JPS61233519A - Mold clamp apparatus of injection molding machine - Google Patents

Abstract

PURPOSE:To enhance the shape accuracy of a molded product, by providing the reinforcing member provided between support plates faced to each other, a tie rod and a clamping nut and acting compression force on the reinforcing member even in such a state that max. mold clamping force is acted on a mold. CONSTITUTION:Predetermined mold clamping force is acted on a movable mold 2 and a fixed mold 34. A molten resin is injected in a cavity 36 in this state and cooled and solidified to obtain a molded product. Larger force is acted on a tie rod 16 during a time when mold clamping force is acted as compared with such a case that no mold clamping force is acted and the tie rod 16 is extended. Because of this, the force forcibly deforming a flange 12 and a fixed plate 14 is acted on the flange 12 and the fixed plate 14 from the tie rod 16 but, because compression force is acted on a reinforcing member 18 during the action of mold clamping force, the flange 12 and the fixed plate 14 can not deform easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a mold clamping device for an injection molding machine capable of molding highly precise plastic products.

(B) Conventional technology The mold clamping device of a conventional injection molding machine has a structure as shown in Fig. 4, for example, in the Mechanical Engineering Handbook (revised 6th edition, published by the Japan Society of Mechanical Engineers), Volume 18, page 33. There is something like that.

The mold clamping device of this injection molding machine includes a mold clamping cylinder 80, a flange 82 provided integrally with the mold clamping cylinder 80, and a mold clamping piston 8 fitted together with the mold clamping cylinder 80.
4. A fixed plate 86, a tie rod 88 connecting the flange 82 and the fixed plate 86, a tightening nut 90, and a tie rod 88.
It has a movable platen 92 guided by and connected to the mold clamping piston 84, a mold mounting plate 94 attached to the fixed platen 86, etc. A fixed mold 96 is attached to the mold mounting plate 94, and the movable platen 92 A movable mold 98 is attached to the. By controlling the supply of hydraulic pressure to the mold clamping cylinder 80, the movable platen 92 is moved back and forth to open and close the mold, and the mold clamping operation is performed in which the movable mold 98 is pressed against the fixed mold 96 with a large force. I can do it.

(c) Problems to be Solved by the Invention During mold clamping, the reaction force of the mold clamping force generated by the mold clamping cylinder 80 acts on the tie rods 88, and the tie rods 88 extend in accordance with the mold clamping force. The force acting from the tie rods 88 deforms the flange 82 and the stationary platen 86 as shown by broken lines in FIG. 4, and the tie rods 88 also receive bending force, which causes the movable platen 92 to deform as well. This deformation of the entire mold clamping device becomes a problem when molding products that require extremely high shape and surface accuracy, such as plastic acid lenses, hard disk substrates, optical disks, etc. It has been impossible to injection mold products with a precision higher than a certain level. That is, since the rigidity of the fixed mold 96 and the movable mold 98 is relatively small, when the fixed plate 86 and the movable plate 92 deform, they deform accordingly, and the cavity 99 also deforms and does not have the predetermined shape, resulting in high Shape accuracy cannot be obtained, and the deformation of the fixed mold 96 and the movable mold 98 increases the surface pressure of the mating surfaces on the outer periphery of the cavity 99, making it difficult to smoothly discharge the air inside the cavity 99 when filling with molten resin. Therefore, it was not possible to increase the filling speed. For this reason, during the filling process, the molten resin cooled and solidified on the surface of the cavity 99 without any pressure being applied, making it impossible to transfer the precision of the surface of the cavity 99 to the molded product. As a result, the surface precision of the molded product was also insufficient. In addition, due to deformation of the fixed mold 96 and movable mold 98 and a decrease in the positional accuracy of the movable platen 92 due to bending of the tie rod 88, unreasonable force is applied to the fitting parts such as guide bins, and when the mold is opened. There is also the problem that galling occurs and the resulting abrasion powder has an adverse effect on the molded product. Furthermore, the mold often needs to be repaired due to galling.The present invention aims to solve these problems.

(d) Means for solving the problem The present invention provides a reinforcing member between one support plate (for example, a fixed plate) and the other support plate (for example, a flange of a mold clamping cylinder), and By tightening the tie rods to apply a compressive force to the reinforcing member so that the compressive force of the reinforcing member is always maintained, the rigidity of the mold clamping device is improved and the above problem is solved. That is, the mold clamping device for an injection molding machine according to the present invention includes a reinforcing member provided between two mutually facing support plates on which a mold clamping reaction force acts, and a force applied to the two support plates in a direction that brings them closer together. It has a tie rod and a tightening nut that can act,
The tightening nut is tightened so that compressive force is applied to the reinforcing member even when the maximum mold clamping force is applied to the mold.For example, one support plate is a flange that is provided integrally with the mold clamping cylinder. The other support plate is a fixed plate, and the fixed mold is attached to a mold mounting plate that is detachably attached to the fixed plate, and the movable mold is attached to a movable plate that is connected to the piston of the mold clamping cylinder. It is attached. Further, the movable platen can be guided so as to be movable in the axial direction by a sliding surface provided on the reinforcing member, and the extension line of the sliding surface of the reinforcing member in the axis-perpendicular cross section can be made to pass through the center of the movable platen.

(e) Operation When hydraulic pressure is applied to the mold clamping cylinder to generate mold clamping force, tensile force is applied to the tie rod, and the tie rod attempts to deform the joints with both support plates in the direction of moving them closer together. . However, since the tightening nuts are tightened so that compressive force acts on the reinforcing member even when the mold clamping force reaches its maximum state, it is necessary to compress the reinforcing member in order for the support plate to deform. , the support plate cannot be easily deformed and has increased rigidity. That is, the reinforcing member functions to prevent deformation of the support plate. When the deformation of the support plate is reduced in this way, the bending of the tie rod is also reduced, and the above-mentioned conventional problems are solved. That is, the deformation of the mold that follows the deformation of the mold clamping device is reduced, the cavity is maintained in a predetermined shape, and the shape accuracy of the molded product is improved. Furthermore, since the air inside the cavity is discharged as specified during filling with the molten material, filling can be performed rapidly and the surface precision of the molded product can be improved. Furthermore, galling of the guide pins is also prevented. When the movable platen is supported by the sliding surface of the reinforcing member as described above, the positional accuracy of the movable platen is ensured regardless of deformation of the movable platen due to temperature changes.

(F) Embodiment FIGS. 1 and 2 show an embodiment of the present invention, which includes a flange 12 (support plate) integrated with a mold clamping cylinder 10, and a fixed plate 14.
(Support board) are arranged so that they face each other, and both are 4
They are connected by a tie rod 16 and a reinforcing member 18 provided on the outer periphery of the tie rod. i.e. flange]
2 hole 12a, the hole 18a of the reinforcing member 18, and the fixed platen 14
A head 1 is attached to one end of the tie rod 16 passing through the hole 14a.
6a, and a male threaded portion 16b is provided at the other end, and a tightening nut 20 is tightened into this male threaded portion 16b, so that a compressive force is applied to the reinforcing member 18. It's Nishide. The tightening force of the tightening nut 20 is such that a compressive force is applied to the reinforcing member 18 under all conditions of use of the mold clamping device (that is, even when the maximum mold clamping force is generated). A mold clamping piston 22 is fitted into the inner diameter of the mold clamping cylinder 10, and the mold clamping cylinder 10 has a sleeve hole 10a and a fob that communicate with both sides of the mold clamping piston 22, respectively. The mold clamping piston 22 is connected to a movable platen 26 by a piston rod 24. The movable platen 26 is supported so as to be movable in the axial direction relative to the reinforcing member 18 via four movable guide members 28 integrally attached thereto. Each reinforcing member 1
8 and the movable guide member 28 are in slidable contact with each other on the slide surface 18a and the slide surface 28a, as shown in FIG. The extension lines of each slide surface 18a and slide surface 28a in the axis-perpendicular cross section (FIG. 2) are all arranged to pass through the center 26a of the movable platen 26.

A movable mold 30 is attached to the movable platen 26. Also, a mold mounting plate 3 connected to the fixed plate 14 by fitting
A fixed mold 34 is attached to 2. A movable mold 30 and a fixed mold 34 constitute a mold, and a cavity 36 is provided in the mold.
and sprue 38 are formed.

Molten resin can be injected onto the sprue 38 from the injection nozzle 4o.

Next, the operation of this embodiment will be explained. When hydraulic pressure is supplied to the sleeve hole 10a with the sleeve hole 10b open, the mold clamping piston 22 moves to the right in FIG.
moves toward the fixed platen 14. As a result, the movable mold 30
The movable mold 30 and the fixed mold 3 are brought into contact with each other to close the mold, and then by further increasing the hydraulic pressure, the movable mold 30 and the fixed mold 3 are closed.
A predetermined mold clamping force can be applied to 4. In this state, the molten resin is injected from the injection nozzle 40 through the sprue 38 into the cavity 36, and the resin is cooled and solidified to obtain a molded product. While the mold clamping force is acting, a larger force acts on the tie rod 16 than when the mold clamping force is not acting, and the tie rod 16 stretches. Therefore, a force is applied from the tie rod 16 to the flange 12 and the fixed platen 14 to deform them, but the deformation of the flange 12 and the fixed platen 14 is reduced by the reinforcing member 18. That is, compressive force is acting on the reinforcing member 18 even during the mold clamping force (that is, the reinforcing member 18 is in contact with the flange 12 and the fixed platen 14 at both ends thereof under pressure), and the flange 12 In order for the fixed platen 14 to deform, it is necessary to further compress the reinforcing member 18, so the flange 12 and the fixed platen 14 cannot be easily deformed. The explanation will be based on the diagram shown in . In FIG. 3, the line segment OC indicates the relationship between the amount of elongation (horizontal axis) and the acting force (vertical axis) on the tie rod 16. Point A on the line segment OC indicates the state of the tie rod 16 before the mold clamping force is applied. At this point, a tensile force f+ (line segment GA) is applied to the reinforcing member 18, while the reinforcing member 18 is receiving a compressive force f1. In this state, the tie rod 16 extends by the alternating current (line segment OG), and the reinforcing member 1
8 is compressed by sentence 2 (line segment GI), and line segment A indicates the relationship between the acting force and the amount of shrinkage of the reinforcing member 18. When a mold clamping force is generated in this state and the force acting on the tie rod 16 is increased, the balance position shifts from point A to point B, for example. That is, the elongation of the tie rod 16 increases by [vertical] (line segment GH), and the amount of contraction of the reinforcing member 18 decreases by fL3. That is, the line segment OH indicates the elongation amount C1t +6Li) of the tie rod 16, and the line segment HI indicates the elongation amount C1t +6Li) of the tie rod 16.
This balance point B indicates the shrinkage amount C1z-fLx) of 8.
The tensile force fz of the tie rod 16 at . Note that when the point B is further shifted to the 0 point, the amount of contraction of the reinforcing member 18 becomes O, and the compressive force no longer acts, but as mentioned above, tighten the tightening nut 20 in advance so as not to exceed the 0 point. It is a complicated assembly. In this way, the tie rod 16 and the reinforcing member 18 are crossed 3 (line segment GH
), a mold clamping force of f4 (line segment BJ) can be obtained. On the other hand, if the reinforcing member 18 is not provided, look at the tie rod 16,
Even if it is extended by (line segment GH), the mold clamping force that increases accordingly is fs (line segment BK). Therefore, in the case of the mold clamping device of the injection molding machine according to the present invention, the conventional It can be seen that the mold clamping force generated for the same amount of extension of the tie rod 16 is increased (f4>f5), that is, the rigidity is increased and it does not easily deform. Therefore, the deformation of the flange 12 and the fixed platen 14 is small, the bending of the tie rods 16 and the reinforcing member 18 is also small, and the movable platen 26 is also hardly deformed. The deformation of the mold 30 and fixed mold 34 is also very small,
The cavity 36 formed by both has a predetermined shape, and the movable mold 30 and the fixed mold 34 are in a state of even contact at their mating surfaces, and the injection nozzle 40
When the cavity 36 is filled with molten resin, the air in the cavity 36 is quickly exhausted, increasing the filling speed of the molten resin. Therefore, the molten resin is pressed against the surface of the cavity 36 under pressure and is cooled and solidified, so that the surface precision of the molded product is improved in accordance with the surface precision of the cavity 36. Further, since deformation of the movable mold 30 and the fixed mold 34 is reduced, galling of the guide pin fitting portion is prevented, and molding defects due to worn metal powder are prevented from occurring. Furthermore, the frequency of mold repair is also reduced.

In addition, since the movable platen 26 has a support structure that is not affected by heat, the movable platen 26 is attached to the mold mounting plate 32.
The positioning is performed accurately, and the movable mold 30 and the fixed mold 34 can be opened and closed with high precision. That is, during the molding operation, the movable mold 30 and the fixed mold 34 are controlled to a predetermined relatively high temperature by a heating device such as a heater, and the heat of the movable mold 30 and the fixed mold 34 acts on the movable platen 26 by thermal conduction. The temperature of the movable platen 26 also rises. As a result, the movable platen 26 expands in the vertical and horizontal directions, but the second
As shown in the figure, the movable platen 26 is guided by the slide surface 18a and the slide surface 28a with respect to the tie rod 16 via the movable plate guide member 28, and the extension line of the slide surface 18a and the slide surface 28a is the extension line of the movable platen 26. Since it passes through the center 26a, even if the movable platen 26 expands, the slide surface 28a only moves on the slide surface 18a and the position of the movable platen 26 itself does not change.
Even if the temperature rises, the movable platen 26 maintains the same accuracy as when it was assembled and adjusted before the start of operation.

In this manner, in addition to the increased rigidity of the mold clamping device described above, the positional accuracy of the movable platen 26 is high, making it even more difficult for galling to occur at the fitting portion of the guide pin. In addition, the mold mounting plate 32 is detachably attached to the fixed platen 14, and this allows the parallelism between the movable platen 26 and the mold mounting plate 32 to be adjusted.
The mold mounting plate 32 can be easily adjusted when performing final assembly adjustments such as straightness.

Molding was actually carried out using the injection molding machine as described above, and it was confirmed that the following good results could be obtained.

Molded product: Plastic substrate material for hard disks Φ
...Polyetherimide outer diameter---130±0.13mm Wall thickness---1.905±0.025mm Surface roughness...
Ra = 0.008 microns Mold lifespan Twice as compared to conventional molded product precision This kind of precision cannot be achieved with conventional equipment, and in particular the surface roughness of the molded product is determined by the surface roughness of the cavity surface of the mold. The accuracy is approximately equivalent to that of .

In addition, although the above embodiment is an application of the present invention to a horizontal type direct pressure type mold clamping device, the present invention can also be applied to a vertical type mold clamping device, and can also be applied to a toggle type or other type of mold clamping device. It can also be applied to The number of tie rods 16 and reinforcing members 18 can be selected arbitrarily. Further, this mold clamping device can also be used for compression molding, transfer molding, insert molding, etc. In addition, reinforcing member 1
8 can also be constructed integrally with the flange 12 or the fixed platen 14. The flange 12 can also have a structure in which a plurality of plate materials are stacked one on top of the other. Further, the arrangement of the injection nozzle 40 with respect to the mold clamping device may also be other than the embodiment described. The sliding surface 18a of the reinforcing member 18 and the sliding surface 28a of the movable platen guide member 28 may have a structure in which surface pressure can be adjusted.

(g) As described in detail, according to the present invention, the rigidity of the mold clamping device is increased by providing a reinforcing member, so that deformation of the mold can be prevented and the movable mold and fixed mold can be connected with high precision. It is now possible to easily mold plastic products with extremely high precision by aligning the position with the mold, and the generation of abrasion powder on the mold is also prevented, significantly extending the life of the mold.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a mold clamping device of an injection molding machine according to the present invention;
Figure 2 is a sectional view taken along line 11-II in Figure 1, Figure 3 is a diagram showing the relationship between the acting force and the amount of expansion and contraction of the mold clamping device shown in Figure 1, and Figure 4 is a diagram showing the relationship between the amount of expansion and contraction of the mold clamping device shown in Figure 1. It is a figure showing a mold clamping device of a molding machine. 10... Mold clamping cylinder, 12... Flange (support plate), 14... Fixed plate (support plate), 16... Tie rod, 18... Reinforcement member, 18aΦ... Slide surface,
20... Tightening nut, 22... Mold clamping piston, 2
6... Movable plate, 28... Movable plate guide member, 28a.
...Sliding surface, 30...Movable type, 32...Model mounting plate, 34...Fixed type, 36Φ...Cavity.

Claims (1)

[Claims] 1. In a mold clamping device of an injection molding machine that applies mold clamping force to a mold using the force of a mold clamping cylinder, between two mutually facing support plates on which a mold clamping reaction force acts. and a tie rod and a tightening nut that can apply a force to the two support plates in a direction that brings them closer to each other, and the tightening nut applies a maximum mold clamping force to the mold. 1. A mold clamping device for an injection molding machine, characterized in that the mold clamping device is tightened so as to apply compressive force to a reinforcing member even in a closed state. 2. One support plate is a flange installed integrally with the mold clamping cylinder, and the other support plate is a fixed plate. The fixed type is attached to a mold mounting plate that is detachably attached to the fixed plate, and is movable. A mold clamping device for an injection molding machine according to claim 1, wherein the mold is attached to a movable platen connected to a piston of a mold clamping cylinder. 3. The movable platen is movably guided in the axial direction by the sliding surface of the reinforcing member, and the extension line of the sliding surface of the reinforcing member in the axis-perpendicular cross section is provided to pass through the center of the movable platen. A mold clamping device for an injection molding machine according to scope 2.