Designed to efficiently process long slender parts for the watch industry, the Swiss-type screw machine has evolved well beyond its original application niche. When equipped with CNC, 11 or more axes of motion--in the form of driven tools, sub-spindles, compound slides, thread whirling and rotary broaching attachments as well as polygon turning--can be brought to bear for single handling (done-in-one) production. Today this class of machine is found in medical, aerospace, automotive, electronics and general metalworking as well as the watch industry—anywhere complex, precision parts with a length to diameter ratio that is subject to deflection in the turning process.
The differentiating feature of the Swiss-type machine tool configuration is use of a sliding headstock to produce its Z-axis feed. This feature sets the design apart from conventional turning centers. Swiss-types use a guide bushing, usually carbide lined and mounted as the spindle nose, to support the blank stock within the work zone of the machine. As the sliding headstock moves in X-plus or minus, the work “slides” through the close coupled bushing allowing movement and as well as support.
To provide X-axis feed, numerous cutting tools on independent slides or gang tool plates are arrayed around the periphery of the spindle and cross feed perpendicularly to the workpiece. These tools are close coupled to the guide bushing support so deflection from cutting forces is mitigated. The cutting action comes from interpolated motion of the Z-axis headstock as it moves the work axially across the X-axis cross-slides. Use of pick-off or sub spindles allows backworking operations to complete the workpiece on the machine.
As the CNC Swiss-type has grown in its application breadth, many parts that are being run on these machines are actually not “Swiss” parts. In order to gain access to the multi-tasking and high precision advantages offered by the sliding headstock design, many shops are running parts that because of their low length to diameter don’t require the support of the guide bushing. In response, most CNC Swiss builders offer a “bushless” Swiss machine. It eliminates the need to adjust the guide bushing, speeding setup, and allows the machine to use bar stock that doesn’t require as tight size tolerances to fit the guide bushing. In other words, the stock need not be ground.
Swiss-Type Screw Machine Trends:
Bushless or fixed headstock Swiss turning
Quick change tooling schemes
In-process tool breakage detection
Off-line tool setting
Synchronous main and sub-spindle
Thread whirling attachments
Rotary broaching attachments
High pressure coolant application