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Metal Casting Technologies : March 2008
This is one of the reasons that SMEs involved in metal casting have not taken up cutting edge automation - most are "jobbing" shops, not operating high volume production lines, making investment in robotics for machining and assembly irrelevant. Programming time and investment in simple fixtures is simply not viable on small runs. Many of the smaller foundries also have reservations about introducing new technology because they believe they don't have adequate skills in-house. At the same time they are aware of the need to upskill in order to survive; to be able to provide more specialised and sophisticated services. Many in this situation are outsourcing these services as needed to fully meet their customer's requirements. This was one finding of a survey funded by the Queensland State Government and commissioned by the Australian Foundry Industry in QLD, in partnership with the Brisbane-based CAST CRC at the University of Queensland. Doug Harland last year completed the survey of Queensland's ferrous cast metals companies. What it showed was that all companies surveyed reported skills shortages, and this varied between both trades and professionals, with a critical shortage of metallurgists identified. Outsourced skills related mostly to electricians and cooling tower, furnace and crane maintenance service personnel - approximately $16.0m is spent each year by the industry on contracted labour. What it showed was that the skills shortage had resulted in escalated wage costs for electricians, welders and fitters, with annual base wages of $150,000 being paid in some mining related positions. One of the recommendations that came out of the Queensland survey was that solid modelling is an emerging skill that needs a strong focus, "as it is critical to the future of the industry", said the report. While some companies were actively running in-house training, all agreed the support of TAFE was critical, and the new Trades and Technician Skills Institute (TTSI) at Acacia Ridge was seen as a vital facility for Australian foundry training in the future. SOLID MODELLING Solid modelling software creates a virtual three dimensional representation of components for machine design and analysis, and has been more widely integrated by Australia's metal casting industry than in any other part of the world, according to Jeff Meredith from Casting Solutions. Agent for solidification software brand SOLIDCastTM, Meredith said, "During the 90's, those foundries doing run- of-the-mill type work realised they needed to specialise...and adopted solidification software. "At one point 15 per cent of total worldwide sales of SOLIDCastTM solidification software were in Australia." METAL Casting Technologies March 2008 29 Casting in three dimensions -- some of the advantages of solidification software According to Jeff Meredith of Casting Solutions, the use of solidification software is able to, within the space of a few minutes, create the adequate design and position of risers for feeding a casting, given a CAD file transmitted from the customer. This process provides more accuracy, in less time, than is achieved through traditional calculations. Starting with a CAD file, the alloy and mould material are selected and a simulation with no risers is run. With a few clicks of the mouse, the system then analyses the simulation results, calculates modulus values, and suggests the number and location of required risers. The details of each riser are then provided by calculations which embody riser design rules based on modulus and volume requirements. This approach could eventually replace current practices which vary widely throughout the industry. Some rely on experience and instinct, which takes the design process essentially into the realm of art. Others rely on calculations to determine riser size and location. The classical approach to estimation of riser size is to calculate the volume and cooling surface area of various parts of the casting. The ratio of volume to surface area (V/SA) is known as the modulus, and is generally expressed in centimetres. Regions of the casting which have the lowest modulus values solidify first, while those parts of the casting which have the highest modulus solidify last. According to Chvorinov's Rule, which has been in use for many years in the foundry industry, solidification time is proportional to the square of the calculated geometric modulus value. While these concepts are relatively simple and straightforward, their implementation in casting design is not. This is primarily due to the difficulty in calculating volumes and surface areas for complex, real-world castings. In recent years, computer simulation of the casting process using accurate three-dimensional models has become increasingly widespread. Such simulations can, in many cases, accurately predict the progressive solidification of the casting and its rigging system, along with the potential for formation of various casting defects. However, one of the significant drawbacks of casting simulation is that it requires an initial design to simulate. The starting point for the latest development was