Mills CNC, the sole distributor of Doosan machine tools in the UK and Ireland, has recently supplied a new Doosan VC630 5AX five-axis machining centre, equipped with a Heidenhain control, to hi-fi design and manufacturing specialist, Linn Products.
The machine has been installed at the company’s factory in Glasgow and is being used to produce a range of precision parts for Linn’s music systems. These components include machined-from-solid aluminium enclosures that comprise a lid and base for the company’s range-topping Klimax systems.

Prior to investing in the VC630 5AX, the machining of these enclosures was subcontracted, and while this situation was satisfactory it had its drawbacks and was always considered to be temporary. The arrangement was superseded by Linn’s desire to become more self-sufficient and vertically integrated, with the decision taken to commence machining the Klimax metalwork in-house.
Explains Fraser Crown, Linn Products’ operations architect: “The more of our manufacturing processes we can bring in-house, the better able we are to manage, control, optimise and ultimately improve them. Linn does not mass produce products; every product we manufacture is built to order. This can potentially cause scheduling and delivery fulfilment issues when relying on subcontractors who, quite naturally, prefer to handle larger and more predictable batch-type work.
“As part of our commitment to continuous improvement, it was a natural progression for us to look at bringing machining processes in-house, such as those employed to manufacture our enclosures,” he adds.
To enable Linn to manufacture all its Klimax metalwork in-house, the company needed to acquire additional machining capability. Linn is certainly no stranger to CNC machining and, some years earlier invested in a three-axis Doosan DNM650 vertical machining centre from Mills to manufacture a range of parts. Since being installed, the machine, according to Crown, “hasn’t missed a beat” and is working near peak production.
With regard to its next investment, three key questions initially confronted Linn: what type of machine tool would best produce the enclosures; which manufacturer would be able to supply the machine, and what support could they provide; and how quickly could Linn develop a reliable and repeatable machining process?

Linn’s ‘milled from solid’ enclosures feature in both the Klimax DS and Klimax DSM streamers, the Klimax amplifier, Klimax Exakt, and the Radikal power supply for the Klimax LP12 turntable. The enclosures are machined (internally and externally) from individual solid aluminium billets. Internally machined features include a number of separate and isolated chambers (divided by walls) where audio/electronic circuitry and power supply units are housed separately. The back of the enclosures contain a variation of machined holes for output and input connectors and ports.
All exterior faces of the enclosure are machined to a mirror-like finish, with the top and bottom being finished using a large diameter fly-cutter (cutting) tool that is able to face mill the entire surface in one pass to produce a uniform finish. “Surface finish imperfections, however small, are not acceptable as they would show up after the enclosures have been anodised,” states Crown.
To meet Linn’s manufacturing imperatives and quality standards, the company researched the market to identify the types of machining centres available.
“We wanted the machine to meet our immediate and future requirements, which is why we looked at large-capacity five-axis vertical and horizontal machining centres,” says Crown. “Although we do not machine parts in high volumes, flexibility, reduced set-up and cycle times, which are key advantages of five-axis machine tool technology, are important to us.
“We ultimately decided on a vertical machine with full five-axis simultaneous machining capability because it enables each side of the billet to be produced continuously without the need to remount the job,” he continues. “As a result, we negate any incremental dimensional inaccuracies and poor finish quality. We believe it will provide us with far more flexibility going forward. Furthermore, for certain machined features, most notably where the front panel display is located on the enclosure lid, we knew that using five-axis simultaneous machining capabilities would enable features to be machined reliably and accurately. In reality, the seamless five-axis movement which creates the ‘Klimax smile’ is dimensionally perfect, has a faultless finish and it is a joy to watch being machined.”

Linn already had a good relationship with Mills CNC following its investment in the Doosan DNM650 vertical machining centre five years ago. Discussing its latest requirements with Mills’ sales and technical staff, Linn decided to invest in a large-capacity VC630 5AX machine with Heidenhain CNC.
Owning a large-capacity machine means that Linn can produce a wide range of components – big and small. The decision to opt for the Heidenhain control (favoured by many mould tool and die makers) was taken for its ease of use and on-board functionality – especially its ability to help machine complex 3D surfaces and curved contours. The VC 630 5AX has a large working envelope (650 x 765 x 520 mm in XYZ), and a 32 kW/12,000 rpm direct-drive spindle.
Bringing any machining process in-house means there is an inevitable learning curve. Add to that the need to get to grips with the Heidenhain control (Linn’s Doosan DNM650 machine is equipped with a Fanuc control), and the curve becomes naturally steeper. However, the skill and experience of Linn’s operators and programmers, combined with technical and applications support (including training) provided by Mills CNC, has helped the company develop a secure and reliable machining process for its enclosures. Further refinement to fully optimise the process is ongoing and part and parcel of Linn’s continuous improvement ethos.
Concludes Crown: “The new machine is working well and we have found that having five-axis machining capability in-house makes us more productive and flexible. We are also able to respond, from a machining perspective, much more efficiently and effectively with regard to product design upgrades and modifications.”
For further information www.millscnc.co.uk