Monitoring of Casting Quality Using Principal Component Analysis Based Self-Organizing Map

The monitoring of casting quality is very important to ensure the safe operation of casting processes. In this paper, in order to improve the accurate detection of casting defects, a combined method based on Principal Component Analysis (PCA) and Self-Organizing Map (SOM) is presented. The proposed method reduces the dimensionality of the original data by the projection of the data onto a smaller subspace through PCA. It uses Hotelling’s T2 and Q statistics as essential features for characterizing the process functionality. The SOM is used to improve the separation between casting defects. It computes the metric distances based similarity, using the T2 and Q (T2Q) statistics as input. A comparative study between conventional SOM, SOM with reduced data and SOM with selected features is examined. The proposed method is used to identify the running conditions of the low pressure lost foam casting process. The monitoring results indicate that the SOM based on T2Q as feature vectors remains important comparatively to conventional SOM and SOM based on reduced data.

A Computational Study on Novel Runner Extension Designs via 3D Sand-Printing to Improve Casting Performance

3D sand-printing (3DSP) has become more popular in foundry applications due to its ability to create complex gating geometries. Since filling related defects, like entrained air and bi-films, are most commonly caused by high melt velocity and turbulence, recent 3DSP research has focused on designing gating systems to reduce melt velocity and turbulence. However, there have been no reported efforts on advancements in the design of runner extensions as a method to improve casting quality, despite its tremendous impact on the initial metal flow characteristics. The ability to fabricate 3DSP molds allow for unique runner extension designs that aid in improving casting quality. This paper is the first study known to the authors that investigates novel 3D runner extension designs to determine the most effective design for reducing sand casting defects. Based on literature review and design principles developed for 3D sprue geometries, six different runner extensions were studied using Computational Fluid Dynamics (CFD) modeling for foundry pouring conditions. The designs were evaluated on their ability to reduce defects like entrained air and bubbles, as well as to prevent backflow and reflected waves. An unweighted ranking matrix and comparison matrix against the control (straight runner extension) has been established based on air entrainment, tracer, voids, and extension volume. The results showed that the by-pass principal and surge control systems are effective at reducing reflective waves and controlling the ingate flow. The novel 3D duckbill trap extension proposed in this study had the best overall performance based on a 16% reduction in entrained air and a 71% reduction in void particles in the casting volume compared to the control extension design. These results provide a framework to further optimize runner extensions, utilize the advantages of 3D Sand-Printing technology to improve mechanical strength and reduce filling defects in sand-casting.

SUITABILITY OF MOULDING MATERIALS FOR Al-Li ALLOY CASTING

The paper describes the production of an AlSi7Mg cast alloy with Li additions and the reactions of the melt with different moulding materials. It is known that Li is very reactive and tends to form various reaction products such as oxides, gases, etc., which can influence the casting quality. The aim of the research was to find a suitable way to produce such an alloy and to describe the reaction products that are formed between the melt and the moulding material and thus to find a suitable moulding material for processing Al cast alloys with Li additions. The melt was produced in an induction furnace under an inert atmosphere. After melting, 1 w/% Li was added and the melt was cast into five different mould materials consisting of graphite, steel, a CO2 sand mixture, Croning mixture and calcium silicate materials. In the last three cases, various alcohol-based coatings were also used, such as graphite, zirconium oxide-graphite coating and aluminate-graphite filler coating. The results showed that the reaction products in the form of powder on the casting surfaces and the gas porosity in the castings occurred in the cast of a calcium silicate mould and sand mould mixtures. In the case of graphite and steel moulds, the casting surfaces were not oxidised, with no reaction products, and no gas porosity.