Casting simulation is a very critical aspect of the casting process which ensures perfect casting in the shortest time span. Casting simulation technique has been proven to be very effective and reliable for a wide category of cast metals and complex processes, but its inaccessibility and high costs makes it practical application very difficult.
Typically the simulation process comprises of processes such as mould filling, grain structure, stress analysis, distortion and solidification. It also takes in account models of product and tool equipment like cores, parting, mould layout, feeders, gates etc., along with temperature regulated properties of mould and part materials and finally the process parameters such as pouring rate, temperature etc. The results from these studies are applied in predicting casting defects like hard spots, blow holes, cold shuts, shrinkage porosity, cracks and distortion.
This method requires expert handling of the inputs which are normally not easily accessible to the product designers. However, best results can be achieved by concurrent engineering approach wherein the foundry and tooling engineers actively participate in the product design phase and simultaneously evolve the product, tooling and process design thereby ensuring mutual compatibility.
Irrespective of the fact that most foundry personnel's accept the benefits of casting simulation programs, the real time application of computer aided casting methods is very less, mainly because of high costs, lack of qualified manpower and poor long term technical support from the software vendors.
To manage the cost and accessibility factors in the casting simulation phases the concept of virtual foundry has been proposed. Virtual foundry, a highly emerging concept, is a collaborative initiative to create a space where virtual casting trials can be conducted to optimize the tooling, methoding and processing parameters. It is anticipated the virtual trials will entail a small fraction of resources as compared to the real trials and offer a better approach to achieve the targeted quality. The virtual foundry would be managed by a team of qualified casting engineers to provide the necessary guidance and technical expertise.
Various advantages of employing computer aided casting development techniques have been cited, listed below are a few of them,
- Saving costs in trials - A significant reduction in costs in different processes such as tooling modification, cast metal, labour, indirect materials and energy can be achieved.
- Savings during regular production- An improved yield with lesser rejections during casting, machining and servicing can be attained.
- Value addition- Computer aided castings offer better perspective and confidence to handle more complex casting tasks. Further the results can be documented for quality certification and in handling export orders.
- Design improvements - A reduced tooling complexity resulting in low costs and better product design with consistent quality can be accomplished by these techniques.
Methodology implemented for casting simulations
The technology for methoding and casting simulation is promoted under the name. AutoCAST. It involves estimation the best casting orientation and parting line to reduce undercuts, draw and draft. Similarly the gating and feeder location is also determined and is automatically operated. Further the feeder dimensions are computed depending on the geometric modulus of the closest hot spot area. Then the gating channel dimensions are determined based on estimating the ideal filling time followed by choke velocity and choke area. The mould filling is simulated to find out the exact filling time and locate metal impingement region and velocity and simultaneously visualize the blow hole formation if any. Casting solidification is largely affected by the thermal gradients initiated during mould filling and other boundary conditions. This process is also simulated using the vector element method which locates the feed metal paths in reverse to precisely locate the extent of shrinkage defects such as porosity, cavity and centerline shrinkage.
These methods are targeted at achieving competitiveness in the foundry industry by offering cost effective and easily accessible casting simulation services