CNC Turning Machining - Repair Bushing

Analysis of Thin-Walled Bushing Machining Deformation
Customer Technical Requirements:
Material: 1.2713
Heat Treatment Requirement: Hardness HRC 45±1
Key Dimensions: Outer Diameter (OD) 123±0.01mm / Inner Diameter (ID) 117±0.01mm / Wall Thickness: 3mm
Quantity: 5 pieces

Quality Abnormalities:
1. Deformation after Heat Treatment: Ovality out of tolerance (measured maximum 0.03mm, standard ≤0.01mm).
2. Finishing Deformation: Clamping deformation resulted in wall thickness deviation of 0.05mm (standard ±0.01mm).

Root Cause Analysis:
1. Structural Factors: The diameter-to-thickness ratio reached 41:1 (critical value >30:1 means high deformation risk).
2. Process Defects: Cutting force F=280N.

Solutions:
✱ Heat Treatment Allowance: Reserve more allowance for subsequent precision machining adjustments.
✱ Process Change: Change from precision turning to precision grinding after heat treatment.
✱ Key Process Controls:
– Grinding with CBN Wheel (120#, B152 type)
– Parameters: V=35m/s, ap=0.005mm/pass
– Clamping: Use magnetic chuck + epoxy resin filling for support.

Result Verification:
By changing the finishing process from CNC turning machining to precision grinding, along with stress control measures, the qualified rate of the thin-walled parts successfully increased from 38% to 100%.