The introduction of a Traub TNC 65 DGY twin-turret CNC mill-turn centre at servo motor manufacturer, SEM, is playing a key role in a dramatic change of fortunes for the Orpington (Kent) based company. The machine's installation by Traub Heckert UK of Brackley in the shaft manufacturing cell has been the catalyst to enable output to be doubled and fuel the company's massive increase in productivity over the last 12 months. It is also producing servo motor shafts faster than an existing CNC lathe.
However, the machine's ability to perform a range of secondary operations in the same set-up is now prompting SEM to consider employing the full capabilities of its opposed spindle and multi-tool turrets for the production of other, more complex, components.
The monthly call for servo motors runs into several thousand split evenly between brushed and brushless versions and are mostly used in CNC machine tool applications.
This means exports account for a large proportion of business generated at the Orpington plant.
During the last two years, the company has seen around ?2 million re-invested in modern production technologies in all areas of manufacturing including, more recently, the machine shop.
Colin Roycroft, who joined SEM a year ago as manufacturing manager, explains: 'With this capital investment we have been able to improve and upgrade our machining capabilities in order to respond to increased demand for our products which we have seen over the last 12 months.
The investment in the Traub mill-turn centre was the first evidence of this.' He follows on to explain: 'Many of the machine tools were originally installed for specific operations and products.
But now that SEM has seen that there is room for substantial growth in the business, we need to invest in more flexible modern machine tools to enable us to increase both our uptimes and our capabilities.' Part of that realisation is based on the fact that SEM is this year planning to achieve a turnover of around 12 million pounds.
As a consequence, the 190-employee company is currently operating a double shift system and constantly working overtime and at weekends.
While the higher efficiency use of the Traub and the implementation of just-in-time manufacturing principles have contributed to significant gains made by SEM, so too has the introduction of computerised planning.
Being able to produce a production schedule that provides a 14-day view of the projected workload is also a crucial element in SEM's productivity gains since, says Colin Roycroft: 'It is enabling us to work 'smarter' and is allowing the shopfloor to plan ahead'.
He continues: 'Rather than having to produce parts on a day-by-day basis, we can now group production requirements within two-week windows and achieve more economic batch sizes through reduced set-ups and the associated time savings.' SEM has a standard catalogue of motors and Colin Roycroft attributes success over the years to the company's ability to supply specials.
'Our strength is that we will design bespoke motors, even a single motor, exactly to customer specification.
The roll-on effect is that batch sizes are variable - perhaps as small as three including spares - and can run into several hundred.' These higher batches usually embrace the production of staging blanks involving shafts turned and ground to a common stage then stored ready to be finally machined.
The final machining can often involve keyways or drilled and tapped ends, to accommodate specific designs of servo motor.' Considering the quick turn-around demand for shafts in low volumes and high variety, SEM operates its machines more like a sub-contractor.
For this reason, the Traub mill-turn centre features an integrated bar feed unit that provides the automatic selection and automatic changeover of bars between 6mm and 65mm diameter and from 130mm to 1,000mm long.
Up to 166 bars of 6mm diameter can be held in the magazine which provides long periods of extended running.
Purchased initially to increase output, the Traub mill-turn centre performs a series of straightforward turning tasks including the generation of 90deg steps as well as angled steps/chamfers on the EN8 and EN16 shafts.
These shafts range in size from 15mm diameter to 120mm long and from 50mm diameter to 400mm long and are mostly turned to within 0.05mm, relying on subsequent grinding to achieve the final tolerances of 0.02mm.
The TNC 65 DGY has a bar capacity of 65mm in both main and opposing spindles, and can accommodate turned lengths of 450mm.
Powered by an 18.5kW motor to the main spindle and 11kW to the opposing spindle, the machine can achieve spindle speeds of 4,000 revs/min.
Equipped with twin 10-tool turrets, Colin Roycroft admits: 'The machine can be tooled to efficiently produce any one of a hundred profiles on a shaft.' In selecting the Traub machine Colin Roycroft points out that SEM's confidence in the machine's quality of build, and the support and back-up offered by Traub Heckert was enough to overcome any fears that may have been held about operating, what was to SEM, new supplier dedicated control technology in the Traub TX8H system.
He explains: 'Rather than programming offline and feeding the Traub with its programs via a DNC link, which is common practice throughout the machine shop, our programmer has spent time on the shopfloor familiarising himself with the control and then uploading the programs back to the server for future use.' Similarly, as SEM develops its programming and operating skills on the machine, Colin Roycroft is confident that it will continue to improve on the cycle time savings already being made over the shaft cell's existing CNC lathe.
The investment will continue at SEM with another CNC lathe and at least three machining centres planned for the near future, with the objective to bring similar gains in the areas where motor bodies and drive ends, for example, are produced.
'However, by investing in the new CNC machines we've already demonstrated that we can transform our uptimes and our capabilities,' concludes Colin Roycroft.
'Indeed, with machines like the Traub not only can we produce more parts faster than before, which has meant additional investment in upstream grinding capacity, but we can also consider further savings by utilising its capabilities to the full.
For example, certain shafts have geared ends, or grooves, which are currently produced downstream.
It is applications such as these that the Traub will be able to eat its way through.
Then perhaps we'll also start looking at other components we can machine on it.'