The Repliwax® Process
Repliwax®* was borne out of the recognition that near net shape technology is an imperative for foundries wishing to find a niche in the casting market of the future. The objective was to develop a process which would reduce manufacturing costs and extend the weight range of investment castings. This has been achieved by enabling thinner ceramic shells to be used and these shells to be handled and poured at (or near) room temperature. The shorter processing time in shelling and improved logistics in melting and pouring is of special benefit to SME casting producers.
Components produced using the Repliwax® Process
The objective of the Repliwax® project was to develop a process which would reduce manufacturing costs and extend the weight range of investment castings. Commercial production has proven that the process does indeed lower material costs, and it also allows faster and more flexible production and improvements in yield. As the process has been found to be suitable for larger castings, customers will, in future, be able to source products not currently available as an investment casting.
In summary the following benefits have been demonstrated:
• Increased shelling capacity of up to 35%
• Reduced shell material usage of up to 50%
• Elimination of pre-heating costs
• No safety risks from handling hot and heavy shells
• Significant increases in pouring capacity (higher volume melts)
• Increased yield through larger numbers of castings per melt
• Increased weight range from grammes to 140Kg or more
• Elimination of metal run-out due to burst moulds
• Reduced distortion due to shell bulging
• Reduced certification costs per component
Benefits of Casting Cold Thin Ceramic Shells
Using the Repliwax® process, wax patterns are assembled onto runners and shelled as in conventional investment casting. However, in this process, the shells are much thinner and they are cast at (or near) room temperature, i.e. without pre-heating, and supported in a sand bed.
The process allows a reduction in the number of coating layers and this has been shown to lower the ceramic material usage by up to 50%, giving a 35% increase in shelling capacity. For example, a large steel casting of 140kg cast weight was produced using an 8-coat shell, compared with 14-coats used in the investment process.
There are further direct savings through the elimination of pre-heating costs and there are no safety risks associated with the handling of hot shells. The arrangement of numerous shells in a casting box prior to pouring can allow a significant increase in pouring capacity with the utilisation of larger melts and a greater number of castings per melt and with the added benefit of reduced certification costs per component. Some foundries have also been able to maximise the yield of every melt by pouring into 'off the shelf' moulds for future use. This flexibility is not always possible when the shells need to be pre-heated.
Customers are gaining benefit in being able to supply waxes from dies located in different parts of the world to small batch production in high specification materials. It is even more pleasing that the turn-around on these jobs is often faster than with their usual commodity sourcing.
In addition to the advantages of near net shape casting and improved surface finish, the process is also environmentally friendly when compared to standard investment casting, in terms of both material usage and energy costs.
*Repliwax® is a registered trade mark of Castings Technology International. The process is patented and may only be used in accordance with the terms and conditions of a Cti licence agreement.
Copyright© 2012 Castings Technology International
Repliwax® Case Study
Low Cost Investment Casting Case Study
ValveWorld 2002 Paper (PDF File 820kB)