Considering that the number of heads of the worm is 4, the lead angle 36.53b is larger than the maximum lead angle 3.5b under self-locking conditions, and the demoulding can be directly rotated. If the gear is placed on the fixed mold side, the ejector pin pushes the gear piece to drive the worm to release the mold. Here, the diameter of the worm core is limited, and the ejector pin cannot be added.
Therefore, the method of flipping is selected, the worm is placed on the fixed mold side, and the gear and the intermediate shaft are placed on the movable mold side. When the mold is opened, the split mode displacement between the fixed and fixed molds is automatically rotated by the plastic part to drive the worm core. mold. The mold structure is as shown.
The mold opening process of the mold is as follows: after the injection machine completes the injection, pressure holding, and cooling, the mold is opened under the parting surface as shown, and the locking block 30 is separated from the two symmetrical sliders 33, and the slider 33 Under the traction of the inclined guide column 34, the two sides are divided into a top view.
In the parting process, due to the frictional force of the worm cavity 26, the movable mandrel 17 and the plastic part 21, and when the opening displacement is smaller than the length of the worm, the slider has not completely separated from the maximum diameter of the gear piece, so in the process The piece is glued to one side of the movable mold, and the worm on the side of the fixed mold is subjected to the pulling force of the movable mold portion, and the hydraulic ejection mechanism of the injection machine pushes the upper ejector plate 10 to eject.
In order to avoid this, the movable mandrel 17 is made of 65Mn and heat treated. One end of the shaft is inserted into the hole of the fixed core 25 to increase the strength of the mandrel. The bearing 27 and the bearing 28 are used to reduce the frictional resistance when the worm cavity is rotated, and to reduce the deformation when the worm is demolded. The worm cavity is controlled by CNC electric discharge machining or by electroforming. The cavity is required to have a good finish and reduce the frictional resistance during demolding.
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