JPH0153618B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for optimally controlling the amount of resin passing through a gate of a molding machine having multiple gates in injection compression molding of plastics and the like.

Conventionally, when a single molding machine is used to produce a large number of long products, large products, or products of different sizes by injection compression molding, a plurality of gates are provided to perform resin casting. In the case of multi-point gates, it is important to appropriately select the amount of resin passing through each gate in order to maintain product quality, but if the length of the path differs, the amount of resin passing through each gate will change. Therefore, it has been extremely difficult to make the amount of resin passing through each gate appropriate. In order to adjust the amount of resin passing through, conventionally, the area of the path is varied in order to equalize the amount, but according to this method, the amount of resin passing through is proportional to the fourth power of the radius of the gate. In order to obtain the correct value, a slight change in the radius has a large effect on the amount of passage, and it takes a lot of time to repeat tests to adjust this. Furthermore, in the case of large products, the temperature distribution of the mold used for molding changes greatly, so the viscosity of the resin passing through changes, and the amount of resin passing through changes accordingly. In some cases, the position of the gate may be restricted by cooling pipes, air pins, etc., and furthermore, in cases where multiple pieces are produced and the products have different sizes, it is desirable to arbitrarily change the amount of resin passing through the gate. In this case, it took a lot of time and effort to adjust the diameter of the gate each time.

The method for controlling the amount of resin according to the present invention solves the above problems, makes it possible to easily adjust the amount of resin passing through, and also solves the problem of non-uniformity in the amount of resin passing through multi-point gates, thereby improving the efficiency of injection compression molding operations. This method was developed to provide a method for controlling the amount of resin that can improve efficiency, and the method is injection compression molding in which a gate for adjusting the resin flow rate is provided in the path from the injection machine to the mold cavity. A pressure-sensitive sensor installed at the exit of the injection machine and the exit of the gate of the device detects the pressure difference between the two, calculates the amount of resin passing through from the pressure difference, and opens and closes the flow rate adjustment gate based on the calculation result. This is a resin amount control method characterized by controlling the amount of resin passing through a gate, and details thereof will be explained below using examples.

FIG. 1 is a schematic side sectional view of an apparatus for explaining an embodiment of the control method of the present invention, in which 1 is an upper mold, 2 is a lower mold, and a mold cavity 3 to be a product is formed between them. . Reference numeral 4 denotes a resin injection machine, and the path leading to the mold cavity 3 is branched into two directions at the exit of the nozzle 4' of the injection machine 4, and is constituted by paths 5 and 6. Gates 7 and 8 are provided in the middle of each of the paths 5 and 6 to control the flow rate of the resin, and the gates 7 and 8 control the amounts of passing resin Q ₁ and Q ₂ set in advance by hydraulic cylinders 9 and 10, respectively. Closes when reached. 11, 12,
Reference numeral 13 denotes a pressure sensor, which is provided at the outlet of the nozzle 4' of the injection machine 4 and the outlet of the gates 7 and 8, respectively.

The injection compression molding apparatus is constructed as described above, and the resin injected into the injection machine 4 is divided into paths 5 and 6 at the exit of the nozzle 4', and is sent to the mold via gates 7 and 8, respectively. In this case, the amount of resin passing through each of the gates 7 and 8 is determined by the following equation according to the Hagen-Poiseuille law. That is, Q = πR ⁴ (P ₁ - P ₂ ) / 8 μL × t × η ... (1) where Q is the amount of passing resin, μ is its viscosity coefficient, R is the radius of the gate, and P ₁ is the pressure sensor 11 P ₂ is the pressure detected by pressure sensor 12 or 13, L is the distance the resin moves, t is time, η
is a correction coefficient (a coefficient corrected based on the resin temperature, the shape of the hole through which the resin passes, the roughness of the surface processing, etc.). If this equation (1) is applied to the apparatus shown in FIG. 1, the viscosity coefficient μ of the resin, the path distance L, and the radius R of each gate are known values, and the time
If , the resin pressures P ₁ , P ₂ between the two points on the path L are determined.
By detecting this, the amount Q of resin passing through can be determined. That is, the pressure sensor 11,1
2 and 13 are respectively detected as P ₁ , P ₂ , and P ₂ ′, the amount of resin passing through the gate 7 Q ₁ can be determined from the pressure difference (P ₁ − P ₂ ), and the pressure difference (P ₁ − P ₂ ′) from gate 8
The amount of resin passing through _Q2 can be determined. That is, the total amount Q _a of the resin that passes through the gate and is cast can be expressed as follows from the above equation (1).

Q _a =C∫ ^t ₀ ΔPdt (2) Here, C is a constant, C=πR ⁴ /8μL·η, and ΔP is P ₁ −P ₂ . Therefore, by integrating the pressure difference between the outlet pressure of the nozzle 4' and the gate 7 or 8 with respect to time, the total amount Q _a of resin passing through each gate is determined, and this total amount Q _a is set to a constant value, for example, as planned. When the casting amount reaches , the hydraulic cylinder 9 or 10 is operated to close the gate and the casting process can be completed.

In addition, as a second embodiment, as shown in FIG. 2, in order to keep the differential pressure ΔP constant, the hydraulic cylinders 9 and 10 are adjusted to adjust the passage area with the gates 7 and 8, so that the amount of resin passing through Q can be adjusted. _b can be controlled.

From the above formula (1), Q _b = C′∫ ^t ₀ dt ...(3) where C′ is a constant and C′ = πR ⁴ (P ₁ − P ₂ )/8μL・
η. Therefore, by controlling the R value, that is, the opening degree of the gates 7 and 8, so as to keep the differential pressure ΔP=P ₁ −P ₂ constant, the amount of resin passing Q _b can be controlled. In this way, for example, if you have a multi-point gate,
By keeping the pressure at each gate outlet constant, it is possible to equalize the amount of resin passing through each gate.

FIG. 3 is a drawing showing a third embodiment, where 14 is a hydraulic cylinder for resin extrusion provided in the injection machine 4 in FIG. 1, and a hydraulic piston 15 provided inside this cylinder is It is connected to an injection piston 17 in an injection cylinder 16 provided in front of the nozzle 4' at the outlet of the injection machine 4. In the above configuration, if the cross-sectional area on the hydraulic piston 15 side is S and the cross-sectional area on the injection piston 17 side is S', then
The pressure increase ratio of this piston system is equal to the ratio of its cross-sectional area and can be expressed as S/S'. Therefore, if a hydraulic pressure of, for example, P ₃ is applied to the hydraulic chamber 18 of the hydraulic cylinder 14, the outlet nozzle The pressure P ₁ at point 4' can be expressed as P ₁ = P ₃ × pressure increase ratio = P ₃ × S/S' (4), and the pressure P ₁ can be obtained by measuring P ₃ . can. Therefore, the pressure P ₁ at the outlet of the nozzle 4' described in the first and second embodiments is determined by measuring the hydraulic pressure P ₃ applied to the hydraulic cylinder 14,
The pressure sensor 11 at the outlet of the nozzle 4' described in the first and second embodiments can be omitted.

As explained above, the resin amount control method according to the present invention is capable of knowing the target amount of passing resin and controlling the amount of passing resin by a simple operation of detecting the pressure at the injection machine outlet and the gate outlet. If the gate is provided, it is possible to resolve the non-uniformity of each gate, and it is also possible to cast an appropriate amount of resin for large products, long items, etc., and it is suitable for injection molding that requires internal density and precision of the molded product. It is possible to maintain the quality of plastic products and improve work efficiency through compression molding.

[Brief explanation of drawings]

FIG. 1 is a schematic side sectional view of the device to explain the control method, FIG. 2 is a schematic side sectional view of the gate part to explain the second embodiment, and FIG. 3 is a hydraulic cylinder to explain the third embodiment. FIG. 3 is a schematic side sectional view of an injection machine outlet nozzle section. 1, 2... Mold, 3... Mold cavity, 4... Injection machine,
4'... Nozzle, 5, 6... Path, 7, 8... Gate, 9, 10... Hydraulic cylinder, 11, 12,
13...Pressure sensor, 14...Hydraulic cylinder, 1
5...Hydraulic piston, 16...Injection cylinder, 1
7...Injection piston, 18...Hydraulic chamber.

Claims (1)

[Claims] 1. In an injection compression molding device that has a gate for adjusting the flow rate of resin in the middle of the path from the injection machine to the mold cavity, the pressure difference between both is detected by the pressure sensor installed at the exit of the injection machine and the exit of the gate. A method for controlling the amount of resin in injection compression molding, comprising: calculating the amount of resin passing through the pressure difference; and controlling the amount of resin passing through the gate by opening and closing a flow rate adjusting gate based on the calculation result.