The installation of a large-capacity travelling-column floor-type CNC milling machine with a16m-long bed allowed 325-employee MacTaggart Scott (based at Loanhead, near Edinburgh) to bring in-house the machining of extra-long workpieces — a move that in itself justified the machine purchase.
Sheffield-based TW Ward CNC Machinery Ltd
(www.wardcnc.com) — the company that supplied the Soraluce FL16000 six years ago — was subsequently asked to add a second machine column onto the original machine bed. This modification allows MacTaggart Scott to machine ‘both sides’ of a component simultaneously, or use one column to machine very long components. This upgrade has provided the company with excellent machining flexibility; it has also made efficient use of the space available in the machine shop.
MacTaggart Scott focuses on the naval defence and marine industries, and it bought the Soraluce to machine a specific component for aircraft-carrier lifts. The workpieces were originally out-sourced, but were then brought in-house so that the company could better control quality and cost. The parts in question required all of the machine’s 16m longitudinal travel.
Production engineering manager Robert Davidson says: “While this lift project alone justified the machine purchase, once we fully appreciated the capabilities of the Soraluce, we knew we could start re-thinking our traditional machining routines and consider producing workpieces in a different and much more economic way.
“Although the Soraluce has a large bed, we machine only a few of the 16m-long workpieces for which the machine was bought. We thought ‘why not install another complete machine column and head, but this time one with a 30-tool automatic tool-changer?’ The idea was to install the new column on the original machine bed at the side of the existing column, thereby creating two machines — each with 7m of X-axis travel — on a common bed. This configuration would allow a pair of medium-size workpieces to be machined on each side simultaneously; it would also allow us to quickly revert to ‘full-length’ machining using one column only.
Complex modification
“The result of the modification is that we have halved the cost of another job that was previously out-sourced, by simply ‘spinning’ the part on its fixturing. On another job, we halved machining times by producing the 4m-long parts in one hit on the Soraluce, rather than machining in two sequences on a 2m-capacity machining centre that would require us to machine one end and then ‘shunt’ the part along to machine the other.”
Engineers from Ward CNC undertook this particularly complex job of installing, integrating and commissioning the second column/head assembly. Because each column and head is working on the same X axis, each column is controlled by its own Heidenhain iTNC 530 CNC, with measurement feedback on all axes via Heidenhain LB382 linear scales. Moreover, the machine PLC was modified to incorporate anti-collision software for safe working.
New approaches to machining
Today, the Soraluce is one of the most heavily worked machines at MacTaggart Scott, and it continues to allow the introduction of new approaches to machining a wide variety of parts in a range of materials. Both of the modified machine’s universal heads feature an ISO 50 spindle driven by a 28kW motor via a two-speed ZF gearbox to give a maximum speed of 6,000rev/min and a maximum torque of 764Nm. Each column offers Y- and Z-axis travels of 1,400 and 1,000mm respectively.
The FL 16000 has a rapid-traverse rate of 35m/min for all the linear axes, while the H20 universal indexing heads feature air and oil lubrication and an indexing increment for both the rotary axes of 2.5deg.
Ward CNC was MacTaggart Scott’s preferred supplier for such a large milling centre. Mr Davidson says: “We have sourced machines — particularly horizontal borers — from the company for a number of years; these have included two Union BFT 130/7s, a Union BFT 130/5 and a Hyundai-Kia SKT 28LB. We also value the support offered by Ward CNC. This relates not only to new machines but also to refurbished and reconditioned ones, and there have been occasions when the company has been able to ‘dig us out of a hole’.
“For example, we had a failure with the head on an ageing borer — a key machine for us — that saw the counterweight fall onto the bed and damage it. Ward CNC had a similar machine at its Sheffield base and was able to ‘cannibalise’ this to repair our machine, which was up and running within just six weeks. That level of service is indispensable when one considers that there is not a Royal Navy ship afloat that does not have a MacTaggart Scott part.”
The company’s main focus is the design, manufacture and life-time support of mainly hydraulic equipment, such as hydroplanes, mast-raising equipment and lifting decks for aircraft carriers. In one case, this included the manufacture of a platform weighing 140 tonnes and able to carry 70-tonne loads (two aircraft).
From initial discussions through to manufacture, the contracts are often very lengthy — and of high value. For example, a contract for four lift units for two ships was worth £13.5 million and stretched over four years, with the manufacture alone taking one-and-a-half years.