Turret-type VMC matches HMCs' output on some jobs

turret-type, twin-pallet, vertical machining centre has proven to be as productive on certain jobs as a company's more expensive twin-pallet, horizontal-spindle machining centres.

Totnes-based Foundry and Fabrication has been machining its aluminium castings for the past 15 years, generating added value that now accounts for 25 per cent of its GBP 3 million turnover.

One of the latest machines to be installed is a Daewoo ACE VC320 turret-type, twin-pallet, vertical machining centre from Mills Manufacturing Technology.

Foundry and Fabrication's production director, Darren Francis, says that for certain jobs it is as productive as the company's twin-pallet, horizontal-spindle machining centres, each of which costs up to four times as much.

For example, he referred to the manufacture of a family of 50 different parts for a customer in the telecommunications industry where margins are particularly tight.

"The hourly charge-out rate on a horizontal is too high to make the job financially viable," he says, "whereas the Daewoo drill / tap centre allows us to get through the same amount of work at a price that is acceptable to the customer." Key to the machine's high productivity are the 48m/min rapid in Z, 36m/min in X and Y, 4-second APC and the 14-station turret's tool-to-tool change time of 1.2 seconds.

These are not as fast as on some other tapping centres on the market, but Mr Francis was looking for robustness as well as speed and says he found the perfect combination in the VC320.

Spindle motor power is 7.5kW - high for this class of machine - providing 4.9 kgf.m of torque to allow a "decent" depth of cut to be taken, helping to reduce cycle times further.

In addition, the machine is less expensive than other twin-pallet tapping centres on the market.

Some of the jobs theoretically need a 5-axis machine to complete them in a single clamping.

However, such an investment would be too high for this type of work and in any case, full 4th and 5th axes were not usually needed.

Foundry and Fabrication solved the problem by fitting a rotary table that indexes at 15 degree increments onto the 3-axis VC320, and asking Mills to interface this B-axis into the machine's Fanuc 21i-M CNC system.

In lieu of a 5th axis, a suite of spacers is used to tilt the table so that holes can be drilled at the correct angle on a PCD according to the component being machined.

Tolerances are generally within +/-0.05mm.

Established in 1959, Foundry and Fabrication is a family-run business now in its third generation, and is one of the largest non-ferrous foundries in south west England.

It specialises in gravity die, greensand and resin-based processes and has a wide customer base outside the automotive industry.

Concluded Francis, "Our business has been built on customer service and satisfaction, so reliability of our machines is paramount.

Good back-up from our suppliers is equally important to maintain production and prompt delivery schedules, and we have found Mills' service to be second to none.

It has prompted us to go back time and again to this supplier; we also have two other ACE twin-pallet machining centres on the shop floor as well as a Daewoo Puma 300S twin-spindle lathe.".

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