 that is in contact with the conical gate 4 is extremely small, and it is constantly being cooled, so the outer surface of the molten resin that is sucked in, including the solidified resin, is very small. It appears to have solidified into a skin.

The suction operation of the molten resin suction mechanism 10 is preferably operated as soon as possible after the molten resin is cooled and solidified into the cavity 4, and depends on the resin used, the size of the gate, the number of cavities, the size of the cavities, etc. You can set the best time.

Next, other embodiments of the present invention will be described.

The same reference numerals are used to designate the same or corresponding configurations as those in the above embodiment, and redundant explanation will be omitted.

This embodiment shows a case in which a manifold 20 is disposed in the middle of a runner 7 to create a so-called multi-piece structure, and a piston-cylinder is provided in the middle of the runner 7 to isolate it from the injection mechanism 9 side. Molten resin suction mechanism 10 by disposing mechanism C
In conjunction with this, it is intended that the suction effect of the solidified resin from the gate 4 will be more effectively performed.

And, the cotton bending runner 21 bored in this manifold 20
A suction runner 11 is bored along the runner 11, and a suction piston rod 12 of a molten resin suction mechanism 10 is slidably disposed within this runner 11.

A wear-resistant material such as cemented carbide is fixed to the tip of this piston rod 12, and a hemispherical push cut is also fixed to the tip of the piston rod 12 so that it can be securely locked at the boundary between the runner 11 and the runner 21. It has become.

Also, the suction piston rod 12 is inserted from the top surface of the cylinder 13.
One end is made to protrude freely in and out, and an adjustment ring body 22 is screwed onto it, and by adjusting the amount of screw engagement of this ring body 22, the stroke amount of the suction piston rod 11 can be controlled. A suction amount adjustment mechanism B consisting of the following structure is attached.

Further, this adjustment mechanism B is provided with a locking nut 23 and a scale plate 24, so that the amount of adjustment of the adjustment ring 22 can be read, accurately set, and reliably fixed in position.

As shown in FIGS. 6 and 7, the operation of the molten resin suction mechanism 10 of this embodiment is such that the injection completion time and the suction time are the first
As shown in FIG. 2 and FIG. 2, since it is completely the same as the previous embodiment, detailed explanation will be omitted.

In the figure, 25 is a piston rod that crosses the runner 7 to open and close the runner 9, and 26 is a cylinder, which can be controlled with a desired gas or liquid.

Although this invention has been described above with respect to a structure in which the runner part is of an external heating type, it can be similarly implemented to a structure of an internal heating type, that is, a structure in which a heating probe is disposed within the runner part.

(Effects of the Invention) As described above, the present invention provides numerous effects as listed below.

(1) After the injection operation, the molten resin at the gate solidifies and closes the gate, allowing for high-density molding, and this solidified resin is immediately drawn into the runner section of the heating area and heated and melted, so the gate closes. The cutting becomes better, and the gate becomes "gate open", allowing the next molding operation to be performed at high speed.

(2) There is no need to derive sprue runners, and waste of raw resin can be avoided.

(3) The injection pressure during injection operation, especially in the case of externally heated runners, can be significantly lower than that of conventional ones because there is almost no pressure loss, which reduces the cost of the injection molding machine. can increase durability.

(4) As described in (3), since the mold clamping pressure can be reduced as well as the injection pressure can be reduced, it is possible to provide an injection molding apparatus that consumes less energy and is more compact overall.

(5) Since the gate is conical, the resin can be peeled off and moved very smoothly by suction. In addition, the taper angle and depth of the conical shape can be freely adjusted, and the hole at the tip of the gate can be reduced to, for example, about 0.5 am, leaving no trace of the gate on the molded product. It is possible to make it less noticeable.

(6) Molding cycles can be set freely. If the molding cycle is delayed, the skin layer at the gate will become thicker, but since it will be sufficiently heated in the runner, there is no risk that it will immediately return to the molten state and inadvertently remain in the solidified state.

(7) Since the molten resin can be suctioned by the molten resin suction mechanism, there is no need for complicated control, the controller is simplified, and the entire system can be configured compactly.

(8) It is possible to completely prevent resin leakage such as dripping and stringing of molten resin from the gate, which are problems in runnerless injection molding.

(9) Runnerless injection molding using a cold gate method that does not produce a so-called sprue runner can be provided.

[Brief explanation of the drawing]

1 to 4 are sectional views of essential parts showing the basic configuration of one embodiment of the present invention, FIG. 5 is a sectional view of essential parts showing another embodiment, and FIGS. 6 and 7. FIG. 2 is an enlarged sectional view showing the same gate portion at the time of completion of injection and at the time of suction. 3------Cavity 4------Gate 5------Runner section 7---One runner 9---Injection mechanism 10---Molted resin suction mechanism 11--- --- Suction runner 12 --- Suction piston rod 20 ... Manifold 21 ... Bend runner 22 --- Adjustment ring A --- --- Molded product B --- Suction amount adjustment mechanism C...- Piston-cylinder mechanism

Claims (2)

[Claims] (1) A synthetic resin injection molding method in which a desired amount of hot molten resin is fed into a runner by an injection mechanism and is injected into a desired cavity from the runner section of the runner through a conical gate. At the same time as the injection operation is completed, the hot molten resin is cooled and solidified using the conical gate, and the gate is closed.
Then, the resin solidified at the gate is immediately sucked together with the hot molten resin in the opposite direction to the injection operation to open the gate, and the resin is heated and melted in the heating area of the runner section, so that the next injection operation can be performed. Characteristic synthetic resin injection molding method. (2) A mold that can be opened and closed, a conical gate leading to a cavity provided in the cooling area of the mold, a runner provided in the heating area through which hot molten resin flows, and a runner for injecting the hot molten resin. The conical gate is kept outside the heating area, and a molten resin suction mechanism is provided at a portion leading to the runner, and during the injection operation by the mechanism,
The gate closed with solidified resin is sucked together with hot molten resin,
A synthetic resin injection molding apparatus characterized in that the gate is opened.