Workholding solutions for 5-axis applications

Whether an application involves simultaneous 5-axis machining or five-sided (3+2) machining, the workholders and fixturing techniques from the 3-axis world typically won’t apply, according to John Zaya, workholding product manager for BIG KAISER Precision Tooling Inc., Hoffman Estates, Ill.

Consider a short vise, one that’s 1½” to 2″ (38.1mm to 50.8mm) high. Although it is commonly employed for 3-axis machining, it is typically not suitable for 5-axis machining. The reason is that those applications require a vise that provides more elevation to avoid having to apply excessively long tools—”the heart of many problems,” Zaya said. “The fastest and easiest way is to use a taller jaw.”

Fixturing of a full 5-axis part using the UNILOCK 5-axis modular riser system from BIG KAISER allows full access to the part. Image courtesy of BIG KAISER Precision Tooling.

However, he added, if an end user exerts too much clamping pressure, the part can get “squished out” from the jaws because they push the material at an angle rather than perpendicular to the jaw faces. To avoid having a part get extruded out of the jaws requires a tall-jaw vise that has the clamping screw significantly closer to the workpiece to prevent tilting of the jaws.

Another vise option is a modular clamping system that elevates the workpiece and has movable pieces to accommodate workpiece geometry, Zaya said. “The clamping screw is always very close to the top of the mechanism that holds the workpiece in order to prevent extrusion of the workpiece.”

A vise is frequently suitable for five-sided machining, which generally involves a prismatic part that starts as a solid block. However, full 5-axis machining can involve parts without any flat surfaces to grip. “Everything [to be machined] may be interior or underneath it, in which case a vise will not work, because you can’t catch or grab a hold of it from the exterior features.”

When that’s the case, the workpiece is gripped from underneath, Zaya noted, with the addition of a dovetail being a common method. But the dovetail will need to be machined from the workpiece, adding time and expense.

As an alternative, Zaya said BIG KAISER offers a modular, retention knob-based system. This system can even use features on a part’s underside, such as bores and locating pilot holes, to place a knob or bolt and hold the part. “We can work entirely within the footprint of the workpiece, meaning that the bases, extensions and reductions get tucked into the entire footprint.”