Waxing lyrical

Paul Boughton

To outsource or not to outsource wax pattern and runner manufacture - that is the question, says Robert Park

High-quality wax patterns and wax runner systems are vital to successful investment casting operations in the aerospace sector, but there is growing debate about whether the manufacture of these patterns and runners systems is best handled in-house or outsourced.

Traditionally, it is an activity that many of the major aerospace manufacturers have in the main preferred to handle in-house. Their perception has typically been that this way of working allows for greater flexibility, precision and control of the process. The issue of control - knowing what is being produced, by whom and when - is perhaps a given, but how necessary is this information? If the required components are available when and where needed, with clear traceability, then exactly where they were made becomes far less relevant.

The issue of precision bears some scrutiny. The level of precision achievable when producing a wax pattern will only ever be as good as the equipment used to produce it, and the post-production treatment, much of which consists of complex, highly-skilled assembly work, is still typically carried out manually. Precision will only therefore be optimised if state-of-the-art equipment is available and is used to its optimum capability, while post-production treatment must be error-free. In these instances, a specialist wax production facility may offer advantages over a production facility handling multiple types of operations.

Flexibility is also open to question. While an in-house resource will only be working on patterns used by that company, the necessarily finite resource will only be able to produce a certain amount of patterns or runner systems within a given shift time, potentially leading to issues and delays during periods of high demand in other parts of the facility.

The case for partial or even full outsourcing is borne out by a topline cost comparison. Smaller, leaner, specialist companies can typically operate significantly more cost effectively than those running large multi-function production facilities.

A further issue can arise when the wax patterns and runner systems are supplied to the company which will undertake the manufacture of ceramic cores for the investment casting process – one which is rarely, if ever, handled in-house. The issue is one of accountability – namely, where does responsibility lie if one or more of the final patterns is found to be out of tolerance? Even a small deviation from CAD design can result in a faulty component, meaning the costs of rework or replacement – costs which often cannot be countenanced in a highly competitive market-place.

All of these factors are behind a move among some of the major players in the aerospace sector outsource some or all of their wax processes to the same companies which manufacture the ceramic cores used in investment casting.

The potential advantages are clear and immediate. The aerospace manufacturer is no longer  burdened with the purchasing and maintenance of capital equipment, or the issues surrounding human resources – recruitment, training, sick pay and so on. These now fall to the supplier – and most suppliers will invariably be seeking to invest in state-of-the-art solutions and highly trained staff in order to remain competitive. As specialists in core manufacture and wax injection, these suppliers will have dedicated resource in situ and so be better placed to deal with periods of high demand, for example through the ability to put on extra shifts at short notice.

Outsourcing also addresses the issues of accountability in the investment casting process. Turning the wax patterns into a ‘bought out’ product provides a guarantee that the cores will conform and match to the patterns, reducing the level of engineering work needed. In any case, while they operate to stringent quality standards, a small element of scrap will generally be accepted by the supplier and this is a cost that will not be passed on to the customer.

The agile, flexible working practices adopted by most specialist suppliers also position them ideally to cope with short lead times when required, with turnarounds of as little as 12 hours achievable – offering peace of mind for customers.

It goes without saying that those companies who still wish to retain some of their wax component production in-house can still benefit from outsourcing during periods of high demand. Indeed, it is this level of flexibility which makes the outsourced solution most attractive to aerospace manufacturers – enabling those companies which are currently used to carry out core manufacturing operations only, to add true value by acting as strategic turnkey partners rather than just suppliers for all aspects of the wax and core process, able to optimise quality, replicability and delivery.

Robert Park is General Manager – Certech UK, Morgan Advanced Materials.

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