Molds are the main elements in the production of metal, plastic and other parts. They determine shape of the structure of manufactured objects. The quality of the final product depends on the accuracy of mold settings.
Mold is an element for forming products of various designs from plastics, rubber, metals and other raw materials under pressure generated on foundry machines. This is a base that repeats the contours of the finished object, which is filled with molten material.
Molds are used during injection molding of metal and plastic details and for molting models, as well as for pressing polymers. Due to the rather high price, they are most often used for mass and serial production.
Molds consist of parts, which are conventionally divided into two groups. The first is represented by elements of technological purpose (working elements). They come into contact with recycled raw materials and are directly involved in giving products the desired shape. These include punches, dies, support bearings, threaded marks.
The second group includes details of constructive significance. When forming products, they do not come into contact with the material. Designed to ensure the operation of the elements of technological purpose and are necessary for the mutual fixation in a certain position of the parts of the form, closing and opening it. They are also crucial for direct contact with the closing unit of the mold of cast equipment. These include clamps, ejectors, guide columns, bushings, support bars, heating and cooling system, mold handles.
Classification of types of molds.According to the principle of operation of the mold, they are divided into:
Direct pressing. Used to develop objects of simple shape. Due to the high cost of production they are not used for the manufacture of large batches of products. The design of mold includes a matrix on which raw materials are laid out, and a punch for its consolidation. The material sandwiched between the two elements thins and fills all the recesses of the form.
Injection molding. The main advantage is the ability to manufacture large batches of products of different configurations and complexity. Before pressing, they are in a closed state. Filling of raw materials in them is carried out by means of the separate loading chamber (top or bottom).
By the nature of use: removable and stationary. Forms of the first type in the process of forming products are not fixed on the plates of foundry machines and are periodically removed from them in order to obtain finished products. Stationary molds are more common than removable ones. Filling of material in them, and also extraction of the made products is carried out without need of their removal from a plate of the automatic machine for molding.
By the location of the connector plane: with vertical and horizontal surface. Forms with one vertical surface are equipped with a connector into two parts (punch and die) in one surface, which is perpendicular to the horizontal position of the closing force. Containers with two vertical surfaces have a connector of three parts in two surfaces.
In molds with a pair of horizontal surfaces, a connector is formed in three segments in two planes, which are perpendicular to the vertical location of the force of the closing unit.
By the number of simultaneously formed objects:B single- and multi-cavity. In the first one product is formed in one cycle of casting, in the second – in several.
According to the method of removing the finished products: with ejection pins or rods, without a piston and with a contact plate. From molds of the last type, objects are removed, by the compressed air or manually. Ejection liners during molding partially or completely form a certain surface of the product, and during ejection - press on it until they fall out of the mold. Ejecting rods during the extraction of the object press only on its individual part.
Running system - is an element of the design of the mold through which the liquid material is fed into the cavity for casting. When using a cold runner system, the spout does not heat up. When the formed casting is cooled, it cools and then falls out of it during or after opening the mold. Products with a cold runner system are reliable, low cost, easy to use and maintain. But often these advantages are overshadowed by the only drawback - the presence of unnecessary castings after each casting cycle.
When using molds with a hot runner system, the spout is molten. The system is heated before the mold is put into operation, and during the entire production cycle the material in the gutters is maintained in a viscous state.
Molds with hot runner system are characterized by high cost and difficult design, require high energy consumption and intensive cooling, are difficult to maintain (there are breakdowns of heaters, the cavity of the hot runner sometimes gets impurities, burns heat-resistant polymer, etc.). The main advantage is the absence of hardened castings (although sometimes they are present), which fall out with the finished product at each casting cycle. This allows not only to save raw materials and prevent the generation of industrial waste, but also to use foundry machines with less injection, as well as to accelerate the cooling process of manufactured objects.
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