Detection of core and processing residues

Detection of core residues and metal chips by CT

Frequently, cores are used in the production of castings. They serve to provide the casting with the constructive cavities that are often of key importance for component functionality. Usually, the cores consist of a mixture of sand and binder. After the casting process is completed and the alloy has hardened, the cores are removed from the casting by means of various methods (e.g. shaking or removal by water jet). In some cases, however, the core cannot be removed completely. Depending on the cast cavities complexity and shape, core residues of varying size might remain inside the component, which might affect component functionality to a greater or lesser extent and – in a worst case scenario – can result in component failure. As an example we would like to mention the water chamber of a cylinder head, which serves for cooling of the component in adjacent areas. At Microvista, computed tomography can be used to digitalise castings suspected of containing sand residues in its cavities.

Detektion_von_Kernresten_gr

Detektion_von_Bearbeitungsresten_gr

In this process, core residues are automatically detected and – based on their differing grey scale values – their position and size (volume) is precisely visualised in a 2D/3D image. The data acquired during core residue detection by means of CT can be used by the foundryman for an optimal evaluation of component condition and for further decisions. In addition, the applied core removal methods can be optimised and cleaning tasks carried out subsequently can be improved to be more effective.

The same applies to processing residues, e.g. metal chips. Due to machining of the casting, these can lodge inside cavities and – like core residues – also result in problems or even failure. However, detection of machining residues is the more demanding task, because the metal chips are of the same material as the casting and are therefore rendered in CT images in the same or a similar grey scale value. Nevertheless, application of advanced CT evaluation software enables Microvista to detect single chips and chip accumulations and to make precise statements on their position and size.