The mold for die casting is composed of two half-molds in which the molten metal is injected. After opening the two mold halves, it is possible to extract the piece made.
Construction, materials and construction
The equipment is commonly known as mold, it die is typically made up of various elements, including matrices and "pins", or anchors, that contribute to the creation of the piece. There are also other mechanical elements most useful to the internal movements of the mold to allow the opening, adapted to the extraction of the piece, but also sometimes essential to obtain particular geometries of the desired object.
The constituent material of the molds for die casting is the steel, which has melting points higher than the injected material. Often, also, the various parts of the mold are made of different types of steel, in order to facilitate certain processes useful for the production of the mold itself, as well as, in particular as regards the parts in contact with the molten metal, are subject to treatments temici to resist better at high temperatures.
To provide a mold for die-casting is required a laboratory equipped with technologically advanced machinery for milling, and now also of other machinery which enable precision machining very high (in the order of hundredths of a millimeter) and are based on technologies such as' EDM. Almost all the tool paths that produce the forms, the dowels, and almost the entire mold for casting, are nowadays designed with the aid of computer and dedicated software. The tool paths are, in fact, sent directly from computers to machines, where operators will take care to implement them and make sure that each job is done properly.
Design and engineering
In the design, the first stage of the realization of a mold for die-casting, it is very important to pay attention to that there are no cavities which may complicate or prevent the extraction of the piece. In particular it is necessary to avoid "undercuts". It should also be taken into account that it is necessary there are draft angles, namely that there are no walls completely vertical, but a certain "conicity" is always guaranteed to, precisely, to facilitate the extraction of the castings.
Always at the design stage it is necessary that we will evaluate the values of weight, pressure, cooling time and many other variables. It should be considered that it is always good there are areas in the massive piece to obtain melting, that is, parts of the object much larger than all the others, because this certainly creates problems of non-uniform cooling of the piece. Other problems that may be encountered, and stay connected to the variables just explained, can be total failure to fill the void from which we get the object melt, or the presence of bubbles or undertows of gas in the jet obtained. To overcome these problems, working on "risers", that is, of the areas of filling of the molten material that are not part of the object to be achieved but have the sole purpose of facilitating the entry of the material in special cavities of the piece, and on outbursts, which similarly have the task of collecting gas and material, apparently surplus, but without which probably would not get a full and good enough, filling piece. In this sense, the engineering of the molds has made a significant step forward with the introduction of software which simulate the fusion and through which and easier to process the path or the mechanical solutions appropriate to obtain castings of quality and at the same time efficient.
Compared to the mold of foundry earth, the mold for die casting may submit thicknesses much thinner, in consequence of a more easy filling due to high pressure. Conversely, the removal of the piece from the mold for die casting is more complicated, since there can be more than two half-molds: the mechanics of the mold for die-casting makes sure that the opening of the hydraulic press, the part is integral with the part "mobile" of the mold, and that, often thanks to the mechanical punches, the piece is extracted from the mold.
A final consideration on the properties and possibilities offered by the casting is that, unlike other fusion systems is possible, for example, enter the "souls" or "serpentine" plants that will be "sunk" into becoming an integral and indivisible part of same.
The modularity of the molds also allows the replacement of some components in consequence of wear or breakage, in this way it is therefore possible to obtain an apparatus always in excellent condition, which results in the continuity of production and saving on high costs to produce a new mold replacement. This does not mean that, for very large production batches, is nonetheless not more profitable to produce in series several identical molds and initiate the die casting in all molds "twins" of different presses.
The die-casting molds are designed and built to withstand the temperatures and pressures in the melt phase. Precisely for this purpose, often in die-casting, the final pieces that are obtained from each "printed" of the equipment are more than one. This solution, typical of small pieces or whose production does not present any particular problems of filling, allows high levels of productivity.