CITIZEN’S LATEST L20 SLIDING HEAD AUTO CUTS IDLE TIME BY 40 PER CENT

An average of 40 per cent of the time lost in a CNC machining cycle time due to data processing, idle time and non-cutting movements can be saved through the latest mechanical engineering, control system development and operating software improvements created by Citizen for its latest L20VIII CNC sliding head auto. The new seventh generation of the highly successful L-Series machine will create new levels of savings, productivity and machine utilisation for producing mill/turn components up to 20 mm diameter.

Available through NC Engineering of Watford, the Citizen L20 VIII has undergone extensive test cycles against the previous generation machine using the same program and tooling. In a 83 sec machining cycle, for instance, of which a quarter of the time was attributed to non-cutting, this lost time was reduced by 63% resulting in a much improved cycle time of 69.5 secs. Another 250 sec machining cycle, for instance, which previously included almost 24 secs of non-cutting time for data processing, positioning, acceleration and manipulation, this non-cutting time was reduced to just 7.9 secs, a saving of almost 67 per cent. A third part with a 53.9 sec cycle involving 17 secs of idle time had it's idle time reduced by 39 per cent to just 10.5 secs.

The machine, with a capacity of 20 mm diameter by 200 mm machining length enables a variety of tool layouts to be selected to service the main 3.7 kW, 10,000 revs/min spindle and 1.5 kW, 8.000 revs/min subspindle according to the priority required 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 which include five turning, seven rotary and six drilling tools. The three cross toolholders may also be used for end face drilling spindles by swivelling the unit through 90 degrees.

When there is a higher demand for end face machining up to 21 tools can be mounted, including five turning tools, 10 rotary and six drilling tools and 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 increased from 20 m/min to 32 m/min, acceleration rates improved by a factor of 1.6 on all axes and the ability to overlap the exiting of one tool with entry into the cut of the next, not only does this contribute to shorter cycle times, but reduces any likelihood of vibration. Vibration is also controlled by the introduction by Citizen of ‘shockless’ acceleration/deceleration curves. These are a feature of the new smaller but higher performance servomotors which now provide up to 30 per cent higher torque.

Driven tools are powered by 1 kW, 4.500 revs/min motors enabling holes to be drilled up to 8 mm diameter and tapped up to M6. By specifying the long part adapter option, shafts between 80 mm and 600 mm in length can be processed and unloaded automatically out to the side of the machine. There is also an option of a parts conveyor to reduce likelihood of damage and to interface with other automation systems.