JPH07195461A - Foam injection molding machine and its operation method - Google Patents

Abstract

PURPOSE:To obtain a foam injection molding machine capable of stably producing a good-quality injection-molded piece and obtain an operation method thereof. CONSTITUTION:A control means 6 is provided for controlling a driver 3 of a screw 54. Under the control of the control means 6, when a weighing detector 2 detects completion of weighing, the screw 54 is moved forward to a top of a barrel 52 while being rotated reversely (reversely to a direction of arrow C) until reaching a predetermined position where a spacer 55 abuts on a check ring 53; when a position detector 1 detects the movement of the screw 54 to the predetermined position, the movement of the screw 54 is stopped. Immediately after completion of weighing, the screw 54 is moved forward to a nozzle 51 while being reversely rotated, whereby the spacer 55 is abutted on the check ring 53. A weighing amount is set larger by the capacity of the barrel 52 corresponding to the amount of the forward movement of the screw 54.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine,
More particularly, it relates to a foam injection molding machine for molding foam material articles and a method of operating the same.

[0002]

2. Description of the Related Art In a conventional foam injection molding machine, as shown in FIG. 5, a weighing section 54 for weighing a material having a thread groove 54a in a barrel 52 to which a nozzle 51 leading to a molding die is connected.
b, a conical head portion 54c, and this head portion 54c
And a screw 54 having a connecting portion 54d for connecting the measuring portion 54b, and a check ring 53 is provided on the barrel 52 around the connecting portion 54d so as to have a gap between the barrel 54 and the connecting portion 54d. A spacer 55, which spreads in a brim shape, is provided so as to have a gap between the barrel 52 and the connecting surface of the measuring portion 54b and the connecting portion 54d.

In the conventional foam injection molding machine having the above structure, the spacer 55 and the check ring 53 are separated from each other during measurement, as shown in FIG. 5 (a), and the screw 54 is not shown. The molten material flows to the nozzle 51 side through the passage indicated by the arrow A as it rotates forward while applying back pressure by the driving device. During metering and injection, as shown in FIG. 5B, the check ring 53 moves in the direction of arrow B due to the reaction force of the molten material, the spacer 55 and the check ring 53 come into contact with each other, and the passage A Prevents backflow of closed material.

As described above, the conventional foam injection molding machine described above
By separating and contacting the check ring 53, the flow of the material being measured and the back flow of the material being injected are prevented, and the contact between the spacer 55 and the check ring 53 is caused by the reaction force of the material being injected. This is performed by the backward movement of 53 toward the spacer 55 side. In this way, by preventing the backflow of the material during injection, it becomes possible to stably manufacture a high-quality injection-molded product without causing sink marks or the like in the molded product.

[0005]

However, in the above-mentioned conventional foam injection molding machine, the contact between the spacer 55 and the check ring 53 is the backward movement of the check ring 53 toward the spacer 55 due to the reaction force of the material being injected. Because the reaction force of the material is insufficient at the beginning of injection immediately after the end of measurement, the check ring 53 does not immediately contact the spacer 55. Therefore, during the backward movement of the check ring 53 to the spacer 55 side, there arises a problem that the material flows backward, or the screw 54 loses the back pressure and advances toward the nozzle 51 side. If the material flows backward or the screw 54 loses the back pressure and advances toward the nozzle 51 side, the screw 5
The amount of material measured by 4 decreases, the amount of material required for injection cannot be supplied to the mold (not shown) through the nozzle 51, which causes sink marks and the like in the molded product, resulting in defective quality. There is a problem that many injection molded products are manufactured.

Further, in order to stably produce a high-quality injection-molded product, it is important that the material temperature at the time of injection is a temperature suitable for molding. Once the predetermined value of the material temperature control factor is set at the start of operation, once the set value is changed appropriately depending on the finished state of the molded product, the amount of heat given to the material in the nozzle or barrel by the heater, The material temperature is roughly controlled by adjusting the rotation of the screw and the back pressure applied to the screw, which also causes the production of many defective injection-molded products. Desired injection temperature Pressure drop between the material just after being metered in the barrel and the material just before being injected in the nozzle or runner Injection volume as a function of the pressure drop Injection speed as a function of the injection volume

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a foam injection molding machine capable of stably producing a good quality injection molded product. And the driving method thereof.

[0008]

SUMMARY OF THE INVENTION A foam injection molding machine and a method of operating the same according to the present invention for solving the above-mentioned problems, when a measurement detector detects the completion of measurement, place a screw at a predetermined position where a spacer and a check ring come into contact with each other. When the position detector detects the movement of the screw to the predetermined position so as to move forward to the barrel tip side while rotating in the reverse direction, the control means for controlling the screw drive device is provided so as to stop the movement of the screw. Immediately after the completion of the measurement, the screw is rotated in the reverse direction and moved forward toward the nozzle side to bring the spacer and the check ring into contact with each other, and the measurement is performed only by the volume of the barrel corresponding to the forward movement amount of the screw. It measures a lot.

Further, in a foam injection molding machine equipped with a hydraulic cylinder for connecting a stretchable rod to a base of a screw and applying a back pressure to the screw, the screw is moved from a predetermined position in a barrel to a back position by a back pressure. A stopper member is provided to connect the main body, which is the fixed side of the hydraulic cylinder, and the root of the screw in order to prevent the screw cylinder from advancing toward the nozzle side.

Further, the foam injection molding machine and the operating method thereof according to the present invention include a thermometer such as a thermocouple for measuring the material injection temperature in the runner or nozzle of the molding die, and the measured injection temperature input from the thermometer. Calculating means for calculating a predetermined value of the material temperature adjusting factor from the following based on the above, and the temperature adjuster so that the measured injection temperature becomes equal to the desired injection temperature based on the calculated value input from the calculating means, A control means for controlling the driving device is provided to adjust the amount of heat given to the material in the nozzle or the barrel by a heater or the like, the rotation of the screw, and the back pressure applied to the screw. Difference from the desired injection temperature Pressure drop between the material just after weighing in the barrel and the material just before injection in the runner of the nozzle or molding die Injection volume as a function of the pressure drop Injection volume as a function of the injection volume speed

[0011]

According to the above means, by moving the screw,
Immediately after the end of the measurement, the spacer and the check ring come into contact with each other to prevent the backflow of the material during injection, thereby preventing the amount of the material measured by the screw from decreasing to an amount insufficient for injection. In addition, the stopper member prevents the screw from advancing from the predetermined position to the nozzle side in the barrel due to the back pressure, and reduces the amount of the material measured by the screw to an amount insufficient for injection. lose.

Further, based on the measured injection temperature of the foam injection molding machine in operation, the amount of heat given to the material in the nozzle or barrel by a heater or the like, the rotation of the screw, so that the measured injection temperature becomes equal to the desired injection temperature. By adjusting the back pressure applied to the screw, the injection temperature of the material can be maintained at a temperature suitable for molding.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a foam injection molding machine of the present invention, and FIG. 2 is a sectional view of a portion showing a moving amount of a screw. In FIG. 1, 1 is a position detector, 2 is a rotation speed detector, 3 is a hydraulic device that constitutes a drive device, 4 is a back pressure applying device for a screw that constitutes the drive device, and 5 is a screw that constitutes the drive device. The rotating device 6 is a control means.
Incidentally, the parts 51 to 55 are the same as those of the conventional one shown in FIG.

The position detector 1 has a gear 1a rotatably provided at a fixed position and an uneven surface for engaging the teeth of the gear 1a. The position detector 1 has a root portion of the screw 54 parallel to the screw 54. It consists of the connected rail 1b,
When the screw 54 moves, the gear 1a rotates, and the position of the screw 54 is detected by this rotation speed. Since the measured value is detected by how many mm the screw has retracted, the position detector 1 detects the completion of the measurement. The rotation speed detector 2 counts the rotation speed of the drive shaft 5a of the rotating device 5 such as a motor that rotates the screw 54.

The drive device includes a rotating device 5 such as a motor for rotating the screw 54, a back pressure adding device 4 such as a hydraulic cylinder for applying a back pressure to the screw 54, the rotating device 5 and the back pressure adding device 4. Is composed of a hydraulic device 3 for hydraulically controlling the. In the rotating device 5, a drive shaft 5a such as a motor is connected in series to the base side of the shaft of the screw 54 to rotate the screw 54. The back pressure adding device 4 includes two hydraulic cylinders, and an expandable rod 4a is connected to the root of the screw 54 so that they are parallel to the screw 54, and a hydraulic pressure is applied to the hydraulic chamber 41 to cause the screw to move. Back pressure is applied to 54. During measurement, the screw 54 rotates in the direction of arrow C in the forward direction, and the screw 54 moves backward while applying back pressure to the resin measured in front of the screw head.

The drive unit is controlled by the control means 6 as follows. When the position detector 1 detects the completion of weighing, a signal is sent to the screw drive device so as to move the screw 54 in the forward direction toward the nozzle 51 while rotating the screw 54 in the reverse direction to a predetermined position where the spacer 55 and the check ring 53 contact each other. When the hydraulic device 3 is instructed and the position detector 1 detects the movement of the screw 54 to the predetermined position, a signal is issued to the hydraulic device 3 of the screw drive device to stop the movement of the screw 54. .

The amount of forward movement of the screw 54 is shown in FIG.
As shown in (a), the spacer 55 and the check ring 5
2 is a distance L that closes the gap between the screw 54 and the screw 54. This is the reverse rotation of the screw 54 by an angle θ given by the following formula, as shown in FIG. 2B of the EE cross section of FIG. You can get it by moving forward.

ΠDcosα * (θ / 360) * h = [π
(D ² −d ² ) / 4] * L where D is the inner diameter of the barrel 52, α is the twist angle of the screw thread, and h is the distance between the inner wall of the barrel 52 and the thread groove 54 a.

Since the amount of material measured by the screw 54 is reduced by the volume of the barrel 52 corresponding to the moving amount of the screw 54 advanced, the reduced volume is included in advance in a large amount. To obtain the desired amount.

When the forward movement of the screw is not accompanied by the reverse rotation, the amount to be reduced by the forward movement of the screw is calculated in advance based on the following equation, and the amount including this amount is set as the desired measurement amount. Specifically, when S is a predetermined amount required for molding, an oversized amount ΔS to be measured in advance is calculated by the following formula.

(S + ΔS) / S = V₀/ V₁  Where V₀Is the tree at 1 atm of the screw tip
Specific volume of fat, V₁Is the tree at the set back pressure of the screw tip
Specific volume to fat.

For example, in the case of PP (polypropylene),
Since V ₁ = 1.23 when the back pressure is 100 kgf / cm ² and V ₀ = 1.24 when the back pressure is 1 kgf / cm ² , (S + ΔS) / S = V ₀ / V ₁ = 1.24 /1.23≒
1.01 Therefore, ΔS = 1% should be increased. In general,
It is within 0.5% to 10%.

Thus, when the screw 54 moves immediately after the measurement is completed and the spacer 55 and the check ring 53 come into contact with each other, the backflow of the material can be prevented immediately after the completion of the measurement, and the amount of the material measured by the screw is injected. It will not be reduced to an insufficient amount.

FIG. 3 is a sectional view showing the screw 54 base side of another foam injection molding machine according to the present invention. This other foam injection molding machine embodying the present invention is provided with a bar 7 as a stopper member for connecting the main body 4b, which is the fixed side of the hydraulic cylinder 4 of the back pressure adding device 4, and the root of the screw 54, and the screw 54 Is prevented from advancing in a predetermined position in the barrel 52 due to back pressure, that is, a position where the metering is completed by the advancing operation, and the amount of material measured by the screw 54 is reduced to an amount insufficient for injection. I have lost it.

As described above, according to the two embodiments of the present invention, since the amount of the material measured by the screw 54 is not reduced to an amount insufficient for the injection, the material required for the injection is eliminated. It is possible to stably manufacture a high-quality injection-molded product without causing sink marks and the like in the molded product by supplying the amount of the above to the mold through the nozzle.

Another foaming injection molding machine according to the present invention will be described with reference to FIG. This foam injection molding machine of the present invention, by maintaining the injection temperature of the material at a temperature suitable for molding,
This enables stable production of high-quality injection-molded products. In FIG. 4, 8 is a mold and 9 is a nozzle 51.
The heaters 10 and 11 provided on the barrel 52 are thermometers such as thermocouples, 12 is a temperature controller for controlling the heater 9, 13 is calculation means, and 14 is control means. Incidentally, 3 to 4 and 51 to 54 have the same functions as those of the foam injection molding machine shown in FIG.

The thermometer 10 such as a thermocouple measures the material injection temperature and is used in the nozzle 51 and the runner 8a of the die 8.
It is provided in. The thermometer 11 such as a thermocouple measures the material temperature immediately after the measurement, and the nozzle 51 on the inner wall of the barrel 52 is used.
It is provided at the side tip. The calculation means 13 calculates a predetermined value of the material temperature control factor from the following based on the measured injection temperature T and the measured measured temperature t input from the thermometer.

Desired injection temperature T₀Difference ΔT:
 ΔT = T−T₀ Immediately after weighing the material in the barrel and the nozzle or molding die
Pressure drop ΔP: ΔP = [(C_P* G) / (2.34 * 10)^-Five)] Δt ∵Δt = T−t (C_PIs the specific heat of the molten material at the desired measuring temperature: g is the molten material
Material at desired metering temperature and desired injection pressure) Injection quantity Q as a function of the pressure drop ΔP: Q = [(π * g) / (n + 3) * η] * [ΔP * (γ
^{n + 3 / n}/ 2J)]]ⁿ  (N is a power when the material is a power law fluid: η is the desired projection
Viscosity at ejection speed: γ is shear rate: J is nozzle length) Injection speed V as a function of the injection amount: V = 4
Q / (πR²) (R is the screw diameter)

The control means 14 controls the temperature controller 12 and the hydraulic device 3 of the drive unit so that the measured injection temperature T becomes equal to the desired injection temperature T ₀ based on the calculated value input from the calculating means. To control.

In still another foam injection molding machine of the present invention having the above structure, the injection temperature of the foam injection molding machine in operation and the measurement temperature immediately after measurement are measured by thermometers 10 and 11 such as thermocouples, and this measurement injection is performed. The heater 9 provided in the nozzle 51 and the barrel 52 has a difference ΔT from the desired injection temperature T ₀ calculated based on the temperature T and the measured measurement temperature t.
The temperature controller is controlled to adjust the amount of heat applied to the material in the nozzle 51 and the barrel 52 so that the measured injection temperature T and the desired injection temperature T ₀ become equal.

Further, the hydraulic system 3 of the drive unit of the screw 54 is controlled by the pressure drop ΔP, the injection amount Q, and the injection speed V calculated based on the measured injection temperature T and the measured metering temperature t, and the screw is driven. The rotation of 54 and the back pressure applied to the screw 54 are adjusted so that the measured injection temperature T is equal to the desired injection temperature T ₀ .

As described above, according to still another foam injection molding machine of the present invention, the measured injection temperature T is equal to the desired injection temperature T ₀ based on the measured injection temperature T of the foam injection molding machine in operation. The amount of heat given to the material in the nozzle 51 or the barrel 52 by the heater 9 or the like, the rotation of the screw 54, and the back pressure applied to the screw 54 are adjusted.

The thermometer may be only one provided inside the nozzle 51 for measuring the injection temperature of the material or on the runner 8a of the die 8. In this case, the measurement temperature t of the material is
It is not a variable that changes depending on the measurement but the set desired temperature t ₀ (constant) in the barrel.

[0034]

The foam injection molding machine and its operating method of the present invention prevent the backflow of the material being injected by the contact of the spacer and the check ring immediately after the end of the measurement by the movement of the screw, or by the stopper member. , It is necessary for the injection because it prevents the screw from advancing from the predetermined position to the nozzle side in the barrel due to the back pressure, and it prevents the measured amount of material from decreasing to the insufficient amount for injection. A large amount of such a material is supplied to the mold through the nozzle, and sink marks etc. do not occur in the molded product. As a result, it becomes possible to stably manufacture a high-quality injection-molded product.

Further, another foam injection molding machine and its operating method of the present invention make it possible to stably manufacture a good quality injection molded product by maintaining the injection temperature of the material at a temperature suitable for molding. To do.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a foam injection molding machine of the present invention.

FIG. 2 is a sectional view of a portion showing a moving amount of the screw in FIG.

FIG. 3 is a cross-sectional view showing another foam injection molding machine of the present invention.

FIG. 4 is a sectional view showing still another foam injection molding machine of the present invention.

FIG. 5 is a cross-sectional view showing a main part of a conventional foam injection molding machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Position detector 2 Rotation speed detector 3 Hydraulic device of drive device 4 Back pressure adding device (hydraulic cylinder) of drive device 5 Rotating device (motor) of drive device 6 Control unit 51 Nozzle 52 Barrel 53 Check ring 54 Screw 55 Spacer C Forward rotation direction L Moving amount

Claims (7)

[Claims] 1. A barrel having a check ring on the inner wall on the tip side to which a nozzle communicating with a molding die is connected, and a collar-shaped spacer for preventing backflow of material when the check ring comes into contact with the shaft. A foam provided with a screw in the barrel provided on the tip side to measure the material by forward rotation, and by separating and contacting the spacer and the check ring, flow of the material during measurement and backflow prevention of the material during injection are foamed. In the operating method of the injection molding machine, immediately after the completion of the measurement, the screw is moved forward to the nozzle side to bring the spacer and the check ring into contact with each other, and the measurement is performed on the barrel corresponding to the forward movement amount of the screw. A method for operating a foam injection molding machine, which is characterized by measuring a large amount by volume. 2. A barrel having a check ring provided on the inner wall on the tip side to which a nozzle communicating with a molding die is connected, and a collar-shaped spacer for preventing backflow of material when the check ring is in contact with the barrel. A screw in the barrel that is provided on the tip side to measure the material by forward rotation, a measuring detector that detects that the desired amount of the material has been measured by the screw, and a position detection that detects the position of the screw And a drive device for rotating the screw while applying a back pressure to the screw, and a control means for controlling the drive device. The control means, when the measurement detector detects the completion of the measurement, the spacer and the check. To move the screw forward to a predetermined position where it abuts the ring, and to confirm that the position detector has moved to the predetermined position of the screw. When detected, control the screw drive device to stop the movement of the screw,
The desired amount of material measured by the screw is an amount including the volume of the barrel corresponding to the moving amount of the screw. 3. A barrel to which a nozzle communicating with a molding die is connected at its tip, a screw that rotates forward in the barrel to measure the material toward the nozzle, and an extendable rod at the root of the screw. In a foam injection molding machine including a hydraulic cylinder connected to apply back pressure to the screw, the hydraulic pressure is used to prevent the screw from advancing from a predetermined position in the barrel to the nozzle side due to back pressure. A foam injection molding machine comprising a stopper member for connecting a main body which is a fixed side of a cylinder and a root portion of the screw. 4. A barrel having a nozzle connected to the tip of a runner of a molding die and a screw provided inside the barrel, and measuring the injection temperature of the material in the runner or the nozzle. Based on the measured injection temperature, a predetermined value of the material temperature control factor from the following is calculated, and based on the calculated value, the heater in the material in the nozzle or the barrel is set so that the measured injection temperature becomes equal to the desired injection temperature. A method for operating a foam injection molding machine, which comprises adjusting the amount of heat given by the above, the rotation of the screw during the measurement, and the back pressure applied to the screw. Difference from desired injection temperature Pressure drop between the material just after being metered in the barrel and the material just before being injected in the nozzle or runner Injection volume as a function of the pressure drop Injection speed as a function of the injection volume 5. The method of operating a foam injection molding machine according to claim 4, wherein in addition to the injection temperature, a measurement temperature immediately after measuring the material in the barrel is measured, and based on the measured injection temperature and the measured measurement temperature. A method of operating a foam injection molding machine, characterized in that the pressure drop, the injection amount, and the injection speed, which are the material temperature control factors, are calculated. 6. A nozzle connected to a runner in a mold, a barrel to which the nozzle is connected to a tip, a screw provided inside the barrel for measuring a material by rotation, and inside the nozzle or the barrel. In a foam injection molding machine equipped with a temperature controller such as a heater that applies heat to the material to adjust the material temperature, and a drive device that rotates the screw while applying back pressure, the runner of the mold or the A thermometer such as a thermocouple for measuring the material injection temperature in the nozzle, and a calculating means for calculating a predetermined value of the material temperature control factor from the following based on the measured injection temperature input from the thermometer,
A foam injection molding machine provided with control means for controlling the temperature controller and the drive device so that the measured injection temperature becomes equal to a desired injection temperature based on the calculated value input from the calculating means. . Difference from desired injection temperature Pressure drop between the material just after being metered in the barrel and the material just before being injected in the nozzle or runner Injection volume as a function of the pressure drop Injection speed as a function of the injection volume 7. The foam injection molding machine according to claim 6, further comprising a thermometer such as a thermocouple for measuring the measuring temperature of the material in the barrel immediately after the measurement, and the measured measuring temperature input from the thermometer and the measured temperature. A foam injection molding machine, wherein the calculating means calculates a pressure drop, an injection amount, and an injection speed, which are the material temperature control factors, based on a measured injection temperature.