JPH043290B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to injection compression molding molds, and particularly to injection molding molds for molding molded products that require shape accuracy and surface accuracy, such as plastic lenses, and are free from internal distortion. This invention relates to an injection compression mold that is a compression mold and is aimed at improving molding efficiency.

[Prior art]

First, we will explain the conventional injection compression mold and its operation.
This will be explained using FIG.

FIG. 1 is a side sectional view showing an example of a conventional injection compression molding mold used for molding a plastic lens. In this FIG. 1, 1 is a fixed mold, 15 is a fixed mold mounting plate, and 4 is a fixed adapter 1 in the fixed mold 1.
4 is a fixed piece inserted into the movable mold, 2 is a movable mold, 20 is a movable mold mounting plate, 5 is a movable adapter 16 in the movable mold 2
A movable insert piece 3 is slidably inserted into the cavity, and 7 is a cavity formed by a fixed insert piece 4 and a movable insert piece 5.
A pressure cylinder 6 capable of pushing out an ultrasonic wave transmitting/receiving element is fitted into the fixed insert piece 4 and the movable insert piece 5 so as to face the cavity surface.

In an injection compression mold for molding such a plastic lens (hereinafter referred to as a molded product), it is necessary to polish the metal forming the surface of the cavity 3 to improve surface precision, so the fixed insert piece 7 and the movable insert piece 8 are used. The fixed insert piece 4 is attached to the fixed adapter 14, so that it can be handled to some extent even if the size of the molded product changes and the external shape and shape of the cavity 3 change to some extent. The insert pieces 5 are respectively fitted into movable adapters 16, and the fixed insert pieces 4, the fixed adapter 14, the movable insert pieces 5, and the movable adapter 16 can be replaced if the shape changes.

First, the resin (not shown) exiting the injection molding machine is
A sprue 11 drilled in a fixed mold 1 is guided into an injection compression molding mold, and a runner 12 and a gate 1 are formed.
3 and is filled into the cavity 3. After a certain period of time has elapsed after the completion of filling, when the hydraulic pressure generated by the hydraulic pressure generator 10 advances the pressure cylinder piston 8 of the pressure cylinder 7 according to a command from the signal controller 9, the front surface of the cylinder piston 8 is pushed out. Board B19
and a movable input piece 5 fixedly connected to the extrusion plate A18.
moves forward and compresses the resin inside the cavity 3. Along with this compression, ultrasonic transmitting/receiving elements (hereinafter referred to as ultrasonic elements) 6A and 6D detect the state of contact between the resin inside the cavity 3 and the fixed insert piece 4 and the movable insert piece 5.

Here, regarding the functions of the ultrasonic elements 6A and 6D,
6A will be mainly explained. When a signal wave (not shown) generated by the signal controller 9 enters the ultrasonic element 6A via the connection cable 21 and is emitted here in the direction of the cavity 3, this signal wave is transmitted to the movable input piece 5. When the surface and the resin in the cavity 3 are in contact, the beam does not return to the direction of the ultrasonic element 6A, but continues in the direction of the cavity, and is received by the ultrasonic element 6D in the fixed input piece 4. On the other hand, when the surface of the movable insert piece 5 and the resin inside the cavity 3 are not in contact, the signal wave emitted from the ultrasonic element 6A is reflected on the surface of the movable insert piece 5 and is not transmitted in the direction of the cavity 3. It does not advance, is not received by the ultrasonic element 6D in the movable input piece 4, returns to the direction of the ultrasonic element 6A, and the signal wave is captured by the ultrasonic element 6A again. in this way,
When the entering piece surface and the resin inside the cavity 3 are in contact, there is no reflected wave, and the signal wave does not return to the ultrasonic element 6A that itself transmitted the signal wave, but is received by the opposing ultrasonic element 6D. . If the entering piece surface and the resin inside the cavity 3 are not in contact, the reflected wave returns to the ultrasonic element 6A, does not reach the opposing ultrasonic element 6D, and is not received. Also, ultrasonic element 6D
The transmission from the 6A side is exactly the same as the transmission from the 6A side, and if the surface of the fixed input piece 4 is in contact with the resin inside the cavity 3, there is no reflected wave and the signal wave is transmitted to the ultrasonic element 6D. If there is no contact, the reflected wave will be captured by 6D and not received by 6A. Note that some signal waves do not pass through the cavity but travel around other parts of the mold, so the contact status between the resin inside the cavity 3 and the surface of the inserted piece is detected as the strength or weakness of the signal wave. In this way, the contact status between the resin inside the cavity 3 and the fixed insert piece 4 and the movable insert piece 5 can be detected based on the strength of the captured signal wave.

Further explaining the functions of the signal controller 9, the signal controller 9 includes (1) the ultrasonic elements 6A and 6;
D, alternately send out signal waves in a constant cycle, and (2) measure the strength of the signal waves received by each ultrasonic element.
(3) Control the hydraulic pressure generator 10 based on the calculation by comparing with the signal wave set and stored in advance, that is,
It has the functions of transmission, storage, comparison calculation, and control.

Now, when the contact between the resin in the cavity 3 and the fixed insert piece 4 and the movable insert piece 5 is detected by the ultrasonic elements 6A and 6D as the resin in the cavity 3 is compressed, the signal controller 9, after calculation, If it is determined that no further compression is necessary, the operation of the hydraulic generator 10 is controlled and the operation of the pressurizing cylinder piston 8 of the pressurizing cylinder 7 is stopped. Furthermore, if the ultrasonic element 6 cannot detect contact between the resin in the cavity 3 and the fixed insert piece 4 and the movable insert piece 5, the pressure cylinder 7 continues to compress the resin, and the contact cannot be detected within a certain period of time. If so, it is determined that the product is defective, and the resin inside the cavity 3 is discharged outside the mold. On the contrary, if contact is detected within a certain period of time, the operation of the pressurizing cylinder 7 is stopped as described above, and when the resin shrinks again and contact is no longer detected,
Compression is performed by a pressurizing cylinder 7. The above operations were repeated to perform compression molding.

However, with the control only during compression molding as described above, it has been almost impossible to compensate for defects that occur during injection and holding pressure. For this reason, for defective products, the entire time from the start of injection until it is determined that compensation cannot be achieved even by applying compressive force is wasted time. In addition, because only one ultrasonic element was inserted into each of the fixed insertion piece 4 and the movable insertion piece 5, it was possible to grasp the situation of only a part of the molded product, which was considered as the situation of the entire cavity. This is disadvantageous in that excessive internal stress is generated in some areas, or insufficient compression occurs in some areas. For example, if a sink mark, that is, a recess due to resin shrinkage, occurs in the center of the cavity 3 due to insufficient injection holding pressure, the injection holding pressure may be controlled even if the presence of the recess is discovered during injection holding pressure. Therefore, the next compression process is carried out. In the compression process, the ultrasonic elements 6A and 6D detect the sink mark in the center of the cavity 3 that has already occurred in the previous process, and the signal controller 9 sends a signal equivalent to the entire cavity surface to the hydraulic generator 1.
0 to the pressure cylinder 7, excessive compressive force was applied to the parts of the resin inside the cavity 3 other than the sink, increasing internal stress and causing a surface peeling phenomenon where the resin surface layer adhered to the mold. . Compression also has the disadvantage that if sink marks cannot be corrected and compensated for within a certain amount of time, the resin inside the cavity will be taken out as a defective product, and the time required until then will be wasted time, reducing molding efficiency. Ta.

[Purpose of the invention]

The present invention eliminates the drawbacks of the prior art described above,
In addition to improving molding efficiency by shortening the time required to set conditions, it also appropriately controls the injection holding force and compression force to produce molded products with excellent shape accuracy, surface accuracy, and other qualities, and no internal distortion. The object is to provide an injection compression molding mold that can perform molding.

[Summary of the invention]

The configuration of the present invention includes at least a fixed type, a fixed piece inserted into the fixed type, a movable type, and a movable piece fitted into the movable type so as to be slidable, the fixed piece being fitted into the fixed type. and a movable insert piece, and the resin is filled into a cavity formed by a movable insert piece, and the movable insert piece is extruded by a pressure cylinder, thereby compressing the resin and shaping the mold. In the injection compression mold, there are multiple ultrasonic transmitting/receiving elements that can detect the contact state between the resin inside the cavity and the surface of the cavity, as well as the temperature and pressure of the resin inside the cavity. A temperature sensor and a pressure sensor are inserted and inserted, and based on the plurality of signals related to the contact state received by the ultrasonic transmitting/receiving element and the temperature and pressure of the resin in the cavity detected by the temperature sensor and pressure sensor. , an injection compression molding mold provided with an injection holding pressure control device for controlling the resin filling pressure and a hydraulic control device for controlling the hydraulic pressure applied to the pressure cylinder.

[Embodiments of the invention]

The present invention will be explained below using specific examples.

FIG. 2 is a side sectional view showing an injection compression molding die according to an embodiment of the present invention. In FIG. 2, the same numbers as in FIG. 1 indicate the same parts. In addition, 22 is an injection molding machine injection control section;
3 is an injection section of an injection molding machine. Further, 26 is a temperature sensor, and 27 is a pressure sensor. Reference numeral 6 designates a plurality of ultrasonic transmitting/receiving elements (hereinafter referred to as ultrasonic elements) inserted into the fixed insert piece 4 and the movable insert piece 5 at intervals. The signal wave emitted from this ultrasonic element 6 towards the cavity 3 is reflected by the cavity surface depending on the contact status between the resin inside the cavity 3 and the fixed insert piece 4 and the movable insert piece 5. If there is no contact, the wave becomes a reflected wave from the cavity surface and is captured by the ultrasonic element 6 again. 9A is a general controller that (1) sequentially sends signals to multiple ultrasonic elements without duplication, and (2) the strength and weakness of signals returned from the ultrasonic elements. For example, when there is no contact between the cavity surface and the resin. When the temperature and pressure of the cavity are set as 100% or higher, a signal is sent to the injection molding machine control unit 22 to increase the holding pressure, etc.
It has the functions of sending control signals to the hydraulic pressure generator 10, signal sending, storage, comparison calculation, and control.

The operation of the injection compression mold constructed in this manner will be explained with reference to FIGS. 2 and 3.

FIG. 3 is a partially enlarged sectional view showing the main parts of FIG. 2, and the same parts are denoted by the same reference numerals as those in FIG. 2. 24 is resin inside the cavity, 2
A void 5 is formed between the cavity surface and the resin 24 inside the cavity due to insufficient filling of the resin into the cavity 3 or due to the resin shrinking as the resin temperature decreases after filling. Reference numerals 6A to 6F indicate a plurality of ultrasonic elements inserted, and a to c indicate regions obtained by roughly dividing the cross section of the input piece and cavity into three.

In the injection molding mold configured in this way, when the fixed mold 1 and the movable mold 2 close at the start of molding, the resin (not shown) injected from the injection part 23 of the injection molding machine flows through the sprue 11 and the runner 12. , passes through the gate 13 and is filled into the cavity 3. During filling, the ultrasonic elements 6A, 6B, and 6C detect the state of contact between the resin 24 in the cavity and the cavity surface in the opposing cavity areas (hereinafter referred to as areas) a, b, and c, respectively. and,
Area a near gate 13 and area b in the center
and information on area c away from the gate are respectively sent to the overall controller 9A, where comparisons and calculations are performed.

Here, to explain the comparison and calculation contents of the general controller 9A, if the ultrasonic wave emitted from the ultrasonic element 6B travels inside the mold and enters the resin 24 in the cavity or the gap 25 on the cavity surface, it becomes an ultrasonic wave. Based on the acoustic characteristics of , transmission or reflection occurs according to the following equation.

Reflectance βr = Reflected wave intensity / Incident wave intensity = [(ρ ₁ c ₁ - _{ρ 2} c ₂ )/(ρ ₁ c ₁ +ρ ₂ c ₂ )] ² Transmittance βt = Transmitted wave intensity / Incident wave intensity = 1−βt=(4ρ ₁ c ₁ ρ ₂ c ₂ )/(ρ ₁ c ₁ +ρ ₂ c ₂ ) ² ρ ₁ : Density of medium 1 that transmits ultrasonic waves c ₁ : Ultrasonic wave length within medium 1 Wave velocity ρ ₂ : Density of medium 2 that transmits ultrasonic waves c ₂ : Ultrasonic longitudinal wave velocity in medium 2 The mold is made of steel (ρ ₁ = 7.8 g/cm ³ , c ₁ = 5.81×10 ⁵
cm/s), the resin 24 in the cavity is filled with polystyrene (ρ ₂ = 1.1 g/cm ³ , c ₂ = 2.67×10 ⁵ cm/s), and the cavity 25 is filled with air (ρ ₂ = 0.0012 g/cm ³ , c ₂ =0.331×
10 ⁵ cm/s), and when the mold cavity surface and the resin inside the cavity are in close contact, the transmittance is 23% from the above equation. Further, when the resin inside the cavity is completely separated from the cavity surface, the transmittance is 0% from the above equation.

Next, the resin injected from the injection molding machine is in a liquid or semi-liquid/semi-solid semi-molten state, and then solidifies as it is cooled in the mold and finally becomes solid. Generally, when the state of the medium changes, the acoustic impedance ρ×c also changes, and therefore the reflectance and transmittance of ultrasonic waves also change. Acoustic impedance is approximately 50% between liquid phase and solid phase
(In general, the liquid phase has 50% of the acoustic impedance of the solid phase.) When polystyrene is in the molten state, the transmittance from the mold is 12% and the reflectance is 88%.As it solidifies, the temperature and Acoustic impedance increases and reflectance decreases as pressure changes. Therefore, the transmittance and reflectance of ultrasonic waves are the same when the resin temperature is high and the resin is in a molten state, and when the resin is solidified and there is a gap between it and the cavity surface. will be shown. Therefore, if the temperature and pressure of the resin 24 inside the cavity are detected using a temperature sensor 26 and a pressure sensor 27 installed near the cavity 3, it is possible to find out whether the resin is in a molten state or solidified and there is a portion between it and the cavity surface. It can be easily determined whether a void has been created or not.

Then, in a preliminary experiment, the ultrasonic transmittance and reflectance of the medium, that is, the resin in the cavity in a state of complete contact, are determined as a function of temperature and pressure, and by inputting these values into the central control device 9A in advance. ,
Transmittance and reflectance corresponding to the temperature and pressure state of the resin obtained from the temperature sensor 26 and the pressure sensor 27 can be calculated.

Furthermore, the degree of contact between the cavity surface and the resin at that point can be calculated by comparing and calculating the transmittance and reflectance in this complete contact state and the transmittance and reflectance in the middle of molding. The upper and lower limits of this degree of contact are given in advance to the integrated control device 9A, and these are compared and calculated with the detected value to control the injection holding pressure and compression pressure so that they are always within the limits. It is. As a result, area c, which is far from gate 13, may have a lower degree of contact than area a, which is closer to gate 13, and may be insufficiently filled with resin, or area b in the center may have less contact than area a, which is closer to gate 13. If the degree of contact is low and a sink mark occurs in the center, the overall controller 9A compares the degree of contact and the contact pattern input in advance, determines that the injection pressure is insufficient, and then controls the injection molding machine injection control section 22. In accordance with this, the injection section 23 of the injection molding machine outputs an instruction signal to increase the injection holding force.
More resin is fed into the mold, eliminating insufficient filling and sink marks, and returning the degree of contact to within limits.

In addition, if the contact situation in all areas a, b, and c exceeds a certain limit and overfilling is performed, the overall controller 9A makes a comparison judgment with a preset limit value, and performs injection molding. A signal for depressurization is sent to the machine control section 22, and the injection section 2 of the injection molding machine is
By reducing the injection holding pressure in step 3 and preventing overfilling,
The degree of contact is brought back within the limits.

Next, when injection filling and pressure holding are completed, compression starts, and a signal is sent from the general controller 9A to the hydraulic pressure generator 10, and the hydraulic pressure (not shown) generated by the hydraulic pressure generator 10 is transferred to the pressurizing cylinder 7. When the pressurized cylinder piston 8 is advanced, the extrusion plate B19 and the extrusion plate A18 on the front surface of the cylinder piston 8 are
A movable inserting piece 5 fixedly coupled to moves forward and compresses the resin in the cavity 3. With compression, the contact situation between the cavity surface and the resin 24 inside the cavity changes.
It is detected in the same way as during injection filling and pressure holding, and the degree of contact is compared and determined with the limit value, and if the limit value is exceeded,
A control signal is sent from the general controller 9A to the hydraulic pressure generator 10 to control the hydraulic pressure of the pressurizing cylinder 7, and the operation of returning the compressive force applied to the resin 24 in the cavity to within the limit value is continuously performed. In parallel with this compressive force correction operation, the resin 24 inside the cavity is also cooled, and when the mold reaches a predetermined temperature, for example 60 to 70°C in the case of polystyrene, the movable mold mounting plate 20 is moved back. When the mold is opened, the dividing surfaces of the fixed mold 1 and the movable mold 2 are opened left and right, and the molded product molded in the cavity 3 is taken out.

Next, the movable mold mounting plate 20 is moved forward to close the mold and return to the state shown in FIG. 2. Thereafter, by repeating the above-described operations, molding can be continued.

In addition, in the above-mentioned operation, if the degree of contact does not fall within the limit or the contact pattern is not improved even after making corrections, stop molding after a certain period of time and remove the molded product. are disposed of as defective products.

According to the embodiment described above, if the permissible value of the degree of contact is set in advance in the integrated controller 9A in correspondence with the position of the molded product, the degree of contact and the contact pattern that change every moment with the ultrasonic element can be controlled. By detecting this, it is possible to immediately control the injection holding force and compression force, making it possible to obtain high-quality molded products within one cycle, and significantly reducing the test molding time for setting conditions. This greatly improves molding efficiency. Furthermore, according to this embodiment, since it is possible to determine whether a molded product is good or defective during the molding process, defective products can be injected without waiting until one cycle is completed as in the conventional method, and wasted time in molding can be eliminated. can. Furthermore, since it has become possible to detect contact patterns, it is now possible to judge the occurrence of sink marks and the distribution of internal distortion during the molding process, making it possible to correct these by increasing or decreasing the injection holding pressure and compression force. This has made it possible to obtain molded products with higher precision and less internal distortion.

〔Effect of the invention〕

As explained in detail above, according to the present invention,
It has at least a fixed type, a fixed insert piece fitted into the fixed mold, a movable type, and a movable insert piece slidably inserted into the movable mold, and the fixed insert piece and the movable insert piece are connected to each other. Fill the resin into the cavity consisting of
In an injection compression molding mold that compresses and shapes the resin by extruding the movable inserting piece with a pressure cylinder, the injection compression molding mold includes a resin in the cavity and a resin in the cavity. A plurality of ultrasonic transmitting/receiving elements that can detect the state of contact with the cavity surface, and a temperature sensor and a pressure sensor for detecting the temperature and pressure of the resin inside the cavity are inserted, and this ultrasonic transmitting/receiving element is installed. an injection holding pressure control device that controls resin filling pressure based on the temperature and pressure of the resin in the cavity detected by the temperature sensor and the pressure sensor and the plurality of signals related to the contact state received by the A hydraulic control device is installed to control the hydraulic pressure applied to the cylinder, reducing the time required to set molding conditions, improving molding efficiency, and adjusting the injection holding pressure and compression force appropriately. It is possible to provide an injection compression molding mold that can be controlled to form a molded product with excellent shape accuracy, surface accuracy, etc., and no internal distortion.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an example of a conventional injection compression molding mold used for molding a plastic lens, and FIG. 2 is a side sectional view showing an injection compression molding mold according to an embodiment of the present invention. 3 is a partially enlarged sectional view showing the main parts in FIG. 2. 1... Fixed type, 2... Movable type, 3... Cavity, 4... Fixed insert piece, 5... Movable insert piece, 6... Ultrasonic transmitting/receiving element, 7... Pressure cylinder, 9A
...General controller, 10...Hydraulic pressure generator, 22...
Injection molding machine injection control section, 24...Resin in cavity, 26...Temperature sensor, 27...Pressure sensor.

Claims (1)

[Claims] 1 At least a fixed type, a fixed piece inserted into the fixed type, a movable type, and a movable piece slidably inserted into the movable type, and the fixed piece and the movable piece. In the compression molding mold, the cavity formed by the resin is filled with resin, and the resin is compressed and shaped by extruding the movable insert piece using a pressure cylinder. A plurality of ultrasonic transmitting/receiving elements capable of detecting the contact state between the resin inside the cavity and the surface of the cavity, and a temperature sensor and a pressure sensor for detecting the temperature and pressure of the resin inside the cavity are installed in the mold. Injection for controlling the filling pressure of the resin based on the plurality of signals related to the contact state received by the ultrasonic transmitting/receiving element and the temperature and pressure of the resin in the cavity detected by the temperature sensor and the pressure sensor. An injection compression molding mold comprising: a holding force control device; and a hydraulic control device that controls hydraulic pressure applied to the pressurizing cylinder.