Micromilling has been increasingly employed for fabrication of micro geometrical features in many miniature parts, but the machining of micro thin walls is considered as difficult due to low material rigidity, and easy deformation by cutting force. In this study, a low-cost and reconfigurable 3-axis micromilling machine was developed by integrating a XYZ precision motion stage with a high-speed spindle. The development and configuration of the micromilling platform is introduced, along with a calibration of the motion accuracy and a vision-assisted tool tip positioning approach. Preliminary experimental study was conducted to fabricate micro thin walls on PMMA workpiece under different conditions. While the thin walls with a target thickness of 300 μm were successfully machined, it was found that there were many issues encountered in the machining of the 30 μm thin walls. The defects were analyzed to identify the root-causes and future research directions.