JPH02202420A - Pressure measuring device of plasticizing material in injection molding and injection molding machine - Google Patents

Abstract

PURPOSE:To precisely measure the pressure of a plasticizing material in both a measuring process and injection process by measuring the pressure of the plasticizing material by a pressure sensor arranged on the rear or the front of an injection plunger. CONSTITUTION:A plasticizing material melted and plasticized by a preplasticizing mechanism 20, for example, molten resin is sent to a resin rich area 18 from the preplasticizing mechanism and a ram 34 and injection plunger 22 are moved backward to an initial position. Then even after filling of the resin rich area 18 with the molten resin, the preplasticizing mechanism 20 keeps sending the molten resin and the injection plunger 22 is pressed rightward by force of the molten resin. The resin pressure pressing the injection plunger 22 rightward presses a pressure sensor 32 of the rear of the injection plunger and the resin pressure is measured by the pressure sensor. The pressure of the plasticizing material in a measuring process is obtained easily in this manner. The resin pressure in the injection process acts upon the injection plunger 22 as reaction force, measured by the pressure sensor 32 of the rear of the injection plunger and also a variation of the resin pressure is secured reliably.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention relates to a method for measuring the pressure of a plastic material in injection molding in which plastic material in a resin reservoir in front of an injection cylinder is injected as an injection plunger moves forward, and a method for measuring the pressure of a plastic material in injection molding. Regarding machines.

[Prior Art] In injection molding, a plastic material such as a resin (Plasti-2) is heated and melted, injected under pressure into a mold cavity, and after cooling, is taken out from the cavity as a molded product. There is. Recently, new materials such as ceramics have also been plasticized and molded using water, resin, etc. as inclusions. In the molding process, it is necessary to mold a molded product of constant quality without variation.

In particular, in the technologically advanced and precise industry, there is a high need for molded products of a certain quantity and quality.Therefore, in conventional technology, certain conditions (optimal conditions) against external disturbances are required. The mechanical molding conditions (injection pressure, injection speed, injection amount, heating temperature, screw rotation speed, back pressure, holding pressure, etc.) are computer-controlled by closed-loop control or the like to maintain the same.

However, variations in the plastic material itself make it difficult to maintain optimal conditions. For example, even if the same plastic material is used, there are variations in material particle size and intrinsic viscosity depending on the loft. Furthermore, variations in the amount of water contained due to uneven drying cause variations in viscosity. Then, in response to fluctuations in the plastic material itself, the flow velocity of the plastic material within the cavity, the pressure distribution, the manner in which a solidified layer is generated, etc. change. Therefore, even if one mechanical molding condition is maintained constant during the molding cycle, variations in dimensions, variations in appearance, and defective mold release occur in the molded products, making it difficult to completely prevent the occurrence of defective products.

Therefore, in the metering process and injection process, the pressure of the plastic material is accurately measured, and the mechanical molding conditions (injection pressure, injection amount IW, injection amount, heating temperature, screw rotation speed) are adjusted according to the fluctuations in the pressure of the plastic material. Detection of hydraulic pressure at the source of pressurized medium, such as pressurized oil, supplied to the injection cylinder during advancement of the injection plunger or screw, where it is important to control the pressure (back pressure, holding pressure, etc.) Therefore, a measurement method is generally used in which the pressure of the plastic material is indirectly determined during the metering process and the injection process.

In addition, the so-called nozzle, the front part of the plunger cylinder,
A pressure sensor is placed on the resin retainer and the back of the screw,
Methods of measuring pressure in plastic materials are also known.

[Problem to be solved by the invention]

However, in the method of determining the pressure of the plastic material from the pressure of the pressurized medium at the source, pressure fluctuations of the pressurized medium may be affected by uncertain factors such as pipe resistance, valve resistance, peak pressure, and pulsation. It is not possible to adequately cope with pressure fluctuations, and therefore the pressure fluctuations of the plastic material cannot be accurately grasped, and the pressure of the plastic material cannot be accurately measured.

In contrast, a pressure sensor is placed in the resin retainer at the front of the nozzle and plunger cylinder.
With the method of measuring the pressure of plastic materials, the pressure of plastic materials can be directly measured, so the pressure of plastic materials can be accurately measured without being affected by uncertainties, and pressure fluctuations in iTT plastic materials can be quickly and easily understood. Here, since the wall thickness of the nozzle and the plunger cylinder is thin, the pressure sensor is fixed to the outer periphery of the nozzle and the plunger cylinder, and the pressure sensor is disposed through the wall of the nozzle and the plunger cylinder.

However, since the pressure of the plastic material pushes the pressure sensor outward, in such a configuration, there is a risk that the pressure sensor may fall off the wall of the nozzle or plunger cylinder due to the pressure of the plastic material. . In addition, when mounting the pressure sensor, so-called resin leakage is likely to occur from the hole, so the hole must be removed and the structure must be designed to prevent resin leakage, which complicates the structure. Furthermore, the mounting position is limited, maintenance is not easy, and there are problems with durability.

Furthermore, in a configuration in which a pressure sensor such as a load cell is placed on the back side of the screw, the screw and mechanism remain for a long time between the plastic material and the pressure sensor. and,
Because the screw and mechanism have considerable mass, elastic strain, and clearance between members, an impact load is generated and acts on the pressure sensor. Therefore, the measured value of the pressure sensor tends to be inaccurate due to the impact load, and also due to the influence of inertia. Therefore,
Pressure of plastic material cannot be measured accurately.

This invention enables the measuring process to be performed without complicating the structure.
A method for measuring the pressure of plastic materials in injection molding that can accurately measure the pressure of plastic materials in both injection processes, and
Regarding the molding machine.

[Means to solve the problem]

In order to achieve this object, the present invention employs a plunger injection method, and measures the pressure of the plastic material by a pressure sensor disposed on the back or front of the injection plunger. Alternatively, the pressure of the plastic material may be measured from a strain sensor disposed on the side surface of the injection plunger.

[Effect]

In this invention, since a plunger injection method is adopted without using a screw, generation of impact load is suppressed and accurate pressure measurement is possible.

In addition, the pressure of the plastic material is not measured indirectly from the pressure of a pressure medium such as pressurized oil, but the pressure of the plastic material at the front of the injection plunger is measured directly or at a point as close as possible. The influence of uncertain factors such as pipe resistance, valve resistance, peak pressure, and pulsation is eliminated, and the pressure of the plastic material can be measured accurately.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, according to the present invention, an injection molding machine 1
0 is configured by a plunger injection method, that is, the injection molding y110 heats and melts the plunger cylinder 14 around which the band heater 12 is wound and the plastic material, such as resin, supplied to the hopper 16. It includes a pre-plastic mechanism 20 that sends the resin to a so-called resin reservoir 18 at the top of the heating cylinder, and an injection cylinder 24 that slidably houses an injection plunger 22. In the embodiment, the pre-plastic mechanism 20 is configured as a plunger type having a plunger 28, but it may be a one-screw type.

The pre-plastic mechanism 20 has a known configuration, and a band heater 12 is also arranged around a heating cylinder 28 of the pre-plastic mechanism. The resin supplied to the hopper 16 is transferred to the heating cylinder 28. Uniform heating with Torpedo 3o,
The resin is melted and sent to the resin reservoir 18 as the plunger 26 of the pre-plastic mechanism moves forward.

The plunger 23 of the injection plunger 22 is arranged in a ram 34 and behind the head a pressure sensor 32 is arranged. In the embodiment, a funnel washer is used as the pressure sensor 32, but a pressure sensor other than a load washer may be used. For example, when pressurized oil is supplied to the injection cylinder 24 from the flow path 3B, the pressurized oil pushes the ram to the left.

Here, since the plunger 23 of the injection plunger 22 is disposed inside the ram, and the pressure sensor 32 is disposed inside the ram at the back of the head, when the ram 34 is pushed to the left, the ram will Injection plunger 2 via pressure sensor 32
Press 2 and move to the left with the injection plunger.

In other words, the ram 34 and the injection plunger 22 move forward together.

Moreover, if pressurized oil is supplied to the injection cylinder 2 from another flow path 38, the ram 34. The injection plunger 22 integrally moves to the right and retreats to the initial position.

In this invention, the pressure sensor 32 is connected to the injection plunger 22.
The injection plunger is interposed between the injection plunger and the ram. And, by this pressure sensor 32,
The pressure of plastic materials such as resins and ceramics in the metering process and the injection process is measured as follows.

First, a plastic material, for example, a molten resin, melted and plasticized in the pre-plastic mechanism 20 is transferred from the pre-plastic mechanism to the resin reservoir 1.
8 to retract the ram 34 and injection plunger 22 to their initial positions. Then, even after the resin reservoir 18 is filled with molten resin, the pre-plastic mechanism 20 continues to feed the molten resin,
The pressure of the molten resin (resin pressure) causes the injection plunger 2 to
2 is pushed to the right.

The resin pressure pushing the injection plunger 22 to the right pushes the pressure sensor 32 on the back of the injection plunger, and the resin pressure is measured by the pressure sensor.

In this way, the pressure of the plastic material in the metering process can be easily determined by the pressure sensor 32 on the back of the injection plunger measuring the pressure of the plastic material. In this invention, an injection plunger method is adopted, and the resin reservoir 18
Since the injection plunger 22 is only interposed between the molten plastic material and the pressure sensor 32, the generation of impact load and inertia is suppressed, and the pressure of the plastic material can be accurately measured. Also, unlike known measurement methods that determine the pressure of the plastic material from the pressure of a working medium, such as pressurized oil, supplied to the injection cylinder 24, such measurement methods rely on pipe resistance, valve resistance, and peak pressure. , the influence of uncertain factors such as pulsation can be eliminated. Therefore, the pressure of the plastic material can be determined accurately from this point as well.

When the pressure sensor 32 reaches a predetermined value, the pre-placing mechanism 20 is stopped and the feeding of molten resin from the pre-placing mechanism to the resin reservoir 18 is interrupted.

When the feeding of molten resin is interrupted, pressurized oil is supplied to the injection cylinder 24 through the flow path 36, the ram 34 moves forward together with the injection plunger 22, and the molten resin in the resin reservoir 18 is transferred to the nozzle 42. is injected into a mold cavity (not shown) through the . Although not shown, the pre-plastic mechanism 20. A check valve is provided in the flow path between the resin reservoirs 18 to prevent backflow from the resin reservoir to the pre-plastic mechanism during the injection process. The resin pressure during this injection process acts on the injection plunger 22 as a reaction force, and is measured by the pressure sensor 32 on the back of the injection plunger, so that fluctuations in the resin pressure can also be reliably grasped.

In this way, in the injection process as well as in the metering process,
Pressure in plastic materials (eg, resin pressure) is accurately measured, eliminating and suppressing the effects of uncertainties, shock loads, and inertia. Further, it is sufficient to dispose the pressure sensor 32 on the back surface of the injection plunger, and the injection molding machine 10 does not become structurally complicated.

In the above embodiment, the pressure of the plastic material is determined by the pressure sensor 32 provided on the back surface of the injection plunger 22, but as shown in FIG. The pressure of the plastic material may be measured by a sensor. In this configuration in which the pressure sensor 132 is provided on the front surface of the injection plunger 22, the pressure of the plastic material can be measured with the influence of uncertain factors impact load and inertia completely eliminated. The pressure of the plastic material in the pool can be directly measured,
Extremely accurate measurements are possible.

In addition, in the configuration in which the pressure sensor 32 is provided on the front surface of the injection plunger 22, since the injection plunger 22 has sufficient wall thickness in the axial direction, the pressure sensor 132 is not installed in a through hole, but is installed in a blind hole shape in the hole 44. be done. Therefore, even if the pressure of the plastic material suppresses the pressure sensor 132, there is no risk of the pressure sensor being removed.

Further, the more the pressure of the plastic material pushes the pressure sensor 132 to the bottom of the mounting hole 44, the more the pressure sensor 132 is pressed against the bottom of the mounting hole 44.
32 is attached tightly to the bottom of the hole 44 to ensure sufficient liquid tightness between the pressure sensor and the bottom of the hole. here,
The insertion hole for the lead wire 46 of the pressure sensor is normally attached at the bottom of the hole and communicated with the hole. Therefore, the insertion hole for the lead wire 46 is sufficiently sealed, resin leakage through the lead wire 4B can be sufficiently prevented, and maintenance is also facilitated. In this way, the pressure sensor 32 can be easily removed and the structure can be constructed without considering resin leakage, so that the structure of the injection molding machine 10 is simplified.

The pressure sensor 132 only needs to be slightly exposed to the resin pool, and the surface on which the pressure of the plastic material acts can be set small.
It is also possible to measure pressures as high as 1,000 kg/sq.

The injection plunger 22 is distorted in the axial direction in proportion to the pressure of the plastic material in the resin reservoir 18. Therefore, as shown in FIG. In this configuration as well, the pressure of the plastic material in the resin reservoir 18 due to the distortion of the injection plunger 22 can be reduced by eliminating and suppressing the effects of uncertain factors and impact loads, as in the above embodiment. , accurate measurements can be made in both the metering process and the injection process.

Further, in this configuration in which the pressure of the plastic material itself is not measured, but the pressure of the plastic material is measured from the strain of the injection plunger 22, high pressure does not act on the strain sensor 232, so a highly durable configuration can be obtained.

In addition, the strain sensor 23 is cheaper than the pressure sensor.
2, an inexpensive injection molding machine 10 can be obtained.

Furthermore, the strain sensor 232 can be easily attached to the side surface of the injection plunger 22 without requiring high-precision machining to the injection plunger. Therefore, a known injection molding machine can be modified to the injection molding machine 10 of the present invention without complicating the structure, and without changing the design such as changing the stroke of the injection plunger or replacing the injection plunger.

In addition, in the embodiment shown in FIG. W42 and FIG. 3, the injection plunger 22. Unlike the embodiment of FIG. 1, the injection plunger and ram can be integrated, since the ram 34 does not need to be constructed separately.

In addition, as shown in FIG. 4, the head 2 of the injection plunger
A configuration may also be adopted in which a chamber 4B is placed in the ram 34 behind the ram 3, and a working medium, for example, hydraulic oil is sealed in this chamber, and a pressure sensor 322 is disposed on the back side of the injection plunger. Pool 1
When the pressure of the plastic material No. 8 acts on the injection plunger 22 and pushes the injection plunger to the right, the hydraulic fluid in the chamber 48 of the ram is pressed and pushes the injection plunger back.
Therefore, even in this configuration in which the pressure of the plastic material in the resin reservoir 18 is measured as four reaction forces by the pressure sensor 322 on the back of the injection plunger, the effects of uncertain factors, impact loads, and inertia are eliminated and suppressed, and the resin reservoir The pressure of 18 plastic materials can be measured accurately. Further, in this configuration, as in the second embodiment, since the surface on which the pressure acts is small is sufficient, a configuration with excellent durability can be obtained, and high pressure can be measured.

Note that in the embodiments shown in FIGS. 1, 3, and 4, the pressure sensors 32, 332, . Since the strain sensor 232 does not come into contact with the high temperature plastic material and is not affected by the temperature of the plastic material, a highly durable configuration can be obtained.

The above-mentioned embodiments are for illustrating this invention, and do not limit this invention in any way, and any modifications, modifications, etc. made within the technical scope of this invention are also included in this invention. Needless to say.

〔Effect of the invention〕

As described above, according to the present invention, a plunger injection method is adopted, and a pressure sensor disposed on the back surface of the injection plunger or a strain sensor disposed on the side surface of the injection plunger is used to inject plastic material. Measuring pressure.

Since such a method for measuring pressure of a plastic material uses a plunger injection method, generation of impact load and inertia is prevented and suppressed, and accurate pressure measurement is possible.

In addition, the pressure of the plastic material is not measured indirectly from the pressure of a pressure medium such as pressurized oil, but the pressure of the plastic material at the front of the injection plunger is measured directly or at a point as close as possible. The influence of uncertain factors such as pipe resistance, valve resistance, peak pressure, and pulsation is eliminated, and the pressure of the plastic material can be measured accurately.

Furthermore, pressure sensors and strain sensors can be easily installed.
There is no possibility that the injection molding machine will become structurally complicated.

Furthermore, since the pressure sensor and strain sensor can be disposed at positions that are not affected by the temperature of the plastic material, a highly durable structure can be obtained.

In particular, a configuration in which the pressure sensor is placed in front of the injection plunger allows for direct measurement of the pressure in the plastic material, completely eliminating the effects of uncertainties, shock loads, and inertia, making extremely accurate measurements possible. .

In this configuration, the pressure sensor can be housed in a blind hole rather than a through hole, so even if the pressure of the plastic material presses on the pressure sensor, there is no risk of the pressure sensor being removed. Moreover, the more the pressure of the plastic material presses the pressure sensor against the bottom of the mounting hole, the more the pressure sensor adheres to the bottom of the mounting hole, ensuring sufficient liquid tightness.

Therefore, resin leakage through the lead wire of the pressure sensor is sufficiently prevented, and maintenance is also facilitated. In addition, the pressure sensor only needs to be slightly exposed to the resin pool, and the surface on which the pressure of the plastic material acts can be set small, so it has excellent durability and can also measure high pressures such as 3000 to 5000 kg/sq. It becomes possible.

Even in a configuration where the strain sensor is placed on the side of the injection plunger, high pressure does not act on the strain sensor.
In addition to providing a highly durable configuration, the strain sensor is relatively inexpensive, so it can be constructed at low cost. Also, the strain sensor.

Since the injection plunger can be easily attached to the side surface of the injection plunger without performing high-precision machining, a known injection molding machine can be modified to the injection molding machine of the present invention without changing the design or replacing the injection plunger.

In addition, even in a configuration in which the pressure of the plastic material is measured with a pressure sensor on the back of the injection plunger via a sealed working medium in a chamber provided in the ram behind the head of the injection plunger, the surface on which the pressure acts is small. Since only a small amount of pressure is required, a structure with excellent durability can be obtained, and high pressure measurements can be made.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a main part of an injection molding machine according to one embodiment of the present invention, and FIGS. 2 to 4 are partial vertical cross-sectional views of main parts of an injection molding machine according to another embodiment. It is. 10: Injection molding machine, 14 nib plunger cylinder, 18:
Resin reservoir, 20: Pre-plastic mechanism, 22: Injection plunger, 23: Head of injection plunger, 24: Injection cylinder, 32, 132.332: Pressure sensor, 232: Strain sensor 42: Nozzle, 44: Mounting hole, 46: Lead wire, 48: Ram chamber.

Claims (8)

[Claims] (1) A method for measuring the pressure of plastic material in injection molding, in which the pressure of the plastic material in the resin reservoir is measured by a pressure sensor installed between the injection plunger and the ram behind the injection plunger. (2) A method for measuring the pressure of a plastic material in injection molding, in which the pressure in a resin reservoir is measured by a pressure sensor provided on the front surface of an injection plunger. (3) A method for measuring the pressure of plastic material in injection molding, in which a strain sensor is provided on the side of the injection plunger and the pressure of the plastic material in the resin reservoir is measured from the axial strain generated in the injection plunger. (4) providing a chamber in the ram behind the injection plunger;
A working medium is sealed in this chamber, and a pressure sensor is installed on the back of the injection plunger.The pressure sensor measures the pressure of the plastic material in the resin reservoir as a reaction force generated in the working medium. Pressure measurement method. (5) In an injection molding machine that injects the plastic material in the resin reservoir at the front of the plunger cylinder into the mold cavity as the injection plunger moves forward, a pressure sensor is installed on the back of the injection plunger, and this pressure sensor An injection molding machine characterized by being configured to be able to measure the pressure of a plastic material in a resin reservoir. (6) In an injection molding machine that injects plastic material from a resin reservoir at the front of the plunger cylinder into a mold cavity as the injection plunger moves forward, a pressure sensor is installed in the mounting hole provided at the front of the injection plunger. An injection molding machine characterized in that the insertion hole for the lead wire of the pressure sensor is communicated with the mounting hole at the bottom of the mounting hole, and the pressure of the plastic material in the resin reservoir can be measured by the pressure sensor. . (7) In an injection molding machine that injects the plastic material in the resin reservoir at the front of the plunger cylinder into the mold cavity as the injection plunger moves forward, a strain sensor is installed on the side of the injection plunger to detect the distortion caused in the injection plunger. An injection molding machine characterized in that it is configured to be able to measure the pressure of a plastic material in a resin reservoir from the strain in the axial direction. (8) In an injection molding machine that injects plastic material from a resin reservoir at the front of the plunger cylinder into a mold cavity as the injection plunger moves forward, the head of the injection plunger is housed in the chamber of the ram. , an injection molding machine characterized in that a working medium is sealed in a chamber behind the head and a pressure sensor is provided on the back of the injection plunger.