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Muffett Gears, a specialist manufacturer of gears for the medical, aerospace, hydraulic, marine, and motorsport sectors, has invested in a Tornos Gamma 20/6b sliding-head turning centre.

A GBP300,000 investment in machine tools at Mach 2010 included a Mori Seiki machining centre and a Tornos Gamma 20/6b sliding-head turning centre, both acquired for the production of the company’s own range of worm gearboxes.

The Mori Seiki NV5000 vertical machining centre (VMC) was acquired for the production of aluminium gearboxes while the Tornos Gamma 20/6b was bought to machine the gears and worm gears that are housed within the aluminium casings.

Alan Kennard, chief production engineer at Muffett Gears, said: ‘We supply an ever-increasing number of our own gearboxes.

‘Each gearbox incorporates a number of individual components and many of these parts require complex operations on different machines.

‘This situation has seen us historically run out of parts.

‘So, we bought the machines to improve continuity of supply and to ensure we never run out of parts, while significantly improving production times,’ he added.

The gearboxes that are used for the motorisation and movement of gantry equipment, patient chairs and beds and additional cancer care equipment for patient scanning were labour-intensive for the AS:9100 company, until the installation of the Tornos Gamma 20/6b.

Muffett selected Tornos for two main reasons: the ability of the 20mm-diameter capacity machine to conduct thread whirling in one operation; and the ability to switch to a guide bush-less system during a set-up that enables machining in the headstock and reduces material waste to circa 35mm per bar.

Kennard said: ‘Before the arrival of the Tornos, we would turn the worm blank on an alternate sliding-head turning centre and then do two grinding operations.

‘This would be followed by thread milling on our Monnier and Zahner machine prior to hardening and assembly.

‘The complete machining process was taking almost 14 minutes.

‘The Tornos has taken this time to three minutes, while eliminating set-up times, operator intervention and improving accuracy and repeatability.

‘To put this saving into perspective, we do more than 5,000 worm gears a year for one customer.

‘We knew that Tornos is an expert in the medical sector and has been developing thread-whirling techniques for a long time.

‘This expertise gave us more confidence in the Gamma’s ability when compared with competitor machines and we haven’t been disappointed.

‘The Tornos is more accurate than our other sliding-head machine, so by moving the worm gear to the Gamma, we have eliminated the grinding and thread milling from the process.

‘The back-end working of the Gamma is more robust than our other sliding-head lathe.

‘When previously doing back-end working and cross-hole drilling, we found cutting tools would break, creating reworking or scrapped parts.

‘The rigidity of the Gamma eliminates this aspect and improves our confidence, so we can leave the machine to run unmanned for long periods,’ Kennard added.

The multiple machine set up is a common factor in a number of components at Muffett’s – something the Tornos Gamma is continually eliminating with its nine driven tools, 19 fixed tools and simultaneous back-end working.

Since the introduction of the Tornos Gamma, the company has also moved the production of its bearing posts to the Tornos.

Previously, the parts were machined on a turning centre and then moved to a grinder for finish machining; again, reducing cycle times on a frequently machined component.

The company was previously machining bronze pins in a time of 20 minutes with four operations on two machines at a cost of GBP9 per pin.

The parts are now produced on the Gamma in one minute and five seconds, at a cost of GBP0.80 per pin.

Tornos introduced the guide bush-less system on its cam automatics many years ago, and it has been a major factor in many customers’ purchasing decisions because of the potential material savings, according to the company.

At Muffett, one example is highlighted with an aluminium bearing-cap component that is only 2mm long.

Any sliding-head machine without the system would waste a considerable amount of material on small parts.

Kennard said: ‘We are currently saving more than 10 per cent of our material costs with the guide bush-less system on the Tornos.

‘The machine is about to start running 16 hours a day, so the material throughput and the potential cost savings are huge.

‘As well as the material saving, the ability to take the cutting tool right up to the headstock is a benefit, giving us improved capabilities and flexibility,’ he added.

In addition, the cost-effective Gamma arrived at Muffett with a Tornos Robobar barfeed fitted as standard, a Fanuc 31i control system and a part catcher and conveyor.

Tony Smith, managing director at Muffett Gears, said: ‘Our shop-floor staff like the integrated barfeed as it simplifies machine setting, as does the Fanuc control that utilises a template program set-up that simplifies use and is very user-friendly.

‘The part catcher drops parts onto the conveyor, which moves the parts to an external part bin for long unmanned machining operations.

‘Putting the acquisition of the Mori and the Tornos Gamma into perspective, we can produce higher volumes and have now reduced cycle times of our gearboxes by more than 50 per cent,’ Smith added.

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