Injection molds are an integral part of injection molding
. The number of cavities, gate positions, hot runners, design principles of assembly drawings and material selection of injection molds are introduced. Today, we will continue to introduce the design of injection mold exhaust system.
In addition to the original air in the cavity, the gas in the cavity also includes low molecular volatile gases produced by heating or curing the injection molding material. It is necessary to consider the sequential discharge of these gases. Generally speaking, for molds with complex structures, it is difficult to estimate the exact position of the airlock in advance. Therefore, it is usually necessary to determine the position through mold testing, and then open the vent slot. Vent slots are usually opened where cavity Z fills.
The exhaust method is to use the matching gap of the mold parts and open the exhaust groove to exhaust the air.
Exhaust is required for the molding of injection molded parts, and exhaust is required for demolding of injection molded parts. For deep cavity shell injection molding parts, after injection molding, the gas in the cavity is blown away. During the demoulding process, the appearance of the plastic part and the appearance of the core form a vacuum, making it difficult to demould. If the mold is forced to be demoulded, the injection molded parts are easily deformed or damaged. Therefore, it is necessary to introduce air, that is, to introduce air between the injection molded part and the core, so that the injection molded part can be demoulded smoothly. At the same time, several shallow grooves are processed on the parting surface to facilitate exhaust.
1. The formwork of the cavity and core needs to use a tapered positioning block or a precision positioning block, which is installed on the four sides or around the mold.
2. The contact surface between formwork board A and reset rod should be flat pad or round pad to avoid damage to board A.
3. The perforated part of the guide rail should be inclined more than 2 degrees to avoid burrs and burrs, and the perforated part should not be of thin leaf structure.
4. In order to prevent dents in injection molding products, the width of the steel bar should be less than 50% (40%) of the wall thickness of the appearance surface.
5. The wall thickness of the product should be the average value, at least a sudden change should be considered to avoid dents.
6. If the injection molded part is an electroplated part, the movable mold also needs to be polished. The polishing requirements are second only to the mirror polishing requirements to reduce the generation of cold materials during the molding process.
7. Ribs and grooves in poorly ventilated cavities and cores must be embedded to avoid dissatisfaction and burnt marks.
8. Inlays and inlays should be firmly positioned, and anti-rotation measures should be taken for the disc. It is not allowed to place copper and iron sheets under the plug-in. If the gasket is tall, the welded part should form a large surface contact and be flat.
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