In box-type parts, the hole system and thin-walled structures are the most difficult to machine. The difficulty lies mainly in precision control and deformation suppression.
Hole System Machining: The hole system on the box, consisting of bearing support holes, bolt connection holes, etc., has extremely high requirements for dimensional accuracy, shape accuracy (such as roundness and cylindricity), and positional accuracy between holes (coaxiality, parallelism, and perpendicularity).
For example, multiple bearing holes must maintain strict coaxiality (e.g., within φ0.04mm), otherwise it will lead to difficulties in shaft assembly or operational misalignment, affecting the overall machine performance. Because the hole system is widely distributed and often requires multi-faceted machining, clamping positioning and machine tool rotation accuracy (e.g., origin drift after the worktable rotates 180°) also directly affect the final accuracy.
Thin-walled structures: The casing typically has thin and uneven walls, resulting in poor overall rigidity. Under cutting and clamping forces, it is highly susceptible to elastic deformation or vibration, leading to springback deformation after machining and affecting the cylindricity of the inner hole and surface roughness. For example, an aluminum alloy fuel tank with a wall thickness of only 4mm experienced a cylindricity that failed to meet the design requirement of 0.032mm due to stress release during machining. Furthermore, thin-walled structures are prone to residual stress during hot working; if not fully released through natural aging, subsequent machining will still cause deformation.
Complex cavities and clamping challenges: The internal cavity of the casing is complex, restricting tool access and creating numerous blind spots during machining. Simultaneously, the clamping method during finishing is extremely critical-cantilever clamping easily generates torque that causes internal stress, while improperly designed encasing fixtures may cause parts to fall off during high-force processes such as honing.
