Ram-type borer cuts machining lead-times

The GBP 1.4 million investment by RWE Power International, TSG Ferrybridge in what is probably the largest and most sophisticated ram-type horizontal boring and milling machine in Europe, a 16m X-axis capacity Union PCR 150 ram-type machine with live spindle and head changing supplied by Ward CNC of Sheffield, is generating equally massive benefits at the West Yorkshire, UK, site - in one case, the one-hit machining from solid of a large gearbox coupling, the machine has slashed lead times from seven weeks down to an amazing seven days. 'Indeed, compared to the two ageing machines it replaces, the new Union is completing in a single shift what used to take a week on the two older Union borers it has replaced,' says process co-ordinator Craig Bill, who adds that the machine has provided the company with an unprecedented level of milling and boring capability and flexibility, with which any other UK company, at least, cannot compete. With complementary Y and Z axes traverses of 4000mm and 1000mm, respectively, plus a 700mm W-axis (spindle) stroke, coupled with twin 40- and 24-tool toolchangers and axis feed rates and rapids of 5-15000mm/min and 15m/min, respectively, the machine can accommodate workpiece loadings of 70,000kg on a traversing and rotating CNC table, so clearly has the capacity to satisfy every machining situation likely to come its way.

But Bill also emphasises the machine's ability to quickly and easily utilise and change between different machining modes as the factor that, he says, 'Effectively transforms what is on paper a six-axis milling and boring machine into an unrivalled and highly productive 11-axis machining centre.' Also supplied with the machine by Ward CNC is the automatic accessory changer that comprises: * A linear motor Cytec gyroscopic two-axis milling head with built-in high-speed electro spindle and served by its own dedicated toolchanger.

* A D'Andrea UT5 800S CNC facing and profiling head with 1000mm facing capacity.

The machine specification is further enhanced with the integration of the 70 tonnes loading capacity Eimeldingen heavy-duty rotary and traversing CNC table, extensive floor plates and zoned guarding allowing the machine to be efficiently set up for pendulum or three-zone machining.

Bill emphasises that such has been the impact of the machine specification and the flexibility offered by the accessory changer system, combined with the inherent power and productivity of the Union machine that, as a result, 'We are able to finish machine component features in a single set-up that would have been very difficult, perhaps even impossible, to achieve any other way.' One example of this concerns the production of a hydro power industry 3200mm by 3400mm by 3000mm main inlet valve (weighing 73 tonnes in finished state) and its accompanying 2500mm diameter by 350mm thick main service seal (reverse engineered and machined from stainless steel).

A number of holes are drilled, tapped, counterbored and thread milled in the bore 'outwards'.

'Without the flexibility of using a variety of heads, we would find it very, very hard to produce these features,' Bill confirms.

'When we decided to replace the two old boring machines, we looked at other boring and milling machines and their suppliers,' continues Bill, 'But the Union PCR and Ward CNC won the contract based on a combination of machine capability, capacity and price as well as on Ward CNC's ability to provide the level of support we needed.' Of heavily ribbed design with three-way, backlash-free, heavy-duty compact roller guide system for highly-accurate guidance of the crossslide, the sturdy machine bed is complemented by a similarly constructed box-type column.

The column saddle also features compact roller guides as well as ballscrew drive for transverse movement.

The vertically travelling headstock with axially traversing ram (Z-axis) accommodates the high-precision main spindle system featuring preloaded spindle bearings with lifetime lubrication.

Speed range changes are catered for by a two-step gearbox having hardened and ground helical gears, and a hydrostatic guiding system of the ram with drop compensation in relation to longitudinal displacement, together with an additional mechanical compensation system, ensures high and accurate cutting data.

For example: * X, Y, Z and W axes positioning of +/-0.005mm (up to 800 mm), +/-0.008mm (to 5000mm) and +/-0.012mm (to 10000mm).

* Repeatability of +/-0.003mm.

The Union was installed as part of the RWE npower company's GBP 3.5 million CNC machine tool investment programme last year as the platform for the company's strategic move into the wider arena of sub-contract machining, based around a quick-response machining service for customers in industries such as oil and gas and automotive.

These sectors have been identified by Bill and the TSG Ferrybridge team as ideal to complement and build on the company's core (and established) skills applied since 1974 in the refurbishment of power station equipment, including rotors, valves, pumps and gearboxes and, in particular, turbines and turbine blades.

RWE Power International, TSG Ferrybridge was established as one of three sites to perform such work for power stations within the RWE group, as well as third party sites (basically, the company has worked on equipment at every coal, gas and hydro/wind power station in the UK).

'We were spending a lot of money on turbine blades,' continues Bill, 'And basically reckoned we could save a lot of cash, and produce the blades quicker, if we did it ourselves.' In some cases a single, large turbine blade could cost GBP 36,000.

That is not surprising when it is realised that the leading blade on a large 5m diameter rotor, revolving at 3,500 rev/min, is actually moving at twice the speed of sound - so the blade has to be right.

Since then, the operation has progressed to a GBP 52 million turnover concern, and involves up to 350 people.

Aside from its high-tech turbine blade high-speed machining production facilities - including the development of a innovative and patented 'blade cropping' process - the company has an impressive range of machine tools throughout its three large workshops alongside the Ferrybridge C power station in West Yorkshire.

In conjunction with a general fitting and assembly area - housing press, welding, heat treatment, grit blasting, NDT, grit blasting and 120-tonne gas turbine rotor de-stacking - the light and heavy machine shops accommodate a wide array of CNC machines.

These extend from milling, turning and machining centre capacity through to 25 tonnes vertical borers and large capacity lathes, including a Safop 100 tonnes capacity machine able to handle 17m between centres.

In addition, the company also offers an on-site machining service, which utilises a battery of 'mobile machine tools' to enable customers' fixed plant and equipment to be re-machined, refurbished, repaired or modified in situ.

While the large capacity Safop is currently being targeted to 'partner' the Union PCR to further extend the machines' capabilities by linking the two via existing Unigraphics/Vericut CAD/CAM facility, Craig Bill and the team have other plans for Union, to further reduce lead times and so magnify the enormous savings already being made.