Precise Castings
Investment casting is a manufacturing process in which a wax pattern is coated with a refractory ceramic material. Once the ceramic material is hardened its internal geometry takes the shape of the casting. The wax is melted out and molten metal is poured into the cavity where the wax pattern was. The metal solidifies within the ceramic mold and then the metal casting is broken out. This manufacturing technique is also known as the lost wax process. The result is casted part, so precise, that mostly does not need CNC finishing. Today we take advantage of the investment casting process to design one piece, near-net shape, complex components.
Why throwing away so much material and waste time with machining?
Compared to the widely accepted practice of machining components from solid raw stock, where material is removed to get to the net end shape and all of the problems associated with that, this is a very simple way to visualize just how much sense it makes to consider investment castings for cost effective manufacturing of many components.
Investment castings are typically selected because they can be produced with fine detail, excellent “as-cast” surface finish, shape into internal or external features, thin walls and internal passageways. This often leads to significant customer cost savings in material, labor and machining.
Investment castings are typically selected because they can be produced with fine detail, excellent “as-cast” surface finish, shape into internal or external features, thin walls and internal passageways. This often leads to significant customer cost savings in material, labor and machining.
Old Technology used in Modern Industry
Investment casting was developed over 5500 years ago and can trace its roots back to both ancient Egypt and China. In fact the sculptors of ancient Mesopotamia and Egypt, the Han Dynasty in China, and the Benin civilization in Africa used this method of casting to produce their intricately detailed artwork of gold, copper and bronze. In Europe we find our technology during the sixteenth century, when Benvenuto Cellini describes in his autobiography the method he used to create the Perseo, a great masterwork of italian renaissance sculpture. Only at the beginning of 1900 people start using this technology for industrial applications. Today, it sets new technological standars in production of aluminium, magnesium and titanium parts.
Investment casting was developed over 5500 years ago and can trace its roots back to both ancient Egypt and China. In fact the sculptors of ancient Mesopotamia and Egypt, the Han Dynasty in China, and the Benin civilization in Africa used this method of casting to produce their intricately detailed artwork of gold, copper and bronze. In Europe we find our technology during the sixteenth century, when Benvenuto Cellini describes in his autobiography the method he used to create the Perseo, a great masterwork of italian renaissance sculpture. Only at the beginning of 1900 people start using this technology for industrial applications. Today, it sets new technological standars in production of aluminium, magnesium and titanium parts.
Design Freedom
In it’s simplest form, investment casting can be thought of as the melting and flowing of any of todays common engineering metals and alloys into molds of virtually any net shape, to produce a near net shape component once cooled.
Using investment castings produces components that are best described as near-net-shape, in other words, components that require little or no further processing. The process is capable of producing precise detail and dimensional accuracy of approximately +/-0,1 mm (in some cases even smaller) in castings of up to 10 kg and walls thin up to 0,5 mm.
Using investment castings produces components that are best described as near-net-shape, in other words, components that require little or no further processing. The process is capable of producing precise detail and dimensional accuracy of approximately +/-0,1 mm (in some cases even smaller) in castings of up to 10 kg and walls thin up to 0,5 mm.
Compared to other Techniques
Production costs are competitive with other techniques due to substantial savings on raw materials and labour costs. Finishing costs are less since only a small amount of or even no-machining is required to achieve high precision dimensions. Overall capital investment is reduced.
INVESTMENT CASTING VS. MACHINING:
Compared to sand casting, lost wax casting offers tighter dimensional tolerances, better surface finishes, produces near-net shape parts which therefore require less machining and other processing and allows for the casting of complex-geometry parts and intricate details such as lettering and logos. |
INVESTMENT CASTING VS. MACHINING:
Precision investment casting offers lower per piece costs over long production runs, significantly less material waste thereby reducing material costs and the ability to work with a larger selection of alloys. Additionally, machining offers no economy of scale (ten thousand parts cost as much per piece as ten parts). |
INVESTMENT CASTING VS. METAL FABRICATION:
Investment casting can be far more accurate and precise that metal fabrication, is less labor intensive, often offers substantial weight savings, costs less, provides more material choices, greater design flexibility, shorter lead times and quicker prototyping. Additionally, while using metal fabrication may require parts to be constructed from multiple individual pieces, precision investment casting allows for the same part to be made in one continuous piece. |
INVESTMENT CASTING VS. DIE CASTING:
Lost wax casting offers far shorter lead times, greater alloy flexibility (including ferrous materials which cannot be die cast), greater design flexibility, better piece to piece consistency and produces parts closer to net shape which therefore require less machining. Tooling for lost wax casting is also dramatically less expensive than die cast tooling. |
INVESTMENT CASTING VS. FORGING:
Precision investment casting offers tighter tolerances, lower tooling costs and provides near-net shape parts which require less machining and additional processing. With investment casting it is also possible to produce cored geometries which forging cannot offer. |
INVESTMENT CASTING VS. 3D PRINTING:
If prototypes are of interest, Rapid Prototyping services utilizing 3D wax printing system to produce wax patterns in only a matter of days, with castings available usually less than 2 weeks later. For larger series 3D printing of wax positive is not cost effective. 3D printing of metal is less precise, expensier than investment casting and too time consuming. At the moment 3D printing does not represent alternative to investment casting, specially for larger production series. (similiar comparison digital print vs offset print, offset print will always be better choice for large runs) |
Technology of the future
Titanium, magneisum and aluminium investment castings have found a wide spectrum of uses in high-technology industries such as aerospace, electronics, optics, engineering, medical technologyand motor racing. In an age when energy is becoming dearer and raw materials scarcer, technology is expected to make a high contribution to saving costs and improving efficiency. The well-considered use of super alloy investment castings makes all this possible.