JP3239097B2 - Method and apparatus for adjusting mold clamping force of toggle injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for adjusting a mold clamping force of a toggle-type injection molding machine, and more particularly to a novel improvement for enabling accurate adjustment of the mold clamping force.

[0002]

2. Description of the Related Art A general injection molding machine is for obtaining a product having a desired shape by injecting a molten resin at a high pressure into a cavity of a closed mold. Such an injection molding machine requires a mold clamping device capable of applying a sufficient mold clamping force to prevent high-pressure molten resin from leaking out of the mold, and a toggle-type mold clamping device is widely used as the mold clamping device. Used. The mold, resin,
A function that can freely change the mold clamping force according to the injection conditions and the like is required.

FIG. 1 is a configuration diagram of an injection molding machine using a toggle-type mold clamping device (hereinafter, referred to as a mold clamping device).

[0004] On a bed 1 of the injection molding machine, a fixed platen 2 on which a fixed-side mold portion 12 is mounted, an end housing 3 slidable on the bed 1, and between the fixed platen 2 and the end housing 3. The movable platen 6 to which the movable-side mold portion 13 is disposed is provided. The fixed platen 2 and the end housing 3 are connected by four parallel tie bars 4 at their four corners. One end of the tie bar 4 is fixed to the fixed platen 2 and the other end is formed with a screw portion 4b. The screw part 4b penetrates the end housing 3 and is inserted from the end of the screw part 4b.
And screwed. The tie bar nut 5 is disposed outside the end housing 3, and the tie bar nut 5
By rotating the end housing 3, the end housing 3 can be moved in the axial direction along the tie bar 4 by a required amount.
Therefore, the end housing 3 can be moved toward or away from the fixed platen 2 in accordance with the rotation amount of the tie bar nut 5. A toggle mechanism 8 is provided between the end housing 3 and the movable platen 6 to form a link for fastening the mold 15.

A mold clamping device includes an end housing 3, a toggle mechanism 8, a crosshead 9 for bending and extending the toggle mechanism 8, a mold clamping cylinder 10 fixed to the end housing 3 for moving the crosshead 9 back and forth, and a mold clamping apparatus. Piston rod 11 for connecting tightening cylinder 10 and crosshead 9
And

In order to adjust the mold clamping force to a predetermined mold clamping force in the thus constituted mold clamping apparatus, first, the mold is opened once, that is, at the crosshead retreat position, the thickness of the mold (actual mold thickness- αm
m (for example, 5 mm)). The measurement and control of the mold thickness are performed by the mold thickness position sensor 14.
In this mold thickness adjustment, as shown in FIGS. 3 and 4, the mold thickness adjustment motor 16 rotates the tie bar nut 5 in the casing 19 via the center gear 17 and the spur gear 18. When the tie bar nut 5 rotates, the end housing 3 approaches the fixed platen 2 along the tie bar 4,
Alternatively, the end housing 3 is moved in the separating direction, and the end housing 3 is moved to the actual mold thickness of -5 mm. For example, in the case of a 300 mm mold, the end housing 3 is moved until the distance between the movable platen 6 and the fixed platen 2 with the toggle mechanism 8 fully extended becomes 295 mm. The reason why the distance is set to minus 5 mm is that the movable side mold part 13 and the fixed side mold part 12 are in contact with each other, that is, when the crosshead 9 is advanced to the mold closing side, the crosshead 9 does not reach the most advanced position. It is.

Here, the theory of the mold clamping force generated by the toggle mold clamping device will be described.

In the toggle-type mold clamping device, even when the movable mold 13 and the fixed mold 12 are brought into contact with each other, the mold is clamped in a state where the toggle mechanism 8 is not fully extended (this is called a mold touch state). The force is adjusted, and from this state, a high pressure is further applied to the mold clamping cylinder 10 to further protrude the piston rod 11 to further increase the interval between the end housing 3 and the crosshead 9 so that the toggle mechanism 8 is finally extended. I do. During this time, the fixed mold 12 and the movable mold 13 are in contact with each other, the movable platen 6 is not moved, and the axial extension of the toggle mechanism 8 is absorbed by the retreat of the end housing 3. Due to the retraction of the end housing 3, the four tie bars 4 are extended due to the position restriction of the tie bar nut 5. As a result, a reaction force accompanying the extension is applied between the movable mold 13 and the fixed mold 12 via the toggle mechanism 8, and the mold 15 is clamped by the mold clamping force corresponding to the extension of the tie bar 4. Is done.

Next, an automatic mold clamping force adjustment method, for example,
The method described in JP-A-1-35924 will be described.

The position of the crosshead 9 at the die touch point for generating a predetermined mold clamping force is theoretically determined. Therefore, the end housing 3 is retracted from the position of the crosshead 9 when the mold is brought into contact with the mold with the mold thickness adjustment being completed to the position of the theoretical crosshead 9.

More specifically, the mold thickness is adjusted by adjusting the mold thickness−α.
Since the end housing 3 has been driven up to the distance of mm, when the mold clamping cylinder 10 is operated at an extremely low pressure to protrude the piston rod 11 and advance the crosshead 9, the toggle mechanism 8 opens in the vertical direction and the movable platen 6 Moves forward. As a result, as shown in FIG. 2, the movable mold 13 and the fixed mold 12 come into contact with each other. At this time, the toggle mechanism 8 tries to extend, but the mold clamping cylinder 10 is operated at an extremely low pressure, and the end housing 3 is driven by −α mm, so that the toggle mechanism 8 cannot extend accordingly. Can not.

A mechanism in which the end housing 3 is retracted by the mold thickness adjusting motor 16 while the ultra-low pressure is applied to the mold clamping cylinder 10 from the state shown in FIG. 2 will be described with reference to FIGS.

The mold thickness adjusting motor 16 is in contact with a center gear 17, and the center gear 17 is in contact with a spur gear 18. The spur gear 18 is fastened to a tie bar nut 5 in a casing 19, and the tie bar nut 5 is screwed to a screw portion 4 b of the tie bar 4. Accordingly, when the mold thickness motor 16 is rotated, the center gear 17 is rotated, and the screw portion 4 of the tie bar 4 is
The tie bar nut 5 tends to move in the axial direction while rotating along the line b. When the tie bar nut 5 moves in the axial direction, the end housing 3 can be moved leftward in FIG. 2 (when the mold thickness is adjusted, it can be moved rightward via the casing 19).

Next, the operation of retracting the end housing 3 by the mold thickness adjusting motor 16 while applying an extremely low pressure to the mold clamping cylinder 10 from the state shown in FIG. 2 will be described.

After the end housing 3 has retreated a predetermined amount,
Ultra-low pressure is applied to the mold clamping cylinder 10 to read the amount of movement of the crosshead 9 by the crosshead position sensor 7 while the toggle mechanism 8 is not fully extended.

Here, how to obtain the value to be read will be described. In FIG. 1, the position of the crosshead 9 in which the crosshead 9 has advanced most is the zero point, that is, the most advanced position. When this position is set as the reference position of the crosshead 9 and an ultra-low pressure is applied to the mold clamping cylinder 10 in a state where the mold thickness adjustment has been completed, the toggle mechanism 8 cannot be extended. The amount of movement of the crosshead 9 in this state is the crosshead position at the mold touch point A at the present time, that is, in the state where the automatic mold thickness adjustment has been completed.

Next, since the amount of movement of the crosshead 9 at the die touch point for generating the predetermined mold clamping force is theoretically determined, the current movement amount of the crosshead 9 and the predetermined mold clamping force are generated. The difference between the theoretical touching point of the die and the theoretical movement amount of the crosshead 9 is calculated, and the difference is calculated by the difference.
The crosshead 9 is advanced while the end housing 3 is retracted by the mold thickness adjusting motor 16 while the ultra-low pressure is applied to the zero.

Next, a description will be given of the spring-loaded mold that poses a problem here.

Since only a very low pressure is applied to the mold clamping cylinder 10, it is not possible to advance further, that is, to completely close the spring in the mold. Therefore, a gap is formed between the fixed mold section 12 and the movable mold section 13. In this state, the mold thickness adjusting motor 16 is rotated and the end housing 3 is rotated.
Is retracted, the crosshead 9 moves toward the most advanced position of the crosshead 9 because the crosshead 9 is pressed at an extremely low pressure. This operation is terminated when the theoretical crosshead movement amount by the preset clamping force is reached. However, in this method, accurate automatic mold clamping force adjustment is not performed because the adjustment is performed with a gap between the fixed mold section 12 and the movable mold section 13.

[0020]

In the above-mentioned conventional method, since the force for extending the toggle mechanism, that is, the force for pressing the movable mold and the fixed mold is an extremely low pressure, a spring is provided in both molds. When the mold is included, a force that tries to separate the molds from each other acts and the spring cannot be completely pressed down. The only way to make the spring completely pressed is to increase the force to press the movable platen.However, in the conventional method, the end housing is retracted while the movable platen is pressed, so that an excessive load is applied to the mold thickness adjustment motor. At the same time, the tie bar and the thread portion of the tie bar nut may be entangled or seized.

According to the present invention, even when using a mold in which a gap is formed between the molds by a spring, an excessive load is applied to the mold thickness adjusting motor, and the tie bar and the screw of the tie bar nut are entangled or seized. It is an object of the present invention to provide a method and an apparatus for adjusting a mold clamping force of a toggle-type injection molding machine, which can adjust the mold clamping force without occurrence of cracks.

[0022]

The present invention has solved the above-mentioned problems as follows. That is, the method and the apparatus for adjusting the mold clamping force of the toggle-type injection molding machine according to the present invention use the most advanced position of the cross-head of the toggle-type mold clamping device as a reference position, and move the cross-head moving amount from the reference position. The data of the movement amount of the board, the data of the relation between the movement amount of the crosshead from the reference position of the cross head at the mold touch point and the generated mold clamping force, and the data of the housing movement amount and the rotation angle of the tie bar nut are stored. Adjust the mold thickness so that the distance between the movable platen and the fixed platen when the movable platen is advanced without the mold attached is smaller than the mold thickness by a predetermined amount, and then attach the mold. The mold in the mold is brought into close contact with the medium pressure as much as possible so that the spring in the mold can be brought into close contact with the mold, and the moving amount of the movable platen based on the data is calculated from the moving amount of the crosshead at this time. Find the difference between the amount of movement and the amount of movement of the movable platen at the mold touch point corresponding to the set mold clamping force, and determine how many times the tie bar nut should be rotated to move the entire toggle mechanism by that difference. Calculation, then open the mold and touch the rotation sensor.
While detecting the rotation angle of the
Is rotated by the calculated rotation angle .

[0023]

Next, an embodiment of the present invention will be described. In the conventional method, if the adjustment is performed while pressing the movable mold and the fixed mold during the automatic mold clamping force adjustment, an excessive load is applied to the mold thickness adjustment motor, and galling and seizure may occur on the tie bar and the tie bar nut thread. In the present invention, there is a possibility that the end housing may be moved away from the movable mold and the fixed mold, and the end housing may be moved. The purpose is to enable automatic mold clamping force adjustment without any problems.

That is, in the method of adjusting the mold clamping force according to the present invention, a force for separating the molds is applied by a compression spring or the like, and a gap is formed between the molds when no external force is applied to each mold. The method is intended to adjust the mold clamping force of a toggle injection molding machine when the mold is mounted, and in advance, the data of the moving amount of the movable plate with respect to the moving amount of the crosshead from the reference position, the mold touch point ( The relationship between the amount of movement of the crosshead from the reference position and the generated mold clamping force, and the amount of movement of the end housing and the tie bar nut when the molds are in close contact with each other (assuming that there is no force to separate the dies). The rotation angle relation data is stored in a controller (not shown), and the distance between the movable platen and the fixed platen when the movable platen is moved forward without the mold attached is completely adhered to the spring. Condition After mold thickness adjusted so reduced by a predetermined amount set in advance than die thickness at, attaching a mold spring is built once open the mold. Next, the mold is closed at medium pressure to bring the molds into contact with each other. The amount of movement of the crosshead at this time is detected, and the movable platen from the crosshead position when the mold is brought into contact at medium pressure is detected based on the above data. Is calculated, and the difference between the calculated movable platen movement amount and the movable platen movement amount calculated from the theoretical position of the crosshead at the die touch point corresponding to the set mold clamping force is calculated. The mold is opened and the entire toggle mechanism is moved by the above difference. In addition, the said medium pressure means the pressure which can fully contact a spring.

Next, the operation will be described.

The data of the moving amount of the movable platen relative to the moving amount of the crosshead from the reference position (most forward position), the moving amount of the crosshead from the reference position of the crosshead at the die touch point, and the generated mold clamping after the completion of the mold clamping operation. Data on the relationship with the force and data on the movement amount of the end housing and the rotation angle of the tie bar nut are stored in a controller (not shown).
The relationship between the screw of the tie bar and the screw of the tie bar nut is as follows. The relationship between the pitch P of the screw, the lead L, which is the movement distance when the screw makes one rotation, and the number N of the screws is P = L / N, and the distance that the tie bar nut moves when it makes one rotation is mechanically determined. Therefore, the rotation angle of the nut with respect to the distance L1 to be moved is X = (L1 / L1).
L) × 360 °.

The mold thickness is adjusted to be smaller than the actual mold thickness by a predetermined amount, and the mold is carried between the fixed platen and the movable platen with the mold opened. Next, the mold is closed at a low pressure, the fixed mold and the movable mold are attached to the fixed board and the movable board, and then the mold is closed at a medium pressure. The molds are brought into close contact with each other (force for separating them).

In this state, the amount of movement of the crosshead is detected. A movable platen movement amount corresponding to the crosshead movement amount obtained from the current crosshead movement amount is calculated from the above data. Also, from the relationship data between the amount of movement from the crosshead reference position at the mold touch point obtained in advance and the generated mold clamping force, from the theoretical position of the crosshead at the mold touch point corresponding to the set mold clamping force. The calculated movable platen movement amount is calculated. The difference between the two movable platen movement amounts is the movement amount of the entire toggle mechanism required to generate the set mold clamping force. Next, how many times the tie bar nut should be rotated to move this movement amount is calculated from the above data. After the calculation, the mold is once opened and the entire toggle mechanism is moved leftward in the drawing by the above-described difference. This means that the mold clamping force has been adjusted.

Next, the method of adjusting the mold clamping force according to the present invention will be described more specifically.

In advance, the most advanced position of the crosshead shown in FIG. 6 is used as a reference position, and the data of the amount of movement of the movable plate with respect to the amount of movement of the crosshead from the reference position. Data on the relationship between the movement amount from the reference position and the generated mold clamping force after the completion of the mold clamping operation, and the data on the housing movement amount and the rotation angle of the tie bar nut shown in FIG. 8 are stored. In FIG. 6, the position of the movable platen is obtained based on the amount of movement of the crosshead from the reference position. According to FIG. 7, to adjust the mold clamping force to be generated, the position of the crosshead at the die touch point is determined. FIG. 8 shows how many times the tie bar nut needs to be rotated in order to move the end housing.

Next, as shown in FIGS. 1 and 2, a mold 15 to be molded is mounted in the fixed platen 2 and the movable platen 6, and
5 is measured and input to a controller (not shown) to perform automatic mold thickness adjustment. By this automatic mold thickness adjustment, the mold thickness is adjusted so as to be smaller by minus α mm than the mold thickness inputted on the software. Therefore, to explain with an example in which minus α is set to 5 mm, when the mold thickness is input to 300 mm and the automatic mold thickness adjustment is performed, the automatic mold thickness adjustment ends at 300−5 mm = 295 mm. This end state is shown in FIG. In the state of FIG. 2, in the conventional method, the crosshead 9 is advanced at an extremely low pressure, that is, the movable mold 13 and the fixed mold 12 are brought into contact with each other. The movable-side mold 13 and the fixed-side mold 12 are brought into contact with each other by pressure, and are crushed by medium pressure even if a spring is contained in the mold. The crosshead position at this time is detected by the crosshead position sensor 7. From the above data, the position of the movable platen 6 corresponding to the detected amount of movement of the crosshead 9 is calculated. This calculated value is defined as (a). Also, based on the relationship data between the movement amount of the crosshead 9 from the reference position at the mold touch point and the generated mold clamping force stored in the controller (not shown) in advance, the mold touch point corresponding to the set mold clamping force. Then, the position of the movable platen 6 is calculated from the theoretical position of the crosshead 9 in step (1).
This calculated value is defined as (b). The difference (c) between the positions of these two movable plates is the amount of movement of the toggle mechanism 8 necessary to generate the set mold clamping force.

Next, the mold clamping force to be formed is input to the controller to perform automatic mold clamping force adjustment. Unlike the conventional method, the mold is once opened and the movable mold 13 and the fixed mold 12 are brought into contact with each other. And remove the end housing 3 by the difference (c).
To move. Therefore, the motor load is small.

[0033]

An embodiment of the present invention will be described with reference to the drawings.

First, the automatic mold thickness adjustment will be described with reference to FIG.

As shown in FIG. 9 (a), the normal mold thickness (d) (dimension in a state where the spring is in close contact) of a spring-loaded mold to be molded without a mold is determined by a controller (not shown). Enter The mold clamping force required for molding is also input to a controller (not shown).

Next, as shown in FIG. 9B, automatic mold thickness adjustment is performed. In this automatic mold thickness adjustment, the mold thickness adjustment motor 16 shown in FIGS. 3 and 4 is driven, the spur gear 18 rotates through the center gear 17, and the tie bar nut fastened to the spur gear 18 in the casing 19. 5 also rotates about the tie bar 4, and the end housing 3 moves forward or backward. With this adjustment, a mold thickness adjustment of minus α (for example, 5 mm) than the normal mold thickness (d) is performed with the toggle fully extended. The state shown in FIG. 9A is changed from the state shown in FIG. 9B to the state shown in FIG. 9B by moving the end housing by the mold thickness moving amount (e).

Next, as shown in FIG. 9 (c), the spring-loaded dies are loaded into the fixed platen 2 and the movable platen 6, and the dies 12,
3 is fixed.

Next, the automatic mold clamping force adjustment after the automatic mold thickness adjustment will be described with reference to FIG.

As shown in FIG. 10 (a), medium-pressure oil is supplied to the oil chamber on the head side of the mold clamping cylinder 10 to resist the force of the spring between the fixed mold 12 and the movable mold 13. And completely adhere. In this state, since the mold thickness is adjusted to minus α mm, the toggle mechanism 8 is not fully extended. In this state, the amount of movement of the crosshead 9 is detected by the crosshead position sensor 7 (see FIGS. 1 and 2). Based on data of the position of the movable platen 6 with respect to the amount of movement of the crosshead 9 from the reference position (see FIG. 6) stored in a controller (not shown) in advance based on the detected value, the detected crosshead 9 The position of the movable platen 6 corresponding to the movement amount is calculated (this value is referred to as (a)).

Next, referring to FIG. 10B, FIG.
(B) shows a final state, that is, a state in which the mold clamping force adjustment operation to be adjusted has been completed. In the state of FIG. 10B, data on the relationship between the amount of movement of the crosshead 9 from the reference position at the mold touch point and the generated mold clamping force stored in a controller (not shown) in advance (FIG. 7). reference)
Then, the movable platen position is calculated from the theoretical position of the crosshead 9 at the die touch point corresponding to the set mold clamping force (this value is (b)). This (b) looks like FIG.
FIG. 10A shows the same position of the movable plate as FIG.
(B) is a state where the end housing has already been moved to the target state of the end housing, that is, a state where the mold clamping force adjustment has been completed, and it is inevitable that the position of the end housing is different from that in FIG. 10 (a). The head position is also different between FIGS. 10A and 10B. Naturally, the position of the movable plate is also different between FIGS. 10 (a) and 10 (b). The difference between the movable plates is the same as the difference between the end housings.
The amount of the end housing moved from (c) is shown in FIG.
This is required in (b). The difference between (a) and (b), that is, the required movement amount of the entire toggle mechanism 8 including the end housing 3 necessary for generating the set mold clamping force (this value is referred to as (c)) is calculated. I do. Next, the required rotation angle (see FIG. 11) is obtained from (c) based on the data of the housing movement amount and the rotation angle of the tie bar nut (see FIG. 8) stored in advance in a controller (not shown).
Ask for.

Next, as shown in FIGS. 10 (c) and 11, the mold thickness adjusting motor 16 is rotated while the rotation sensor 20 detects the rotation angle by the rotation angle. At the end of the rotation, the end housing 3 has moved by (c), and the automatic mold clamping force adjustment ends.

[0042]

As described above, according to the present invention, an excessive load is applied to the mold thickness adjusting motor or the tie bar is not used even when using a mold in which a force for separating the molds is applied. It is possible to adjust the mold clamping force without worrying about screwing and seizure of the tie bar nut screws.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an injection molding machine using a toggle-type mold clamping device, showing a state in which mold clamping has been completed.

FIG. 2 is a configuration diagram of an injection molding machine using a toggle-type mold clamping device, showing a state in which mold thickness adjustment has been completed and the molds have come into contact with each other.

FIG. 3 is a view taken in the direction of arrow B in FIG. 1;

FIG. 4 is a detailed view of a tie bar screw portion and a tie bar nut.

FIG. 5 is a diagram illustrating a relationship between a screw pitch, a lead, and the number of threads.

FIG. 6 is a diagram illustrating a relationship between a crosshead movement amount and a movable platen movement amount.

FIG. 7 is a diagram illustrating a relationship between a moving amount of a crosshead and a mold clamping force.

FIG. 8 is a diagram illustrating a relationship between an end housing movement amount and a tie bar nut rotation angle.

FIG. 9 is a process chart of a mold clamping force adjusting method according to the present invention;
It is a figure showing automatic mold thickness adjustment.

FIG. 10 is a process chart of the mold clamping force adjusting method according to the present invention, showing the automatic mold clamping force adjustment after the automatic mold thickness adjustment.

FIG. 11 is an explanatory diagram of a required rotation angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bed 2 Fixed board 3 End housing 4 Tie bar 4b Screw part 5 Tie bar nut 6 Movable board 7 Cross head position sensor 8 Toggle mechanism part 9 Cross head 10 Molding cylinder 11 Piston rod 12 Fixed mold part 13 Movable mold part 14 Mold thickness position sensor 15 Mold 16 Mold thickness adjustment motor 17 Center gear 18 Spur gear 19 Casing 20 Rotation sensor

Claims (2)

(57) [Claims] 1. A method for adjusting a mold clamping force of a toggle-type injection molding machine having a mold in which a gap is formed between molds by a spring, wherein a most advanced position of a crosshead (9) of the toggle-type mold clamping device is determined. As the reference position, data of the amount of movement of the movable platen (6) with respect to the amount of movement of the crosshead (9) from the reference position, the amount of movement of the crosshead (9) from the reference position at the die touch point, and the generation mold clamping. The movable platen when the movable platen (6) is advanced without the mold (15) attached is stored with data on the relationship with force and data on the housing movement amount and the rotation angle of the tie bar nut (5). After adjusting the thickness of the mold so that the distance between (6) and the fixed platen (2) is smaller than the thickness of the mold by a predetermined amount, the mold (15) is attached and the spring in the mold is removed. Gold with medium pressure that allows perfect adhesion (15)
The movable platen movement amount based on the data is calculated from the movement amount of the cross head (9) at this time, and the movable platen movement amount at the mold touch point corresponding to the calculated movable platen movement amount and the set mold clamping force is calculated. The difference from the board movement amount is obtained, and how many times the tie bar nut should be rotated to move the entire toggle mechanism by the difference is calculated. Then, the mold is once opened, and the rotation sensor (20) is used. Tie bar nut
While detecting the rotation angle of (5), tie bar nut
(5) The mold clamping force setting method for a toggle type injection molding machine, characterized in that: (5) is rotated by the calculated rotation angle . 2. A device for adjusting the clamping force of a toggle-type injection molding machine used for carrying out the method according to claim 1.