As a result, Replicast can now be used to produce correctly balanced impellers up to a metre in diameter with high dimensional accuracy and superior surface finish. Furthermore, an optimisation of the Replicast process has reduced the cost of impellers by around 30%.
Replicast uses ceramic shells formed around sacrificial replica patterns, made directly from CAD designs using additive manufacturing technologies or machined from polystyrene.
At the same time, the company says that there has been shift of focus among pump users and manufacturers towards the total cost of pump ownership and ‘up time’. At least one manufacturer has moved from focusing on a casting’s ticket price to how much it costs them to buy the raw casting, process it and install it in a pump.
“The oil and gas, chemical process, power and water purification industries are all beginning to focus on total cost and realising how financially damaging it can be to suffer any down time because of pump failures,” says Cti’s Richard Gould.
The switch makes Cti’s impellers far more attractive since they have significantly lower, to zero, non-conformance costs, require little or no detailing and far less finish machining, thanks to the company’s near-net-shape process, the company says.
Using traditional casting processes, ensuring impeller blades are perfectly balanced and of a suitable surface quality, thickness and geometry to ensure a long service life, delivering maximum flow rates, is difficult to achieve, the company says. It is not unusual for blade thicknesses to vary when impellers are made using sand moulds and, although they can be dynamically balanced in air, that does not mean they will remain balanced during operation, when pumping a fluid. Improving the surface quality of the impeller’s blades is also difficult and expensive because protective shrouds severely restrict access.
The company adds that new designs can be produced in half the time it would take if a conventional wooden pattern had to be made, modifications can be made just as rapidly and it is far easier to reverse engineer a product, using a coordinate measuring machine to collect the data to produce a CAD design from which the sacrificial pattern can be made.
Tests have shown that pumps using Replicast impellers are 10% more efficient than impellers made by traditional methods, which means pumps can be smaller, further reducing material and manufacturing costs.
