FIVE-AXIS MACHINING
Innovative Workholding for Five-Axis Machining W
orkholding is a key element of any metal cutting operation because it infl uences dimensional accuracy, surface quality and total process time. Five-axis machining combines movement of X, Y and Z linear axes with A and B rotary axes to permit fi ve sides of a part to be machined without refi xturing. With it, shops can machine part features in precise relation to each other and save the time that would otherwise be required to refi xture the part for sequential machining of multiple sides. Plus, full simultaneous fi ve-axis machining makes easy work of complex contours that otherwise would be extremely diffi cult, if not impossible, to machine. However, fully exploiting the ben-
efi ts of fi ve-axis technology involves special considerations. Users must write complex toolpath programs and choose optimal cutting tools. Then, simply holding the workpiece provides signifi cant challenges. Machining mul- tiple sides of a part requires the spindle to move throughout the machine’s work envelope, and deep features demand the use of long-reach tools. To provide suffi cient room for spindle movement and tool clearance, workholding must be as compact as possible and also position the part high enough above the table so that tools can reach all necessary features. Typically, to achieve this, shops will mount a vise on custom-machined riser plates to enhance spindle and tool access, but such plates can compromise rigidity and degrade dimensional accuracy as well as surface fi nish. Engineering and machining the plates also consumes time and money. Productivity issues exist as well. For top effi ciency, workholding equipment must be able to grip a wide variety of parts but still permit quick setup and change- overs without a need for expensive custom fabrication of clamping devices. To address the challenges of fi ve-axis machining,
Röhm Products of America (Lawrenceville, GA) developed 54
AdvancedManufacturing.org | July 2015
the RZM centric clamping vise system engineered with as small a footprint as possible and bodies that position workpieces for maximum tool and spindle access on all fi ve sides. The special RZM jaws telescope into one another in a patent-protected method that adds stability and rigidity and provides centering within 20 µm and safe part machining with up to 900 N•m material strength. The vise base is a precision-ground, hardened-steel rail, with cylindrical recess for a center locating pin and grooves for precise alignment with the T slots in the machine tool’s worktable. Because chip accumulation can
hinder fi ve-axis machining operations, the RZM’s clean interior and exterior surfaces are smooth for problem-free chip and coolant evacuation. This greatly minimizes, if not eliminates, the need to stop the machining process for cleaning and clearing away chips—es- pecially benefi cial for untended opera- tions. Plus, the vise’s jaw-adjustment screw is located high on the vise body for easy access and to further stream- line chip evacuation.
A variety of jaw styles for the RZM RZM centric clamping vise.
enhance fl exibility of application and speeds changeovers. Flat jaws are suited for a range of simple parts, while claw and serrated jaws provide added grip. Jaws are available for horizontal
or vertical setups, and for holding round pieces of material. SNF jaws feature a spring plate that provides a drawdown action. Jaws allow for installation of an adjustable work- piece locator stop to ensure repeatability when machining a series of similar parts. The vises are supplied with SKB claw jaws that provide a tighter hold with less force and minimal material loss.
RZM vises comes in two versions engineered to handle a wide range of part sizes. The long version with a base rail length of 260 mm has a maximum jaw capacity of 222 mm. The short version with a 180-mm long base rail has jaw capacity of 141 mm. The height of both versions is 196 mm.
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