subject: Rapid-prototyping Of Cast Iron: A Foundry Breakthrough [print this page] Being a Foundry with a Competitive Edge Being a Foundry with a Competitive Edge
In past years, the pressure exerted by emerging markets on North-American foundries has increased dramatically. With their cheap labour and lower environmental requirement, production costs are often much lower. To keep a competitive edge, it is often necessary to find a niche market that will ensure that the price of transportation will become prohibitive.
Short productions runs are such a niche, especially when the part required is crucial and must be delivered very fast. Before now, these parts were fabricated from weld steel plates. The final part would have neither the same structural integrity nor the optimal mass distribution of a casting, but they were more cost-effective because of low initial investment compared to casting produced in an iron foundry. They would also be delivered much faster.
This was due entirely to the long, costly process of pattern fabrication. Castings have been done for thousands of years with a pattern use to make an imprint of the final part in the sand. This technique has been used for so long with good reason: it offers quality and consistency, and can be easily amortized over long production runs. But the drawbacks of pattern fabrication are that you will need to wait weeks and invest thousands of dollars before the first part is produce.
There were some alternative like foam patterns, which were a bit cheaper, but it lacked the freedom of other materials for pattern-making because of low resistance.
Rapid-Prototyping with Nopatech
To get the best of both worlds: fast and cost-effective parts with all the freedom of casting, some very innovative foundries are developing rapid prototyping technologies to produce castings without pattern.
One of the leading methods is using the recent advances in robotic technologies because of the fluid motions and high flexibility of those tools. They are, after all, a proven concept use in manufacturing plants for years, although their applications were more focused on repetitive process like welding or buffing.
The Process of Patternless Casting
The process of patternless casting starts with a 3D model of the part that has to be done. Machining stock and shrinkage allowance are added directly on the model. Then, the gating system, the risers and the sprue are all added to the model. Finally, the part is split if required and cores are planned if the part contains cavities that cant be done otherwise.
When the final 3D model of the part is done, it can be converted to code for the robotic arm which then used specially designed tools to machine a sand mould directly with both accuracy and consistency. This mould and its cores can then be assembled as a regular mould, before being poured with the proper material. All of this can be done in 1 to 3 weeks, depending on the complexity of the part, when a pattern would take 4 to 8 weeks to be fabricated.
