Production of molds from cold-setting mold materials without physical pattern. This is a basic technology for the production of large molds and castings that is derived from rapid prototyping.
By “direct mold milling”, mold segments with dimensions that clearly exceed the known dimensions of laser sintering systems are produced. Currently, systems for mold segments with external diameters of up to 3.5 x 2.2 x 0.8 m are in operation. Also in this process, time and cost-intensive production of pattern facilities is prevented and the mold is directly milled into a mold material block. The size of the produced casting molds is only limited by the mechanical strength of the applied mold material, the available milling equipment and the casting capacity (Video 1).
Video 1:Direct mold milling (ACTech GmbH, Freiberg/Sa., Germany)
The molds and cores are designed based on the CAD data of the casting. In this process, potentially required cooling dies, risers, filters, ceramic inserts, handling tools, reinforcements, runners and sections are included to create a virtual mold as template for machine programming. The massive or pre-formed mold material blocks are then processed with special equipment. The result is a mold that has been processed with machine accuracy for quick and easy installation.
The basic material is a cold-setting mold materials which is not subject to any restrictions. This means, the original molding material can be used that is usually used in the foundry. The combination of various mold sands and binder systems is also very common and can partly be easier implemented than in pattern-based processes. Further options are chromite inserts for the sprue or special mold sections to modify the cooling behavior.
No pattern deforming is required. This means that no deforming-related inclinations are required and considerably more sophisticated geometries without additional separation can be realized. This usually reduces the required number of cores and the effort for cleaning and mechanical treatment.
The combination of milled mold parts or cores with conventional mold segments further extends the application range in such a way that variants of parts, which are documented by means of a data record, can be produced quickly and cost-efficiently even on already existing pattern facilities.
Direct mold milling perfectly lends itself for the production of large-surface car body structures for later series production, e.g. as die cast parts. Another example for the application of this new technology is the production of tailor-made unfinished castings to considerably reduce the processing time for pressing tools.