Repeatability of Nakamura Puts Aerospace Subcontractor on Runway to Success

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With more than 38 machine tools on the shop floor, Shannon Precision Engineering Ltd (SPE) is a major subcontract machining outfit on the Emerald Isle. With a world-class manufacturing program that utilises systems like Kaizen, the SPE staff includes Six Sigma Black Belts and Lean Manufacturing Green Belts. To ensure production meets the stringent quality levels the company sets, it has recently invested in two Nakamura-Tome mill/turn centres, the WT150II and the SC100X2 from the Engineering Technology Group (ETG).

Located in Shannon, the 80 employee manufacturer is AS: 9100 and ISO: 9001 certified, and it frequently works on high-profile projects for Airbus, Lear, Bombardier, Collins Aerospace, Liebherr, Safran, Spirit and many other leading names in the aerospace, automotive, offshore, rail and power generation sectors. Machining everything from inconel, titanium, hastelloy, duplex and nitronic 40 and 60 as well as hardened steels, the stability and performance of its machine tools are of paramount importance. With the company winning a significant automotive order as well as major opportunities in the aerospace sector, SPE needed a new strategy in its mill/turn department.

Recalling the situation, Dominic Murphy, the Managing Director at SPE says: “On some projects, we have been struggling with repeatability when machining particularly difficult materials. We won a contract to machine electro-mechanical connections for the aerospace industry from nitronic 40 and titanium, and we needed to be very responsive with our changeovers and lead times. With regular batches from 200 to 500 and up to 20 different part families in the series, the project has some very ambitious cycle time targets. With tolerances of +/-5 and +/-10µm on many features, we didn’t want to be chasing repeatability – we needed a more robust process than we had.”

The County Clare company investigated the mill/turn market extensively and it was the Nakamura WT150II that won the day with cycle times more than 20% faster than its rivals. “We gave ETG and other vendors a series of components as a prove-out. ETG built a machine set up around the family of components and they delivered a turnkey solution to our facility that was best suited to our requirements. We already have a lot of mill/turn centres on-site, so the Nakamura-Tome WT150II wasn’t just about cycle times. We needed a turnkey solution that could meet our ambitious cycle times and tight tolerances with relentless repeatability for long batch production – the Nakamura-Tome WT150II certainly delivered on that. Unlike many machine tool brands, Nakamura is a specialist in mill/turn centres, their pedigree stands out. We really liked the compact work envelope as well as the ability to bar feed up to 71mm diameter, which gives us options on some of our larger components.”

The twin spindle twin turret turning centre provides 15/11kW and 11/7.5kW of power to the main and sub-spindle respectively. Complementing the spindle power are 5.5/3.7kW motors on the left and right tooling turrets to provide high-performance milling capabilities. With simultaneous cutting on both the upper and lower tool turrets on opposing spindles, the WT150II provides balanced turning to drastically reduce cycle times.

What no one else has to offer

Whilst ETG Ireland Managing Director Jamie Fletchmore was visiting SPE, Dominic mentioned an extremely complex automotive part that required machining on three machine tools, a 4-axis HMC, and two single-spindle turning centres. With an annual output of 40,000 units, the forged automotive tensioning assembly component is permanently absorbing the capacity of all three machines. The solution was the Nakamura-Tome SC100X2.

Alluding to this, Dominic adds: “We’ve run this family of parts for more than 2 years and we have investigated the market for a solution on numerous occasions – without success. There just hasn’t been a machine on the market that can do the parts in ‘one hit’ – until now. The challenges have included the turning of two spindles on either side of the part that is 40-50mm off-centre. Added to this, we have to mill features that require long-reach tools to overcome interfering features. ETG has overcome this issue with the SC100X2. It has cut the cycle time by almost 50% from 14 minutes to 7.26, but more importantly, it has freed the capacity of two single spindle turning centres and a 4-axis HMC whose capacity we desperately needed. We’ve reclaimed three machines and two employees and massively improved our throughput. We are delighted with both the new Nakamura-Tome machines.”