How To Optimize The Mold

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-05-24 11:12

Die casting is a molding process for the serial production of workpieces made of aluminum, zinc, magnesium, copper, lead, tin and their alloys. The casting process takes place in die casting machines, which are divided into hot chamber and cold chamber casting machines. The main difference is that the container with the molten metal is located in the machine in hot chamber casting machines, in the other case outside of it. In both types of machine, the molten metal is pressed from a casting chamber via one or more pouring channels into the hollow space of a steel permanent mold, where it takes on the shape given by the mold and solidifies. So that the casting can be removed from the mold, the die casting molds consist of two halves. The mold half on the sprue side is mounted on the rigid side of the die casting machine on a fixed platen, the mold half on the ejector side on a movable plate. The halves are sprayed with a release agent before closing so that the cast part can be easily removed from the mold later and the plates do not overheat. Depending on the size of the cast parts, up to 300 casting cycles per hour can be carried out.

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Extreme stress in the process

When the mold is closed, the melt is pressed into the mold under a pressure of up to 1200 bar, reaching mold filling speeds of up to 150 m / s (540 km / h). Large clamping and locking forces are required to press the mold halves together and to keep the molds closed: up to 8000 kN work in hot chamber casting machines, up to 45,000 kN in cold chamber casting machines. Large-scale castings can be produced with such great forces. The molds used for this must be designed in terms of materials and construction in such a way that they can withstand the loads associated with large quantities of melt. Once the metal has solidified, the mold halves open and the cast part is ejected by bolts or removed by a robot and transported for further processing.

Euro cast 2020

Die casting industry meets in Nuremberg

High performance steels for tools

The shape is of central importance for the die casting process. It specifies the contours that are transferred to the casting and is also intended to help the casting to solidify as quickly as possible. This promotes the formation of a fine-grained structure, which benefits the cast part quality. In order to achieve optimal cooling, the molds are cooled at certain points.

The structure of die casting tools is described in the DIN 16760-1 standard. In addition to the shapes mentioned, they also include mold inserts, cores, sliders and ejectors. In order to withstand the high thermal and mechanical loads, they are made from high-strength hot-work steels such as X40CrMoV5-1 (1.2344) or special materials, such as hard metals. Properties that play a very important role in these tools are high wear resistance, high ductility, high heat resistance, high resistance to hot cracks and hot wear as well as good thermal conductivity. When selecting the materials, in addition to their technological properties, the design of the tools,their heat treatment and last but not least the complex interaction between the tools and the metal to be cast are taken into account. Molds for die-cast zinc, for example, have a service life of 500,000 to two million cycles.

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Extend the life of die casting molds

Simulations optimize the shape

In the past, tools for die casting technology were manufactured according to drawings, today designers work with 3D CAD data and use modern IT technologies. When designing molds, the casting process - and thus the melt flow and cooling - as well as the geometry and dimensions of the die-cast parts to be manufactured must be taken into account. The cast parts should be characterized by a uniform, fine-grained structure, high dimensional accuracy and dimensional accuracy and a high surface quality. Computer-aided simulation calculations help to design the tools optimally for the respective casting. Tool and mold makers use CAM systems for production. The shaping contours are worked into the molding material with high precision by CNC-controlled milling machines as well as sinking and cutting EDM machines. The production of the molds is very complex and therefore expensive. The tool accounts for up to 20% of the cost of a die-cast aluminum workpiece. For the production of components in large series, however, from a certain batch size, this is more cost-effective than producing the parts in another way, for example by machining processes. In addition, the manufacturing time for each part is shorter.than producing the parts in a different way, for example by machining processes. In addition, the manufacturing time for each part is shorter.than producing the parts in a different way, for example by machining processes. In addition, the manufacturing time for each part is shorter.

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Optimize casting quality

Additional information on the subject of the Euroguss 2020 trade fair

The Euroguss 2020, international trade fair for die casting, which takes place in Nuremberg from January 14 to 16, gives an insight into the entire die casting value chain. All important die casting foundries and their suppliers are represented among the exhibitors. There are also offers for post-treatment of castings, quality assurance, control and drive technology, rapid prototyping and software.

The topic of additive manufacturing is taken up in the "Additive Manufacturing" pavilion. The special show offers an ideal platform to deal extensively with this manufacturing technology and to discover its potential for die casting foundries.

The winners of the die casting competitions for aluminum, zinc and magnesium will also be announced at Euroguss. The awards recognize innovative die-cast parts. The aim is to highlight the variety of applications for the materials as well as the performance and innovative strength of the participating die casting foundries.

The 20th die casting day will take place parallel to the Euroguss. International die-casting experts meet here over three days to discuss new technologies and process and material developments.

Integrate 3D printing

The creative diversity of die-cast parts and the demands placed on them are constantly growing. This also increases the requirements for the properties of the tool steels used for die casting and the structural design of the tools and molds made from them. 3D printing can be a solution. Die casting molds or parts thereof, such as cores and sliders, must be cooled so that the cast die cast parts solidify as quickly as possible. Additive processes can be used to manufacture complex-shaped inserts for die casting molds, in which close-contour, curved cooling channels are integrated. This benefits the quality and economy and does not put excessive strain on the molds. (qui)