Based at High Peak, Derbyshire, Alken Engineering is part of the four-company Alken Holdings Group and is a specialist machining and fabrication company that counts many ‘blue chip’ companies — such as Bentley Motors and Volvo — as customers; it also does work for the aerospace, power generation and general sub-contracting sectors.

Alken Engineering is a long-term user of ProtoTrak mills from XYZ Machine Tools (www.xyzmachinetools.com), and it was an early user of the ProtoTrak control, which was introduced to the UK in 1993.

The company now has 10 XYZ ProtoTrak mills and three XYZ ProTurn lathes, but until recently it had resisted purchasing a ‘full CNC’ machine from XYZ.

While most of Alken’s work involves machining steel and ‘more exotic’ materials, the company also gets involved in components made from aluminium and nylon.

Indeed, it was the latter work that led to the purchase of its first XYZ LR (linear-rail) machining centres.

Managing director Paul Coverley said: “Even though the ProtoTrak mills and lathes had provided flawless service, I hadn’t considered XYZ machining centres, as I didn’t believe they could compete quality-wise — until I had a demo of the new LR machines with the Siemens Shopmill control.

“In addition to the capability of the machines, the Shopmill control also appealed to me, as we get involved in machining a range of quantities — from one-offs to series production.

“The Siemens control readily accommodates both of these — and all quantities in between; and while I still needed to be persuaded about the ability of XYZ LR machines to undertake heavier machining work, that was soon to change.”

The ‘connecting link’

That ‘persuasion’ came about when Alken won a contract to machine a series of connector blocks that would be used in the construction of the new bridge at Tintagel Castle in Cornwall.

These connectors are machined from solid blocks of duplex stainless steel, with the finished parts measuring up to 460 x 237 x 237mm and featuring slots that are 135mm deep in places.

The work came to Alken Group after 10 other sub-contractors had withdrawn from the contract due to the difficulty of machining these parts, which meant that the company was faced with a tight deadline — and a capacity issue.

Mr Coverley said: “We knew that any delay would put the bridge project back, which was unacceptable to the main contractor — American Bridge — and its customer, English Heritage.

“Our main concern was that the parts might well have been described as ‘unmachinable’, but changes were made to the design following discussions with our customer, Underhill Engineering.

“However, we were still faced with machining duplex stainless — and those deep slots.”

To start with, machining was undertaken by two other companies within the Alken Group, using what Mr Coverley describes as ‘high end’ machining centres.

“These companies had what I thought was the experience and equipment to handle this work, but we found ourselves falling behind schedule as the machines struggled with the volume and complexity of the parts.

“We had to bring work in to Alken Engineering, but the only capacity we had available was on our XYZ LR 500, 750 and 1000 machining centres.

“At this point, we still had doubts that the LR VMCs could handle materials such as duplex stainless, even though XYZ was telling us otherwise.”

Protracted cycle times

With each of these connector blocks requiring 70-80hr of machining, there was a lot at stake, but Alken — with assistance from XYZ Machine Tools and tooling supplier Ceratizit UK & Ireland — began to test the capabilities of the LR machines to the full.

The indexable-insert tooling for machining the slots required an overhang of four x diameter and featured 12mm Dragonskin-coated button inserts.

The tools were run at a cutting speed of 140m/min and a feed rate of 0.3mm/rev per tooth. Both the machines and tooling produced the quality and finish required.

“Now we know how to machine duplex stainless, we haven’t looked back. Indeed, the LR machining centres are producing these parts better and quicker than the high-end machines we started with.

“As a result, we have got the project back on schedule, and any doubts that I had about the capability of XYZ machining centres have been eliminated.”

XYZ Machine Tools introduced the LR range in 2017; they were the first of the company’s machining centres equipped with linear-rail technology.

XYZ says it had held off developing a linear-rail machine, as it did not believe that early systems were robust enough to meet its performance standards, adding that recent developments in linear-rail technology have seen these concerns eliminated and their capabilities substantiated by applications such as those undertaken by Alken.

There are three machines in the LR range; the 500 LR, 750 LR and 1000 LR, with the number equating to the X-axis travel in mm.

All the machines feature a 13kW 8,000rev/min spindle and 20m/min traverse rates; there is a 12-position carousel-type tool changer on the smallest machine, while the two larger machines have a 20-position carousel (a 24-position arm-type changer is an option).

Also included in the XYZ range are the heavy-duty and more-powerful HD VMCs. The 660 HD, 800HD and the 1100 HD have boxway slides and are available with a Siemens or Heidenhain control.