The foundry ETA d.o.o. in Cerkno, Slovenia, belongs to the E.G.O. group and produces grey iron parts using alloys EN-GJL-150 to EN-GJL-300 from 0.1 up to 50 kg on horizontal molding lines. Stove hot plates in different sizes belong to their major products. To cast these types of parts, it is necessary to keep the alloy composition within reasonable tolerances, control the quality of the sand and design a proper gating system in order to fill the castings smoothly and homogeneously.
A poorly designed gating system for these kinds of castings can easily lead to a high scrap rate (up to 75%), as the whole surface will typically be machined. This means no defects such as sand inclusions or blowholes are acceptable. Therefore, the main target in designing a proper gating system is to keep metal velocities and related turbulence as low as possible.
When the foundry started producing a new hot plate with a 360 mm diameter and a thickness of 5 mm, ETA ended up with substantial quality problems. Many parts had to be rejected because of sand inclusions and blowholes.