Challenging times for tooling
Demand from the aerospace sector has driven product development, quality and conformity for Industrial Tooling Corporation (ITC) cutting tools.
As one of the founding partners of Tamworth-based Industrial Tooling Corporation (ITC), and now sole owner Peter Graves is in a strong position to comment on changes in the cutting tool requirements of the aerospace sector. Customers include Rolls-Royce, Airbus, GKN and JJ Churchill, and developments in both materials and tooling he says, have matched changes in the way engine and airframe components are produced. Graves reflects: 'Over ten years ago, composite machining was a new technology; and aero engines and frames were produced from exotics such as Inconel and titanium alloys.'
'The cutting tools have evolved from HSS to solid carbide, and then carbide with coatings, to accommodate exotic materials - and more recently, composites.' He recalls that in the early days, the transverse rupture strength of solid carbide tooling rendered it brittle and susceptible to snapping - 'a major issue when machining expensive parts.' Improvements in carbide have meant finer grades offering improved strength and productivity, characteristics supported by the development of new geometries and coatings. These new geometries have been partly driven by aerospace sector suppliers' need for a single tool capable of multiple operations.
ITC has been active in machining composites from the time they were first introduced for wing and frame components; and early problems associated with the inability of standard tooling to penetrate the abrasive composite skin drove the company to develop diamond coated tooling. This in turn created its own challenges, specifically that the temperature needed for effective diamond coating is also high enough to melt the braze which holds the cutting tip in place. A patented shrink-fit technique for attaching tool holders resolved the problem, and over time ITC has been among the companies which have developed a range of diamond coated carbide grades for hole making and form machining, matched to composite type. This is also true for a range of PCD tooling for milling and routing composite sheets.
Graves says the development of diamond coatings and carbide grades for composite and exotic alloy machining are just one element of change over the last ten years. ‘The main challenge for manufacturers of cutting tools for the aero industry is meeting the increasingly tight tolerance bands and the remarkably complex cutter forms required - and then adding the specific coating for the particular tool. If you look at the tolerance levels of so-called critical components on WW1 aircraft, you wonder how they even got off the ground. Modern day aircraft work at extreme speeds with remarkable pressure and forces acting on the critical parts; the faster the turbine rotation, the tighter the manufacturing tolerance required - there is no room for loose tolerances. To make parts to these increasingly critical tolerances with ever more complex components and form tools is an ongoing challenge.
'Ten years ago we were using a projector to ensure our cutters were to within a tolerance band of ±12 to 15 microns. At that time, this was considered overkill - but also a mark of quality. We then progressed to a CNC grinding machine with a camera, which enabled us to clearly see whether we were in or out of tolerance. Only a couple of years ago this machine was considered groundbreaking, and it still is an extremely accurate machine. But to stay ahead of the competition and serve the aero industry, we had to continue investing. In the last two years we have acquired a number of Walter grinding machines and we became the first UK cutting tool company to purchase two Walter Helicheck Tool checking systems to guarantee the cutting tools would be machined to a tolerance band of ±5 microns - in practice the machines can achieve ±2 to 3 microns.' He observes that this has effectively more than trebled accuracy levels of cutting tools within a decade.
ITC, says Graves, is the first UK manufacturer to link Helicheck machines directly to the grinding machines, and the dialogue between the two guarantees that all cutters come off the machine to the exact dimension required by the customer. What’s more, the Helicheck enables individual inspection reports to be produced for each tool, a growing demand from the sector, especially on special form tools. 'Having two machines means that we can provide this service when required, whilst still having capacity to check our more standard tools required by other customers.'
The inspection report guarantees that every tool meets an exact size, tolerance band and standard. This gives aerospace customers the confidence that each cutting tool can go straight on its machine tools to cut multi-million pound critical components with no possibility of error. At present the system is most commonly demanded for blade root form tooling - which cuts the parts with the tightest tolerance bands. The conformity certificates enable the OEMs to push repetitive QC procedures onto the supplier.
It’s also the case nowadays that OEMs often expect suppliers to do the R&D work in-house. The convention of OEMs giving suppliers a machine or section of the factory for the day is being replaced by a culture whereby the supplier proves the job out at its own facility. To this end, ITC has invested in a Matsuura machining centre to develop and prove tools in-house prior to delivery.
Graves says: 'A decade ago, all the tools we supplied to the aero industry were standard items. Nowadays, 60% of our aerospace tooling tends to be specials.' However, even the standard tools are special in some respects. 'Most standard tools for the aero industry have a radius or form, and ITC has to hold an immense level of stock to supply the aero industry as well as its other key industry sectors. The issue appears to be a lack of standardisation in the industry. For example, one wing could have hundreds of holes of various different sizes. To meet this demand we have to hold thousands of tools, and many tools have to have the ability to drill, ream and countersink in a single operation – with a multitude of different countersink angles, hole sizes and reamed tolerances.'
