24-hour running using wire cut EDM machines

Based at Larkhall, south of Glasgow, Gilmour Tools includes two Fanuc Robocut Alpha wire cut EDM machines in its plant to complement its state of the art CNC profile grinding machines

Based at Larkhall, south of Glasgow, Gilmour Tools has supplied the automotive, aerospace, oil and other industries with cutting tools for over two decades.

For the past seven years, it has held an exclusive contract in the UK to produce and supply special carbide cutting tools for Kennametal.

This has meant investment in the most efficient manufacturing plant, which is why it includes two Fanuc Robocut Alpha wire cut EDM machines in its plant to complement its state of the art CNC profile grinding machines.

As a result of these machines the company has been able to run 24 hours a day including 'lights-out', increase flexibility and material utilisation, shorten delivery times, and improve and maintain high levels of quality of carbide inserts.

The 35-strong Gilmour business specialises in the manufacture of indexable carbide inserts for internal and external threading, grooving and profiling as well as the compatible tool holder systems.

These are designed by Gilmour using state-of-the-art CAD followed by manufacture to meet Kennametal's exact specifications.

As General Manager, Gary Gilmour, explains: "Our investment in wire cut EDM to replace optical profile grinding has made us very cost-efficient." The first Fanuc Robocut Alpha OC was purchased from 600 Centre of Shepshed near Loughborough in 1998, followed by the latest Alpha OiA installed last year.

Gary Gilmour says: "When wire erosion was first introduced it had little relevance to our type of production work.

But over the last few years significant developments mean it is now an advanced process that is easy to operate and is very economic for production machining of tungsten carbide.

It is a very accurate process of producing form tools and we can produce features on the Fanuc machines that are impossible to grind - such as the multiple interpolation of radii in a single set-up." One feature of the Robocut that is important to tungsten carbide machining is non-electrolysis AC cutting, which Gilmour adopts for both roughing and finishing.

This prevents any formation of a thick re-cast layer that would be detrimental to the appearance and performance of the tool's cutting edge.

With AC machining, the layer is limited to a few microns, and Gilmour has developed its own process to remove even this thin layer.

"Non-electrolysis cutting prevents burning or marking of the cutting edge and leaves a very good surface," comments Gary Gilmour.

"It is smooth, which the customer likes, and extends the effective cutting life of the tool." Similar benefits apply to the production of tool holders.

Complex tool tip receptacle pockets are readily cut on the Fanuc Alphas with a higher finish and more rounded edges than if milled.

"With EDM you don't get tool and chatter marks, which gives the tool holder have a real quality appearance," he insists.

One of the key benefits of wire erosion being experienced by Gilmour is flexibility.

The company maintains that optical profile grinding requires a highly skilled operator in constant attendance, but that CNC wire cutting is simple and quick to set up, and it runs unmanned.

One man on each shift looks after the two Fanuc machines and he still has time to operate one or two CNC grinding machines, which Gary Gilmour maintains: "Is an efficient utilisation of labour." The fast set up and minimal fixturing on the Robocuts also accommodates smaller batch production which in turn means faster response and deliveries.

"We can deliver tools produced on the Fanuc machines in two days compared to two weeks if we had to rely on the optical grinder process route," says Gary Gilmour.

The Fanuc machines also have low consumable costs requiring only wire and filters, which are much cheaper than grinding wheels.

Much of the cutting is performed with standard brass wire but where the highest quality finish is required, Gilmour will use zinc-coated wire - which leaves the barest minimum of re-cast layer.

While both Alpha machines have a capacity of 700 mm by 500 mm by 180 mm, the latest OiA machine has a totally new power supply, improved corner control software with non-electrolysis AC cutting and adaptive control over variations in material thickness being processed - which can improve existing speeds by up to 30 per cent.

The two Fanuc machines are applied to producing the most complex tool and tool holder forms, as well as slicing blocks and cutting very thin pieces preventing damage because of the gentleness of the process.

The machines also allow maximum material utilisation; for instance, two tools can be machined from one block of carbide with the form on each end and then sliced into two.

"When grinding, only one tool could be made out of one block," adds Gary Gilmour.

The company has been operating the Alpha OC for two years and the Oi for 12 months, but both have run continuously, 24 hours a day including 'lights out'.

"They are extremely reliable machines and we have been well supported by 600 Centre," he says.

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