At the Hailsham, East Sussex, factory of sub-contract machinist Dicker Precision Components, an Italian-built Biglia twin-turret twin-spindle CNC turning centre has streamlined the production of a family of aluminium switch-cover assemblies.

The savings are so great that the cycle time for producing one part of the assembly has been halved, while the other is produced in just over a third of the time.

One reason for the substantial reductions offered by the Biglia B465-T2Y2 lathe — supplied by Kenilworth-based Whitehouse Machine Tools Ltd (www.wmtcnc.com) — is a second live turret with a Y axis; the previous version of the machine only had one turret.

Moreover, the second turret can operate at either spindle, allowing balanced machining operations at one side or simultaneous cutting at both spindles.

A maximum driven-tool speed of 12,000rev /min (three-times higher than on its predecessor) is another factor contributing to the increased output of the new machine.

Moreover, this not only increases productivity but also reduces the incidence of tool breakage.

Lee Chapman, shopfloor manager at Dicker Precision, said: “Modern cutting tools benefit from higher machining speeds, but tools suffer if they are run too slowly.

“In particular, when profiling the outside of the assembly components, our rippers and end mills used to break frequently on the previous lathe, with one or two having to be replaced every day. On the new Biglia, we only needed to change two cutters during the first six weeks of operation, which started early in March this year.”

Unlike with the former lathe, Mr Chapman is confident of leaving the Biglia to operate unattended, so it runs overnight seven days a week, and all parts are in tolerance the following morning.

Moreover, he says that once the B465-T2Y2 is set, the required ±25µm on some dimensions is held with ease; it is also rarely necessary to change the offsets.

Common stock

The family of switch covers comprises eight variants; they range in thickness from 6 to 10mm and are all machined from 50mm-diameter aluminium stock fed from a Hydrafeed MSV65 short-bar magazine.

The tools required to machine all of the component varieties are resident in the two 12-station turrets, so the daily change-over to the next batch run just requires the next program to be called up.

Each assembly comprises a base and a cover. The former requires only a single turret to complete the machining cycle, so halving the machining time to 2min is down to the higher spindle speeds and the ability to increase feed rates without risking tool breakage. However, the cover does benefit from twin-turret operation.

Synchronous transfer of the component after parting-off to the second spindle allows simultaneous machining of the reverse face of one component and the front of the next; this sequence results in a cycle time of 2min instead of the previous 5.5min.

Moreover, extra time is saved by including a routine for deburring the periphery of the cover and ‘spotting’ holes on the back face eliminates the former need to finish each component by hand. With several thousand switch-cover assemblies produced every month, the overall advantages in terms of higher productivity and reduced manufacturing costs are considerable.

For the first few months of operation, the B465-T2Y2 was devoted to machining switch covers, but Dicker Precision was soon well ahead of its production targets as a result of adopting the new process (bottlenecks were frequent
before). Additional work was soon put onto the new Biglia, including a contract for the production of stainless-steel door-lock components for vans.

The work came from another customer of Whitehouse Machine Tools in south-east England (through the machine supplier’s local sales engineer, Mark Drummond, who happened to hear that the business was available).

Summing up his latest machine purchase, Mr Chapman said: “Whitehouse provided us with a turn-key installation comprising the Biglia lathe complete with tooling, programs and operator training — and the company has offered to program future jobs for us.”