Sliding head automatics

If anyone has any ‘fear’ of using CNC machines, this subcontractor’s experiences with CNC sliding had automatic lathes , show how that fear was lost and more profits were gained

Owner of Stroud, UK-based company, Precision 82, Tony Mathews, readily admits that he used to be afraid of CNC machines. That was back in 1988 when, as a user of plugboard lathes, manual cam automatics and cam sliding head lathes, he had seen competitors investing in citizen cnc sliding head machining.

Matters are now quite different in 1997: Precision 82 has successfully achieved the official recognition of being the top supplier for a major office furniture company.

The subcontractor has a consistent record of delivering parts with zero defects in the six sigma regime of the company.

Looking back to 1988, Mathews said: ‘I was a firm believer that nothing matched the production time of a cam auto for volume turned parts – despite what was happening all around me’.

For example, when Precision 82 won a monthly contract to produce 500,000 heat sink pins it took just 10s to produce each fairly straightforward part on a cam machine compared to 18s on a CNC lathe.

Mathews said: ‘Of course, then you couldn’t match the overlapping operation advantage of a cam auto, so I was therefore a firm believer in ‘cam could and CNC couldn’t’.’ Mathews changed his mind when he found that a multi-operation part for the photocopier industry was taking 3 min to turn and produce with cross holes, milled flats and countersinks.

Worse still, the part required a second operation set-up just for radiussing and cleaning – yet it could be completed in a single set-up in under a 1 min on a Citizen CNC sliding head machine.

What convinced Mathews that CNC sliding head technology was the best way forward, was a visit to a customer who was installing a Citizen to replace a machine that he was about to buy.

Mathews doubts if he’d still be in business if it were not for Citizen CNC sliding head technology and the help and support of the machine supplier, NC Engineering of Watford.

‘By investing in the multi-axis Citizen L20-VIII I immediately scrapped five cam autos.

It was the best thing I’d ever done,’ he insisted.

Mathews related that with 21 tool positions and simultaneous cutting with two tools, the machine’s ability to minimise idle times combining simultaneous axis movements during tool changes and screw threading cycles initially presented a scenario where he was really in the ‘wilderness’ in terms of ‘managing’ the technology and realising its potency.

Mathews said: ‘But in addition to acquiring a cost-effective, first-class machine, I also gained a brilliant level of support and back-up from NC Engineering’.

‘Nothing has been too much trouble for them’.

* About the Citizen L20-VIII I – the machine has a capacity of 20mm diameter by 200mm machining length.

It enables a variety of tool layouts to be selected to service the main 3.7kW, 10,000 rev/min spindle and 1.5kW, 8.000 rev/min sub-spindle for cross-machining, end face features or turning cycles.

When cross-machining is the priority, up to 18 tools can be mounted on cross toolholders.

These include five turning, seven rotary and six drilling tools.

Additional flexibility is available as the three cross toolholders may also be used for end face drilling spindles by swivelling the unit through 90 deg.

When there is a higher demand for end face machining, Mathews has found that up to 21 tools can be mounted, including five turning tools, 10 rotary and six drilling tools.

When inside diameter turning cycles predominate, a toolholder can be added to the driven tool mounting to provide three additional drilling and boring positions.

With rapid traverse rates of 32m/min and the ability to overlap the exiting of one tool with entry into the cut of the next, the result is not only shorter cycle times but also a reduced likelihood of vibration being induced.

Vibration is also controlled by ‘shockless’ acceleration/deceleration curves developed within the control software.

These are a feature of the small but high performance servomotors.

Driven tools are powered by 1kW, 4.500 rev/min motors enabling holes to be drilled up to 8mm diameter and tapped up to M6.

With such a specification, the Citizen has given Precision 82 a competitive advantage that is way ahead of its humble beginnings, said Mathews.

The cam auto route – initially with a secondhand machine – was embarked upon after one customer placed an order for 10,000 turned parts, then came further automation through plugboard machines.

‘Up until the mid-1990s I could pick and choose which jobs I wanted – for straightforward turning applications, using the cam autos meant every job was really like shelling peas,’ he said.

‘But as with so many other small sub-contract companies in the UK, I then started to see a lot of the high volume work go to China and India – the heat sink pin job was a classic where the customer found he could buy the whole assembly abroad for less than I was charging to machine the pin alone,’ said Mathews.

‘However,’ he reasoned, ‘Every cloud has a silver lining, as ‘they’ say, and as the simple turning contracts disappeared, the Citizen technology has enabled me to move into more complex applications involving milling, for example, as well as turning, where the machines’ ‘one-hit’ capabilities have truly saved the business’.

With two full-time and one part-time staff, plus his partner ,Samantha Turner, Precision 82 currently has a nationwide customer base and while still utilising its cam auto capacity on appropriate jobs.

The company primarily depends on the Citizen to process varying batches of often complex turn-mill parts in all materials, particularly Duplex/22% chromium.

Parts from a few millimetres diameter up to 20mm diameter are processed (investment is now contemplated in larger diameter machining capacity) in varying batch sizes for a wide range of industry sectors.

The machine is regularly run unattended overnight and at weekends – a practice that provides the company with an invaluable cost-competitive edge, said NC Engineering in a report to manufacturingtalkmold.wiki, for both retaining contracts and when quoting for new business.

Today, armed with CNC sliding head capability, Mathews said: ‘Even the most complex turn-mill part holds no fear at all.’ Request a free brochure from NC Engineering….