CNC automatic lathes are fast to program

Precision turned parts subcontractor said Star CNC automatic lathes are fast to set and program, so they are back in production quickly for the next batch run.

UK precision turned parts subcontractor, BGT Automatics, is steadily changing over from using cam-operated automatic lathes to using sliding-headstock, multi-axis CNC lathes Established in Aldershot in 1965, BGT increased the number of Star machines on its shop floor in 2007 by 30% The company acquired a Star SR-20RII, with extensive facilities for driven tool work, and an SV-32 that extends the subcontractor's sliding-head capacity to 32mm.

The other Star CNC automatics used by BGT have bar capacities of 12, 16 or 20mm diameter.

The machine tool supplier, Star Micronics, said that the SV-32had filled a capacity gap between the smaller automatic lathes and a 52mm bar capacity, fixed-head, CNC turning centre. Manager of the family-run company, Carol Naismith, said that the additional lathes and a more even spread of maximum bar sizes enabled BGT to offer a more comprehensive service.

Naismith commented: "It is the policy of large manufacturers and multinationals not to award contracts to subcontractors whose turnover is below a certain level, so we have been missing out on some of the bigger turned parts contracts, even though we would be perfectly capable of fulfilling them".

So BGT decided to increase its capacity to expand the business and raise company turnover.

Naismith added: "It also puts us in a stronger position to handle overflow work from larger subcontractors that may be struggling to fulfill large contracts, or that may not have sliding-head mill-turning capacity".

BGT has only replaced half of its cam automatics.

Eight of these are used to cost-effectively machine relatively simple components very cost-effectively, allowing the CNC automatics to machine the more complex, close-tolerance work.

BGT's customers are spread across many engineering sectors.

The company said two-thirds of its output is in machining stainless steel (303, 304, 316, 321).

Aluminium (HE30, FC1), steel and brass are also turned.

The Aldershot facility runs 24h/day, producing batches ranging between 100- and 50,000-off.

Machining tolerances down to 10 micron total are routinely held.

Less 'second operation' work is needed owing to the twin-opposed-spindle configuration and extensive driven tool capabilities of the Star CNC automatic lathes, and of the fixed-head lathe.

All of BGT's CNC lathes are able to perform in-cycle cross and reverse end machining.

Naismith related something of BGT's history: "Our father, Peter Ball, took over BGT Automatics in the early 1980s and shortly afterwards bought the first Star CNC lathe.

It was a JNC-16 and is still running today, so we have stayed with the same supplier ever since".

She continued: "We find the Stars fast to set and program, so they are back in production quickly for the next batch run.

This is important to us, as machine downtime would eat into our profits".

CNC sliding head turn-mill centres aid Adaero

Citizen Machinery has revealed how its CNC sliding head turn-mill centres have helped Adaero Precision Components secure lucrative components contracts.

Adaero Precision has two Citizen machines installed in its newly extended facility at Crediton, Devon; an M32-III and a mid-range L20 with the high pressure Coolblaster 2,000 lb/in2 coolant system The machines produce batches of 500 or so parts in Acetal, aluminium, brass and a variety of stainless steels Such is the complexity of some of the single operational cycles - for instance, an optical focus component that uses 24 tools on the Citizen M32 - that while cycle times can be relatively long at 5.5min, the overall benefits are significant through combining operations and shortening lead times.

Indeed, it was the purchase of the Citizen L20 in June 2007 that led Adaero to win an important medical contract for three variants of an air flow adjuster in 316 stainless steel for anaesthesia equipment.

Consistency of production from the two Citizens has never been an issue, resulting in the company's high level of confidence for long periods in limited manning and unattended running.

Such is the level of setting expertise that requirements to maintain grinding tolerances can be met when turning on features such as seal diameters and grooves, that are then monitored using the latest optical inspection equipment to ensure full compliance to drawing requirements.

Changeover normally takes between two and three hours depending on the complexity of the batch but, according to Mark Pearson, engineering sales manager at Adaero Precision Components, this time is minimised due to machine's flexibility in being able to accommodate different tooling layouts.

Also, as most programming is performed offline and most jobs have been previously run, efficiency is high, keeping lead times short.

The 13-axis Citizen M32-III is able to hold up to 80 tools.

Common tooling can be left set on the vertical tool platen and drilling station for back machining as well as on the Y-axis fed, 10-station turret that is able to accommodate up to 50 tools by using its half index capability and special tool holders.