Five-axis machining requires workholders with maximum versatility

BIG KAISER Precision Tooling Inc. held its Breakfast & Learn 2018 open house May 8-10 at its headquarters in Hoffman Estates, Ill. Each day included a technical presentation. On the third day, John Zaya, workholding product manager for BIG KAISER, covered multiple-axis, quick-change workholding systems.

According to Zaya, five-sided machining requires workholders that offer maximum versatility and functionality, while providing interference-free spindle-to-workpiece access.

^{John Zaya, workholding product manager for BIG KAISER, discusses 5-axis workholding at the Breakfast & Learn event.}

Zaya said the types of machines that are suitable for 5-axis machining include a vertical machining centers with an aftermarket 4th- or 5th-axis indexer, a horizontal machining center with a B-axis and a trunnion. All of these options require three linear axes and two rotational axes. Full simultaneous 5-axis machining also requires a robust CAD/CAM package and a machine control with far look-ahead capabilities.

The spindle housing and the table size are common interference areas on a machine when 5-axis machining, he added. The housing OD limits how close the table can come to the part and the fixture. To overcome that limitation, an end user might have to extend the tool, such as by using a long-reach toolholder or elevating the workpiece further off the table. While shops often size a machine table for the largest parts they expect to produce, 5-axis machining small parts on a large table often requires long tools running at lower cutting speeds and lower DOCs. In addition, those tools are prone to chatter.

“Keep the tool length to the minimum requirement to get ‘inside’ the part,” Zaya said. There are a variety of 5-axis workholding systems, including standard vises, tall-jaw and modular vises, he said. The tall-jaw style may provide sufficient vertical clearance, but it also may sacrifice holding force. It’s important to have the clamping force as close to the workpiece as possible to prevent the workpiece from slipping or moving while maintaining repeatability.

Zaya added that modular vises are adjustable to part size changes, can elevate a part and keep the clamping force close to the workpiece.

In addition, monolithic and/or modular risers offer a common workholding method to access a workpiece when 5-axis machining, he said. They are commercially available but users often make their own risers. BIG KAISER’s 5-axis modular stacking system provides similar functionality. 

Zaya emphasized that although more axes complicates workholding, quick-change solutions are available to those who are flexible, and “… the mindset from the 3-axis world doesn’t always work in 5-axis machining.”