Rapid Casting
In addition to the mechanical machining, CRP enforced and optimized the Rapid Casting technology, which is
lost wax casting with disposable patterns made by RP.
In fact, while
RP allows the designer almost total freedom to create shapes that would be impossible to machine, on the other side the
materials have limited performances.
Rapid casting in Titanium alloys or
special steels allows those shapes to be realised very quickly and in small quantities, even one offs, with top performance.
It is therefore possible to optimise the function of the product along its mechanical stress axes and obtain a perfect reproduction of all details of the RP pattern, with tolerances and surface finishing of a very high quality.
Very big parts, like gearbox cases, were initially manufactured, for instance, with titanium machined sheets welded together. Now it is possible to use this new technology to manufacture such parts.
The Rapid Casting procedure is composed of a number of steps:
- A disposable pattern is made by RP;
- The pattern undergoes wax infiltrations (immersion and capillarity) to increase its strength (to avoid handling breaks);
- The pattern is immersed in a ceramic bath: slurries, stuccoing and exsiccation;
- The lost pattern is evacuated: dewaxing with flash firing or in an autoclave and subsequent sintering of the ceramic shell
- Alloy casting with inductor or voltaic arc;
- Pouring, cooling, reduction of the shell, shot peening, gate cutting, heat treatments.
The casting structure is formed of an aggregate of grains or polyhedral crystallites which produce isotropy compensation, while in a solid metal they are anisotropic: it is obvious that isotropy has great advantages, for instance, FEM calculations are very close to the real behaviour thanks to the isotropy of the piece.
This is also a major step forward for aerospace and medical applications.
Some treatments are usually applied to Titanium alloy castings, due to Titanium high reactivity, besides typical methods to obtain a good casting:
- Chemical mill: to remove alpha case structure that originates from the contact between metal and ceramic shel
- Hip: Hot Isostatic Pressure applied in an inert atmosphere (argon) to eliminate micro- porosity and porosity of material inside the casting
- Weld repair: TIG weld repair in inert atmosphere, to fill in porosity or HIP hollows, tested with real time RX inspections.
- Shot peening: under-control shot-peening to reduce stress and increase fatigue resistance.
The final product is supplied fully CNC machined and complete of treatments with inspection certificates (material, RX, FPI, HT, etc…), according to the ISO9001:2000 certification.
The process was optimized to ensure the maximum reliability: the usual post casting treatments are required to ensure the integrity of the structure while the chemical mill is used to remove the alpha case which forms when the Titanium comes into contact with the ceramic shell which would be harmful for the casting reliability. Moreover, Hot Isostatic Pressing (HIP) is also applied to castings to remove any internal porosity.
This is definitely a winning strategy that allows us to provide a “turnkey” product, immediately ready for the race, where CRP is involved and collaborates with the customer from the beginning, supplying a huge engineering and co-design contribution.
The optimization of the 3D design is the main issue, in order to exploit all the potential and the advantages coming from the “CRP method”.
From a technical point of view, CRP uprights, for instance, have higher mechanical performance and greater reliability, as well as providing a weight saving which is a key property for all non suspended masses of a vehicle.
Rapid Casting technology was immediately highly appreciated by customers because it provided significant advantages: durability and reliability (a casting is naturally isotropic for compensation), fewer design and shape limitations and the possibility to reduce weight and increase stiffness.
Rapid Casting 
