JP4292406B2 - Injection foam molding method and injection foam molding apparatus - Google Patents

Description

  The present invention relates to a resin injection foam molding method and an injection foam molding apparatus in which a resin is filled and foamed, and in particular, a high-quality foam molded product having a dense surface and little variation in foaming magnification and bubble diameter. The present invention relates to an injection foam molding method and an injection foam molding apparatus.

Foamed molded products that exhibit excellent effects in physical properties such as lightness, heat insulation, sound absorption, and rigidity at the same mass due to a large number of bubbles present in the resin have been used in various fields for a long time. Particularly in recent years, a technique of foaming a resin has been used to reduce the amount of resin used in a product to reduce the weight, and the application of foamed molded products has been further expanded in combination with the reduction in weight leading to cost reduction. A high pressure method is known as an injection foam molding method for a resin in which the surface of a foam molded product is dense and surface roughness due to swirl marks is small.
In the high pressure method, molten resin containing a foaming agent is injected and filled into a mold cavity in a full shot state, the surface layer is solidified to form a skin layer, and then the resin is foamed by expanding the mold cavity volume. Is the method. In this molding method, the amount of expansion of the mold cavity volume is an important factor affecting the foaming ratio, bubble diameter, thickness of the molded product, etc. of the molded product, and it is required to control with high accuracy and high reproducibility. .

The conventional method for controlling the expansion of the mold cavity volume using the toggle type mold clamping device uses the boost characteristic of the toggle mechanism to move the movable platen of the mold clamping device at the die touch point toward the anti-fixed platen. The relationship between the position of the movable plate and the position of the crosshead detected at the time of the movement is stored as position data (hereinafter referred to as crosshead position data), and the position of the movable plate is crossed based on the stored crosshead position data. Control by head position. According to this method, for example, even if the position of the crosshead varies by 1 mm, the position variation of the movable plate is 1/10 mm or less (the actual position of the crosshead can be easily controlled with an accuracy of 1/10 mm or less). Position control of the position of the movable plate can be realized with extremely high accuracy and high reproducibility. (See Patent Document 1)
JP-A-9-193221 (pages 5-6)

  However, the conventional method of controlling the position of the movable platen by using the crosshead position data when the movable platen at the mold touch point is moved in the anti-fixed platen direction by utilizing the boost characteristic of the toggle mechanism. When injection foam molding is performed by the pressure method, there are the following problems.

Usually, a link node which is a hinge part of a toggle mechanism is configured by a link and a toggle pin which is loosely inserted into a pin hole provided in the link with a minute gap. Since the link node has a minute gap in this way, when the mold cavity volume is enlarged by the conventional technique, the movable plate moves backward after the crosshead is retreated by a dimension corresponding to the total gap of the link node. It becomes. In a general injection molding method in which resin does not foam, the volume of the mold cavity is increased by controlling the position of the movable plate based on the position data of the cross head when the movable plate is moved in the anti-fixed plate direction. Even if the position is held, since the resin pressure in the mold cavity does not act on the movable platen after injection filling, the gap of the link node does not become a problem.
However, in the injection foam molding method in which the resin foams in the mold cavity, even if the crosshead is stopped and held at the position of the movable plate expanded to the volume of the desired mold cavity, the resin in the mold cavity The foaming pressure acts on the movable platen, and the movable platen is pushed back to the crosshead stop position by a dimension corresponding to the total clearance of the link nodes. As a result, the mold cavity volume will be increased by an extra dimension corresponding to the total gap of the link nodes, and the desired foaming ratio, bubble diameter and molded product thickness will change, resulting in a good injection foam molded product. It had a problem that it could not be obtained.

  Even if the expansion of the mold cavity volume is set to zero, the crosshead moves backward by a dimension corresponding to the total clearance of the link nodes and stops and holds the position. As a result, the dimension corresponding to the total clearance of the link nodes is pushed back, and therefore it is not possible to control the expansion of the mold cavity volume in a range smaller than the dimension corresponding to the total clearance of the link nodes.

  The object of the present invention was made in view of the above-mentioned problems of the prior art, and in the expansion control of the mold cavity using the toggle mechanism, there is no excessive volume expansion due to the total gap of the link nodes, and the desired expansion ratio and bubble An object of the present invention is to provide an injection foam molding method and an injection foam molding apparatus for obtaining an injection foam molded product having a diameter and a molded product thickness.

  In the first invention according to the present invention, an injection foam molding apparatus provided with a toggle type mold clamping device for freely opening and closing a mold disposed between the movable platen and the fixed platen by moving the crosshead. , And an injection filling process in which a mold cavity clamped between the movable platen and the fixed platen is filled with a molten resin containing a foaming agent, and after the injection filling step, the movable platen is moved toward the anti-fixed platen. In the injection foam molding method comprising a resin foaming step of expanding the volume of the cavity from the injection filling step and foaming the molten resin in the enlarged cavity, the movable platen is fixed in the fixed platen direction in advance. The relationship between the position of the cross head and the position of the movable plate when moved to the position is stored as positional relationship data, and the position of the movable plate is moved so that the cavity volume becomes a desired volume at the start of the foaming step. On the occasion Then, the crosshead position corresponding to the position of the movable platen after the movement is calculated from the position data, the crosshead is moved to the calculated crosshead position, and the crosspiece after the movement is completed until the completion of the foaming step. The head position was held.

And in 1st invention, the teaching process for measuring and memorizing | stores the said positional relationship data previously is provided, and this teaching process is a movable platen in the teaching mold open position which opens a metal mold | die completely. When the crosshead is moved so as to move in the direction, the position of the crosshead where the movable plate starts to move is detected and stored as the forward movement reference point (Smc), and movable from the forward movement reference point (Smc). And a step of detecting and storing the position of the crosshead as the mold touch point (Stc) when the clamping force starts to change from zero when the crosshead is moved so that the board moves toward the fixed board. By measuring the position of the crosshead and the position of the movable platen when the crosshead is moved from the forward movement reference point (Smc) to the mold touch point (Stc), the crosshead can be used. It was be stored as the positional relation data between the board.

Furthermore, in the first invention, the teaching step includes the first step of detecting the clamping force by clamping the mold with a predetermined clamping force, and moving the cross head from the clamping state toward the anti-fixing platen. A second step of detecting and storing the position of the crosshead where the mold clamping force becomes zero when the mold is moved as a temporary mold separation point (Sto), and the mold from the temporary mold separation point (Sto). A third step of detecting and storing the crosshead position, which has been stopped by moving the crosshead in the direction of the anti-fixed plate to the fully open predetermined position, and the backward movement reference point (Smo); ) To detect and store the position of the crosshead at which the movable plate starts to move when the crosshead is moved in the direction of the fixed plate as the forward movement reference point (Smc), and the forward movement reference point ( Smc) so that the movable platen moves toward the fixed platen When moving the Rosuheddo, it includes a fifth step of detecting and storing the position of the crosshead clamping force starts to change from zero as the mold touch point (Stc), the first step of the fifth The relationship between the position of the cross head and the position of the movable platen is stored as positional relationship data while sequentially performing the steps.

The second invention has a toggle type clamping mechanism, a cross head, and a link drive mechanism that drives the toggle type clamping mechanism via the cross head, and is attached to one end of the toggle type clamping mechanism. A mold clamping mechanism is provided for moving the plate toward and away from the fixed platen to freely open and close the mold disposed between the movable platen and the fixed platen, and detects the position of the movable platen. A movable platen position sensor, a position sensor for detecting the position of the crosshead, and a mold clamping force sensor for detecting a mold clamping force of the mold clamping device; While measuring the position, move the crosshead so that the movable platen at the fully open position of the teaching die moves toward the fixed platen, and advance the position of the crosshead where the movable platen starts moving When detected as an operation reference point (Smc) Furthermore, the position of the crosshead where the mold clamping force starts to change from zero is detected as the mold touch point (Stc), and the movable position is movable with the crosshead from the forward movement reference point (Smc) to the mold touch point (Stc). A mold clamping control unit that stores the positional relationship with the panel as position data, and can control the position of the movable board by moving the position of the crosshead based on the stored position data. When the position of the movable platen is moved so that the cavity volume becomes a desired volume at the start, the crosshead position corresponding to the moved movable platen position is calculated from the position data, and the calculated crosshead position is set. The crosshead is moved, and the crosshead position after the movement is held until the foaming step is completed.

In the second invention, the teaching step for measuring and storing the positional relationship data in advance is provided, and the mold touch point (Stc) obtained by the teaching operation and the temporary mold separation point (Sto) are obtained. The difference and the difference between the backward movement reference point (Smo) and the forward movement reference point (Smc) are detected and stored as the movement distance of the crosshead as the total gap dimension of the link node, and the stored movement of the crosshead is also stored. It was set as the structure which detects the secular change of the total clearance dimension of a link node by comparing distance.

  According to the injection foam molding method of the present invention, it is possible to obtain a high quality foam molded product having a dense surface by preventing the surface of the molded product called a swirl mark from being rough. In addition, since the position of the movable platen can be controlled with high accuracy and high reproducibility when the resin is foamed, it is possible to obtain an injection-foamed molded product with uniform foaming magnification, bubble diameter, and molded product thickness with little variation. In addition, it is possible to control even the expansion of the cavity volume having a dimension corresponding to the total gap of the link nodes, which could not be molded by the prior art, and injection of an injection molded product having a small foaming ratio of 1.1 or less. Molding is now possible.

Further, according to the injection foam molding apparatus of the present invention, the position data of the crosshead corresponding to the position of the movable platen when the movable platen is moved in the fixed platen direction is stored in the control device in advance by the teaching operation, and the stored data is stored. By controlling the expansion amount of the mold volume at the position of the crosshead based on the data, the foaming magnification, the bubble diameter, and the thickness of the molded product change according to the gap of the link node, which is a problem of the prior art, and good injection The problem that a foam molded product cannot be obtained can be prevented, and a high quality injection foam molded product can be obtained by the high pressure method.
Furthermore, the difference between the mold touch point (Stc) obtained by teaching operation and the temporary mold separation point (Sto) and the difference between the backward movement reference point (Smo) and the forward movement reference point (Smc) are linked. The total clearance dimension of the nodes can be detected and stored as the movement distance of the crosshead, and the secular change of the total clearance dimension of the link nodes can be quantitatively detected by comparing the stored movement distance of the crosshead. .

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
1 and 2 relate to the best mode for carrying out the present invention, FIG. 1 is an overall configuration diagram of an injection foam molding apparatus according to the present embodiment, and FIG. 2 is crosshead position data corresponding to a movable platen position. It is a flowchart explaining the procedure of teaching operation which memorize | stores. FIG. 3 is a diagram schematically showing the relationship between the movable platen position of the toggle mechanism and the crosshead position.

  As shown in FIG. 1, an injection foam molding apparatus 100 used in an embodiment of the present invention controls a mold 10, a mold clamping device 20, an injection device 30, and a mold clamping device 20 and an injection device 30. Device 60. As shown in FIG. 1, the mold 10 includes a fixed mold 3 and a movable mold 4. The fixed mold 3 and the movable mold 4 have a half-push structure and are fitted in a fitting portion, and the fitted state is obtained. Thus, the cavity surface formed on the fixed mold 3 and the cavity surface formed on the movable mold 4 are combined to form a mold cavity. The fitting portion of the half-push structure is formed over the entire circumference of the mold cavity and prevents the resin filled in the mold cavity from leaking out of the mold 10 even if the volume of the mold cavity is increased after injection filling. is doing.

  Further, in the present embodiment, a hole (not shown) into which the temperature sensor 80 can be inserted from the side surface of the mold toward the mold cavity surface is formed in the fixed mold 3, and the temperature sensor 80 is provided in the vicinity of the mold cavity surface. The mold temperature near the cavity is measured, and the measured temperature near the mold cavity is input to the control device 60. The purpose of providing the temperature sensor 80 is to detect the surface temperature of the filled resin. In the present embodiment, as one of the preferred embodiments for determining the formation of the skin layer, attention is paid to the fact that the mold temperature in the vicinity of the mold cavity changes to reflect the temperature change of the filled resin. The surface temperature of the filled resin is predicted by measuring the mold temperature, and when the surface layer reaches the solidification temperature, control is performed so that the mold is opened as a skin layer is formed. Is.

Therefore, in the present embodiment, the temperature sensor 80 capable of measuring the temperature in the vicinity of the mold cavity with the above-described configuration is provided. However, the type and attachment method of the temperature sensor 80 are not limited thereto, and do not depart from the above purpose. In the range, the sensor type and the mounting position may be changed, and the surface temperature of the molded product may be directly measured. Furthermore, the time until the skin layer of the required thickness is formed after filling the mold with the resin by trial and error in actual molding is determined, and it is determined that the skin layer has been formed over the time. Control may be performed to enlarge the mold cavity volume.
In the embodiment of the present invention, a mold having a half-push structure in which the resin filled in the mold cavity does not leak even when the mold 10 is opened by a predetermined stroke is used. However, the present invention is not limited to this. Instead, other molds such as a flat push structure may be used if applicable to foam molding.

  A mold clamping device 20 shown in FIG. 1 includes a link drive mechanism 26 using a movable platen 2, a fixed platen 1, and an electric servomotor 25 as drive sources, a toggle type mold clamping mechanism 8 driven by the link drive mechanism 26, and an electric drive. And a control driver for driving the servo motor 25. The movable platen 2 is guided by a tie bar 7 installed between the fixed platen 1 and the end plate 5, and is moved forward and backward together with the movable die 4 by a toggle type mold clamping mechanism 8. It is structured to be able to advance. A stroke sensor 74 is attached to the crosshead drive shaft 27 of the link drive mechanism 26 provided in the mold clamping device 20 as a position sensor for detecting the position of the crosshead 28. 28 positions can be accurately detected.

  In the present embodiment, the stroke sensor 74 is arranged as a position sensor for detecting the position of the crosshead 28. However, the position sensor for detecting the position of the crosshead 28 is used in this configuration. Of course, there is no limitation, and a method of detecting by a sensor built in the electric servomotor 25 may be used.

  In addition, the injection foam molding apparatus 100 includes a mold clamping force detection sensor 75 at one end of the tie bar 7 on the fixed platen side as a sensor for detecting the mold clamping force, and the mold clamping force detection sensor 75 is an extension amount of the tie bar 7. By detecting this, the mold clamping force is detected. Furthermore, the injection foam molding apparatus 100 is arranged such that the movable platen position sensor 71 detects the position of the movable platen 2 as a mold open / close stroke sensor for detecting the mold open / close stroke. The mold opening / closing stroke of the mold 10 is detected from the value.

  In this embodiment, the movable platen position sensor 71 is arranged as the mold opening / closing stroke sensor for detecting the mold opening / closing stroke. However, the form opening / closing stroke sensor is not limited to this. A method of directly attaching a mold opening / closing stroke sensor to the mold 10 may be used.

  The control device 60 that controls the operation of the injection foam molding apparatus 100 includes a movable platen position sensor 71 that detects the opening / closing stroke of the mold 10, a mold clamping force detection sensor 75 that detects the mold clamping force of the mold clamping device 20, and a cross. The detection value of the stroke sensor 74 for detecting the position of the head 28 is input, and the position of the cross head 28 when the mold clamping force starts to rise by the mold closing operation of the mold 10 is determined by the mold clamping force detection sensor 75. After detecting the touch point (Stc) and moving the crosshead 28 at the die touch point (Stc) to the teaching die open position where the die is completely opened, again to the die touch point (Stc) The position of the cross head 28 corresponding to the position of the movable platen when moved is stored as positional relationship data.

  The toggle type mold clamping mechanism 8 in this embodiment is a five-joint double toggle type having five link nodes 6a to 6e, and controls the movement of the movable platen 2 and the mold clamping force by operating the cross head 28 in the mold opening / closing direction. However, a four-bar double toggle type clamping mechanism having four link nodes may be used. In the present embodiment, the electric servo motor 25 as shown in FIG. 1 is used as the moving means for the crosshead 28. However, the present invention is not limited to this embodiment, and a hydraulic cylinder is used as the moving means for the crosshead 28. Etc. may be used in the present invention.

Next, the configuration of the injection device 30 used in this embodiment will be described.
The injection device 30 shown in FIG. 1 includes a barrel 32, a screw 34 that is built in the barrel 32 and has a flight, and a hopper 38 that supplies a molding resin material into the barrel 32, and a screw movement that moves the screw 34 forward and backward. A means 40 and a screw rotating means 42 for rotating the screw 34 are provided. A heater (not shown) is attached to the outer peripheral surface of the barrel 32.

  The injection device 30 is configured such that a pellet-shaped molding resin material is supplied from the hopper 38 into the barrel 32 when the screw 34 is rotated by the screw rotating means 42, and the supplied pellet-shaped molding is performed. The resin material is heated by a heater attached to the barrel 32, and melted by receiving a kneading compression action by the rotation of the screw 34, and is sent to the front of the screw 34. The molten resin sent to the front of the screw 34 can be injected and filled into the mold from the nozzle 39 attached to the tip of the barrel 32 by the screw 34 advanced by the screw moving means 40.

  As shown in FIG. 1, the screw moving means 40 of the injection device 30 in this embodiment is a hydraulic cylinder and the screw rotating means 42 is a hydraulic motor. However, the embodiment applicable to the present invention is not limited to this example. The screw moving means 40 and the screw rotating means 42 using an electric servo motor may be used. The control device 60 used in the present embodiment includes a mold clamping control unit 61 that controls the mold clamping device 20, a mold clamping condition setting unit that sets the mold clamping conditions, and an injection control unit 63 that controls the injection device 30. An injection condition setting device for setting the injection conditions.

Hereinafter, the teaching operation which is one of the features of the present invention will be described.
As a preparation step before molding, a teaching operation for storing the position of the crosshead 28 corresponding to the position of the movable platen 2 as positional relationship data is performed. The teaching operation is performed when the mold 10 is replaced, and the position data of the cross head 28 corresponding to the position of the movable platen 2 which changes depending on the thickness of the mold 10 and the set clamping force is controlled by the control device 60. It is the process of memorizing.

  FIG. 2 shows a teaching operation procedure for storing the position data of the crosshead 28 corresponding to the movable platen position, and FIG. 3 schematically shows the relationship between the movable platen position of the toggle mechanism and the crosshead position. Is.

  After the mold 10 is replaced, the mold clamping force is reduced by gradually moving the cross head 28 in the anti-fixing plate direction from the state where the mold 10 is clamped with a predetermined mold clamping force. The crosshead position at which the detection signal of the sensor 75 becomes zero is detected as a temporary mold separation point (Sto) and stored in a memory built in the mold clamping control unit 61 provided in the control device 60. Then, the mold is completely opened by opening the predetermined amount (for example, 50 mm) by moving the movable plate 2 by continuously moving the cross head 28 in the anti-fixed plate direction (teaching die opening limit position). As a state, the position of the crosshead in this state is detected as a backward movement reference point (Smo) and stored in a memory built in the mold clamping control unit 61 provided in the control device 60.

  Next, the movable platen 2 at the teaching-type open limit position is moved forward from the reverse movement reference point (Smo) toward the fixed platen by the cross head. At this time, the crosshead position at which the output signal of the movable platen position sensor 71 starts to change from zero is detected as the forward movement reference point (Smc) and stored in the memory built in the mold clamping control unit 61 provided in the control device 60. At the same time, the crosshead position corresponding to the movable platen position is sequentially stored in a memory built in the mold clamping control unit 61 provided in the control device 60. Then, the crosshead position when the detection signal of the mold clamping force detection sensor 75 starts to rise from zero is detected as a mold touch point (Stc), and is stored in a memory built in the mold clamping control unit 61 provided in the control device 60. Remember. Based on the crosshead positional relationship data in the fixed platen direction from the forward movement reference point (Smc) of the crosshead 28 stored in this way to the die touch point (Stc), the desired volume of the cavity at the start of the foaming process. When the position of the movable platen 2 is moved so as to become, the crosshead 28 corresponding to the moved movable platen position is calculated from the position data, and the crosshead 28 is moved to the calculated crosshead position. The crosshead position after the movement is held until the foaming step is completed.

FIG. 4 shows the link node 6c of the movable platen 2 when the cross head 28 is moved in the anti-fixed plate direction and stopped to expand the volume of the mold cavity. In this state, when the resin foaming pressure in the mold cavity as a load acts on the movable platen 2 as described above, the movable platen 2 moves in the anti-fixed platen direction until the toggle pin and the link come into contact with each other and the gap disappears. The cavity volume is expanded from a predetermined dimension, and the expansion ratio, the bubble diameter, and the molded product thickness change.
In the present invention, the cross head 28 is controlled to stop at a position where the movable platen 2 moves backward and stops by the resin foaming pressure acting on the movable platen 2 after the volume of the mold cavity is enlarged. That is, when the position of the movable platen is moved so that the cavity volume becomes a desired volume at the start of the foaming process, the crosshead position corresponding to the moved movable platen position is changed to the crossing direction corresponding to the fixed platen direction of the movable platen. Calculated from the head position data, the cross head is moved to the calculated cross head position, and the cross head position after the movement is held until the foaming step is completed. As a result, since an enlarged dimension of a desired mold cavity volume can be obtained, the expansion ratio, the bubble diameter, and the molded product thickness do not change.

  FIG. 3 schematically shows the relationship between the movable platen position and the crosshead position described above. In FIG. 3, the X-axis (horizontal direction) represents the crosshead position, and the left end represents the forward limit position where the toggle is fully extended. The Y axis (vertical direction) represents the position of the movable platen, and the intersection with the X axis represents the mold touch point (Stc). The dimension (L value) of the die touch point (Stc) at the forward limit position of the X-axis crosshead and the front side (anti-fixed platen direction) shown in this figure indicates the magnitude of the clamping force. According to this figure, it is clear that there is a difference in the crosshead position between the data in the fixed platen direction and the data in the anti-fixed platen direction when the same movable platen position is obtained. Represents the total gap. In addition, since there is a difference in the crosshead position corresponding to the movable platen position depending on the set mold clamping force, the crosshead position corresponding to the movable platen position is stored in the memory by teaching operation every time the mold is replaced. is there.

The difference between the mold touch point (Stc) and the temporary mold separation point (Sto) obtained by the above teaching operation and the difference between the backward movement reference point (Smo) and the forward movement reference point (Smc) are linked. This indicates the dimension corresponding to the total clearance of the nodes, and is detected as the crosshead moving distance. By continuously detecting and comparing, it is possible to quantitatively grasp the secular change in the total gap size of the link nodes 6a to 6e.
Note that the teaching operation is performed by detecting a minute mold clamping force and a change in the position of the movable platen. Therefore, it is preferable to perform the teaching operation in advance under the conditions of the molding operation.

Hereinafter, the injection foam molding method of the present invention will be described.
The resin applicable to the present invention is obtained by mixing a foaming agent with a thermoplastic resin material typified by polystyrene or polypropylene that can be injection-molded. As the foaming agent, an inorganic foaming agent typified by sodium bicarbonate, a chemical foaming agent such as an organic foaming agent typified by azodicarbonamide, or the like is used.

  By driving the electric servo motor 25 shown in FIG. 1 and moving the cross head 28 forward, the link drive mechanism 26 of the mold clamping device 20 is operated, and the toggle type mold clamping mechanism 8 is extended and the movable platen 2 is fixed. The mold 10 is moved in the direction of the board 1 and the mold 10 is clamped, and the toggle is not extended. The mold clamping force is preferably set to a minimum value that does not open at the resin filling pressure at the time of resin filling, from the viewpoints of energy used and life of the molding apparatus.

After completion of the mold clamping, the resin is injected and filled into the mold cavity based on the preset injection filling amount, injection pressure, and injection speed. After the injection filling is completed, the holding pressure is applied so that the molten resin in the mold and the injection apparatus 30 does not foam until the surface layer of the molded product is solidified and the skin layer is formed. The pressure holding process is performed until the mold temperature is measured by a temperature sensor 80 built in the mold 10 and reaches a preset temperature. The solidification temperature of the surface layer varies depending on the thickness, shape, mold temperature, resin temperature, resin type, etc. of the molded product, and it is desirable to set it while observing the state of the molded product.
The pressure holding step is a method based on measuring the mold temperature and based on the solidification temperature of the surface layer. However, the method is not limited to this, and the output signal of a timer that starts timing upon completion of injection filling may be used as a reference. And after forming the skin layer in which the molded product surface layer is solidified, the mold 10 is opened and the process proceeds to the foaming step.

  The expansion control of the cavity volume of the mold in the foaming process is performed by moving the crosshead 28 stored in the memory of the mold clamping control unit 61 built in the control device 60 by the teaching operation from the forward movement reference point (Smc) to the mold touch point ( Stc) is performed based on the positional relationship data of the cross head 28 corresponding to the position of the movable plate moved forward to Stc), and the cross head 28 is stopped at the preset position of the movable plate 2 and the resin foam pressure in the mold Thus, the movable platen 2 is held in position so as not to be pushed back. By thus performing mold volume enlargement control and enlarging the mold cavity, the pressure in the mold cavity begins to decrease, and at the same time, foaming begins to occur inside the resin. Then, after a cooling process in which the cavity volume is maintained for a preset cooling time of the molded product, the mold is retracted to the position where the molded product is taken out to obtain a high-quality foam molded product.

  In the present embodiment, even when the mold 10 is slightly opened, the fixed mold 3 and the movable mold 4 are fitted in the fitting portion, and the molten resin in the mold cavity is the mold 10. It does not leak out. Further, in the foaming process after the skin layer is formed, the total gaps of the link nodes 6a to 6e are preliminarily taught by the teaching operation so that the position where the resin foaming pressure acting on the movable platen 2 moves backward and stops becomes the desired movable platen position. A control method and apparatus in which the dimension corresponding to is detected and stored as the movement distance of the cross head 28 and the enlarged dimension of the mold cavity volume is reduced by the stored dimension. That is, when the position of the movable platen 2 is moved so that the cavity volume becomes a desired volume at the start of the foaming process, the crosshead position corresponding to the moved movable platen position corresponds to the fixed platen direction of the movable platen. Calculated from the crosshead position data, the crosshead is moved to the calculated crosshead position, and the crosshead position after the movement is held until the foaming process is completed. As a result, since an enlarged dimension of the desired mold cavity volume can be obtained, there is no excessive volume expansion due to the total gap between the link nodes 6a to 6e of the toggle mechanism, and a desired molded product thickness can be obtained.

Here, the moving stroke of the movable platen 2 with respect to the moving stroke of the cross head 28 immediately before the die 10 touches the die is approximately 10: 1. Further, the moving speed of the movable platen 2 with respect to the moving speed of the cross head 28 also exhibits a behavior of approximately 10: 1. In other words, in the mold clamping device 20 of the toggle type mold clamping mechanism 8, if the position of the crosshead 28 is controlled, the movable platen 2 is controlled with an accuracy that is 10 times the crosshead position accuracy. Position control can be performed. However, the conventional injection foam molding method and the injection molding apparatus for expanding the cavity volume of the mold and foaming the resin are movable according to the positional relationship data when the cross head 28 is moved in the anti-fixing plate direction as described above. The position of the board is controlled. Therefore, even if the crosshead 28 is stopped and held at a predetermined movable platen position, when the resin foam pressure in the mold is applied to the movable platen 2, the movable platen 2 reaches the total gap of the link nodes 6a to 6e. As a result, the mold 10 is further increased in volume by a dimension corresponding to the total gap of the link nodes 6a to 6e, and the foaming ratio, bubble diameter, thickness of the molded product, etc. of the desired molded product can be obtained. There is a problem that there is no.
In contrast, in the present embodiment, in the expansion control of the cavity volume of the mold 10 at the time of foaming, the position of the crosshead position and the position of the movable platen 2 when the movable platen 2 is moved in the fixed platen direction. This is done using relational data. Therefore, even if the resin foaming pressure in the mold acts on the movable platen 2, the mold 10 does not increase in volume by the dimension corresponding to the total gap between the link nodes 6a to 6e. Therefore, the present invention can accurately control the opening of the mold during foaming, and can obtain a high-quality foam-molded product having a dense surface and less variation in foaming ratio and bubble diameter by the high pressure method. it can.

  The conventional injection molding device using the toggle type mold clamping device has the characteristic that the movable platen position is excellent in accuracy for the reason described above, but the link nodes 6a to 6e of the toggle mechanism. However, there is a problem in that a foamed injection molded product having a desired molded product thickness or expansion ratio cannot be obtained because of having a minute gap. The injection foam molding method and the injection foam molding apparatus according to the present invention provide a position of the movable plate so that the cavity volume becomes a desired volume at the start of the foaming process regardless of the crosshead positional relationship data corresponding to the conventional anti-fixed plate direction. When moving the crosshead, the crosshead position corresponding to the moved movable platen position is calculated from the crosshead position data corresponding to the fixed platen direction of the movable platen, and the crosshead is moved to the calculated crosshead position. At the same time, the above-mentioned problem was overcome by maintaining the crosshead position after the movement until the completion of the foaming step.

Then, even if the molding conditions were adjusted, it was possible to mold a molded product that could not be molded by the conventional method and apparatus. That is, a molded product having a wall thickness of 1.9 mm, a mold cavity volume expansion size of 0.2 mm, and an expansion ratio of about 1.1, and 3% by weight of azodicarbonamide, an organic foaming agent, are mixed with polypropylene resin. Molding was possible with the molding method and apparatus of the present invention.

It is a whole block diagram of the injection foam molding apparatus used for the injection foam molding method of this invention. It is a flowchart explaining the procedure of teaching operation | movement. It is a schematic diagram which shows the relationship between a movable board position and a crosshead position. It is a figure explaining the link node in a movable board.

Explanation of symbols

Reference Signs List 1 fixed platen 2 movable platen 3 fixed die 4 movable die 6a link node 6b link node 6c link node 6d link node 6e link node 7 tie bar 8 toggle type mold clamping mechanism 10 mold 20 mold clamping device 26 link drive mechanism 28 crosshead 30 Injection device 60 Control device 71 Movable platen position sensor 74 Stroke sensor 75 Clamping force sensor 100 Injection foam molding device

Claims (2)

Using an injection foam molding device equipped with a toggle type clamping device that freely opens and closes a mold placed between the movable platen and the fixed platen by the movement of the crosshead, the movable platen and fixed platen An injection filling step of filling a mold cavity clamped with a molten resin containing a foaming agent, the injection filling step, and after the injection filling step, the movable platen is moved in a direction opposite to the fixed platen In the injection foam molding method comprising a resin foaming step of expanding and holding the volume of the resin from the injection filling step and foaming the molten resin in the enlarged cavity,
The relationship between the position of the cross head and the position of the movable platen when the movable platen is moved in the direction of the fixed platen is stored in advance as positional relationship data so that the cavity volume becomes a desired volume at the start of the foaming process. When moving the position of the movable platen, the crosshead position corresponding to the moved movable platen position is calculated from the position data, the crosshead is moved to the calculated crosshead position, and the foaming step Hold the crosshead position after the movement until completion,
A teaching step for measuring and storing the positional relationship data in advance is provided, and the teaching step includes a crosshead so that the movable platen at the teaching die open position that completely opens the die moves toward the fixed platen. A step of detecting and storing the position of the crosshead at which the movable platen starts moving as a forward movement reference point (Smc) when moved, and the movable plate moves in the direction of the fixed platen from the forward movement reference point (Smc). A step of detecting and storing a position of the crosshead as a mold touch point (Stc) when the mold clamping force starts to change from zero when the crosshead is moved as described above, and the forward movement reference point (Smc) ) To the mold touch point (Stc), the position of the crosshead and the movable platen are measured when the crosshead is moved, and the positional relationship data between the crosshead and the movable platen are measured. A foam injection molding method for storing Te,
The teaching step includes a first step of detecting the clamping force by clamping the mold with a predetermined clamping force, and a clamping force when the cross head is moved in the anti-fixing plate direction from the clamping state. A second step of detecting and storing the crosshead position at which zero becomes zero as a temporary mold separation point (Sto), and from the temporary mold separation point (Sto) to a predetermined position where the mold is completely opened A third step of detecting and storing the crosshead position stopped by moving the crosshead in the direction opposite to the fixed platen as a reverse operation reference point (Smo), and the crosshead from the reverse operation reference point (Smo) A fourth step of detecting and storing the position of the crosshead at which the movable plate begins to move when moved in the direction as the forward movement reference point (Smc), and the movable plate is fixed from the forward movement reference point (Smc). Move the crosshead to move in the direction of the board When allowed, it comprises a fifth step of detecting and storing the position of the crosshead clamping force starts to change from zero as the mold touch point (Stc), sequentially from the first step to the fifth step An injection foam molding method for storing the relationship between the position of the cross head and the position of the movable plate as positional relationship data. A toggle type clamping mechanism, a cross head, and a link drive mechanism for driving the toggle type clamping mechanism via the cross head, and a movable plate attached to one end of the toggle type clamping mechanism in the fixed platen direction. A movable platen position sensor for detecting the position of the movable platen, including a mold clamping mechanism that moves forward and backward to freely open and close a mold disposed between the movable platen and the fixed platen. A position sensor for detecting the position of the crosshead, and a mold clamping force sensor for detecting the mold clamping force of the mold clamping device, while measuring the positions of the crosshead and the movable platen, The crosshead is moved so that the movable platen in the teaching die open position that completely opens the mold moves in the direction of the fixed platen, and the position of the crosshead where the movable plate begins to move is determined as the forward movement reference point (Smc). And the clamping force is The position of the crosshead that starts to change from the position is detected as the mold touch point (Stc), and the positional relationship between the crosshead and the movable platen is determined from the forward movement reference point (Smc) to the mold touch point (Stc). A mold clamping control unit that stores data as data and controls the position of the movable plate by moving the position of the crosshead based on the stored position data, and the desired cavity volume at the start of the resin foaming process. When the position of the movable plate is moved so that the crosshead position corresponding to the moved movable platen position is calculated from the position data, the crosshead is moved to the calculated crosshead position, A resin foam injection molding apparatus that holds the crosshead position after the movement until the completion of the foaming process,
The teaching step for measuring and storing the positional relationship data in advance is provided, the difference between the die touch point (Stc) obtained by the teaching operation and the temporary die separation point (Sto) , and the backward movement reference point The difference between (Smo) and the forward movement reference point (Smc) is detected and stored as the movement distance of the crosshead as the total gap dimension of the link node, and the link node is compared by comparing the stored movement distance of the crosshead. Injection foam molding equipment that detects secular changes in the total gap size.

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