Why precision injection molding is difficult?
Injection molding:
it is an injection molding method. The injection molding method has the advantage of production speed, high efficiency. It can realize automation operation, breed of design and the color is much, can shape by Jane to numerous. It can from big to small size, and precise in dimension and product upgrading. Can into complex shape parts. Injection molding is suitable for mass production with complex shape products and processing fields.
After a product is designed, usually by an industrial designer or an engineer. Molds are made by a mold maker (or toolmaker) from metal. Usually, either steel or aluminum and precision-machined to form the features of the desired part. Cost savings are highest when components have a minimum wall thickness. As long as that thickness is consistent with the part’s function and meets all mold filling considerations. As would be expected, parts cool faster with thin wall thicknesses. This means that cycle times are shorter, resulting in more parts per hour. Further, thin parts weigh less, using less plastic per part.
On average. The wall thickness of an injection molded part ranges from 2mm to 4mm (.080 inch to .160 inch). Thin wall injection molding can produce walls as thin as .05mm (.020 inch). Injection mold tooling is a very specialized profession requiring highly skilled engineers to create the injection mold tool.
Precision injection molding:
It is to point to the precision of molding parts and surface quality requirements are a very high process. Also, some people think, precision injection moulding is the plastic part of the size accuracy to achieve 0.01 ~ 0.001 mm injection molding process. In recent years, with electronic, medical, communications, automotive, and other industries. With the rapid development of plastic products of high precision, high-performance requirements increasing. The traditional plastic molding process has been difficult to meet the requirements of the current high standards. At the same time, injection molding is one of the most important plastic molding methods. Therefore, precision injection molding technology is getting more and more get the attention from people, make the precision injection moulding technology constantly progress, new technology constantly emerging.
Precision injection moulding for products not only has high dimensional precision, lower buckling deformation, good transfer characteristics. But also should have excellent optical performance and so on. Therefore, it is for injection molding machine, mold, injection molding technology, performance and the formula of raw material and so on all have special requirements, there are many factors which can affect the precision injection moulding.
According to the current actual production, the difficulties in precision injection molding mainly include the following aspects:
1) Shrinkage of plastics: Shrinkage of plastics should be considered when designing precise plastics products.
(2) Shape and size of products: The shape and size of plastic parts have a great influence on the precision of products. Production practice shows that the more complex the shape and size of products are, the lower the precision will be.
(3) Mold structure: The precision of injection parts is closely related to the number of mold cavities and production batch. It also shows that the precision of a single-cavity mold structure is higher than that of a multi-cavity mold structure, and the precision of small-batch production is higher than that of large-batch production.
(4) Mold processing accuracy: Because the injection products must be molded in the mold cavity. The precision of the products will not exceed the precision of the mold cavity in any case. In general, injection products accuracy than the molding accuracy of one or two tolerance grade. As far as mold manufacturing technology is concerned. The mould cavity is mostly made by high-speed milling, grinding, polishing, or electric machining.
(5) Injection molding machine: Due to precision injection molding products have a higher precision requirement. Therefore, they generally need to be carried out in a special precision injection machine. The injection power of the precision injection molding machine should be large, the control precision should be high, the response speed of the hydraulic system should be fast, the mold closing system should have enough rigidity.
Selection of precision injection moluding materials:
Plastic molding shrinkage rate fluctuation is bigger. In addition, different varieties of plastic, because of the polymer and additives used in different kinds and their performance in injection molding of the flow properties and forming performance will have a big difference. Because of injection molding manufacturers, factory season, and environmental condition factors. Such as injection molding of products with them also exist between the question of whether or not too stable size and shape.
Therefore, precision injection moulding plastic in addition to the requirements of good flow and molding performance. And molded products can have shape and size stability. Otherwise, the accuracy of the product is difficult to ensure. Therefore, when injection molding precision plastic products, it must be on the plastic variety and its molding properties in the consideration of life. As far as possible to choose small shrinkage, long-term stability of good materials.
