Difficult duplex components

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At CIRC Manufacturing in Westbury, Wiltshire, Low Frequency Vibration (LFV) technology on its Citizen sliding head turning centres ensures productivity and quality on difficult materials.

A tubular Duplex stainless steel weld collar for the oil and gas industry is a good example of how the benefits of LFV can be utilised. The high strength material has a tendency to work harden as it is being machined, the impact of which can be reduced by taking deep cuts to remove the work-hardened layer from the previous pass.

The problem is that taking deep cuts in such tough, ductile materials inhibits chip breaking and normally results in a bird's nest of swarf wrapping itself around the component and tool, to the detriment of both and perhaps even rendering them useless. LFV prevents this from happening, so every part produced is perfect and tools last longer. In the case of the weld collar, LFV is switched on for facing the bar and turning a chamfer, then to maintain a high production rate it is switched off for simultaneously boring and turning the OD.

Mr Pearce explained, "Sliding-head lathes when used with the guide bush in place have an inherent drawback. It is not really feasible to rough and then finish turn a part, as the smaller diameter of the roughed section when drawn back into the guide bush would cause vibration and impair the finishing pass.

"It is therefore necessary to turn to size in one operation, but that tends to produce long, stringy swarf when machining certain malleable materials. The LFV software prevents this from happening by lifting the tool tip away from the surface of the material periodically for a few microseconds.

"The frequency of the oscillation can be adjusted in the part program to control the size of the much shorter chips, added to which the LFV function can be turned off by G-code when it is more expedient, i.e. slightly quicker, to cut without it.

"Overall, productivity is increased by enabling reliable unattended operation, eliminating the need to include axis shuffles in programs to shake swarf off components, especially from grooves, and avoiding the need to stop the machine to clear swarf."

Mr Pearce is enthused that the chip breaking software also reduces problems and raises productivity when machining other materials such as pure copper, exotic alloys, other stainless steels and most plastics, especially nylons.

Commenting on his Citizen Cincom machines, Mr Pearce concluded, "The three Cincoms are the bedrock of our subcontract machining service. All feature main and sub spindles, full length bar feeds and a multitude of tools for driven cross working, end face milling and off-centre drilling.

"They enable us to offer economical done-in-one manufacture, without the need for secondary operations. This in turn allows us to run our machines unmanned, so we can offer competitive prices and hence fantastic value to our clients.

https://www.circmfg.co.uk/

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