Production of pressmolds
Pressmolds are intended to shape composition and size of the particular configuration of the product out of specific amount of rubber. Our molds are intended to manufacture the so-called molded general mechanical rubber goods – rings of different cross-sections, collars, bushings, covers. Due to the powerful tool-making facilities, all necessary components of molds are made within the enterprise.
Pressmolds for the molded mechanical rubber goods manufacture are classified by a number of characteristics.
The first characteristic is the process of manufacturing. Mechanical-rubber industry uses methods of compression molding (compression method), high-pressure casting and transfer molding.
The difference between these methods is substantial.
The compression molding: rubber compound is put into open mold and is compressed and maintained at a certain temperature and pressure until full cure.
The transfer molding: specific amount of rubber compound is put into the loading chamber and heated and extruded into closed mold.
High-pressure casting: the rubber compound is extrudedfromheating cylinder through runner pipe into closed mold. It defines specific requirements for the design and molds manufacture.
Another criterion of classification is operational features.
Operational features of the molds are divided into hand tool, powered crossing hand tool and fixed press mould.
Hand tool molds are molds which are removed from the press to extract the cured items and place bars and blank parts.
The division of the molds is made with the help of pressing devices or reloading mechanisms. Fixed press moulds (or their separate plates) are rigidly connected to the heating plates of the press.
Division of the hand tool molds is made with the help of press.
According to design features, molds are devided into unilocular and multilocular.
According to the way of opening, molds are devided into molds with vertical, horizontal and combined division.
The amount of division planes depends on the design of the mold and the item.
Molds with one horizontal division are called two-plate press, molds with two horizontal slots are called three-plate press etc.
There are multi-plate presses or stacked molds, they serve for the production of simple goods, which are produced with only one division plane.
Pressmolds for high-pressure casting
The condition of successful foundry machinery usage is the correct calculation and design of injection molds. The design data of casting machines, features of molded articles and properties of rubber compounds should be taken into account.
Injection molds for rubber goods manufacture are classified according to the following features: connection with the machine, the location and number of connectors, the number of slots, the way of filling with the rubber compound, the degree of automation of the mold.
According to the connection with the machine, molds are devided into fixed press molds (the whole cycle of the products is performed on the machine), and hand tools (the details, such as matrix, lining, center hub are removed after each cycle to extract full cured items).
According to the location of planes, connectors are devided into: horizontal (the planes of the mold and the heating plates are parallel); a mold with combined connector (additional connectors are required for the manufacture and extraction of items with complex configuration). Generally, multiple cavity molds for high-pressure casting are distinguishedby runner system.According to the number of cavities, molds are devided into one-cavity molds and multiple-cavity molds.
Modern presses for high-pressure casting is characterized by a high level of automation. It can significantly increase productivity by facilitating of the molds opening using provided complementary mechanisms.
The rubber compound goes from the heating cylinder through the mouthpieceshot for pressure rubber casting in molds for high-pressure casting . The main feature of such machines is the automatic saving of the amount of rubber compound in the cavity mold. It is achieved not due to the accuracy of subproductweight quantity, butdue to the disposable setup of time and injection pressure with wide control range.
In comparison with compression molding, high-pressure casting is used under more favorable conditions. The closed mold is filled with the rubber compound. The rubber compound at a temperature of 80 - 140 ° C has a significantly lower viscosity. The molds are fixed, and injection molding machines are equipped with devices for goods extraction without damaging the surface of the mold.
Compression press molds
Compression press molds are used for the manufacture of goods with relatively simple configuration and low altitude, such as rings of various cross-sections, bushings, shock-absorbers, seals and some kinds of dust guards.
These molds are characterized by exposed cavity mold, the workpiecе is placed directly into the matrix. The design of these molds is usually simple.
However, the disadvantage of these molds is unguaranteed monolithic part and large volumes of rubber compound waste (casting material).
Removable plate molds
Removable plate mold is a variety of molds for compression molding. They may be removable or fixed. Removable plate molds are used on presses, they are equipped with rechargers (mechanisms, ensuring the opening of molds). fixed press mould are automatically opened when the press opens due to rigid attachment to the heating plates of the press.
Typically, removable plate molds are multilocular. That significantly contributes the increase in efficiency by placing sets of similar products on the same plate.
Removable plate mold is a steel plate (two for two-plate press, three for three-plate press). Holes for cavity mounting (matrix, movable dies, holder blocks) have boring line. The number of holes and their bores corresponds to the number of cavities.
To provide bar plate assembly after the workpiece placement they are equipped with pilot bushing and subpress. Bar molds with one joining plane are easy-to-use, their plates are kept together by pin joints, which let rotate the upper plate against the lower one at an angle of 70° in order to recharge, inspect and clean the cavities.
Bar molds have grippers for placing the whole mold into press and back, and also special keys on the upper plate with the help of which initial mold opening is performed in the process of its extraction from the press.
Implementation of bar molds in the manufacture of molding GMRG with mechanisation of their recharger is quite effective while producing armoured collars, rinds and other items. Usage of bar molds increases the extraction of production from equipment due to increase of cavities and mold recharge time reduction. Also mold plate area usage factor is increased, and thermal loss is decreased.
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