Marvellously miniature

Citizen's micro-machining R04-VI, a 4mm capacity, 6-axis CNC sliding head turn/mill centre can now be specified with fully programmable high speed drilling/milling spindles capable of up to 100,000rpm to take maximum advantage of the latest ultra fine coated cutting tools and perform operations such as high speed thread whirling on diameters smaller than 1mm.

Now available through Citizen Machinery UK, the R04 and larger capacity R07 have been widely specified in the precision machining markets of watch making, medical and miniature electronics sectors for combining precision ‘one-hit' machining cycles with highly optimised cycle times on often difficult-to-machine materials.

Central to its success was the development of high speed linear motor technology to remove any likelihood of deflection and backlash from the power transmission system and the ability of the drive to enable the structure of the slideway to be optimised for precision cycles in a compact (560mm by 1,265mm floor requirement) and rigid structure.

Due to the basic design criteria, up to three high speed spindles can be mounted in the driven tool positions that enable both end and cross working plus, through special adapters, an angled approach to be made to a component feature all within the same cycle. The spindle and its electronic control are fully integrated into the CNC system of the R04 for positioning, spindle start and stop and it can also be preset for the designated speed. There is a range of spindles available to suit the application including a higher torque variant.

A recent example of the level of productivity gain was demonstrated involving the milling of a Torx female drive socket on a bone screw made from 316 stainless steel saving some 70% over a standard milling spindle application. The 0.8mm diameter, four flute end mill was run at 35,800rpm and a feed rate of 0.005mm/revolution to produce a clean, burr free milled finish on the component.

The Citizen R04-VI has a 20,000rpm ceramic bearing main spindle and 8,000rpm sub-spindle and has up to 13 tool positions of which five are for turning and three driven. The toolpost design allows two tools to be engaged with the workpiece simultaneously on components up to 40mm long making the machine significantly faster than a conventional cam auto when producing small parts in a single cycle.

Accuracy is high with increments of 0.0001mm in each axis and repeatability through high precision glass scale encoders is 1µm. The linear drive systems ensure rapid acceleration to a maximum rapid traverse rate of 20m/minute.

Citizen UK
www.citizenmachinery.co.uk