CNC sliding head automatic lathes focus on the development of high speed processing and the substantial reduction of idle and non-cutting times in machine cycles with better flexibility.
By MACH 2006 NC Engineering of Watford will have more than 1,000 installations of citizen cnc turn/mill lathes in the UK demonstrating its significant market leading position in sliding head auto technology. The rate of development in this ever growing in popularity sector is far superior to fixed head lathe technology. Sliding heads have been seized upon by OEM and the subcontract sector for their high return on investment potential, their ability to reduce cost per part and in particular, the production of very complicated multi-feature components to high orders of accuracy and surface finish in a single hit cycle.

Citizen's focus is now on the development of high speed processing and the substantial reduction of idle and non-cutting times in its machine cycles with improved flexibility and features to assist unattended running, all prime requirements of users of these machines.

Examples are the latest Citizen K-Series and L20-VIII launched recently.

The K-Series in 12mm and 16mm capacity are lower cost machines and the L20-VIII is now proving at subcontract customers to be at least 30% quicker using the same program to produce parts than could be achieved on the previous generation machine.

At the smaller end of the Citizen range the RO7 with a maximum capacity of 7mm diameter by 40mm long was launched in 2005 developed around linear drive technology.

The machine is reckoned to be significantly faster than a traditional cam auto and combines the flexibility of a main and subspindle, has a 13 tool capacity and 20m/min rapid traverse rate.

But it is the linear drive to both tool posts that removes any likelihood of deflection and backlash from the power transmission system and optimises the structure of the slideway in a very compact and rigid machine footprint.

As a result, the RO7 with the help of ceramic spindle technology giving 16,000 rev/min and glass scale encoders to provide an ultra-high surface finish capability is able to provide close tolerance production with an incremental adjustment of 0.0001mm in each axis and repeatability of one micron.

The K-Series in 12mm and 16mm capacities employs a special version of the Fanuc 31i Series control with newly developed processors and Citizen developed software in order to easily optimise the cutting process and simplify programming.

Available at a lower price than the L20 it still combines two opposed spindles, will carry six turning tools, eight end working tools and seven driven tools.

The new Citizen L20, now in its seventh generation, is not aimed at the same market as the RO7 but still retains high accuracy and introduces new levels of flexibility and productivity through its 21 tool (9 driven) capability.

Rapid traverse rates have been increased from 20m/min to 32m/min and acceleration improved by a factor of 1.6 in each axis with the addition of shockless acceleration and deceleration curves from newly developed servo motors having 30% greater torque.

Further improvements include the ability to overlap an exiting tool from a cut with the next entry tool which not only reduces lost time but reduces vibration.

Additional flexibility has also been created from the new L20 design which has been developed to enable a variety of tool layouts to be selected according to the required cycle priority for cross-machining, end face feature or turning cycles.

When cross-machining is a priority, up to 18 tools can be mounted on cross toolholders which include five turning, seven rotary and six drilling.

If there is a higher demand for end face machining up to 21 tools can be mounted including five turning, 10 rotary and six drilling and when inside diameter turning predominates, toolholders can be added to the driven tool mounting to provide an additional three drilling and boring positions.