Nissei Plastic Industrial Co., Ltd.

Masahiko Miyajima

Makoto Nakazawa

Takashi Hakoda

Fumio Shiozawa

Daiki Tanemura

Masaaki Minamimura

Kenichi Shimizu

In a mold protection method for a mold clamping apparatus, a predetermined mold protection zone is set in a zone in which a mold is closed, and an anomaly such as presence of a foreign object is detected on the basis of a change in a physical quantity in the mold protection zone so as to protect the mold. The method includes the steps of previously setting, as a reference position, a closed position of a movable platen at which a target mold clamping force is obtained; setting an end position of the mold protection zone with respect to the reference position; obtaining, during a production operation, an actual closed position (detected position) of the movable platen; and correcting the end position of the mold protection zone on the basis of a deviation between the detected position and the reference position.

Mold protection method for mold clamping apparatus

Gas (air) is supplied into an oil transfer line extending between a front oil chamber of an injection cylinder and an oil tank during a molding cycle, excluding an injection step, thereby preventing impact which would otherwise occur due to oil pressure generated upon start of injection in the injection step. Thus, immediately before the start of the injection step, the oil transfer line becomes empty of or almost empty of oil. Accordingly, even when high-pressure oil is supplied into the injection cylinder in an impactive manner upon start of injection, pressure oil ejected from the injection cylinder flows swiftly through the oil transfer line.

Method for preventing occurrence of impact pressure in injection molding machine

An injection molding method for an injection molding machine in which molten resin in an injection barrel is injected and charged into a cavity of a mold through advancement of a screw in order to form a thin molding product. When the screw reaches a first set point that is set in advance and corresponds to completion of charge during the advancement of the screw, the screw is immediately and forcibly retracted to a second set point that is set in advance. With is operation, when the screw reaches the first set point X1 corresponding to completion of charge during the advancement of the screw, the internal pressure of the cavity is relieved quickly. Therefore, the cavity, which has deformed due to high pressure resin, is restored to its designed shape before the resin solidifies.

Injection molding method for an injection molding machine

An injection pressure is detected as a pressure detection value Dp during injection and filling, and the thus obtained pressure detection value Dp is multiplied by a preset predetermined coefficient so as to be converted into a desired mold clamping force Fc with which the mold clamping force is controlled. The desired mold clamping force Fc is set to a minimum value which a mold does not open, that is, the desired mold clamping force Fc is calculated with the use of Fc=(.alpha.*S*.beta.)Dp, where .alpha. is a charging rate of resin in a mold cavity, S is an entire projected area of a molding article, .beta. is a safety factor, and Dp is a pressure detection value Dp. With this arrangement, in a section where the injection pressure gradually increases from zero during injection and filling, the profile (variation curve) of mold clamping force gradually increases as the injection pressure varies. At this stage, the mold clamping force during injection and filling is set to a minimum value with which the mold does not open so that the power consumption can be minimized.

Method of controlling mold clamping force for injection molding machine

An improved injection molding method comprising, tightening an injection molding die with a die tightening force lower than that corresponding to a conventionally rated pressure, injecting a molten resin in a die cavity with an injection molding pressure of which intensity is determined corresponding to the die tightening force so that a gap is formed so as to permit only gas to flow outside of the die cavity via the gap, after completion of injecting temporarily interrupting injection molding so as to release a part of the injection molding pressure from the die cavity so as to maintain the reduced injection molding pressure in the die cavity in the uniformalized state, and raising the die tightening force up to a level corresponding to the rated pressure, and moreover, raising the injection molding pressure in the die cavity. Since a molten resin is injected in the die cavity with a low intensity of injection molding pressure with a low corresponding die tightening force, and moreover, the injection molding pressure is held in the die cavity in the uniformalized state before it is retained in the die cavity, a molded article having a small thickness and a large projected area can easily be produced without any occurrence of a malfunction such as warpage or the like.

Growing community of inventors

Nagano, Japan

Masahiko Miyajima