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Tool Grind Workholding System Limits Runout
March 20, 2013
MicroPlus, ANCA's new high accuracy workholding and tool support system, significantly reduces tool runout during grinding, enabling the production of higher precision tools with no additional cycle time.
The two-component system consistently limits radial and axial runout to less than 3 micron (0.0001 in. for tools 50mm (2 in.) from the face of the collet. Typical tool grinder runout is about 0.0002 in. Suitable for both manual and automated tool loading, it is suitable for the production grinding of 3 to 13 mm diameter tools. A conveniently packaged system, collets are easily changed over and the machine work envelope is unrestricted.
How it works: The ANCA MicroPlus system consists of two separate assemblies: the Flexi-Chuck assembly for workholding and the Overhead Top Clamp Assembly (OTC) for tool guidance. Together, these devices provide a system that delivers consistently lower runout than any existing system.
The Flexi-Chuck clamps and rotates the tool to be ground, preventing any negative influences from affecting the guidance provided by the OTC, such as collet inaccuracy, inconsistent collet clamping and any misalignment caused by loading tools.
The clamping force is generated by disc spring stacks within the Flexi-Chuck assembly. This provides sufficient force to clamp tools effectively. Flexi-Chuck does not use the conventional draw bar design and so is not affected by a drawbar system’s potential negative influence on tool runout.
In other systems, if the drawbar and tool are misaligned and not in a completely straight line, the the drawbar tends to pull the tool at an off-center angle causing runout. Also, rigid draw bar-mounted collets can over-constrain the workholding system, preventing the V-steady from controlling tool guidance, a common occurrence.
The Flexi-Chuck, on the other hand, allows the tool and the internal components that lead to it to move independently of each other, absorbing any potential misalignment. With MicroPlus, tool guidance is achieved by the Overhead Top Clamp assembly and the collet float of the Flexi-Chuck. This allows the Overhead Top Clamp to guide the tool into a accurate workholding position without the Flexi-Chuck influencing tool alignment accuracy. The innovative new workholding part of the MicroPlus uses the flat-nose Schaublin W20 range of collets. Collet sizes range from 1 mm - 13 mm (1/32" - 1/2").
Providing runout and alignment accuracy for the tool, the Overhead Top Clamp consists of a rigid V block that supports the tool to assure axial and angular alignment. The OTC retains the tool in the precision V block with an overhead clamp. The clamp is a rigid metal finger with an acetal pad to prevent damage to the tool shank during grinding. The OTC is mounted on a rigid steady bed, and the tool is clamped and unclamped by a pneumatic actuator. The operator can adjust pneumatic clamping pressure of the finger to suit different tool types and diameters.
Software set-up: Automated set-up assistance for MicroPlus is provided in ANCA's ToolRoom software. This helps the operator to set the centerlines of the Overhead Top Clamp assembly with the Flexi-Chuck, in both vertical and horizontal planes. The MicroPlus is currently available for the MX7, GX7 and RX7 tool grinders as an option and can be retrofit to these machines.