Machining cells provide continuous production

With the success of Seco's Jetstream Tooling range, the Swedish company's UK subsidiary, where all the tools are manufactured, has had to increase production capacity.

In July 2008, automation equipment was retrofitted to its first Hermle five-axis C 30 U vertical machining centre and a second, identical automated cell has been installed.

UK agent, Geo Kingsbury Machine Tools, undertook both turnkey projects, which were proved out at its Gosport technical centre before delivery.

Seco's custom tools manager, John Upton, said: 'The latest investment is part of a major expansion programme to extend our manufacturing facility in Alcester, as it is our company policy not to outsource production.

'We are in the process of upgrading every area of manufacture, including CAD/CAM, production planning, tool setting, finishing, dimensional inspection and leak testing.

'In addition, we are going through a continuous improvement programme based on 5S and LIFE (little improvements from everyone).

'With regard to machining of the steel toolholders and coolant inducers for the standard range of Jetstream Tooling, we are already considering buying two more Hermle flexible machining cells.' Jetstream Tooling was originally developed in partnership with an aero engine manufacturer as a bespoke tool for machining exotic alloys.

However, accurate through-tool coolant has been shown to increase productivity when machining virtually any metal, even with coolant pressures as low as 5 bar.

Hence, take-up of the tool has been far wider than was initially anticipated.

Consequently, Seco decided to introduce a range of over 300 standard shank and Capto tools in imperial and metric sizes.

The first Hermle machining centre with bespoke fixturing was purchased in 2006 to help make the Alcester factory the European centre for the manufacture of semi-standard toolholders in Seco's MDT (multi-directional turning) range.

From the outset, fast set-ups were essential due to the hundreds of MDT tooling variants in four product families, so quick-change pneumatic fixtures from Erowa were supplied by Geo Kingsbury.

In the pair of automated Hermle cells at Alcester, a mix of semi-standard and standard tooling products can be flexibly produced on either machine.

Off-line set up means that an economic batch can be of any size, typically from a maximum of 400-off down to one-off, even during unmanned running.

Both of the C 30 Us are fed from an Erowa 12-station pallet loader, the one on the first Hermle forming part of the retrofit.

Installed at an angle of 45deg to the left side of each machine, rather than directly in front, the configuration affords the operators better access to the working areas when proving-out jobs and fixturing the occasional one-off during the day.

Up to 24 different jobs can be fixtured at any given time across the two cells.

Continuous production is achieved, as average machining time per toolholder is 15 minutes and as four tools are fixtured per pallet, approximately 12 hours unattended running is possible on each machine.

A 157-position tool magazine was specified for the second Hermle and the magazine on the first machine was extended to the same number of pockets, allowing space for sister tools during a ghost shift between 23.00 and 06.00.

This will start before the end of 2008 to provide 24-hour production.

Options included as part of the machine packages include four-arc-second accuracy for both of the rotary axes, tool length measuring with offsets sent automatically to the Siemens control, tool breakage detection and high-pressure, through-tool coolant.

In conclusion, Upton said: 'Hermle machines are becoming the standard five-axis production centre within the Seco Group, as they are used at our factories in Sweden, Germany, the US and India.

'They have excellent accuracy and repeatability, partly because the trunnion-mounted rotary table is integral, not an add-on, and also because the mineral-cast bed minimises vibration.

'Accuracy is important, as some features on our tools are tied up to 10 micron total.

'Access for changing tools and components is good, and there are the added advantages of interchangeability of machine programs between our divisions, and commonality of post-processor software.

'We find that the 18,000rpm spindle and 45m/min linear rapid feeds of the Hermle machines translate into cycle time reductions of between 10 and 20 per cent compared with standard VMCs that we formerly used for toolholder production.'.

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