When purchasing a CNC milling machine, how do ball screw preload class and backlash affect positioning accuracy, and how to test at acceptance?
• Preload classes P1/P2/P3 give different axial rigidity; P1 backlash ≤0.005mm suits finishing.
• Double-nut preload is stiffer than single-nut but raises friction torque, requiring matched servo power.
• Use a laser interferometer for positioning accuracy and a dial indicator for backlash reversal test.
• Excessive backlash causes arc interpolation overcut; measured reversal difference should be ≤0.01mm.
• Preload changes with thermal growth; re-test positioning accuracy after 2 hours continuous running.
• Double-nut preload is stiffer than single-nut but raises friction torque, requiring matched servo power.
• Use a laser interferometer for positioning accuracy and a dial indicator for backlash reversal test.
• Excessive backlash causes arc interpolation overcut; measured reversal difference should be ≤0.01mm.
• Preload changes with thermal growth; re-test positioning accuracy after 2 hours continuous running.