What’s the difference of Swiss type CNC automatic lathe with guide bush and without/non guide bush?

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What’s the difference of Swiss type CNC automatic lathe with guide bush and without/non guide bush?

The Swiss-type automatic lathe was devised as watch component processing machinery in Switzerland in 1870s. Known as a “sliding head-type automatic lathe” as well, it has remarkable characteristics of high-precision cutting of components with longer length compared with the diameter.

In general, if long and narrow parts are processed with a general-purpose lathe, flexure will occur on the workpiece, making finishing with the correct dimensions impossible. The Swiss-type automatic lathe utilizes a guide bush to function as a material steady rest. The tool, positioned at a certain distance from the guide bush, gives a cutting motion only the direction of outside diameter. This allows the workpiece to be cut accurately with no flexure. As for axial motion, the headstock, rather than the tailstock, moves while clamping a workpiece.

With guide bush diagram

With a guide bush, it is well suited for machining narrow and long parts.The guide bushing lets the machine feed the work out through the headstock during cutting. This makes the machine effective for the turning of parts that are relatively long and slender. The tool can remain close to the workpiece's point of support throughout the length of a long part, dramatically reducing the risk of deflection.

Non/without guide bush type

Without a guide bush, it is not well suited for machining narrow and long parts. If the workpiece is short and does not deflect, however, such material can be handled effectively.

With the Swiss-type automatic lathe, the rear side of a bar material needs to be handled as waste as a portion equivalent to the size of the guide bush structure which functions as a steady rest for the material cannot be machined.

The non-guide bush type reduces the waste to about 1/3 in length compared to the waste made by the guide bush type.

Securing the work more rigidly. Without the bushing, the collet is closer to the work. More rigid clamping lets the machine take deeper cuts, achieve better finishes and take on more demanding materials.

Reduced setup time. Changing jobs on a conventional Swiss-type machine can involve the time necessary to adjust the bushing to size. Without the bushing, loading the same new job may be as easy as just closing the collet down on the work.

Material cost savings. There are multiple reasons for the material cost savings. One relates to the remnant. A machine with a guide bushing generally must leave about 6 inches of barstock behind. In addition, unlike the bushing-equipped machine, the lathe without a bushing may not require precision barstock of such high dimensional quality.