A cell capable of the robotic loading of unmachined material from a 10-pallet pool to a five-axis machining centre, followed by the automatic return of finished components, was BTL Precision’s first investment specifically targeting sub-contract work in the aerospace industry. The cell was installed in March 2013 at the company’s factory in Bishop’s Stortford.
The ISO 9001:2008-registered firm is in the process of gaining AS9100 approval for aerospace quality management and will be implementing SC21, which promotes best practice in supply chains serving the aerospace and defence industries. The latter is an established sector for BTL, accounting for around half of its turnover.
Managing director and joint owner Julian Bedford says the company is already carrying out second-tier aerospace work. For example, an on-going contract awarded mid-2013 involves the manufacture of a family of non-flight-critical aluminium housings for a business jet. Production of 120 of each of six parts is initially required; to meet cost and quality targets, the job is being undertaken in the new machining cell from Coventry-based DMG Mori (UK) Ltd (
www.dmgmori.com).
The DMU 40 eVo, which has a work envelope of 400 x 400 x 375mm, is BTL’s third vertical-spindle five-axis machining centre from this supplier, the others being two DMU 50 eVo machines of slightly larger capacity. The company also has an even bigger DMG Mori machine; its three-axis DMC 1035 V ecoline with a 1m bed replaced two smaller three-axis machining centres.
First five-axis machine
The first DMG Mori machine to be installed at Bishop’s Stortford — a five-axis DMU 50 eVo — was bought in 2009. At the time, BTL had six three-axis vertical machining centres, one fitted with a fourth axis and two with twin pallet changers. Mr Bedford says: “As soon as the five-axis machine was installed, our productivity improved dramatically, and it was immediately apparent that this was the future for us.
“Almost all of our work requires operations on multiple faces, and our five-axis plant is used mainly for 3+2-axis machining. It allows parts to be re-orientated in-cycle, saving machine stoppages and component relocation. Six or seven ops on a three-axis machining centre are typically compressed into two hits on a five-axis machine, and cycle times are down 30% on average, shortening lead times. Furthermore, accuracy is improved by not having to reposition workpieces repeatedly.”
The year after the DMU 50 eVo was installed, Mr Bedford and his business partner (technical director Andy Moodie) attended a defence spending review seminar in London, where it was emphasised that the UK Government was intent on engaging with smaller firms as well as the traditional supplier base of larger companies to drive efficiency.
However, the speakers also made it clear that production plant of the right quality had to be in place to win the work, as well as the requisite management, traceability and quality procedures. Messrs Bedford and Moodie also realised that the same prerequisites applied to gaining aerospace business, which was one of their target markets in view of the sector’s long-term growth prospects.
Investment programme
With the lessons learnt, they started an investment programme that has since seen the installation of two further machining centres from DMG Mori, which is now BTL’s preferred supplier of all prismatic metal-cutting equipment. Similar brand loyalty is shown to CAM system company Open Mind, as well as to cutting-tool company Walter and material supplier Thames Stockholders. Moreover, Mr Bedford is keen for these associations to be seen by all parties as ‘partnerships’; he has even had the suppliers’ logos stitched onto his machine operators’ shirt sleeves.
Consistent with automatic pallet loading and long periods of unattended running, the DMU 40 eVo has 60 tools instead of the 30-position magazines on the other five-axis machining centres. It is also equipped with high-pressure through-spindle coolant delivery to assist when cutting stainless steels and tough alloys.
The first two jobs put on the machine were both made from EN100 and destined for the defence industry; they were required in batches of 100-off and 200-off. Nine pallets were devoted to producing one of the components in a 50min cycle, while a single pallet was sufficient for the second part, as the cycle time was 15min.
Mr Bedford sees the ability to produce a mix of different parts as an important benefit of the five-axis cell, as it allows BTL to produce both small and large batches economically on a 24/7 basis; it also allows a rush job to be set up on one or more pallets if the need arises.
In conclusion, he says: “We are excited by introducing automation to our shopfloor, as it is one of the ways British manufacturers can compete with overseas firms, particularly in Eastern Europe and the Far East. It is our hope that the aerospace side of our business will grow quickly, and we expect it to account for 50% of our turnover in a few years’ time.”