Soft machine

Robust and stiff often come to mind when considering the characteristics that make for a productive milling machine. However, Juanjo Zulaika, a researcher at the applied-research center Tecnalia Research & Innovation, thought otherwise and developed a “softer” milling machine with reduced weight and stiffness. That’s achieved while increasing productivity. “Normally, the aim of these designs is to make the machine as stiff as possible,” he said. “But that is not the case in my model, and this signifies a profound change in this area.”

Courtesy of Tecnalia Research & Innovation

The low-energy consuming and reduced-weight 4m-high prototype milling machine from Nicolás Correa (top) was able to achieve greater DOCs than the initial machine (bottom).

Working with the Spanish University of the Basque Country, Zulaika created a simulation model that incorporates finite element analysis to analyze chatter and determine how much mass can be removed from a machine component without reducing productivity. “We calculate the eigenvectors and eigenfrequencies of the machine and, once we have the cutting coefficients of a machining operation, use those for calculating the machine’s stability lobes for the machining process,” he explained. (According to Merriam-Webster’s dictionary, an eigenvector is a nonzero vector mapped by a given linear transformation of a vector space onto a vector that is the product of a scalar multiplied by the original vector. An eigenfrequency is one of the frequencies with which a given oscillatory system is capable of vibrating.)