Home / News / Industry News / What are the characteristics of the incision and insert of the blow mold

Industry News

What are the characteristics of the incision and insert of the blow mold

The die portion of the blow mold should be a sharp cut to facilitate cutting the parison. The Z minimum longitudinal length of the jaw for cutting the parison is 0.5-2.5mm. If it is too small, it will reduce the thickness of the joint seam of the container, reduce its joint strength, and even easily cut the parison without blowing it up. If it is too large, the tail cannot be cut off. material, even the mold cannot be fully closed. The shape of the incision is generally triangular or trapezoidal. In order to prevent the wear of the incision, the cemented carbide material is commonly used to make the inserts tightly on the mold. The angle of the end of the incision expanding to the surface of the mold varies with the type of plastic. LDPE can be 30° to 50°, and HDPE is 12° to 15°.

The opening and closing of the mold is usually controlled by compressed air, and the closing speed can be adjusted to meet the requirements of different materials. For example, when processing PE, the mold closing speed is too fast, and the incision is easy to cut through the parison, so that the parison cannot be well welded. This needs to establish a balance between speed and clamping action, so that the clamping part can be fully welded, and the flash is not difficult to remove. A tailing trough is opened under the blank clamping edge, which is located on the parting surface of the mold.

The depth of the tailing trough has a great influence on blow molding and automatic product trimming, especially for parisons with large diameters and small wall thicknesses. If the groove depth is too small, the tailings will be extruded by excessive pressure, and the mold, especially the clamping edge, will be subjected to excessive strain, and even the mold cannot be completely closed, making it difficult to cut the tailings; if the groove depth is too large, the tailings cannot be In contact with the tank wall, rapid cooling is not possible, heat is transferred to the joint of the container, softening it, and stretching the joint when trimming. (The depth of the tail trough of each half of the mold is 80% to 90% of the wall thickness of the parison.

The selection of the included angle of the tail trough should also be appropriate, usually 30° to 90°. When the width of the blank edge is large, generally Take the larger value. A separate insert is generally set at the bottom of the blow mold to squeeze and seal one end of the parison and cut off the tailings. When designing the inserts at the bottom of the mold, the blank-clamping knife and the tailing trough should be mainly considered. It has an important influence on the molding and performance of blow-molded products. The inserts of the neck of the molding container mainly include the die neck ring and the shear block. Wear of the small die neck ring. The opening of the shear block is conical, and the included angle is generally 60°. The die neck ring and the shear block are made of tool steel and hardened to 56-58HRC.