The installation of two programmable surface grinders has allowed toolmaker Tarpey-Harris to reduce lead times by up to 25% and optimise grinding times for dies, moulds and precise parts.

The installation of two Okamoto ACC 450 DXA surface grindingmachines by 600 Centre of Shepshed, Loughborough has allowed theBelper-based toolmaker Tarpey-Harris to reduce lead times by upto 25 per cent, have one operator to look after both machines formost of the day and optimise grinding times for a wide range ofdies, moulds and precision parts. In addition, the company hasfound the Okamoto machines very easy to operate and to make itspurchase justification more significant, the final machinespecification worked out 20 per cent less than comparable surfacegrinders on the UK market. Established in 1969 as precisionengineers and toolmakers specialising in tooling for theinvestment casting industry, Tarpey-Harris is now part of theFairbrook Group.

The 32-strong Derbyshire company producesextrusion dies, injection mould tools, rubber mould tools and waxpattern dies that are mainly used for plastics window elementsand profiles as well as cladding for buildings.

The wax andrubber tooling it produces is primarily used in the manufactureof seals for hatches, doors and other openings for the aerospaceindustry.

However, the company also manufactures injection mouldtooling for a range of medical products and provides a componentmachining subcontract service for an array of different industrysectors.

With over 80 per cent of its machining work involvingtool production, grinding is therefore a key process.

So when thecompany decided to replace a couple of ageing manual surfacegrinders it looked around for the most suitable machine on themarket in terms of performance, accuracy, ease of use andespecially set-up and cost effectiveness.

As works director TonyHarris explained: 'After seeing an Okamoto 450 DXA in actionat a 600 Centre customer, we decided that this machine was idealfor our needs, combining precision with affordability.

Sinceinstallation the repeatability, ease of operation and minimalmanning requirements of the machines has transformed ourbusiness.

I look out of my office window and they are runningthroughout the day with hardly anybody ever near them.' Some90 per cent of the company's surface grinding work is nowchannelled through the Okamotos for processing a wide range ofdie parts, bolsters, die blocks, top plates, ceramic core diesplus a range of blank strips for components which aresubsequently profiled by wire-cut EDM.

Work can range fromgrinding the ends of 3 mm by 5 mm probes right up to quite largebolster elements, measuring 350 mm by 400 mm.

Although the tableof the Okamoto ACC 450 DXA is hydraulically actuated, the machineincludes a fully automatic grinding cycle controlled viamicroprocessor with digital readout (DRO) in two axes.

'Thisprovides us with maximum flexibility in terms of just how themachines can be operated,' maintains Tony Harris.

Each ofthe Okamoto grinding cycles tend to be split between variousmodes of operation for which a quarter accounts for manual andsemi-automatic cycles but fully automatic operation is nowapplied to half the work flow passing though the machine.Depending on the mix of work, one man can look after the twomachines for most of the time and in a typical working day, theoperator is only present at the machine for as little as 12 percent of the time which includes wheel dressing, outlines TonyHarris.

He maintains: 'This means we get 16 hours worth ofproduction from the two machines each day with an operator inputof around two hours.' However, he says: 'The biggestsingle saving has been the ability to measure components directlyon the machine using its integral, two-axis DRO.

Here thecontribution to productivity is much higher because parts do nothave to be removed from the table to perform key measuring tasksand we reckon this reduces our lead times by some 20 per cent.While the Okamoto's automatic operation, using auto downfeedand crossfeed has proved of major benefit to the company, thisfeature was not high on the list of priorities when the machinewas initially selected.

As Tony Harris recalled: 'Comingfrom purely 'hands on' manual machines, we were not toofussed about automatic cycles.

However, now that we have such aneasy to use facility, we are making more and more use of autocycling on specific types of work because it is dramaticallyincreasing the flexibility of labour.

Combined with quick set-uproutines, the Okamoto machines have proved to be a really soundinvestment and their repeatability is first class.' Equippedwith 450mm by 150mm magnetic chucks, the Okamoto machines areused on a wide range of tooling work - much of it involvinghardened steel elements.

Typical metal removal rates on hardeneddie blocks, for example, is about 0.5mm and tolerances as tightas two microns are regularly achieved.

Maintains Tony Harris:'Surface finish is another important consideration,particularly on mould type work, and the machines regularlyproduce finishes to 0.05 micron Ra.' The installation of thetwo Okamoto machines has made a big impact on surface grindingefficiency, accuracy, productivity and cost-effectiveness.

And asTony Harris concluded: 'When we need additional surfacegrinding capacity we will undoubtedly go back to the 600 Centre,because these two machines have transformed the way we wereworking.