24 July 2012
Kennametal KM4XTM spindle connection meets metal removal challenge of tough materials
Kennametal's KM4XTM quick change tooling system is the latest evolution of its KM system. It has been designed to exploit the potential of special milling and turning centres that feature improved stiffness and damping on spindles and sizable machine structures to meet the challenges posed by difficult materials. The remaining weak point has often been the spindle connection itself.
Initially a joint development by Kennametal and Krupp Widia in the mid-1980s, the KMTM universal quick-change system consists of two basic components – the clamping unit and the cutting head. The clamping unit mounts to the machine tool (a turret or tool block for stationary applications and a rotating spindle to accommodate rotating applications) and is the receptacle for the interchangeable cutting unit/toolholder. When a tool change is necessary, an operator simply releases the locking system, replaces the cutting unit and locks it into position.
By combining high clamping force and optimised interference levels, Kennametal says the KM4XTM provides a robust connection, extremely high stiffness, and bending load capacity for greatly improved performance and productivity in machining high strength alloys and other challenging materials.
Kennametal explains: "When meeting such tough challenges, the spindle connection must provide torque and bending load capacity compatible with machine tool specifications and productivity requirements. In end-milling applications, where projection lengths are typically greater, the limiting factor is the spindle interface's bending capacity.
"As an example, an indexable helical cutter with 250 mm projection from spindle face, 80 mm in diameter generates 4620 Nm of bending moment and less than 900 Nm of torque when removing 360 cm3/min of Ti6Al4V at RDOC of 12.7 mm and an ADOC of 63.5 mm. The most critical parameters of a taper-face spindle connection are the clamping force and radial interference. Maximising clamping force and selecting appropriate values of interference can further improve connection rigidity."
The KM4XTM system uses three-surface contact for improved stability and optimised clamping force distribution and interference fit which typically improves the bending moment resistant capacity by a factor of three over other systems, Kennametal claims. Thus speeds and feeds in difficult machining can be increased; a smaller KM4X connection can be used to meet the productivity potential of the specific machine tool and the system can be used on multi-tasking, turning machining centres and transfer machines in manual, semi-automatic and fully automatic mode.
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