F268-Z4778 and Z4779 metal spining machine loadcells.

The F268-Z4778 and Z4779 loadcells are designed for use in a high-precision CNC metal spinning machine. The loadcells were developed during the initial concept stage for the machine and form an integral part of the drive chain / control system. This offers direct measurement of the applied force and accurate feedback to the automated drives, allowing smooth and precise control during the spinning process. Facilitated by the provision of complete, detailed CAD layouts, governed by a Non-disclosure Agreement, Novatech was able to provide a solution that fitted into the available space, requiring only minor modification of a single part.

As a general process, metal spinning usually involves the cold forming of a thin disc of metallic material around a solid 3D forming element. When done using semi-automated machines, the tool applying pressure to the work piece is often a uniquely profiled roller, mounted on an x/y stage. These are guided by linear guide rails and positioned using servomotors connected to precision ball screw assemblies. In this case, the loadcells were mounted on blocks that were connected to the individual stages, one for the x-axis and one for the y-axis, each housing a supporting bearing for the corresponding ball screw assembly. The flanged nut of the ball screw assemblies were then fixed to the live end of the loadcells in such a way that they could not rotate. Subsequently, when the ball screws are driven by the servomotors, the nuts are forced to travel up or down the length of the ball screw and take with them the loadcell and connected x/y stage. The loadcells measure the force exerted between the ball screw nut and the block that moves the relevant stage. This force will be greater the more the servomotor has to work against the reaction force at the forming roller. A feedback loop is thereby created, allowing the servomotor to maintain the correct force at the roller. Due to frictional forces, the ball screw nut exerts a torque on the loadcells, which needed to provide accurate axial force measurement whilst negating any torque induced error.

F268-Z4778 application drawing