Granting users access to five sides of a part in a single setup enables tighter tolerances. Parts with 3D contoured surfaces (such as mold cavities and electrodes) tend to be great candidates for five-axis machining. For example, flexibility in accessing deep cavities enables shops to use tool assemblies with reduced lengths and aspect ratios for these operations.
Improved tool orientation control also helps with tool breakage and chatter when working with difficult-to-machine materials. For example, the surface speed of a ball mill depends on the contact angle between tool and surface. On three-axis equipment, this angle changes as machining proceeds. When the bottom of the ball mill contacts the part, surface speed becomes an unproductive zero. Surface speed then reaches its peak when the tool’s equator contacts the part. These variations in surface speed cause variations in surface finish, create premature and unpredictable tool wear, and reduce productivity.
Active orientation enables five-axis contouring: the angle of the tool changes relative to the machine axes in real time. This enables a constant angle and surface speed, leading to higher programmed feed rates and better surface finishes.
Orientation control also boosts performance of flat-bottom and bull-nose end mills that need a constant 5- or 10-degree angle between the cutter axis and the plane normal to both the surface tangent plane and the direction-of-motion plane. The angle increases the effective radius, reducing the scallop height, improving surface finish and reducing the number of tool passes required to complete the operation. Controlling tool orientation also enables a constant depth-of-cut and accounts for variations in the stock-on condition of parts.
Source: Machining 101: What is Five-Axis Machining?