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Citizen has developed an adaptive guide bushing (AGB) solution, which is intended to enable the use of a cheaper bright bar instead of the normal ground or specially prepared bar material.

The AGB solution is available on the company’s range of CNC sliding-head lathes.

The system will accommodate any tolerance variation on the outside diameter of the cheaper material, while allowing the normal machining speeds and feeds, consistent accuracy and high concentricity levels to be maintained on components.

Available on all new Citizen machines supplied through Citizen Machinery UK of Watford, the AGB system replaces the standard rotary guide bushing, which, because of its operating diameter, is fixed and requires the use of close-tolerance ground material when strict size and geometric tolerances have to be maintained.

The problem with more standard bright bar material is the wider tolerance limits of the rolled material, which permits the outside diameter to fluctuate in size from bar to bar, according to the company.

On all sliding-head machines, the standard rotary guide bush uses a single taper to provide the mechanical actuation, meaning that the length of the bearing surface of the bush to support the bar is normally restricted to between 15mm and 19mm.

It also creates a non-parallel closing action for the bush, meaning that if the barstock is on minimum tolerance, it is only gripped by the front of the collet.

This effect can also cause the headstock collet to lose position and have a detrimental influence on the surface finish of the part.

If, however, the material is close to its top limit, the gripping action of the collet is only applied to its back end.

Further problems can also emerge when machining titanium, for instance, or gummy materials such as certain stainless steels when the sliding-head machining process attempts to draw the bar back into the guide bush.

The Citizen AGB has a double taper that initiates a more positive parallel closing action along its material support length of 50mm, which is up to three times longer than is achieved with the single taper.

As a result, constant pressure is applied around the bar material and, as a result of its positive action, the bushing is able to accommodate material with a size variance of +/-0.1mm in diameter.

Since the Citizen AGB always maintains a constant pressure, the bar material will remain on the machine centre line, minimising run-out and enabling tighter concentricity to be maintained during the cutting process.

With the AGB system, a protective shield disc is provided to minimise contamination from fine particles of swarf and, with its locking nose cap, quick and easy removal from the front of the machine spindle is possible using a wrench and pin spanner.

The unit can also be assembled away from the operating area.

Citizen Machinery

Citizen is the world leader in CNC sliding head ‘one-hit’ turn-milling technology. It has a range of machines having a maximum bar capacity between 4 mm on the compact micro-machining capable Citizen R04 to 32 mm on the top of the range Citizen M32-VII which has the added capability of two Y-axis cross-feeds.   

The M32 can carry up to 80 tools, of which 20 can be driven, and can cut with three tools simultaneously giving low cycle times and high levels of productivity.  Also, fully automated unmanned cycles can be utilised through an integrated gantry option and conveyor system that helps ensure damage free parts during uninterrupted batch production.  A high pressure 2,000 psi CoolBlaster coolant system is a further option to optimise swarf control, tool life and machining difficult materials.

Following the acquisition in Japan in 2008 of 65 per cent shares in Miyano, the fixed head turning centre specialist, the two companies are maintaining their separate high profile brand names utilising a single sales operation.  However, turn-milling solutions from bar up to 64 mm diameter can now be provided.  In addition, with the Miyano range of turning and turn-milling machines for chucking operations, cell-type applications can now be accommodated with a wide range of automation options.   

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