The control of multi-bending: A flexible method to fabricate complex structural parts

The CNC multi-axis bending process can achieve high productivity and flexibility over conventional forming processes for fabricating long slender structural components of arbitrary shape. However, generating a CNC program to produce an accurate part shape is currently a laborious procedure involving trial-and-error by the machine operator. A systematic method has been developed to replace the manual control method and increase the dimensional accuracy. The concept of an intrinsic representation from differential geometry is applied as a basis to represent the part shape and develop the process model. The feedback control is derived from two transfer functions that represent the bending and twisting processes. By applying shape errors to the inverse transfer functions, incremental control commands can be determined and used to improve the control performance. Experimental results have demonstrated that shape errors decrease on subsequent iterations.