The milling machine before the retrofit Our technical service engineers were asked to retrofit a spindle inverter on an #Okuma horizontal CNC milling machine at a large engineering company. The machine dates from the 1980s and we received the enquiry as a spindle motor repair – but with no fault found, the machine's inverter was diagnosed to be the issue. The inverter had undergone several repair attempts prior to our involvement, so a retrofit was decided. After reverse eng