Factory

Metal cutting gets all sparked up

Metal cutting by spark erosion, seen until recently as too slow for a production environment, has been adopted by Lucas Aerospace. It is being used to produce parts for stainless steel valves found in pumps and fuel meters on the Rolls-Royce Trent and other aircraft engines.

Two Agie EDM machines a Classic wire-cutting machine and an Innovation diesinker form a branch line between two of the five £1m machining cells that make up a single-part, random-flow manufacturing system at Lucas’s ‘centre of excellence’ in Birmingham.

The aim is to increase productivity, reduce work in progress and reduce lead times by up to eightfold.

The Agie machines were chosen for their ability to hold a tolerance of 10 m on small parts with curved surfaces that would be difficult to machine conventionally.

The branch line to the Agies ensures there are no bottlenecks at the main machining cells, each of which has an annual throughput of 16,000 parts, taking 15 minutes to complete a valve.

AGIE

Centreline’s Galaxy gear-driven multihead toolholder allows two or more widely spaced holes to be drilled or tapped simultaneously.

Targeting automotive applications, the new design makes it possible to produce holes anywhere within a radius of up to 15′, using an infinitely adjustable setting. Resetting the head takes no more than 15 minutes, according to Centreline’s Derek Price.

He says the Galaxy name comes from a ‘moon-around-the-earth-around-the-sun’ arrangement of the tool spindle drive gears to ensure the correct drilling and tapping torques are maintained.

Price reports that business is slow but steady, and the firm is benefiting from investment in the US and other export markets. Repeat orders are helping to spread engineering costs.

CENTRELINE

Removing taps and other broken tools from a workpiece is the job of the 600 TR100, a low-cost portable spark erosion machine suitable for making start holes for wire-cut EDM machines.

Once installed on its magnetic stand, the machine cuts tungsten carbide and other hardened steels with ease, it is said, and removes broken tools without causing damage to surrounding, softer, material or to existing machined threads.

The TR100 uses domestic water as the dielectric and brass bar between 1.2mm and 6mm as the electrode. The machine can be used for large workpieces using putty to construct a surrounding pool of dielectric. Machining is possible to within 30 of vertical.

600 CENTRE

Holding irregularly shaped parts for machining could prove a moveable feast, especially for a company such as Stanmore that makes up to 800 hip replacements and other surgical implants a year from titanium.

Neither conventional nor customised fixturing could cope with the unique variety of components. But a method used to machine-jet engine turbine blades, based on a fusible alloy developed by Mining and Industrial Products, has provided an inexpensive, quick and reusable work-holding method.

A special property is the ability of the molten alloy to expand rather than contract on cooling to provide a rigid fixture for the workpiece.

One end of the workpiece is encapsulated in a cylinder, made, typically, from aluminium filled with the MCP alloy. The precise position of the workpiece within the fixture is programmed into the CAD/CAM computer system used to mill the component to tolerance through the fixturing. Cycle times between components are typically 35 minutes.

Impurities in the reusable MCP alloy float on the molten surface and can be skimmed from the material, which is relatively dense. It is denser than titanium, Inconel or aluminium material from which the encapsulating cylinder is made.

MCP

Sheffield Measurement has extended the capacity of its workshop-hardened Discovery coordinate measuring machine.

The D-28 has a measuring volume of 760mm in X, 1,000mm in Y and 600mm in the vertical Z axis and is said to be ideal for shopfloor inspection of larger or multiple table loadings of components.

The machine is accurate to 0.013mm, repeatable to to 0.0025mm and has a resolution of 1 m.

DISC GB

Bio EST, said to be non-toxic and non-irritant, is a new soluble cutting fluid developed to inhibit bacterial growth and remain clear throughout its working life.

Through a process called inverse solubility, the fluid becomes less soluble in water as the temperature rises around the cutting tip and workpiece, coating the metal surface with lubricant while retaining the benefit of the cooling water.

EP SPECIALISED FLUIDS