Finishing Stringers

The productive advantages of Kyocera SGS Precision Tools’ range of solid carbide cutting tools have been engineered for Total Process Optimisation. This is great news for the whole aerospace supply chain, where improvements to business efficiencies are required to meet increased demands from the OEMs.

For any machine shop producing aircraft grade aluminium stringers the headache of finishing the parts will be all too familiar, as it often requires a manual final polishing process. This is labour intensive, uncontrolled and can lead to high value scrapped components and, subsequently, failed delivery schedules.

A European customer recently approached us, faced with these exact problems. Following a detailed process evaluation, our engineering team recommended the S-Carb APF range of advanced finishing tools. A 0.2 to 0.5 mm finishing allowance was applied to the component, and as is often the case the floors were machined first with 16 and 20 mm diameter tools with an allowance for the extra wall stock programmed in the toolpath to avoid any collision. The tools run at 16,000 and 13,000 rpm respectively, at feedrates of 6,500 to 7,000 mm/min.

The APF is designed for single pass wall finishing, greatly improving cycle time and surface finish – and we produce exact length tools specifically matched to the application. For best results on thin wall sections, such as ribs, we recommend using the smallest diameter tool possible as it reduces the contact area on the wall.

Running at over 21,000 rpm, a 12 mm diameter tool proved ideal for this application at a feedrate of 6,000 mm/min. We often lift the tool off of the floor by 0.05 mm so that we only cut on one side of the tool. Finally, a 16 mm S-carb ball end tool running 12,000 rpm is used to generate the floor to wall blend radius.

Results were exceptional, including better surface finish; elimination of the machining steps that were creating quality issues on the parts, and a 60% cycle time reduction from 1 hour 40 minutes, including manual polishing, to 33 minutes in total with no manual polishing operations required.

With potential savings of nearly 500,00 Euros per year based on the annual production requirement of this component the customer stated: “After the results obtained, our company has entered a new era in manufacturing.

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