METHOD FOR INJECTION MOLDING PLATE-LIKE PRODUCT HAVING RECESS OF EXTRA-THIN BOTTOM THICKNESS

摘要

PROBLEM TO BE SOLVED: To excessively thin a recess bottom of a plate-like product by complementing an unfilled part generated from a difference of a flowing speed of a resin flow due to a core from a downstream side of a recess with an excess resin generated by a compression. SOLUTION: A method for injection molding the plate-like product having a recess of an extra-thin bottom thickness comprises the step of movably projecting the core 3 compression molded in an extra-thin recess, at one side of an inner surface of a plate-like body 10 in the cavity 2 except a compression margin of 2 to five times as large as a thickness of the recess bottom. A gate 4 is provided at a center of a cavity side opposed to the core 3. The resin 4 is injection filled toward the core of a side gate 4. The method further comprises the step of preceding injection molding of two corners of an upstream side by utilizing a flowing resistance of the core 3. The method also comprises the steps of stopping the injection filling of the resin 5 when the downstream side of the recess primarily molded by the core 3 and centers of both sides of a cavity end exist flowing spaces 6, 7 in an incomplete state. The method also comprises the steps of compression molding the recess bottom in an extra- thin thickness from the core 3 in this state, simultaneously extruding excess resin of the recess to the spaces 6, 7 to extrapolate the resin of the uncompleted part.