JPH0313052B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an injection compression molding apparatus.

In injection molding, molten resin is injected into a cavity that is strictly fixed by the mold structure, and the sprue and runner parts are released from the injection cylinder through an operation called holding pressure until the thin part of the gate part solidifies. Pressure is applied through the resin to prevent the resin in the cavity from flowing back, and after solidifying the gate, the heat in the resin in the cavity is transferred to the mold and cooled to form a product.

The density of a molten resin is usually lower than that of a solid, and as the molten resin solidifies, its volume decreases, that is, shrinkage occurs. As an example, consider a product with a diameter of 100 mm and a wall thickness of 10 mm. Assuming that the resin density is 1.17 in the molten state and 1.20 in the solid state, when the volume in the molten state is equal to the volume of the cavity (78.54 cc), it solidifies and reaches room temperature. It becomes 76.57cc. If we assume that this reduced volume is caused by contraction only in the thickness direction, the thickness of the finished product will be 9.75 mm, which is 0.25 mm.
The wall thickness is insufficient by mm.

In order to deal with such shrinkage, a method of overpacking the mold until it opens slightly at the parting line has been considered, and a method of controlling the amount of mold opening at that time (Japanese Patent Application Laid-open No. 50-39351) and a method of overpacking the mold until it opens slightly at the parting line have been studied. Use a cavity that makes it easy to
Rolinx method (“New concept in injection”
molding, Rolinx process extended
application of plastics”Plastics, 30, 330,
Apr. (1965)) has been proposed. In addition, a small hydraulic cylinder is buried in the mold so that the cavity core can be moved forward and backward, or an ejector cylinder is used to intentionally enlarge the cavity for injection, and after filling is completed, the hydraulic cylinder is moved forward. It was proposed to reduce the cavity and obtain a molded product with a predetermined thickness by using micromolder method (H. Holt: “New
techniques in shrinkage control”SPE J.p519,
Jun. (1964)).

Of course, the most basic method is to design the cavity larger in anticipation of this contraction.
In the case of thick-walled products or products with uneven thickness, such a design is virtually impossible and requires repeated trial and error.

It has been recognized that the above-mentioned overpacking method also has the drawback of requiring high injection pressure, and that when the product has uneven thickness, the shrinkage correction effect is limited in the thin wall portion where shrinkage is small. In the case of the micromolder method, the cylinder drum advances as it contracts, and although the product surface on the moving core side is produced with good precision, the facing precision is not sufficient.

In view of this current situation, ENGEL (LUDWIG ENGEL KG MACHINEN) has developed an injection compression molding method that uses mold clamping force to perform compression operations.
FABRIK, A-4311 SCHWERTBERG
AUSTRIA), this method uses the toggle type mold clamping force as compression pressure, and is an innovative method in which the toggle is held so that it is not fully extended during the injection process, and is fully extended during the compression process. It is something.

However, the toggle compression method has the disadvantage that the compression pressure cannot be controlled. The necessity of controlling the compression pressure indicates the relationship between "pressure applied to the resin - specific volume of the resin - temperature of the resin"
This can be explained using the PVT curve as follows.
The horizontal axis shows the resin temperature T, the vertical axis shows the specific volume V of the resin, and the relationship between V and T of the resin under a constant added pressure P (which can be considered as the pressure of the resin as a reaction) The PVT curve in Figure 1 shows this.

Using the above-mentioned injection compression molding equipment, let's follow this graph to see how resin is injected into the mold cavity, compressed, and taken out. If the end point of the primary injection pressure is indicated by (V→P)A, it is the process A- where the resin pressure increases while the resin temperature decreases due to injection.
Even if pressure holding is completed, the resin temperature continues to fall, and since there is no external pressure, the volume contracts and becomes the specific volume when the pressure is low, so the process B-C is followed. If the toggle is fully extended and the compression operation is performed while taking into account backflow, the resin pressure will increase while the resin temperature has hardly cooled, resulting in process C-D. If the toggle is fully extended at this time, then the resin temperature will drop and the pressure will decrease, a process D-E.
It is. At this time, since the accommodation is reduced, the resin is moved, and pressure is applied to the resin in a state where its fluidity is deteriorated, causing distortion. After this, when the mold is opened after reaching the ejecting temperature, the resin pressure increases in the process of increasing the specific volume because the external pressure decreases E-F
This is followed by process FG in which the resin temperature reaches room temperature under atmospheric pressure, and the molding is completed.

The molding shrinkage rate in this case can be determined from the difference in specific volume between E and G. In the toggle compression method, the arm length is fixed, so the pressure is adjusted by positioning, but the pressure varies depending on the mold temperature, tie bar temperature, and position settings, so the pressure cannot be fixed. Have difficulty. For this reason, it is difficult to control the compression pressure, and on the PVT curve, the end point when the toggle is fully extended is D.
It is unclear whether it is D' and cannot be controlled.

On the other hand, in the compression method using direct pressure hydraulic pressure, the maximum compression pressure can be precisely adjusted, and the
If the compression pressure is controlled to decrease so that the specific volume of the resin remains constant as the resin temperature decreases as shown in the figure, the resin will not deform at all during the solidification process, so distortion may occur. do not have. This shows that if steps A to G in the upper part of FIG. 2 are followed, molding with a constant molding shrinkage rate is possible. In this case, the difference in volume between the cavity and the resin is the difference in the specific volumes of D and G. Since it is possible to control the volume of the cavity to be constant, it is possible to perform molding with a constant molding shrinkage rate from cycle to cycle.

Based on the above considerations, the present invention proposes an injection compression molding device that enables direct pressure compression. (1) How to increase the volume of the cavity and how to control it. (2) The purpose is to solve the following problems: (3) how to smoothly open and close the mold to take out the product; and (3) how to obtain a compression process that allows compression to be controlled.

In order to achieve the above object, the present invention provides compression allowance setting fine adjustment means for finely adjusting the compression allowance of the mold by regulating daylight at the time of first mold clamping. A means is installed between the plates to release the daylight regulation by the compression margin setting fine adjustment means, and compression molding of the mold by high-pressure mold clamping after filling the cavity in the mold with molten resin is provided. It made it possible.

Figure 3 shows the distance between die plates (daylight) in each process in the injection compression molding apparatus of the present invention, the distance between the mold clamping cylinder fixed plate or the tie bar support plate fixed thereto and the movable die plate, and the tie bar length. Correlation is shown and used to explain the concept of the invention.

Figure 3a shows the distance between each plate during low-pressure mold clamping, the tie bar length is l, and the distance l' between the stationary die plate 1 and the movable die plate 2 corresponds to the mold thickness. . The distance l'' between the movable die plate 2 and the tie bar support plate 3 can be varied by moving the cylinder ram.

FIG. 3b shows a high-pressure mold clamping state in which the mold clamping cylinder ram is driven forward by high-pressure oil pressure from this state. At this time, when the molds can be sufficiently joined by low-pressure mold clamping, l' hardly changes even with high-pressure mold clamping, but the tie bar length increases by Δ (l
+Δ), and the increase corresponds to a change in distance of approximately l″, resulting in (l″+Δ).

In the injection compression molding apparatus of the present invention, as shown in FIG. A mechanism is incorporated in which the length becomes (l' + δ) by adding a predetermined compression margin δ, and the tie bar length is (l + Δ) in that case, so the movable die plate 2 and tie bar support plate 3
The distance is (l″+Δ−δ).

In the compression step after injection, the force holding the mold thickness at (l'+δ) is released, so the mold thickness becomes l', and compression is performed by the compression margin δ.

The mold clamping force F ₁ during injection and the mold clamping force F ₂ during compression are set as F ₁ ≦F ₂ . When F ₁ < F ₂ , low pressure mold clamping → injection → compression (end) l→l+Δ″→l+Δ l′→l′+δ→l′ l″→l″+Δ″→δ→l″+Δ It changes with each process like this.

When F ₁ becomes smaller than the resin pressure during injection, the mold opens by a predetermined compression margin δ or more. For this reason, the mold clamping force F ₁ during injection and the amount of opening of the mold, that is, the compression margin δ, must be determined experimentally, taking into account the shape of the product, the temperature of the resin, the injection pressure, and the like. Therefore, it is easy to compress and readjust δ,
Moreover, an accurate compression margin adjustment means is extremely important.

The present invention relates to a means for maintaining the mold thickness at (l' + δ) under high-pressure mold clamping during injection filling. The present invention relates to an injection compression molding apparatus characterized in that the mold can be freely opened and closed for the next cycle, and furthermore, it is provided with means for setting the compression margin in microns (μm).

An embodiment of the present invention will be described below based on the drawings. Figure 4 shows an example in which compression margin setting fine adjustment means is provided between the fixed die plate and the movable die plate to obtain a predetermined required amount of compression margin.
is its cross-sectional side view, and FIG. 4b is taken along the line X-X in FIG.
It is an arrow view. Here, a tie bar 16 is stretched between the four corners of each of the fixed die plate 1 and the tie bar support plate 3 and fixed thereto, and the main cylinder 8 attached to the tie bar support plate 3 is attached to the movable die plate 2. It is directly connected to the cylinder ram and is movable along the tie bar 16. Figure 4a
, the compression margin adjustment unit 5 of the compression margin setting fine adjustment means 4, which can set any length with high precision, adjusts the compression margin δ to the required amount, and between the daylight (fixed die plate 1 and movable die plate Die plate 2
The compression margin setting fine adjustment means 4 is brought into contact with the fixed side fine adjustment means receiving part 6 provided at any predetermined location of the fixed side die plate 1 in the mold opening state using the mold opening cylinder 7, Next, when low-pressure mold clamping is performed using the main cylinder 8, the movable die plate 2
The movable side fine adjustment means receiving part 9 provided corresponding to the fixed side fine adjustment means receiving part 6 comes into contact with the end face of the compression allowance adjustment part 5 of the compression allowance setting fine adjustment means 4, and the fixed side mold 1
0 and the parting surface of the movable mold 11 (the mating surface of the fixed and movable molds), a compression margin δ of a predetermined required amount is set by the compression margin setting fine adjustment means 4. Next, the molten resin is injected and filled into the cavity 13 of the mold from the injection nozzle 12.
Next, while preventing backflow by solidifying the gate or other methods, the compression allowance setting fine adjustment means 4 is pulled out using the mold size opening cylinder 7, and high-pressure mold clamping is performed using the main cylinder 8, compressing the compression allowance δ, and molding the mold. The parting surfaces come into contact. The compression margin δ is set by rotating the compression margin adjustment section 5 of the compression margin setting fine adjustment means 4 based on the pitch, diameter, and rotation speed of the screw. Therefore, it is possible to set the compression margin with high accuracy. Further, this compression margin setting fine adjustment means 4 is attached to the fixed die plate 1 via a mold size opening cylinder 7, but it can be installed at a place where it can be installed between the daylights on the movable die plate 2 or the molding machine body. You can install it anywhere. Furthermore, if the length of the fine adjustment means is made the same as that of the daylight, the fine adjustment means receiving parts 6 and 9 will be unnecessary since they will come into direct contact with the fixed die plate 1 and the movable die plate 2.

FIG. 5 shows an example in which a compression margin setting fine adjustment means is attached to the stationary die plate or the movable die plate, and a predetermined required amount of compression margin is obtained by the insertion plate 14 coming into contact with it. . In FIG. 5, the compression margin δ is set by the pitch, diameter, and rotation speed of the screw of the compression margin adjustment section 5 of the compression margin setting fine adjustment means 4 attached to the movable die plate 2, and the compression margin δ is set on the mold opening cylinder 7. When one side end surface of the inserted plate 14 is brought into contact with the stationary side fine adjustment means receiving part 6 and the mold is then clamped, the compression margin adjustment part 5 comes into contact with the opposite end surface of the insertion plate 14, thereby tightening the mold. A compression margin δ is set on the parting surface or other mold mating surface. The compression of the resin filled in the mold cavity 13 is as follows:
By contracting the mold opening cylinder 7, the insertion plate 14 is pulled out and compressed by the main cylinder 8 at high pressure. In this case, the mold opening cylinder 7 and the compression allowance setting fine adjustment means 4 are not connected to the fixed die plate 1 and the movable die plate 2, but to the movable die plate 2.
and may be provided on the fixed die plate 1. In addition, an insertion plate 14 attached to the mold opening cylinder 7
The mechanism may be any mechanism as long as it is not inverted tapered, such as a flat plate or a round bar wedge.

Figure 6 shows the compression allowance setting fine adjustment means 4 and the insertion plate 14.
A few examples of various variations of are shown. In A, the fine adjustment means is cylindrical, in A is circular, and in B is elliptical. B is a rectangular tube shape, and indicates that it may also be a square (A) or a polygon (B). C has a tapered end surface, A is circular, B is square, and C is polygonal. In this case, the fixed side fine adjustment means receiving part 6 is also tapered. D shows various examples of shapes of the insertion plate 14, in which A is circular and B is square, but the end surface of the insertion plate 14 may have a tapered shape as shown in C. Here, A, B, and C are main part sectional views of A to D.

FIG. 7 shows an example in which the fine adjustment means 4 and the adjustment section 5 are provided concentrically with the tie bar 16, and an insertion plate 14 as shown in A or B is used, which straddles the tie bar 16. Here, A and B are sectional views of the main parts of A.
In this case as well, the end face of the insertion plate 14 may be tapered to facilitate insertion.

Figure 8 shows a case A in which a rotational fine adjustment means is provided on the tie bar 16 between the daylights, and a case B in which it is provided in the stationary die plate 1 other than the tie bar 16.
The compression margin formation state (a) and the compression state (b) are shown. The compression allowance setting fine adjustment means 4 is shown in the upper half when the compression allowance is formed, and the state of the insertion plate 14 or the fine adjustment means 4 is as shown in A. At the time of compression, the insertion plate 14 or the fine adjustment means 4 is rotated by the motor 17. The main cylinder 8 then performs compression. Here, A and B are main part sectional views of A and B.

As described above, according to the present invention, by providing the compression margin setting fine adjustment means between the daylights, the compression margin can be set accurately by regulating the distance between the daylights, and a resin molded product of a predetermined wall thickness can be manufactured without sink marks or cavities. It can be finished with precise dimensions and shapes. Moreover, by lifting the daylight restriction, high-speed mold tightening can be carried out without any trouble.

[Brief explanation of the drawing]

Figure 1 is a PVT curve diagram showing the relationship between "pressure applied to resin - specific volume of resin - temperature of resin" by a toggle type molding machine, and Figure 2 is a PVT curve diagram by a molding machine with a direct pressure compression process. In the figure, A to G
Figure 3 shows the basic conceptual diagram of the present invention, Figure 4 shows an embodiment of the present invention, and Figure 4 a shows the movement of the specific volume between injection, compression, and removal of the resin. Fig. 4b is a cross-sectional view when the compression allowance setting fine adjustment means is directly inserted and removed, and is a view taken along the line X-X in Fig. 4a. FIG. 5 shows another embodiment, in which a compression margin setting fine adjustment means is installed on the movable die plate, and a sectional view when the insertion plate is inserted and removed; FIG. 6 is a cross-sectional view as shown in FIG. An example of a change in the structure of the compression allowance setting fine adjustment means in the apparatus shown in FIG. 5 is shown, where A is cylindrical;
B is a rectangular cylinder shape, C is a shape with a tapered end face, D is a shape when using an insertion plate, Fig. 7 is a diagram showing an example when fine adjustment means is provided concentrically with the tie bar, Fig. 8 The figure is a diagram showing an example of a fine adjustment means using a rotation method. DESCRIPTION OF SYMBOLS 1... Fixed side die plate, 2... Movable side die plate, 3... Tie bar support board, 4... Compression allowance setting fine adjustment means, 5... Compression allowance adjustment part, 6... Fixed side fine adjustment means receiving part, 7... Mold size opening cylinder , 8... Main cylinder, 9... Movable side fine adjustment means receiving part, 14... Insertion plate,
16...Tie bar.

Claims (1)

[Claims] 1. Compression allowance setting fine adjustment means is installed between the stationary die plate and the movable die plate to finely adjust the compression allowance of the mold by regulating daylight during initial mold clamping. and a means for canceling the daylight regulation by the compression margin setting fine adjustment means is provided to enable compression molding of the mold by high-pressure mold clamping after filling the cavity in the mold with molten resin. Characteristic injection compression molding equipment. 2. Injection compression molding according to claim 1, characterized in that daylight is regulated by inserting and removing the compression margin setting fine adjustment means itself between the stationary die plate and the movable die plate. Device. 3. The compression allowance setting fine adjustment means is attached to the fixed die plate or the movable die plate, and an insertion plate is inserted and removed between the compression allowance setting fine adjustment means and the movable die plate or the fixed die plate to regulate daylight. An injection compression molding apparatus according to claim 1, characterized in that: 4 The compression margin setting fine adjustment means is attached to the fixed die plate or the movable die plate concentrically with the tie bar between the fixed die plate and the movable die plate, and the daylight is regulated by an insertion plate that engages and disengages from the tie bar. An injection compression molding apparatus according to claim 1, characterized in that the injection compression molding apparatus is configured to: