It's no coincidence that the turnover of sub-contract turning specialist Unicut Precision has mushroomed since it bought its first Citizen B12 sliding head CNC lathe.
It's no coincidence that the turnover of sub-contract turning specialist Unicut Precision based in Hertfordshire has mushroomed since it bought its first Citizen B12 sliding head CNC lathe back in March 1999. The 14-strong company has spent some GBP1 million installing three more Citizen B12s, two L32s, an L20 and a top of the range 13-axis M20, from NC Engineering of Watford. The performance and productivity of these eight citizen machines has been a mainstay behind Unicuts growth, with last years turnover double that of two years ago.

This year, business is expected to increase by a further third.

Founded in 1990 by co-directors Charles Kenny and Jason Nicholson, Unicut Precision specialises in the production of precision turned parts for the aerospace, automotive, electronics and telecommunications industries.

Most work is between 2mm and 30mm diameter and batch sizes are from 50 right up to a 1,000,000 or more.

From fairly humble beginnings, the company has grown progressively resulting in new larger premises moves four times in the last 10 years bringing it to the current location in a 6,500ft2 factory unit on the Tewin Court trading estate at Welwyn Garden City.

Only three years ago Unicut's production was based around 11 single spindle cam automatics, six multi-spindle autos and a couple of second-hand CNC lathes.

While work was plentiful, the directors were having problems obtaining skilled labour and were becoming concerned and frustrated over the length of time taken for machine set-up and changeover.

Also, the high levels of work-in-progress fuelled lots of discussions over the amount of second-operation work having to be carried out.

Looking to the future the nature of the work being machined rang warning bells as it tended to be for the more simple types of components where fierce competition from the likes of Eastern Europe and China was squeezing margins and forcing prices down.

The ultimate threat of customers having to take work away was a result of simple economics.

As director Jason Nicholson recalled: 'Our experience with used CNC machines showed the way ahead.

We became determined to take full advantage of the rapid developments made in CNC sliding head lathe technology and investigations of the machines on the market led to our first Citizen in 1999.

We have not looked back since.' He follows on to describe how throughput on the Citizens is phenomenal.

'These machines have transformed our business by significantly improving our all-round capability, flexibility, response and increasing the complexity of work we can now handle.

Our capability to maintain accuracy is now superb and we have eliminated the need for second operation work with virtually all jobs now machined in a 'one-hit' cycle.' Switching over completely to CNC machining has brought major additional benefits.

He describes how work-in-progress queues have been reduced to zero whereas before, it could have accounted for 50 per cent of a months work.

Being able to run completely unmanned at night and weekends means they have the flexibility to maintain a round the clock production schedule.

Representing an investment of some GBP1 million in just two years, the Citizen sliding head lathes have made Unicut ultra-competitive and enabled it to take on new work which would not have been economical to even try to quote for before.

'What's more, this technology has given our existing customers even more confidence in our capability, resulting in quite a few increased contracts,' maintains Jason Nicholson.

Two of the Citizen B12s are fully engaged in the production of between 350,000 and 400,000 mild steel fasteners a month which are just 6mm diameter by 5 mm long.

Cycle times on the B12s are rapid and often as low as nine to 10sec for the simpler type of components with lost production to account for changeover averaging less than one hour against over six hours on the single spindle autos and days on the multis.

Machining routines have also been easy to optimise compared with fixed headstock CNC lathes.

A prime example is a stainless steel connectors for the telecomms industry measuring 8mm diameter by 10mm long.

The part has an M6 internal thread, which is produced on a B12 in 56 ecs and used to take around 85sec to machine before.

'With quarterly orders of up to 5,000, the savings are significant,' says Jason Nicholson.

Typical parts produced on the Citizen L32 include special security nuts, bolts and keys for the automotive industry.

Measuring 24mm diameter by 30mm long, the EN8 steel nuts used to be machined in two separate operations taking 90secs.

Cycles involved turning the profile, threading, producing various grooves, drilling three 5mm diameter holes and milling a special cam-shaped form.

Tolerances are +/-0.05mm and batch quantities are up to 4,000.

The milling/drilling operations were a constant concern before causing hold-ups due to their labour-intensive nature.

Now, each nut is produced in a single cycle on the L32 in just 45secs.

On 24mm diameter by 50mm long locking bolts, the Citizen L-Series machine has been able to cut cycle times from 80secs to 50secs.

The very latest Citizen to be installed is the 13-axis M20 CNC sliding head lathe.

This advanced model was bought to further increase the company's capability to produce more complex components.

Here, the machines multi-axis capability with 10 station turret and a further eight driven tool stations for milling and drilling type work are being put to good use.

The main components include a selection of engine manifold parts and a steel throttle linkage shaft for the automotive industry.

The throttle shaft involves extensive milling as the 6mm diameter by 90mm long component has a 2mm wide by 40mm long central slot, twin milled flats, two spot faces, a couple of counterbored holes, two drill and tapped holes and a thread on one end.

As this is a totally new job, before and after time comparisons are not available.

However, the large amount of milling would previously have called for a significant level of second operation work involving extensive setting, machine operators, fixturing and gauging and problems of geometric relationships of features.

The M20 is able to produce the shaft complete in a one-hit cycle time of under 120 secs.

Running the Citizen lathes is also very cost-effective with the eight machines looked after by just three operators.

The company operates a double-day shift which goes through to 10 pm followed by unattended working at night and weekends.

For safety sake this work normally involves parts which have been well- proven on manned shifts and do not involve difficult to machine materials so tool life is predictable.

This does mean the company has to structure its machining schedules to ensure that suitable work is available.

However, on certain jobs, they make the decision to throttle-back feed rates to around 70 per cent of the day rates to ensure uninterrupted production when the lights are out.