Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1995-11-22
1999-05-25
Heitbrink, Tim
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264 407, 425149, 425150, 425152, B29C 4577
Patent
active
059067772
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an injection molding control method intended for speeding and stabilizing an injection molding cycle by controlling injection pressure in accordance with the mold clamping force and the mold clamping condition so that any excessive mold clamping force will not be applied during the injection process.
BACKGROUND ART
In an injection molding field, when mold closing operation in mold clamping process is completed, a mold clamping force durable to the entire injection processes including a hold pressure process is applied to a mold, and thereafter, a molten resin injecting operation is started. As a result, a movable side mold and a stationary side mold are kept firmly pressed against each other at the initial injection stage, so that gas breathing from a mold cavity becomes poor. This sometimes entails the hindrance to a filling operation of the molten resin or a molding failure such as a burn of the molding. Also, since it is necessary to start the injection operation after completing the mold clamping operation, the speeding of the molding cycle has been limited. Such a problem caused by the gas breathing fault can generally be solved by providing a gas vent in a mold. However, there is a dilemma as follows; if the gas vent is carelessly provided in the mold, burrs may be formed when a high holding pressure is applied to the mold, and, in the case where a wall thickness of the molding products is relatively large, a sink mark may occur unless a holding pressure is applied.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an injection molding control method, which is capable of preventing defective molding caused by gas breathing fault, synthetically shortening time required for clamping and injection processes, and reducing the causes of burrs and sink marks of products.
To achieve the above object, according to one embodiment of the present invention, in executing mold clamping and injection operations, in a period between mold touch and clamping completion in a mold closing process, an injection start timing and a clamping speed are preset so that the sum of a resin pressure acting on parting plane of a mold cavity will not exceed clamping force outputted at the point of time at which the sum is calculated.
According to another embodiment of the present invention, in executing mold clamping and injection operations, in a period from a mold touch until a clamping completion in a mold closing process, an injection start timing and either an injection pressure or an injection speed are preset so that the sum of a resin pressure acting on a parting plane of a mold cavity will not exceed clamping force outputted at the point of time at which the sum is calculated.
Preferably, the aforesaid injection start timing is set on the basis of any of an elapsed time starting from the mold touch, feed of a movable platen, extension of a tie bar or mold clamping force.
The present invention, with the above-described constitution, enables an injection operation to be started during the period in which mold clamping force is relatively low within the period between the mold touch and the clamping completion. Therefore, even if a gas vent is not provided in a mold, gas can be released easily from a mold cavity, so that the failure of resin filling or burning can be prevented. Also, the clamping and injection operations are carried out overlapping with each other, so that time required for clamping and injection processes can synthetically be shortened; as a consequence, a molding cycle can be performed at a higher speed. Moreover, there is no need of providing a gas vent in a mold, and the molds are firmly pressed against each other after the completion of the clamping, so that no resin leakage occurs, thereby preventing sink mark from forming in the portions of products with large wall thickness by applying a high holding pressure to the resin.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing main parts of an electric
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Hosoya Yuichi
Kamiguchi Masao
Uchiyama Tatsuhiro
Fanuc Ltd
Heitbrink Tim
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