No Guide Bushing On A Swiss-type?

Is a Swiss-type screw machine still a Swiss- type if it doesn't use a guide bushing? It's not a question to spend much time pondering, but it's certainly one that Index Corporation (Shelton, Connecticut) brings up with its new Traub model TNL 12K moving headstock machine.

Like much of the metalworking lexicon, often our words fail to adequately describe, or keep up with, our technological innovations. The truth is, in the business of making precision parts it really doesn't matter much if a lathe is a turning center or a mill is a machining center. A shop wants to know how a machine (whatever it's called) is going to help get good parts out the door at the lowest possible cost.

This is the case in point for Traub's new machine. It's a moving headstock or Swiss-type machine that doesn't use a guide bushing. Instead, a quill extension on the headstock carries a collet that extends into and out of the cutting zone.

Without a guide bushing, setup times for the machine are reduced—one less set of components and adjustments to fool with. Instead, for shorter workpieces, a rigid set of spindle bearings, coupled with a precision collet, provide support for the workpiece without sacrificing the precision machining advantages of a moving headstock design.

Traub designed this machine for use on applications that make a guide bushing impractical. Plastic workpieces and those cut from non-round stock are examples. In general though, the need for a guide bushing is reduced on parts that are shorter and don't need the support.

Eliminating the guide bushing also eliminates the need for high precision or ground raw stock. The company says bar quality up to IT 11 (similar to cold drawn) can be used.

Without the need to bridge the gap between a collet and the guide bushing, the bar stock remnants are shorter, allowing more parts to be made from a given length of bar stock. The TNL 12K is currently available with 13 mm and 16 mm diameter bar capacity.

An inherent advantage of any screw machine is the ability to overlap cutting tools. This new machine is no exception. It can engage up to four cutting tools simultaneously for efficient production.

All four tool carriers, with a 20-tool capacity total, are arranged in two intersecting work planes. Both turrets have six stations each and can be configured with driven or stationary tools at any of the stations. Both these carriers are equipped with a precise and fast indexing mechanism. Chip-to-chip index time is 0.03 second. The front and rear side tools carriers each accommodate up to four stationary or individually driven cutting tools.

The main and secondary spindles are matched in power and performance. Both are capable of a maximum of 12,000 rpm. When the sub-spindle is used in process, all four tool carriers can be engaged in work at the same time.

According to the company, the TNL 12K machine represents a new concept for machining small workpieces below 0.625 inch. Without sacrificing the inherent advantages of a moving headstock design, precision and overlapping cuts, it is able to eliminate the sometimes problematic guide bushing for shorter parts.

It also gives shops a wider choice of raw stock options. The machine can easily be bar fed, but without the need for ground stock. It can also work as a chucker when fed from a magazine or bowl feeder unit.

Like all of metalworking and especially the production of precision parts, matching the machine tool to the application is the key to successful and profitable production. With that in mind, Traub's new moving headstock fixed chuck machine may be a fit for some of your work.