Botini is a manufacturer of machines and equipment, particularly for the food industry. The required castings are produced in its own foundry. In the foundry, further improvement of existing production processes is part of day-to-day business. The driving factors are quality requirements and costs. If production changes are made, the entire process chain must be analyzed and optimized with regard to the respective requirements. The initial situation for a gray cast iron “support” weighing 1.5 kg was as follows: Four castings each were produced in one mold level. Three mold levels were stacked upon each other. They were connected via the casting system to form the entire mold. This arrangement allowed pouring 12 castings simultaneously, with a yield of 73 %. One limiting factor was that the core elements required for stacking the levels were manufactured manually. The limited possibilities for achieving uniform and high-density compaction of the sand necessitated increased wall thicknesses to attain the required mechanical strength. The reproducible compactibility of the sand and the achievable mechanical strength limited stacking to no more than three levels (Fig. 1).

When designing the core box, it was soon decided that a vertically parted core box layout was the best solution. For the initial design, three larger shoot nozzles were evenly distributed. Thanks to the expertise of Automatic Foundry Solutions, core box vents were positioned in the same way (Fig. 2).

With MAGMA C+M, core shooting and core curing were calculated and evaluated for this first design. The core box design proved the basic feasibility of core shooting, but also revealed some weaknesses. Although completely filling the contoured upper area was possible, the sand compaction between the nozzles tended to be too low (Fig. 3).

During pouring, these differences in density would lead to surface defects in the casting or even to metal leaking from the mold in the event of breakage. The middle nozzle was dimensioned in such a way that the sand hit parts of the contour during core shooting, which would typically result in increased core box erosion (Fig. 4).

Positioning core box vents in such a way as to accommodate both core shooting and core curing is often difficult. In this case, while vents in the upper core box area supported the compaction of the sand in critical locations, for gassing, it was more important that catalytic amine also reached the lower core box areas as quickly as possible. A larger number of core box vents in the upper part of the core box prevented amine from efficiently reaching all areas located in the lower core box regions (Fig. 5). For core curing, a disproportionately large amount of amine and a relatively long gassing time were required.

After systematic testing of a number of simulation-led modifications, a compromise was worked out, leading to excellent shooting results, while also ensuring effective core gassing. The three large shoot nozzles were replaced by seven smaller nozzles. As a result, the sand in the mold was compacted more uniformly and with a higher density, especially near the shoot nozzles (Fig. 6). The smaller shoot nozzles also ensured that the core box surface suffered only minor erosive wear from the sand flow.

Reducing the number of core box vents in the upper area improved the amine flow throughout the core box. In a short time, amine could now also reliably flow through the lower core areas (Fig. 7).