JP5125085B2 - Injection foam molding method and injection foam molding apparatus - Google Patents

Description

  The present invention relates to an injection foam molding method and an injection foam molding apparatus in which resin is filled in a mold and foamed, and the surface is dense and high quality foam molding with no variation in foaming magnification, bubble diameter and thickness of the molded product. It relates to technology for obtaining goods.

Foam-molded articles having an effect excellent in physical properties such as lightness, heat insulation, and sound absorption due to a large number of bubbles in the resin have been used in various fields for a long time.
In particular, 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 reduction in cost has led to a reduction in cost, further expanding the field of foam molded products.
As a molding method that prevents the surface property from being lowered due to the entrainment of the foaming gas into the skin layer and has a dense surface with little rough skin, the molten resin containing the foaming agent is fully filled into the mold cavity and the surface layer is solidified. After the skin layer is formed, a high-pressure method is known in which the resin is foamed by expanding the volume of the mold cavity. In this high-pressure method, the amount of enlargement of the mold cavity is an important factor that affects the foaming ratio of the molded product, the bubble diameter, the thickness of the molded product, etc., and is required to be controlled with high accuracy and high reproducibility. (See Patent Document 1)

Expansion of the mold cavity volume, which is performed by moving the movable platen in the mold opening direction using a mold clamping device equipped with a conventional toggle type mold clamping mechanism, is at the mold touch point using the boost characteristic of the toggle mechanism. The relationship between the position of the movable platen detected when the movable platen of the mold clamping device is moved in the mold opening direction and the position of the crosshead is stored as position data, and the position of the movable platen is determined based on the stored crosshead position data. Is controlled at the crosshead position. In this control method using the toggle mechanism, for example, even if the position of the crosshead fluctuates by 1 mm, the position fluctuation of the movable plate is 0.1 mm or less, and the position control of the movable plate can achieve extremely high accuracy and reproducibility. A high mold cavity volume expansion control can be realized. (See Patent Document 2)
JP-A-48-22164 JP-A-9-193221

  However, the above-described conventional high pressure method described in Patent Document 1 is a molding apparatus using a mold clamping device that uses the boosting characteristics of the toggle mechanism shown in Patent Document 2 to control the position of the movable platen at the position of the crosshead. When done, there were the following problems.

  FIG. 4 is an explanatory view showing an outline of a conventional injection molding apparatus 100 provided with a toggle type mold clamping device. Since the mold clamping device 20 using the toggle mold clamping mechanism 8 shown in FIG. 4 generates a mold clamping force with the link extended, when the thickness of the mold 15 changes, the toggle mold clamping is accordingly performed. A die height adjusting mechanism 9 for adjusting the position of the mechanism 8 is provided. The die height adjusting mechanism 9 includes, for example, a tie bar nut 5 that is rotatably provided on the rear platen 4 and is screwed to the tie bar 7, and a drive device (not shown) that rotationally drives the tie bar nut 5. Since there are gaps for rotational sliding between the thread portions of the tie bar nut 5 and the tie bar 7 and between the tie bar nut 5 and the rear platen 4, the rear platen 4 becomes a mold when the mold cavity volume is increased. In response to the reaction force of opening, it moved in the mold closing direction as shown in FIG. 5 and stopped after forming gaps δ5 and δ6 in the mold opening direction.

  Further, in FIG. 4, link nodes 6 a to 6 e which are hinge portions of the toggle type mold clamping mechanism 8 are constituted by a link and a toggle pin inserted through the pin hole provided in the link with a minute gap. . Since the link nodes 6a to 6e have the minute gaps as described above, when the mold cavity volume is enlarged by the conventional technique, the cross head 28 is retracted by a dimension corresponding to the total gap of the link nodes 6a to 6e. The movable platen 2 moved and stopped. For example, FIG. 6 shows a state where the gap δ2 of the movable plate link node is formed when the movable plate 2 stops after the mold cavity is enlarged.

  When injection foam molding in which resin is foamed in the mold cavity 18, even if the crosshead 28 is stopped and held at the position of the movable plate 2 in which the mold cavity is expanded to a desired volume, the movable plate 2 The resin-type foaming pressure of the mold cavity 18 acts on the mold-type cavity 18 and the toggle-type clamping mechanism 8 moves backward, so that the mechanical clearance of the toggle mechanism, that is, the total clearance of the link nodes 6a to 6e and the clearance in the die height adjustment mechanism 9 mold opening direction. The mold cavity volume is increased by (total of δ5 and δ6), and the foaming magnification, the bubble diameter, and the thickness of the molded product are changed, resulting in a problem that a high-quality foamed molded product cannot be obtained.

  Therefore, the present invention has been made in view of the above problems, and in the foam injection molding of a resin using a mold clamping device having a toggle type mold clamping mechanism, it is not affected by the mechanical gap of the toggle mechanism. Another object of the present invention is to provide an injection foam molding method and an injection foam molding apparatus for obtaining a high quality foam molded product having no variation in foaming magnification, bubble diameter and thickness accuracy of the molded product.

In order to achieve the above object, an injection foam molding method according to claim 1 of the present invention freely opens and closes a mold disposed between a movable platen and a fixed platen by movement of a crosshead, and a mold clamping force. Using an injection foam molding apparatus equipped with a toggle type mold clamping device that acts on the mold, an injection filling step of filling the mold cavity with a molten resin containing a foaming agent, and anti-fixing the movable plate after the injection filling is moved to the board direction cavity volume of the mold and held in an enlarged than the injection filling process it comprises a foaming process of the resin to foam the molten resin in the enlarged within much cavity, a foaming of the resin pressed to fix the tie bar nut axially upon process, a foam injection molding method for holding the retracted position of the movable platen after the foaming process, the pressing of the tie bar nut to linear motion a rotational motion of the electric motor Performed using the conversion driving mechanism, the foaming process of the resin detects the clamping force by the load sensor, the expansion of the cavity volume, and characterized by performing under the action of a predetermined clamping force.

  According to a second aspect of the present invention, there is provided an injection foam molding method according to the first aspect of the present invention, wherein the position of the movable platen is moved so that the mold cavity volume becomes a desired volume at the start of the resin foaming step. The positional relationship between the position of the crosshead and the movable platen when the movable platen is moved in the fixed platen direction is stored in advance as positional relationship data, and the crosshead position corresponding to the moved movable platen position is stored in the position. The crosshead is calculated from the relational data, moved to the calculated crosshead position, and the moved crosshead position is held until the resin foaming step is completed.

According to a third aspect of the present invention, there is provided an injection foam molding method according to the second aspect of the present invention, further comprising: a teaching step for storing the positional relationship data, wherein the teaching step includes an axis line of the tie bar nut by the locking means. The process of pressing and fixing in the direction, and the crosshead that starts moving when the crosshead is moved so that the movable platen at the fully open position of the teaching die moves in the direction of the fixed platen. The process of detecting and storing the position as the forward operation reference point (C0) and the mold clamping force when the crosshead is moved from the forward operation reference point (C0) so that the movable platen moves toward the fixed platen. Detecting and storing the position of the crosshead starting from zero as the mold touch point (C1), and storing the position from the forward operation reference point (C0) to the mold touch point (C1). Suheddo by detecting the positions of the movable platen of the crosshead at the time of moving the is characterized by storing the positional relationship data between the crosshead and the movable platen.

In order to achieve the above object, an injection foam molding apparatus according to a fourth aspect of the present invention includes a cross head and a link driving mechanism that drives the toggle mechanism via the cross head, and is provided at one end of the toggle mechanism. A toggle mold clamping device for moving the attached movable plate toward and away from the fixed platen and freely opening and closing a mold disposed between the movable platen and the fixed platen and clamping the mold; A position sensor for detecting the position, a position sensor for detecting the position of the crosshead, and a mold clamping force sensor for detecting the mold clamping force, and the position memorized in the teaching step a mold clamping control unit for controlling the position of the movable platen by moving the position of the crosshead based on the relationship data, in the foaming step of the resin, and fixed by pressing the tie bar nut in the axial direction, the friendly after the foaming step Comprising a plurality of locking means for preventing movement of the panel in the die opening direction, and in a case where the cavity volume of the mold at the start of resin foaming process moves the position of the movable platen so as to be desired volume, said The crosshead position corresponding to the position of the movable platen after movement is calculated from the positional relationship data, the crosshead is moved to the calculated crosshead position, and the crosshead position after movement until the foaming step is completed. the a apparatus for injection foaming molding for holding under the action of a predetermined clamping force, said plurality of locking means is characterized by being configured by a driving mechanism for converting rotational motion to linear motion using an electric motor.

  In the injection foam molding method according to the first aspect of the present invention, the movable platen is moved in the mold opening direction to fix the mold cavity volume by pressing the tie bar nut in the axial direction, and at a predetermined mold clamping force. Since it is performed under the action, the mechanical gap of the toggle mechanism can be eliminated, and the desired mold cavity volume can be realized, and the foaming magnification, the bubble diameter and the thickness of the foamed molded product do not vary. A high-quality foam molded product can be obtained.

In the injection foam molding method according to the second aspect, the position of the movable platen is controlled by the position data of the cross head using the toggle type mold clamping mechanism, so that it is extremely highly accurate and highly reproducible. Position control of the movable plate can be realized.
In the injection foam molding method according to the third aspect, the position control of the movable platen is performed by the position data of the crosshead when the movable platen stored by the teaching operation is moved in the fixed platen direction. Even if the foaming pressure of the resin acts on the movable plate after the enlargement, the movable plate is not retracted from a predetermined position under the restriction of the toggle pin.

In the injection foam molding apparatus according to the fourth aspect, the position of the movable platen is controlled by the position data of the cross head using the toggle type mold clamping mechanism, so that the position is extremely high and the reproducibility is high. Position control of the movable plate can be realized.
In addition, using a toggle type clamping mechanism, the movable platen is moved in the mold opening direction to expand the mold cavity volume, pressing the tie bar nut in the axial direction and fixing it, and under the action of a predetermined clamping force. Since the mechanical gap of the toggle mechanism is eliminated, the desired mold cavity volume can be achieved, and there is no variation in the foaming ratio, bubble diameter, or thickness of the molded product. Has the effect of obtaining a foamed molded product.
Furthermore, since the position control of the movable plate is performed by the position data of the cross head when the movable plate stored by teaching operation is moved in the direction of the fixed plate, the foaming pressure of the resin is applied to the movable plate after the mold cavity volume is expanded. Even if it acts, the movable platen is not retracted from a predetermined position under the restriction of the toggle pin.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram schematically showing the overall configuration of an injection foam molding apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the state of the movable plate link node gap formed when the movable plate is stopped according to the present invention. FIG. 3 is an explanatory view schematically showing the gap of the die height adjusting mechanism including the outline of the locking means for pressing the tie bar nut of the present invention. FIG. 4 is an explanatory diagram for explaining the overall configuration of a conventional injection foam molding apparatus. FIG. 5 is an explanatory view schematically showing a gap formed when the mold of the conventional die height adjusting mechanism is opened. FIG. 6 is an explanatory view showing a state of a movable platen link joint gap formed when the conventional movable platen is stopped.

The structure of the injection foam molding apparatus 100 which is embodiment of this invention is demonstrated.
As shown in FIG. 1, an injection foam molding apparatus 100 of the present invention includes a mold 15, a mold clamping device 20, an injection device 30, and a control device 60 that controls the mold clamping device 20 and the injection device 30. . As shown in FIG. 1, the mold 15 includes a fixed mold 16 and a movable mold 17. The fixed mold 16 and the movable mold 17 have a half-push structure and are fitted in a fitting portion. in and cavity surface formed on the stationary mold 16 and the cavity surface formed on the movable mold 17 are combined state are configured to form a mold cavity 18. The fitting portion of the half-push structure is formed over the entire circumference of the mold cavity surface, and the resin filled in the mold cavity 18 leaks from the mold 15 even if the volume of the mold cavity 18 is increased after injection filling. It prevents it from being put out.
Although the mold is used in a half-pressing structure in which the resin filled in the mold cavity 18 does not leak even if the mold 15 is opened by a predetermined stroke, the present invention is not limited to this, and can be applied to foam molding. If there is, other molds such as a flat push structure may be used.

A mold clamping device 20 shown in FIG. 1 includes a link driving mechanism 26 having a fixed platen 1, a movable platen 2, and an electric servo motor 25 as driving sources, a toggle type clamping mechanism 8 driven by the link driving mechanism 26, and an electric motor. A control driver for driving the servo motor 25 and a die height adjusting mechanism 9 for adjusting the mold thickness are provided, and the movable platen 2 is guided by a tie bar 7 installed between the fixed platen 1 and the rear platen 4, and is toggled. The mold clamping mechanism 8 is configured to move forward and backward together with the movable mold 17.
A stroke sensor 66 as a position sensor for detecting the position of the crosshead 28 is attached to the crosshead drive shaft 27 of the link drive mechanism 26 provided in the mold clamping device 20. The position of the head 28 can be accurately detected.

  In the present embodiment, the stroke sensor 66 is provided as a position sensor for detecting the position of the crosshead 28. However, the position sensor is not provided in order to detect the position of the crosshead 28. Needless to say, the detection method may be a method using a sensor built in the electric servomotor 25.

Further, the mold clamping device 20 includes a mold clamping force sensor 67 at one end of the tie bar 7 on the fixed platen side as a sensor for detecting the mold clamping force. The mold clamping force sensor 67 detects the extension amount of the tie bar 7. Thus, the mold clamping force is detected.
Further, the mold clamping device 20 is provided with a movable platen position sensor 65 as a mold opening / closing sensor for detecting the mold opening / closing stroke so as to detect the position of the movable platen 2. The opening / closing stroke of the mold 15 and the amount of expansion of the mold cavity volume are detected.

  In the present embodiment, the movable platen position sensor 65 is arranged as a mold opening / closing stroke sensor for detecting the mold opening / closing stroke. However, the mold opening / closing stroke sensor is not limited to this. Alternatively, a system in which a mold opening / closing stroke sensor is directly attached to the mold 15 may be used.

Further, the mold clamping device 20 shown in FIG. 1 includes a die height adjusting mechanism 9 that adjusts the position of the movable plate according to the change of the thickness of the mold 15, and the die height adjusting mechanism 9 is rotatable to the rear platen 4. The tie bar nut 5 that is screwed to the tie bar 7 and a drive device (not shown) that rotationally drives the tie bar nut 5 are provided, and it is possible to attach molds having different mold thicknesses and set the clamping force. .
To adjust the position of the movable platen, the toggle-type mold clamping mechanism 8 is moved in the mold opening direction where the gap between the movable platen 2 and the fixed platen 1 is large when the thickness of the die to be attached is large. It is performed by moving in the mold opening direction where the distance between the movable platen 2 and the fixed platen 1 becomes small. The mold thickness can be detected by a method using a rear platen position detection sensor (not shown) that detects the position of the rear platen 4 or a detection method based on the number of rotations of a drive device that rotates.

Furthermore, the injection foam molding apparatus 100 shown in FIG. 1 is provided with a plurality of locking means 10 for eliminating the total gap of the die height adjusting mechanism 9 that presses and fixes the tie bar nut 5 in the axial direction. In this embodiment, the lock means 10 is provided on the tie bar nut portion, and can move the tie bar nut 5 in the mold closing direction and press it against the nut pressure receiving surface of the rear platen 4.
2, the lock means 10 is driven by hydraulic oil supplied from a hydraulic source (not shown) to a plurality of hydraulic cylinders 11 provided in the die height adjusting mechanism 9, and the tip of the piston rod 12 forms the tie bar nut 5 as a mold. It is configured to be pressed and fixed in the closing direction.
In this embodiment, the tie bar nut 5 is pushed to the rear platen 4 by a plurality of hydraulic cylinders 11. However, the pushing means for the tie bar nut 5 is not limited to this, and the electric The structure using the drive means which converts a rotational motion into a linear motion using a motor may be sufficient.

  The control device 60 that controls the operation of the injection foam molding apparatus 100 moves the movable platen when the crosshead is moved so that the movable platen in the teaching mold open position that completely opens the mold moves in the direction of the fixed platen. The mold clamping force changes from zero when the crosshead is moved so that the movable head moves in the direction of the fixed platen from the forward movement reference point (C0) and the forward movement reference point (C0). The position of the crosshead that starts to be detected is detected as the mold touch point (C1), and the mold 15 is moved when the movable platen is moved in the direction of the fixed platen from the forward operation reference point (C0) to the mold touch point (C1). Detection values of the movable platen position sensor 65 for detecting the opening / closing stroke and the stroke sensor 66 for detecting the position of the crosshead are input, and the positional relationship between the position of the crosshead and the movable platen is used as positional relationship data. Memory to.

The toggle type mold clamping mechanism 8 in the present 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 moving the crosshead 28 in the mold opening / closing direction. However, the above-described system having a four-bar double toggle type clamping mechanism having four link nodes may be used. Further, in this embodiment, the electric servo motor 25 as shown in FIG. 1 is used as the moving means for the crosshead 28, but the present invention is not limited to this embodiment, and a hydraulic cylinder is used as the moving means for the crosshead 28. You may use for this invention.
Then, the toggle pin of the link node 6c shown in FIG.

The configuration of the injection device 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 the screw 34 moves forward and backward. A moving means 40 and a screw driving 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 first-stage injection device 30 is configured such that a pellet-shaped molding resin material is supplied from a hopper when the screw 34 is rotated by the screw rotating means 40, and the supplied pellet-shaped resin molding material is a barrel Heated by a heater attached to 32, and melted by receiving a kneading compression action by the rotation of the screw 34, and sent to the front of the screw 34. The molten resin sent to the front of the screw 34 can be attached to the tip of the barrel 32 by the screw 34 advanced from the screw moving means 40 and injected and filled into the mold cavity 18 from the nozzle 39.
As shown in FIG. 1, the injection moving means 40 and the screw rotating means 42 in this embodiment are configured using an electric servo motor. However, the present invention is not limited to this embodiment, and the screw moving means is a hydraulic cylinder. And a hydraulic motor may be used as the screw rotating means.

  The control device used in this 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. And an injection condition setting device for setting conditions.

  A foam molding method using the injection foam molding apparatus 100 of the present invention will be described with reference to FIGS. The resin molding material applicable to the present invention is obtained by mixing a foaming agent with a thermoplastic resin material typified by polystyrene (PS) or polypropylene (PP) that can be injection molded. As the foaming agent to be mixed with the resin molding material, an inorganic foaming agent represented by sodium bicarbonate, a chemical foaming agent such as an organic foaming agent represented by azodicarbonamide, or the like is used.

  1 is driven to operate the link drive mechanism 26 of the mold clamping device 20 and to move the cross head 28 forward, thereby extending the toggle type mold clamping mechanism 8 and fixing the movable platen 2 to the fixed platen. The mold 15 is moved in the direction 1 and the mold 15 is clamped to hold the toggle fully extended. The magnitude of the mold clamping force is desirably a minimum value that does not open the mold 15 by the resin filling pressure at the time of injection filling from the viewpoint of the energy used and the life of the mold and the mold clamping apparatus.

After completion of the mold clamping, the molten resin is injected and filled into the mold cavity 18 on the basis of injection conditions such as a preset injection filling amount, injection pressure, and injection speed. After the injection filling is completed, if the surface layer of the molded product is solidified and the skin layer is formed, the holding pressure is applied so that the molten resin in the mold cavity 18 and the injection device 30 does not foam.
The pressure holding process is based on the output signal of a timer that starts timing when injection filling is completed, and the set time varies depending on the thickness, shape, mold set temperature, molten resin temperature, and type of molded resin material of the molded product. It is desirable to set while looking at the state of the molded product taken out from the mold. And after formation of the skin layer which the surface layer solidified, the mold cavity volume is expanded and it transfers to a foaming process.

In the foaming step, a plurality of locking means are operated as shown in FIG. 2 in the mold clamping state of the mold clamping device 20 to move the tie bar nut 5 in the mold closing direction and press the nut pressure receiving surface of the rear platen 4. Next, the volume of the mold cavity 18 is expanded under the action of a predetermined mold clamping force.
The mold cavity volume is enlarged when the movable plate stored in the mold clamping control unit 61 built in the control device 60 is moved in the direction of the fixed plate from the forward operation reference point (C0) to the die touch point (C1). Based on the positional relationship data between the position of the crosshead and the movable platen, the crosshead 28 is stopped at a preset stop position of the movable platen 2 and held on the crosshead drive shaft 27.

In the enlargement of the mold cavity volume using the locking means 10, as shown in FIG. 2, there is no gap formed in the die height adjusting mechanism section in which the cavity volume changes due to the foaming pressure.
Further, since the mold cavity volume is enlarged under the action of a predetermined mold clamping force, for example, as shown in FIG. 3, the gap of the link node is not formed in the direction in which the cavity volume changes due to the foaming pressure. The gap between the die height adjusting mechanism and the link node of the toggle mechanism does not affect the foaming ratio, the bubble diameter, the thickness of the molded product, and the like. For this reason, it is possible to obtain a high-quality foam-molded product having no variation in the thickness, foaming magnification, and cell diameter of the molded product.

Here, the movement stroke of the movable platen 2 with respect to the movement stroke of the cross head 28 immediately before the mold 15 touches the mold is approximately 10: 1. Further, the moving speed of the movable plate 2 with respect to the moving speed of the cross head 28 also exhibits a behavior of about 10: 1. In other words, in the mold clamping device 20 having the toggle type mold clamping mechanism 8, if the position of the cross head 28 is controlled, the movable platen 2 is controlled with an accuracy approximately 10 times that of the cross head position system, and a high accuracy is achieved. It is possible to perform mold opening / closing position control.
However, in an injection foam molding apparatus using a mold clamping device having a conventional toggle mechanism, there is a gap in the link node or a die height adjusting mechanism, and the movable platen is moved by the resin foaming pressure after the mold cavity volume is expanded. It has a problem that the foaming ratio, the bubble diameter, and the thickness of the molded product are varied by retreating by the amount.

  In comparison, the present embodiment uses a plurality of locking means for pressing the tie bar nut against the rear platen in the die height adjusting mechanism, and further, the volume of the mold cavity 18 is adjusted under the action of a predetermined mold clamping force. By expanding the volume, the above-mentioned problems can be solved, and a high-quality foamed molded product having no variation in the foaming ratio, the bubble diameter and the thickness of the molded product can be obtained.

It is explanatory drawing which shows roughly the whole structure of the injection foam molding apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows roughly the whole structure of the injection foam molding apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows typically the clearance gap of the die height adjustment mechanism part containing the outline | summary of the locking means which presses the tie bar nut of this invention. It is explanatory drawing explaining the whole structure of the conventional injection foam molding apparatus. It is explanatory drawing which shows typically the clearance gap formed at the time of mold opening of the conventional die height adjustment mechanism part. It is explanatory drawing which shows the state of the movable board link node gap formed at the time of the conventional movable board stop.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixed platen 2 Movable platen 4 Rear platen 5 Tie bar nuts 6a-6e Link node 8 Toggle type clamping mechanism 9 Die height adjustment mechanism 10 Locking means 15 Mold 18 Mold cavity 20 Clamping device 30 Injection device 60 Control device 100 Injection foam molding Devices δ1, δ2 Movable platen link joint gaps δ3, δ4 Die height adjustment mechanism Rear platen part gaps δ5, δ6 Die height adjustment mechanism Screw part gap C0 Advance operation reference point C1 Mold touch point

Claims (4)

Using the injection foam molding apparatus provided with a toggle type mold clamping device that freely opens and closes the mold arranged between the movable platen and the fixed platen by the movement of the cross head and applies the mold clamping force, the mold An injection filling step of filling a molten resin containing a foaming agent into the cavity of the mold, and after the injection filling, the movable platen is moved in the anti-fixed platen direction so that the cavity volume of the mold is expanded as compared with the injection filling step. And a resin foaming step of foaming the molten resin in the enlarged cavity, and fixing the tie bar nut by pressing in the axial direction during the resin foaming step, An injection foam molding method for holding a retracted position ,
The pressing of the tie bar nut is performed using a drive mechanism that converts the rotational motion of the electric motor into linear motion,
The resin foaming process detects the clamping force by a load sensor,
An injection foam molding method, wherein the cavity volume is enlarged under the action of a predetermined clamping force .   When the position of the movable platen is moved so that the mold cavity volume becomes a desired volume at the start of the resin foaming step, the position of the crosshead and the movable platen when the movable platen is moved in the direction of the fixed platen in advance. The positional relationship is stored as positional relationship data, the crosshead position corresponding to the movable platen position after movement is calculated from the positional relationship data, the crosshead is moved to the calculated crosshead position, and the resin 2. The injection foam molding method according to claim 1, wherein the crosshead position after movement is maintained until the foaming step is completed. Comprising a teaching step for storing the positional relationship data, the teaching step comprising:
Pressing and fixing the tie bar nut in the axial direction by the locking means;
When the crosshead is moved so that the movable platen in the fully open position of the teaching die moves toward the fixed platen, the crosshead position where the movable plate begins to move is defined as the forward operation reference point (C0). Detecting and storing; and
When the crosshead is moved so that the movable platen moves toward the fixed platen from the forward operation reference point (C0), the position of the crosshead at which the mold clamping force starts to change from zero is indicated by the die touch point (C1). And detecting and storing as,
Data on the positional relationship between the crosshead and the movable platen by detecting the position of the crosshead and the position of the movable platen when the crosshead is moved from the forward operation reference point (C0) to the mold touch point (C1). The injection foam molding method according to claim 2 , wherein: A cross head and a link drive mechanism for driving the toggle mechanism via the cross head, and moving the movable plate attached to one end of the toggle mechanism toward and away from the fixed plate; In addition to a toggle type clamping device that opens and closes the molds placed between them and clamps them,
The teaching step comprising a position sensor for detecting the position of the movable platen, a position sensor for detecting the position of the crosshead, and a mold clamping force sensor for detecting the mold clamping force. A mold clamping control unit for controlling the position of the movable platen by moving the position of the crosshead based on the positional relationship data stored by
In the resin foaming step, the tie bar nut is pressed and fixed in the axial direction, and includes a plurality of locking means for preventing movement of the movable platen in the mold opening direction after the foaming step .
When moving the position of the movable platen so that the mold cavity volume becomes a desired volume at the start of the resin foaming process, the crosshead position corresponding to the moved movable platen position is calculated from the positional relationship data. An injection foam molding apparatus that moves the cross head to the calculated cross head position and holds the cross head position after the movement under the action of a predetermined clamping force until the foaming step is completed.
The injection foam molding apparatus according to claim 1, wherein the plurality of lock means are constituted by a drive mechanism that uses an electric motor to convert rotational motion into linear motion .

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