Investment casting producer RelyIntraCast has increased the diameter size of its pump impeller range from 250 mm to 400 mm by investing R7-million in casting equipment.

“Investment castings are traditionally small, but with the larger capacity wax-injec- tion presses and robotic dipping machines, RelyIntraCast can produce castings of up to 50 kg net cast weight and up to 500 mm in diameter. Previously, the company was restricted to net cast weight of not more than 25 kg,” says RelyIntraCast MD Mark Hughes.

He adds that increased market demand necessitated the company to invest in these larger capacity machines.

The company sourced the bulk of the equip-ment from India-based investment casting machinery and solutions manufacturer Modtech, which installed the equipment and provided training for operators on how to operate the new equipment.

The equipment is largely automated, owing to its computer numerically controlled system, and is connected to the Internet. This allows for the machinery to be diagnosed remotely and, therefore, potential issues, such as equipment failure or maintenance requirements, can be identified early limiting downtime.

Together with diversified engineering com-pany Unique Engineering and a Germany-based company, RelyIntraCast is developing rotors used in positive displacement pumps. The prototype rotor patterns were developed at tertiary education institution the Central University of Technology, in Bloemfontein, and used to manufacture prototype castings of the rotors this year.

RelyIntraCast is developing several dies so that it can produce rotors in a range of different alloys.

The impellers that the company manufac-tures, which are commonly used in industrial pumps and in mining and chemicals applica-tions, can be cast using various alloys, includ-ing 27% chrome iron, stainless steel, hastelloy and precipitation hardening steels.

RelyIntraCast uses the investment casting process to produce its impellers, which have a higher quality surface finish than that of sand-cast impellers. Investment castings reduce and sometimes negate the need for machining, says Hughes, adding that investment cast impellers also increase pump efficiency, as surface friction is reduced, owing to the smoother finish.

For example, the thread on chrome iron impellers are cast in, which negates the need to machine the thread that allows the impeller to be fitted onto the pump spindle, he notes.

“Investment castings are made using an aluminum die with a negative cavity of the product. Wax is injected into the negative cavity and, once the wax hardens, varying grades and grains of ceramic are layered over the wax. “The wax is removed and the ceramic heated, leaving a cavity into which the molten metal can be poured,” Hughes explains.

Owing to the investment casting process, casting dimensions are repeatable and also more accurate than traditional sand castings.

Hughes says the total cost of ownership of investment castings is often lower than that of sand castings when considering the total cost of casting and machining.

has made more than 5 000 casting dies and the company produces up to 4 000 pump impellers from 20 different designs a year.

The company mainly casts open-vane impellers, but is running a development programme to produce 500 mm to 600 mm open-vane and shrouded impellers to increase market share, he says.