Five-axis turn-mill centre investment

New machine speeds up production of titanium aero-engine components

Posted on 22 Jul 2019 and read 513 times
Five-axis turn-mill centre investmentSilcoms — a niche supplier to the aerospace industry of nickel-alloy, titanium, stainless-steel and aluminium aero-engine ring components and assemblies (including seals, shrouds, segments and casings) — was awarded another contract last year to supply a complex rotating-fan seal for a large civil-aircraft engine programme.

Additional capacity was needed at Silcoms’ Bolton factory to cope with the increased workload; and while researching the most appropriate new equipment, managing director Jim Hill took the opportunity to “develop a new process route that would speed production of the rotational titanium part while maintaining the tight tolerances needed”.

The new method of manufacture is based on the use of a German-built Hermle C 50 UMT five-axis machining centre fitted with a torque table that allows in-cycle turning operations to be undertaken.

The machine — supplied by Gosport-based Kingsbury (www.kingsburyuk.com), the sole sales and service agent for Hermle in the UK, Ireland and Middle East — now performs three operations in two set-ups (the part previously required five operations on three different machines).

KingsburyAs a result, the floor-to-floor time is drastically reduced, while fewer set-ups mean that the risk of accumulative
tolerance error is minimised.

Machined from a titanium forging, the 1,015mm-diameter fan seal has to be turned to a final wall thickness of 3mm, while maintaining dimensional accuracy and avoiding distortion.

After a number of preparatory machining stages, the Hermle mill-turn centre completes the next five operations in two set-ups, taking 20hr.

Semi-finish and finish turning have been compressed into one operation on each side; while during the second clamping on the Hermle, turned and milled features are completed (these prismatic cycles were formerly undertaken on a different five-axis machining centre on site).

Tight tolerances


Critical dimensional features are held to ±20µm over the full diameter of the part, and ‘post operations’ remain the same; these include balance testing and machining to correct any imbalance, surface treatment and final turning to ‘restore’ the seal surface.

Mr Hill said: “Consolidating turning and milling on one machine has significant benefits for us.

Apart from a reduction in component handling and an improvement in accuracy, it shortens the lead time for converting a titanium forging into a finished seal — and reduces the total number of tools we need.

“Around 90% of machining on the Hermle is turning, so we wanted to be sure that the torque table on the C 50 UMT was up to the task, bearing in mind that titanium is a tough material to cut.

Kingsbury 2A demonstration at Hermle’s factory in Gosheim convinced us that the machine was ideal for the task, added to which the manufacturer has an excellent reputation for quality, reliability and service — as does Kingsbury.

“Moreover, it is possible to optimise the turning conditions by fully utilising the five-axis capability of the Hermle. As aerospace parts are being designed with ever-more-complex features, such capability and versatility are particularly important.”

The specification of the Hermle C 50 UMT includes: a 56kW 12,000 rev/min spindle (356Nm of torque); a trunnion swivel range of +100 to -130deg (this trunnion is driven from both sides to ensure the high level of rigidity needed for the ‘rigorous’ machining of titanium); a 500rev/min torque table; a work envelope of 1,000 x 1,100 x 750mm; and 6m/sec2 acceleration in each axis to 60m/min rapid-traverse in X and Y, and 55m/min in Z.

Absolute measurement of all axis positions is fed back to the Siemens Sinumerik 840D control.

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