US 6,555,035 B2 · Method for injection molding

Abstract

The retreat completion position of the screw in the charging step in actual production is controlled based on the result in pilot production as follows. In pilot production, the measurement value Ts of the screw driving torque is integrated with respect to the screw position P from the forward limit to the retreat completion position Ps. When conforming item is produced in the pilot production, the value ΣTs·dP obtained as a result of the integration is stored as a reference value. After actual production begins, the measurement value Tx of the screw driving torque is integrated in real time with respect to the screw position P from the forward limit to the screw position at each time. The obtained value ΣTx·dP is monitored. When this value ΣTx·dP coincides with the reference value ΣTs·dP, it is determined that the charging step has been completed, and the retreat operation of the screw is stopped.

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Drawings

Claims16

Dependent claims

A method for injection molding for introducing and melting molding material in a barrel containing a screw, and thereafter injecting a molten material into a mold, said method comprising the steps of:

carrying out pilot production to collect data showing a relationship between a screw retreat distance from a forward limit and screw driving torque when introducing and melting the molding material in the barrel, and integrating the screw driving torque with respect to the screw retreat distance from the forward limit to a retreat completion position of the screw, thereby obtaining a first integral value;
storing as a reference value the first integral value obtained when a conforming item is produced in the pilot production;
carrying out actual production to measure screw driving torque when introducing and melting the molding material, and integrating in real time the screw driving torque with respect to the screw retreat distance from the forward limit to a screw position at each time, thereby obtaining a second integral value;
and
monitoring the second integral value, when the second integral value coincides with the reference value, determining that the step of introducing the molding material is completed, and stopping a rotation of the screw.

2 more elements

A method for injection molding for introducing and melting molding material in a barrel containing a screw, and thereafter injecting a molten material into a mold, said method comprising the steps of:

carrying out pilot production to collect data showing a relationship between a screw retreat distance from a forward limit and screw driving torque when introducing and melting the molding material in the barrel, and integrating the screw driving torque with respect to the screw retreat distance from a reference position, which is preset near the forward limit, to a retreat completion position of the screw, thereby obtaining a first integral value;
storing as a reference value the first integral value obtained when a conforming item is produced in the pilot production;
carrying out actual production to measure screw driving torque when introducing and melting the molding material, and integrating in real time the screw driving torque with respect to the screw retreat distance from the reference position to a screw position at each time, thereby obtaining a second integral value;
and
monitoring the second integral value, when the second integral value coincides with the reference value, determining that the step of introducing the molding material is completed, and stopping a rotation of the screw.

2 more elements

A method for injection molding for introducing and melting molding material in a barrel containing a screw, and thereafter injecting a molten material into a mold, said method comprising the steps of:

carrying out pilot production to collect data showing a relationship between elapsed time from a beginning of retreat of the screw from a forward limit and screw driving torque when introducing and melting the molding material in the barrel, and integrating the screw driving torque with respect to the elapsed time from the forward limit to a retreat completion position of the screw, thereby obtaining a first integral value;
storing as a reference value the first integral value obtained when a conforming item is produced in the pilot production;
carrying out actual production to measure screw driving torque when introducing and melting the molding material, and integrating in real time the screw driving torque with respect to the elapsed time from the forward limit to a screw position at each time, thereby obtaining a second integral value;
and
monitoring the second integral value, when the second integral value coincides with the reference value, determining that the step of introducing the molding material is completed, and stopping a rotation of the screw.

2 more elements

A method for injection molding for introducing and melting molding material in a barrel containing a screw, and thereafter injecting a molten material into a mold, said method comprising the steps of:

carrying out pilot production to collect data showing a relationship between elapsed time from a beginning of retreat of the screw from a forward limit and screw driving torque when introducing and melting the molding material in the barrel, and integrating the screw driving torque with respect to the elapsed time from a reference position, which is preset near the forward limit, to a retreat completion position of the screw, thereby obtaining a first integral value;
storing as a reference value the first integral value obtained when a conforming item is produced in the pilot production;
carrying out actual production to measure screw driving torque in the step of introducing and melting the molding material, and integrating in real time the screw driving torque with respect to the elapsed time from the reference position to a screw position at each time, thereby obtaining a second integral value;
and
monitoring the second integral value, when the second integral value coincides with the reference value, determining that the step of introducing the molding material is completed, and stopping a rotation of the screw.

2 more elements

Dependencies are inferred from the claim text.

Description4,742 words

Summary1,463 words

#The present invention relates to a method for injection molding, and more particularly to a method for melting a molding material and storing a constant amount of molten material in a barrel of an injection unit.

#An injection unit of an injection molding machine in general has the barrel containing therein a screw for melting a constant amount of molding material and injecting the melted material to a mold. Generally, the molding material is resin formed as pellets, which are stored in a hopper connected to a rear end portion of the barrel. When the screw is rotated in a forward direction within the barrel, the resin is introduced into the barrel from the hopper. The introduced resin is heated and melted. It is supplied to a front end portion of the screw while it is being kneaded, and then successively stored in a top end portion of the barrel. Accordingly, the screw is retreated by the pressure of the molten resin in the top end portion, and the molten resin of an amount substantially corresponding to the retreated distance is stored in the top end portion of the barrel (this step is called a charging step). Then, the molten resin is injected into the mold by moving the screw forward (this step is called an injection step). After the resin is hardened in the mold, the mold is opened and a molded product is taken out.

#The amount of the molten resin finally injected into the mold is determined by the position of the screw when the charging step is completed (retreat completion position). Further, the amount of the molten resin varies depending on conditions, such as the temperature in the barrel and the number of revolutions of the screw at a time of introducing the resin in the barrel, and the pressure in the barrel at that time (the back pressure of the screw).

Brief description of the drawings9 figures

#The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.

#FIG. 1 is a diagram showing the relationship between the screw driving torque and the amount of the molten resin stored within the barrel in a unit time in the charging step;

#FIG. 2 is a diagram showing an embodiment of the structure of an apparatus and a control system employed in the case where a method for injection molding based on the present invention is applied to an electric injection molding machine;

Detailed description2,978 words

#Embodiments of the present invention will be described with reference to the accompanying drawings.

#FIG. 2 shows an embodiment of the schematic structure of an apparatus and a control system employed in the case where a method for injection molding based on the present invention is applied to an electric injection molding machine. In the drawing, a reference numeral 1 denotes a barrel; 2 a screw; 3 a hopper; 5 a motor for charging; and 6 a motor for injection.

#The screw 2 is contained in the barrel 1 and a heater 7 is provided around the barrel 1. The hopper 3 is connected to a side near the rear end of the barrel 1 (the right end in the drawing). The top end of the barrel 1 (the left end in the drawing) is connected to a rear surface of a mold (not shown). A molding material 9, i.e., resin formed as pellets, is introduced from the hopper 3 into the barrel 1 and melted therein.

Method for injection molding

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Method for injection molding

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Life of this patent

Abstract

Drawings

Drawings

Claims16

Description4,742 words

Drawings

Classification15 codes

Life of this patent

Description4,742 words