WO2003080307A2 - Method of determining a hold pressure control start pressure for resin injection molding - Google Patents

Method of determining a hold pressure control start pressure for resin injection molding Download PDF

Info

Publication number
WO2003080307A2
WO2003080307A2 PCT/JP2003/002841 JP0302841W WO03080307A2 WO 2003080307 A2 WO2003080307 A2 WO 2003080307A2 JP 0302841 W JP0302841 W JP 0302841W WO 03080307 A2 WO03080307 A2 WO 03080307A2
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
cavity
gate
hold
control start
Prior art date
Application number
PCT/JP2003/002841
Other languages
French (fr)
Other versions
WO2003080307A3 (en
Inventor
Kouichi Odaka
Kenichi Suzuki
Akihiro Yuasa
Original Assignee
Honda Giken Kogyo Kabushiki Kaisha
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Honda Giken Kogyo Kabushiki Kaisha filed Critical Honda Giken Kogyo Kabushiki Kaisha
Priority to KR10-2004-7006742A priority Critical patent/KR20040097118A/en
Priority to GB0409755A priority patent/GB2396840B/en
Priority to CA002467594A priority patent/CA2467594A1/en
Publication of WO2003080307A2 publication Critical patent/WO2003080307A2/en
Publication of WO2003080307A3 publication Critical patent/WO2003080307A3/en

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/76Measuring, controlling or regulating
    • B29C45/766Measuring, controlling or regulating the setting or resetting of moulding conditions, e.g. before starting a cycle
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/76Measuring, controlling or regulating
    • B29C45/77Measuring, controlling or regulating of velocity or pressure of moulding material
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/76Measuring, controlling or regulating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17Component parts, details or accessories; Auxiliary operations
    • B29C45/76Measuring, controlling or regulating
    • B29C45/77Measuring, controlling or regulating of velocity or pressure of moulding material
    • B29C2045/776Measuring, controlling or regulating of velocity or pressure of moulding material determining the switchover point to the holding pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76003Measured parameter
    • B29C2945/76006Pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76177Location of measurement
    • B29C2945/76254Mould
    • B29C2945/76257Mould cavity
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76177Location of measurement
    • B29C2945/76254Mould
    • B29C2945/76274Mould runners, nozzles
    • B29C2945/76277Mould runners, nozzles nozzles
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76451Measurement means
    • B29C2945/76454Electrical, e.g. thermocouples
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76494Controlled parameter
    • B29C2945/76498Pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76655Location of control
    • B29C2945/76732Mould
    • B29C2945/76735Mould cavity
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2945/00Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
    • B29C2945/76Measuring, controlling or regulating
    • B29C2945/76655Location of control
    • B29C2945/76765Moulding material

Definitions

  • the present invention relates to an improvement in a method of determining a hold pressure control start pressure for resin injection molding.
  • Japanese Patent Publication No. (Hei) 4-48339 discloses an injection control device for an injection molding machine, which is designed to start hold pressure control when the pressure on a resin filled in a mold exceeds a preset pressure or when a predetermined time elapses after the start of the injection operation.
  • the resin pressure inside the mold may be measured by a pressure sensor built in the mold.
  • Figs. 6A and 6B are graphs illustrative of two different ways conventionally taken to determine the preset pressure.
  • the horizontal axis represents the time elapsed after the start of the injection process and the vertical axis represents the pressure inside the mold.
  • a pressure curve denoted by "a” indicates that a large peak occurs at the final stage of the injection process due to an excessively high injection speed.
  • a pressure curve denoted by “b” in Fig. 6 shows that a peak occurring at the final stage of the injection process is smaller than that of the pressure curve "a” because of a reduced injection speed.
  • a pressure curve indicated by the phantom line “A” represents an optimum pressure curve. Theoretically, the optimum pressure curve "A” can be determined by repeating a test injection process under the conditions that the peak occurring at the final stage of one injection process becomes smaller than that of the preceding injection process, as evidenced by the pressure curves "a” and "b” shown in 6A.
  • Fig. 6B shows a different procedure, in which for protection of the mold, the test injection process starts with an injection speed sufficiently reduced to prevent the occurrence of a peak pressure, as evidenced by pressure curve "c" shown in Fig. 6B.
  • the injection speed is slightly increased, so that a pressure curve denoted by "d” is obtained.
  • the test injection process is repeated while increasing the injection speed gradually until the phantom-lined optimum pressure curve "A" is obtained.
  • This procedure requires many nuns of test injection operation and hence the efficiency is low.
  • Fig. 7 shows a typical example of conventional pressure-sensor arrangements.
  • a pressure sensor 104 is embedded in a movable mold 102 so as to face substantially the center of a cavity 103 defined between the movable mold 102 and a stationary mold 101.
  • a resin melt issued from an injection nozzle 105 is injected through a hot runner 106 and an internal nozzle or gate 107 into the cavity 103.
  • the resin melt undergoes turbulence
  • the cavity pressure i.e., the resin pressure inside the cavity
  • a method of determining a hold pressure control start pressure for resin injection molding comprising the steps of- while performing injection speed control, effecting a test injection process to obtain a pressure curve under conditions that the pressure curve includes a peak drawn due to a cavity pressure occurring at a final stage of the test injection process; finding a pressure at which the pressure curve forms a valley occurring first after the peak; and setting the thus found pressure as a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation.
  • the hold pressure control start pressure is determined on the basis of the pressure curve, it is essentially possible to obtain a setting pressure for the hold pressure control start pressure through a single run of test injection molding process. This procedure provides a great reduction in man-hour of the test injection processes.
  • the cavity pressure is measured at a position where a resin melt which has been injected from a gate into a cavity of a mould assembly is permitted to flow stably. That portion of the cavity which is located in the proximity to the gate is filled with a resin melt before the remaining portion of the cavity, and the cavity pressure (i.e., the pressure on the resin melt) at this cavity portion soon becomes stable.
  • a pressure sensor used for the cavity pressure measurement is located in the cavity portion, and preferably at the center of the cavity portion.
  • the cavity has a cavity portion located in proximity to the gate and having a larger space than the gate.
  • the cavity portion has a first region located immediately downstream of the gate, a second region located far away from the gate and blending into a main portion of the cavity, and a third region disposed between the first and second regions.
  • the position for measurement of the cavity pressure is located in the second region of the cavity portion, and preferably at the center of the second region of the cavity portion.
  • Fig. 1 is a vertical cross-sectional view of a mold assembly provided for carrying out a method of the present invention
  • Fig. 2A is a horizontal cross-sectional view taken along fine 2Aof Fig. 1 '
  • Fig. 2B is a graph showing a pressure distribution in a portion of the mold cavity located in the proximity to a gate of the mold;
  • Fig. 3 is a graph illustrative of the manner in which a hold pressure control start pressure is determined through a test injection process according to the present invention
  • Fig. 4 is a flowchart showing a sequence of operations achieved in a service run of an injection molding machine according to the present invention
  • Fig. 5 is a graph showing a pressure curve representing the cavity pressure during the service run of the injection molding operation
  • Figs. 6A and 6B are graphs showing two different methods conventionally taken to determine a hold pressure control start pressure
  • Fig. 7 is a view showing a typical example of sensor arrangements conventionally taken to install a pressure sensor in a mold.
  • Fig. 1 shows in cross section a mold assembly used for carrying out a method of the present invention.
  • the mold assembly 10 is composed of a movable mold 11 and a stationary mold 12.
  • the stationary mold 12 has formed therein a hot runner 13 and an internal nozzle or gate 14.
  • the movable mold 11 and the stationary mold 12 define therebetween a cavity 15 that communicates successively through the gate 14 and the hot runner 13 with an injection nozzle 18.
  • the stationary mold 12 has a pressure sensor 17 embedded therein in such a manner that the pressure sensor 17 faces that portion 16 of the cavity 15 which is located in proximity to the gate 14.
  • the cavity portion 16 has a cross-sectional area sufficiently larger than that of the gate 14 so that the resin melt issued from the gate 14 can be smoothly introduced through the cavity portion 16 into a main portion of the cavity 15.
  • the main cavity portion has a volumetric space excessively larger than that of the cavity portion 16.
  • the cavity portion 16 has a square shape in cross section.
  • the pressure sensor 17 is preferably disposed at the center of the cavity portion 16, as will be understood from a description given below with reference to Figs. 2A and 2B.
  • Fig. 2B is a graph showing a pressure distribution inside the cavity portion 16 that is obtained through measurement using the pressure sensor 17 while changing the position of the pressure sensor 17 relative to the gate 14
  • FIG. 2A Figs. 2A and 2B are shown related with each other such that the origin of the coordinate axes of the table shown in Fig. 2B is coincident with the position of an outlet of the gate 14 shown in Fig. 2A.
  • a first region E (Fig. 2B) of the cavity portion 16 which is located immediately downstream of the gate 14, the pressure on the resin melt undergoes fluctuations. This is because the pressure on the resin melt widely varies with locations due to turbulence, swirl or the like disturbing phenomenon occurring when the resin melt is allowed to suddenly blow off from the gate 14 into an excessively large space of the cavity portion 16.
  • a third region F (Fig. 2B) of the cavity portion 16 which is located substantially centrally between the first and second regions E and G, the pressure on the resin melt is free from fluctuations and falls gently at a substantially uniform rate as the distance from the gate 14 increases. It may be considered that once the resin melt fills in the cavity portion 16, the pressure on the resin melt inside the cavity portion 16 becomes stable. It appears clear from the pressure distribution shown in Fig. 2B that the pressure sensor 17 is preferably disposed in the third region F and, more particularly, at the center of the third region F that is far distant from both of the first region E and the second region G.
  • Fig. 3 shows a graph illustrative of the manner in which a hold pressure control start pressure is determined through a test injection process according to the present invention. While the test injection process is achieved, injection pressure control is not performed but injection speed control is done.
  • the test injection process is conducted under conditions that a pressure curve H, representing the pressure on a resin melt, includes a peak occurring at a final stage of the test injection process. When the pressure curve H forms a valley J occurring first after the peak, a pressure Ps at this time point is found.
  • the pressure Ps is then set to be a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation. Since the hold pressure control start pressure Ps is determined on the basis of the pressure curve H, it is essentially possible to obtain a setting pressure value for such hold pressure control start pressure through a single run of test injection molding process.
  • Fig. 4 is a flowchart showing a sequence of operations achieved during a service run of an injection molding machine according to the present invention.
  • an injection molding machine incorporating the mold assembly 10 (Fig. l) is set to operate in an injection speed control mode.
  • extrusion speed of a screw of an injection device is controlled in accordance with a predetermined program to thereby control the injection speed of the injection molding machine.
  • a step ST02 starts an injection process while performing the injection speed control.
  • the pressure on a resin melt issued from the gate 14 into the cavity 15 is measured by the pressure sensor 17 (Fig. l) as at a step ST03.
  • a step ST04 determines whether or not Pact is equal to or greater than Ps where Pac is an actually measured pressure obtained through the pressure sensor 17 (Fig. l), and Ps is the hold pressure control start pressure determined in the manner previously described with reference to Fig. 3.
  • the procedure goes on to a step ST05 where the injection speed control mode is switched to a hold pressure control mode. Subsequently, a hold pressure control process is performed.
  • Fig. 5 is a graph showing a pressure curve representing the pressure on a resin melt within the cavity 15 that are observed during service runs of the injection molding machine. While performing injection speed control, an injection process is conducted. The injection process continues until the pressure on the resin melt obtained by actual measurement reaches the preset hold pressure control start pressure Ps, whereupon the injection speed control is switched to pressure control (hold pressure control). A pressure curve obtained through the operations described above is well matched with the optimum pressure curve A shown in Figs. 6A and 6B. This means that the hold pressure control start pressure Ps determined in accordance with the method of the present invention is practically useful.
  • a method of the present invention for determining a hold pressure control start pressure for resin injection molding comprises the steps of while performing injection speed control, effecting a test injection process to obtain a pressure curve under conditions that the pressure curve includes a peak drawn due to a cavity pressure occurring at a final stage of the test injection process, ' finding a pressure at which the pressure curve forms a valley occurring first after the peak; and setting the thus found pressure as a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation. Since the hold pressure control start pressure is determined on the basis of a pressure curve, it is essentially possible to obtain a setting pressure value for such hold pressure control start pressure through a single run of test injection molding process. This procedure provides a great reduction in man-hour of the test injection processes.
  • the cavity pressure is measured at a position where a resin melt which has been injected from a gate into a cavity of a mould assembly is permitted to flow stably. Especially, that portion of the cavity which is located in the proximity to the gate is filled with a resin melt before the remaining portion of the cavity, and the cavity pressure (i.e., the pressure on the resin melt) at this cavity portion soon becomes stable.
  • a pressure sensor used for the cavity pressure measurement is located in the cavity portion, and preferably at the center of the cavity portion. This arrangement ensures stable injection molding operation.
  • the present invention can be used advantageously as a method of determining a hold pressure control start pressure for resin injection molding with utmost ease and high efficiency.

Abstract

A hold pressure control start pressure for resin injection molding is determined by finding a pressure (Ps) at which a pressure curve (H) representing the pressure on a resin melt inside the mold cavity forms a valley (J) occurring first after a peak of the pressure curve, and setting the thus found pressure (Ps) as a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation. Since the hold pressure control start pressure is determined on the basis of the pressure curve, it is essentially possible to obtain a setting pressure value for such hold pressure control start pressure through a single run of test injection molding process.

Description

DESCEIPTION
METHOD OF DETERMINING AHOLD PRESSURE CONTROL START PRESSURE FOR RESIN INJECTION MOLDING
Technical Field The present invention relates to an improvement in a method of determining a hold pressure control start pressure for resin injection molding.
Background Art Japanese Patent Publication No. (Hei) 4-48339 discloses an injection control device for an injection molding machine, which is designed to start hold pressure control when the pressure on a resin filled in a mold exceeds a preset pressure or when a predetermined time elapses after the start of the injection operation. The resin pressure inside the mold may be measured by a pressure sensor built in the mold.
According to an investigation conducted by the present inventors, it has been found that the technique disclosed in the above-mentioned Japanese publication is not fully satisfactory and still has two problems to be solved. One problem is that the preset pressure is not easily determined, and the other problem is that the resin pressure inside the mold is difficult to measure due to the occurrence of great pressure changes or fluctuations. These problems will be described below in greater details with reference to Figs. 6A and 6B and Fig. 7.
Figs. 6A and 6B are graphs illustrative of two different ways conventionally taken to determine the preset pressure. In the graphs shown in Figs. 6A and 6B, the horizontal axis represents the time elapsed after the start of the injection process and the vertical axis represents the pressure inside the mold.
In Fig. 6A, a pressure curve denoted by "a" indicates that a large peak occurs at the final stage of the injection process due to an excessively high injection speed. A pressure curve denoted by "b" in Fig. 6 shows that a peak occurring at the final stage of the injection process is smaller than that of the pressure curve "a" because of a reduced injection speed. A pressure curve indicated by the phantom line "A" represents an optimum pressure curve. Theoretically, the optimum pressure curve "A" can be determined by repeating a test injection process under the conditions that the peak occurring at the final stage of one injection process becomes smaller than that of the preceding injection process, as evidenced by the pressure curves "a" and "b" shown in 6A. This procedure is not preferable from the viewpoint of mold protection because the mold is subjected to excessively large pressure loads during the repeated test injection processes. Fig. 6B shows a different procedure, in which for protection of the mold, the test injection process starts with an injection speed sufficiently reduced to prevent the occurrence of a peak pressure, as evidenced by pressure curve "c" shown in Fig. 6B. In the next run of the test injection process, the injection speed is slightly increased, so that a pressure curve denoted by "d" is obtained. Thus, the test injection process is repeated while increasing the injection speed gradually until the phantom-lined optimum pressure curve "A" is obtained. This procedure requires many nuns of test injection operation and hence the efficiency is low.
Fig. 7 shows a typical example of conventional pressure-sensor arrangements. As shown in this figure, a pressure sensor 104 is embedded in a movable mold 102 so as to face substantially the center of a cavity 103 defined between the movable mold 102 and a stationary mold 101. In an injection process, a resin melt issued from an injection nozzle 105 is injected through a hot runner 106 and an internal nozzle or gate 107 into the cavity 103.
For some time after the start of injection, the resin melt undergoes turbulence
(which may involve generation of swirls and collision of resin melt) and the cavity pressure (i.e., the resin pressure inside the cavity) fluctuates abruptly.
The pressure fluctuations make the cavity pressure measurement difficult to achieve. Accordingly, consideration must be given to the location where the pressure sensor is to be mounted.
It is accordingly an object of the present invention to provide a method which is capable of determining a hold pressure control start pressure easily, speedily and highly efficiently.
Disclosure of the Invention
According to the present invention, there is provided a method of determining a hold pressure control start pressure for resin injection molding, comprising the steps of- while performing injection speed control, effecting a test injection process to obtain a pressure curve under conditions that the pressure curve includes a peak drawn due to a cavity pressure occurring at a final stage of the test injection process; finding a pressure at which the pressure curve forms a valley occurring first after the peak; and setting the thus found pressure as a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation.
Since the hold pressure control start pressure is determined on the basis of the pressure curve, it is essentially possible to obtain a setting pressure for the hold pressure control start pressure through a single run of test injection molding process. This procedure provides a great reduction in man-hour of the test injection processes.
It is preferable that the cavity pressure is measured at a position where a resin melt which has been injected from a gate into a cavity of a mould assembly is permitted to flow stably. That portion of the cavity which is located in the proximity to the gate is filled with a resin melt before the remaining portion of the cavity, and the cavity pressure (i.e., the pressure on the resin melt) at this cavity portion soon becomes stable. A pressure sensor used for the cavity pressure measurement is located in the cavity portion, and preferably at the center of the cavity portion.
In one preferred form of the invention, the cavity has a cavity portion located in proximity to the gate and having a larger space than the gate. The cavity portion has a first region located immediately downstream of the gate, a second region located far away from the gate and blending into a main portion of the cavity, and a third region disposed between the first and second regions.
The position for measurement of the cavity pressure is located in the second region of the cavity portion, and preferably at the center of the second region of the cavity portion.
Brief Description of the Drawings
Fig. 1 is a vertical cross-sectional view of a mold assembly provided for carrying out a method of the present invention;
Fig. 2Ais a horizontal cross-sectional view taken along fine 2Aof Fig. 1', Fig. 2B is a graph showing a pressure distribution in a portion of the mold cavity located in the proximity to a gate of the mold;
Fig. 3 is a graph illustrative of the manner in which a hold pressure control start pressure is determined through a test injection process according to the present invention; Fig. 4 is a flowchart showing a sequence of operations achieved in a service run of an injection molding machine according to the present invention;
Fig. 5 is a graph showing a pressure curve representing the cavity pressure during the service run of the injection molding operation;
Figs. 6A and 6B are graphs showing two different methods conventionally taken to determine a hold pressure control start pressure; and
Fig. 7 is a view showing a typical example of sensor arrangements conventionally taken to install a pressure sensor in a mold.
Best Mode for Carrying Out the Invention
One preferred embodiment of the present invention will be described in greater detail with reference to the accompanying sheets of drawings.
Fig. 1 shows in cross section a mold assembly used for carrying out a method of the present invention. The mold assembly 10 is composed of a movable mold 11 and a stationary mold 12. The stationary mold 12 has formed therein a hot runner 13 and an internal nozzle or gate 14. The movable mold 11 and the stationary mold 12 define therebetween a cavity 15 that communicates successively through the gate 14 and the hot runner 13 with an injection nozzle 18. The stationary mold 12 has a pressure sensor 17 embedded therein in such a manner that the pressure sensor 17 faces that portion 16 of the cavity 15 which is located in proximity to the gate 14.
As shown in Fig. 2A, the cavity portion 16 has a cross-sectional area sufficiently larger than that of the gate 14 so that the resin melt issued from the gate 14 can be smoothly introduced through the cavity portion 16 into a main portion of the cavity 15. The main cavity portion has a volumetric space excessively larger than that of the cavity portion 16. In the illustrated embodiment, the cavity portion 16 has a square shape in cross section. The pressure sensor 17 is preferably disposed at the center of the cavity portion 16, as will be understood from a description given below with reference to Figs. 2A and 2B.
Fig. 2B is a graph showing a pressure distribution inside the cavity portion 16 that is obtained through measurement using the pressure sensor 17 while changing the position of the pressure sensor 17 relative to the gate 14
(Fig. 2A). Figs. 2A and 2B are shown related with each other such that the origin of the coordinate axes of the table shown in Fig. 2B is coincident with the position of an outlet of the gate 14 shown in Fig. 2A.
In a first region E (Fig. 2B) of the cavity portion 16, which is located immediately downstream of the gate 14, the pressure on the resin melt undergoes fluctuations. This is because the pressure on the resin melt widely varies with locations due to turbulence, swirl or the like disturbing phenomenon occurring when the resin melt is allowed to suddenly blow off from the gate 14 into an excessively large space of the cavity portion 16.
In a second region G (Fig. 2B) of the cavity portion 16, which is located far away from the gate 14 and is blending into the main portion of the cavity 15, the pressure on the resin melt shows a steep drop. This is because the resin melt flows from the cavity portion 16 into the main cavity portion that has an excessively great space as compared to the cavity portion 16.
In a third region F (Fig. 2B) of the cavity portion 16, which is located substantially centrally between the first and second regions E and G, the pressure on the resin melt is free from fluctuations and falls gently at a substantially uniform rate as the distance from the gate 14 increases. It may be considered that once the resin melt fills in the cavity portion 16, the pressure on the resin melt inside the cavity portion 16 becomes stable. It appears clear from the pressure distribution shown in Fig. 2B that the pressure sensor 17 is preferably disposed in the third region F and, more particularly, at the center of the third region F that is far distant from both of the first region E and the second region G.
Fig. 3 shows a graph illustrative of the manner in which a hold pressure control start pressure is determined through a test injection process according to the present invention. While the test injection process is achieved, injection pressure control is not performed but injection speed control is done. The test injection process is conducted under conditions that a pressure curve H, representing the pressure on a resin melt, includes a peak occurring at a final stage of the test injection process. When the pressure curve H forms a valley J occurring first after the peak, a pressure Ps at this time point is found. The pressure Ps is then set to be a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation. Since the hold pressure control start pressure Ps is determined on the basis of the pressure curve H, it is essentially possible to obtain a setting pressure value for such hold pressure control start pressure through a single run of test injection molding process.
Fig. 4 is a flowchart showing a sequence of operations achieved during a service run of an injection molding machine according to the present invention.
At a first step ST01, an injection molding machine incorporating the mold assembly 10 (Fig. l) is set to operate in an injection speed control mode.
In the injection speed control mode, extrusion speed of a screw of an injection device is controlled in accordance with a predetermined program to thereby control the injection speed of the injection molding machine.
Then, a step ST02 starts an injection process while performing the injection speed control.
During the injection process, the pressure on a resin melt issued from the gate 14 into the cavity 15 is measured by the pressure sensor 17 (Fig. l) as at a step ST03.
A step ST04 determines whether or not Pact is equal to or greater than Ps where Pac is an actually measured pressure obtained through the pressure sensor 17 (Fig. l), and Ps is the hold pressure control start pressure determined in the manner previously described with reference to Fig. 3.
When the determination is affirmative, the procedure goes on to a step ST05 where the injection speed control mode is switched to a hold pressure control mode. Subsequently, a hold pressure control process is performed.
When the determination at the step ST04 is negative, then the procedure returns to the step ST03, and the injection process continues further.
Fig. 5 is a graph showing a pressure curve representing the pressure on a resin melt within the cavity 15 that are observed during service runs of the injection molding machine. While performing injection speed control, an injection process is conducted. The injection process continues until the pressure on the resin melt obtained by actual measurement reaches the preset hold pressure control start pressure Ps, whereupon the injection speed control is switched to pressure control (hold pressure control). A pressure curve obtained through the operations described above is well matched with the optimum pressure curve A shown in Figs. 6A and 6B. This means that the hold pressure control start pressure Ps determined in accordance with the method of the present invention is practically useful.
As thus for described, a method of the present invention for determining a hold pressure control start pressure for resin injection molding comprises the steps of while performing injection speed control, effecting a test injection process to obtain a pressure curve under conditions that the pressure curve includes a peak drawn due to a cavity pressure occurring at a final stage of the test injection process,' finding a pressure at which the pressure curve forms a valley occurring first after the peak; and setting the thus found pressure as a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation. Since the hold pressure control start pressure is determined on the basis of a pressure curve, it is essentially possible to obtain a setting pressure value for such hold pressure control start pressure through a single run of test injection molding process. This procedure provides a great reduction in man-hour of the test injection processes.
Furthermore, according to the method of the present invention, it is possible to increase the injection speed and cut or lower a peak pressure during injection. Reduction of the peak pressure allows the use of a mold with reduced rigidity, leading to downsizing of the mold. According to the method of the present invention, the cavity pressure is measured at a position where a resin melt which has been injected from a gate into a cavity of a mould assembly is permitted to flow stably. Especially, that portion of the cavity which is located in the proximity to the gate is filled with a resin melt before the remaining portion of the cavity, and the cavity pressure (i.e., the pressure on the resin melt) at this cavity portion soon becomes stable. A pressure sensor used for the cavity pressure measurement is located in the cavity portion, and preferably at the center of the cavity portion. This arrangement ensures stable injection molding operation.
Industrial Apphcabihty With the arrangements so far described, the present invention can be used advantageously as a method of determining a hold pressure control start pressure for resin injection molding with utmost ease and high efficiency.

Claims

1. A method of determining a hold pressure control start pressure for resin injection molding, comprising the steps of- (a) while performing injection speed control, effecting a test injection process to obtain a pressure curve under conditions that the pressure curve includes a peak drawn due to a cavity pressure occurring at a final stage of the test injection process;
(b) finding a pressure at which the pressure curve forms a valley occurring first after the peak; and
(c) setting the thus found pressure as a hold pressure control start pressure that is used for performing pressure control during a subsequent resin molding operation.
2. The method of claim 1, wherein said cavity pressure is measured at a position where a resin melt which has been injected from a gate into a cavity of a mould assembly is permitted to flow stably.
3. The method of claim 2, wherein said cavity has a cavity portion located in proximity to the gate and having a larger space than the gate, the cavity portion having a first region located immediately downstream of the gate, a second region located far away from the gate and blending into a main portion of the cavity, and a third region disposed between the first and second regions, and wherein said position for measurement of the cavity pressure is located in the second region of the cavity portion.
4. The method of claim 3, wherein said position for measurement of the cavity pressure is located at the center of the second region of the cavity portion.
PCT/JP2003/002841 2002-03-26 2003-03-11 Method of determining a hold pressure control start pressure for resin injection molding WO2003080307A2 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
KR10-2004-7006742A KR20040097118A (en) 2002-03-26 2003-03-11 Method of determining a hold pressure control start pressure for resin injection molding
GB0409755A GB2396840B (en) 2002-03-26 2003-03-11 Method of determining a hold pressure control start pressure for resin injection molding
CA002467594A CA2467594A1 (en) 2002-03-26 2003-03-11 Method of determining a hold pressure control start pressure for resin injection molding

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2002087075A JP3778441B2 (en) 2002-03-26 2002-03-26 Method for determining holding pressure start pressure for resin injection molding
JP2002-087075 2002-03-26

Publications (2)

Publication Number Publication Date
WO2003080307A2 true WO2003080307A2 (en) 2003-10-02
WO2003080307A3 WO2003080307A3 (en) 2008-01-10

Family

ID=28449353

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2003/002841 WO2003080307A2 (en) 2002-03-26 2003-03-11 Method of determining a hold pressure control start pressure for resin injection molding

Country Status (6)

Country Link
JP (1) JP3778441B2 (en)
KR (1) KR20040097118A (en)
CN (1) CN100418731C (en)
CA (1) CA2467594A1 (en)
GB (1) GB2396840B (en)
WO (1) WO2003080307A2 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004051109A1 (en) * 2004-10-19 2006-05-04 Siemens Ag Method for operating an injection molding machine
DE102014008055B4 (en) * 2013-06-05 2017-07-06 Fanuc Corporation Pressure control device of an injection molding machine
US11867600B2 (en) 2017-08-22 2024-01-09 Lg Chem, Ltd. Assessment method for injection molding property of plastic form

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104527010B (en) * 2014-12-10 2017-01-18 浙江师范大学 Polymer melt pressure monitoring system used for micro injection molding process
US10836088B2 (en) * 2017-04-25 2020-11-17 Kistler Holding, Ag Method for reproducing injection molded parts of quality and injection molding unit for performing the method
CN107310118B (en) * 2017-07-26 2020-04-10 华域视觉科技(上海)有限公司 Switching method from speed control to pressure control in injection molding process and injection mold

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0747198A2 (en) * 1995-06-06 1996-12-11 Niigata Engineering Co., Ltd. Molding condition optimizing system for injection molding machine

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60239219A (en) * 1984-05-11 1985-11-28 Toshiba Mach Co Ltd Switchover apparatus for speed control-pressure control of injection molding machine
JP2746474B2 (en) * 1990-11-09 1998-05-06 住友重機械工業株式会社 Control method of electric injection molding machine
US6309571B2 (en) * 1998-02-27 2001-10-30 The Hong Kong University Of Science & Technology Method and apparatus for the control of injection molding

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0747198A2 (en) * 1995-06-06 1996-12-11 Niigata Engineering Co., Ltd. Molding condition optimizing system for injection molding machine

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 010, no. 109 (M-472), 23 April 1986 (1986-04-23) & JP 60 239219 A (TOSHIBA KIKAI KK), 28 November 1985 (1985-11-28) *
PATENT ABSTRACTS OF JAPAN vol. 016, no. 480 (M-1321), 6 October 1992 (1992-10-06) & JP 04 175135 A (SUMITOMO HEAVY IND LTD), 23 June 1992 (1992-06-23) *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004051109A1 (en) * 2004-10-19 2006-05-04 Siemens Ag Method for operating an injection molding machine
DE102004051109B4 (en) * 2004-10-19 2007-01-18 Siemens Ag Method for operating an injection molding machine
DE102014008055B4 (en) * 2013-06-05 2017-07-06 Fanuc Corporation Pressure control device of an injection molding machine
US11867600B2 (en) 2017-08-22 2024-01-09 Lg Chem, Ltd. Assessment method for injection molding property of plastic form

Also Published As

Publication number Publication date
CN1791500A (en) 2006-06-21
GB0409755D0 (en) 2004-06-09
CA2467594A1 (en) 2003-10-02
WO2003080307A3 (en) 2008-01-10
GB2396840B (en) 2006-01-11
GB2396840A (en) 2004-07-07
CN100418731C (en) 2008-09-17
JP3778441B2 (en) 2006-05-24
JP2003276070A (en) 2003-09-30
KR20040097118A (en) 2004-11-17

Similar Documents

Publication Publication Date Title
EP1091842B1 (en) Automated molding technology for thermoplastic injection molding
US20090194249A1 (en) Die and Method of Manufacturing Cast Product
EP1771288B1 (en) Injection molding method
WO2003080307A2 (en) Method of determining a hold pressure control start pressure for resin injection molding
US20090151889A1 (en) Die for Die Casting, Method of Manufacturing Cast Product, and Cast Product
Moayyedian et al. Improved gate system for scrap reduction in injection molding processes
US6994537B2 (en) Electrical injection velocity-pressure switching and pressure holding device
WO2002034499A1 (en) Method of predicting optimal injection molding cycle time
JP5980842B2 (en) Method for determining molding quality of hollow molded products
KR20010020317A (en) Method and apparatus for the control of injection molding
JPH1190609A (en) Injection molding device
JP5370824B2 (en) Gas counter pressure molding method.
US20120319334A1 (en) Internal gas pressure method for producing plastic parts
KR100726217B1 (en) Reduction of pressure apparatus for thin a cast-iron product
JPH1044179A (en) Hollow injection forming method and its device, and inspection method for hollow injection molded product
CN117103601B (en) Ultrasonic energy field fluctuation control method
CN104822474B (en) A kind of method for the thin-wall metal element for manufacturing die casting
JP2002292694A (en) Method for detecting gas venting state of injection mold
CN216861151U (en) Product with variable wall thickness and reduced product flash and product mold
JP2003025392A (en) Method for injection molding plastic product
DE502005008549D1 (en) TEMPERATURE DEPENDENT DEFORMATION
JP2001198958A (en) Injection mold and injection molding method
JP2799669B2 (en) Control method of injection molding machine
JP3341334B2 (en) Cold runner type injection mold
CN113059774A (en) Method for controlling injection molding pressure maintaining process

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): CA CN GB KR

ENP Entry into the national phase

Ref document number: 0409755

Country of ref document: GB

Kind code of ref document: A

Free format text: PCT FILING DATE = 20030311

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
WWE Wipo information: entry into national phase

Ref document number: 1020047006742

Country of ref document: KR

WWE Wipo information: entry into national phase

Ref document number: 2467594

Country of ref document: CA

WWE Wipo information: entry into national phase

Ref document number: 20038016966

Country of ref document: CN