Study on Strain Energy Transfer and Efficiency in Spatial Micro-forming of Metal

In spatial micro-fabrication on metallic surface, the mechanical machining consumes material shear deformation energy, while the laser machining energy is greatly converted into material melting heat energy. In production, the micron-scale material-removal machining requires the CNC system to long-time tool path interpolation for high energy-consumption. According to dynamics and kinematics of metallic plastic deformation, a strain energy transfer is proposed to deform micro-topographic shapes by differentiated surface stress. The objective is to realize the precision forming of spatial microstructure surface through the strain energy conversion and conservation. First, the energy transfer and strain variations were modelled in relation to die curvature radius, workpiece thickness, initial microstructure angle and depth. Then, the strain energy consumption was investigated in relation to material properties, die movement, and micro dimensions. Finally, it was applied to industrial cold-pressing. It is shown that the strain energy of a single microstructure formation transfers from centre to outer part. The spatial microstructure forming may change from diversified strain stage to uniform strain state with the highest energy efficiency at a critical strain energy, while the surface roughness remains unchanged. Under the strain energy transfer, the microstructure shape changes with increasing energy consumption to a critical value. The metal compressive strength, die curvature radius and workpiece thickness promotes energy consumption, while descending velocity promotes processing efficiency. By controlling the energy conversion, the spatial microstructure sizes may be fabricated with an error of about 1.0% and the energy consumption of about 10 mm3/J. In industrial production, it contributes high energy efficiency without coolant pollutant in contrast to mechanical machining and laser machining. As a result, the strain energy conversion and conservation may be regarded as an evaluation for an eco-friendly micro-fabrication.