Machining Center for Boring Bars(with the U axis)

In machining center we all recognize the 3 major axis which are the x,y and z respectively. Then if the machine is equipped with additional axes the rotary axis is added in the situation which are the A,B and C. An additional linear axis that provides some very unique application possibilities is commonly called the U axis. The U axis allows a cutting tool (commonly a boring-bar-type tool) to move in a direction perpendicular to the spindle centerline. This allows the diameter being machined by the tool to change during operation.

During a machining operation, there are two primary applications with the ability to change the diameter of the machine being machined. The first is related to holding size when boring holes. As you know, traditional boring bars must be manually adjusted. During setup, the setup person will commonly set the boring bar undersized, try machining a hole, measure the hole and re-adjust the boring bar based upon the measurement. This trial machining of the hole may have to be repeated several times before the hole is on size. During the production run, as the boring bar shows signs of wear, the hole will get smaller and manual adjustments to the boring bar will have to be made. Then when the boring bar eventually dulls and is replaced, the whole process must be repeated. Conventional boring bars almost eliminate the possibility of attaining fully unattended operation.

In this first application category for the U axis, the user is simply gaining the ability to achieve unattended operation for the critical boring operations (and/or making it easier to adjust hole size with attended operation). Since the diameter of the hole being machined is now programmable, hole size can be easily (and automatically) adjusted. The same kind of automatic sizing currently being done for other tools now can be done for boring bars.

The second application for the U axis is more complex and requires much greater U axis travel. A hole contour must be machined in the machining center, though this may look more like a turning center application. This kind of hole is conventionally machined with special form tooling.

In essence, the U axis for this application gives a machining center the ability to machine contours that would normally be machined in turning centers. Several special features are included, like threading.