'Streamline Machining' depicts the benefits achieved from the new control system, software and mechanical developments resulting in up to 40 per cent faster machining cycles.
Streamline Machining' is a new term adopted by Citizen for its latest generation of CNC sliding head turn/mill centres that depicts the benefits achieved from the new control system, software and mechanical developments resulting in up to 40 per cent faster machining cycles than could be achieved using the same program and tooling on the previous generation machines. At MACH 2006 on NC Engineering Stand 5262, the latest L20-VIII and K12 and K16 citizen machines will be demonstrating the benefits of these new levels of flexibility and the ability to cut with two tools simultaneously at the main and subspindle involving single 'one-hit' cycles. Central to streamline machining is the Citizen software development for the new control systems.

The low-cost Citizen K12 and K16 machines have a special version of the latest Fanuc 31i Series control and the L20-VIII an advanced Mitsubishi 700 control.

Both the K and L ranges can perform with the involvement of up to five-axes with full synchronisation of the main and subspindles, direct spindle indexing that is able to pre-select the reference point of the C-axes even while the spindle decelerates.

This saves valuable time against the previous generation control operating routines that required the spindle to be stationary before the protocol sequence could seek the reference point.

What has to be considered is that many of the Citizen cycles used at customers involve considerable C-axis spindle positioning for cross drilling and milling.

Both machine types have had rapid traverse rates increased by 60 per cent to 32 m/min with the added advantage that acceleration and deceleration rates are improved by a factor of 1.6 on each axis.

By utilising the new shockless acceleration/deceleration curves, each machine is now able to give greater machining consistency with extended tool life and improved levels of surface finish.

Also, as a tool enters a cut, it is now able to overlap with the exiting tool that once again saves non-productive time and reduces any likelihood of vibration or pick-up on a machined surface as the new tool engages with the workpiece.

A further significant factor is idle time reduction on the new machines, especially when thread cutting and tool changing.

Here, the ability of the control to read ahead, enables the pre-emption of simultaneous axis movements.

The Citizen L20-VIII with a 20 mm capacity by 200 mm machining length can carry up to 21 tools with nine driven.

In recent trials a 240 second machining cycle was reduced to 164 secs - a 29 per cent saving.

At a UK customer, Unicut Precision of Welwyn Garden City, an L20-VIII was able to reduce cycle times against a previous L20 installed in the works, by almost a third.

The K12/K16 with 12 mm (1/2 inch) and 16 mm capacity will carry 19 tools with eight driven and compared to the B12 Citizen machine replaced at Tenable Screw of Merton, a K16-VII was able to reduce the cycle time on one part from 55 secs to 36 secs, a 35 per cent saving on each part produced.