Rigidity is the core performance indicator of machine tool castings including beds, columns, worktables and spindle boxes. When castings lack enough structural stiffness, a series of precision, processing and service failures will appear during cutting, directly lowering product qualification rate and shortening equipment service life.
1. Severe cutting chatter and poor surface finish
Under cutting force, the low-rigidity casting frame produces obvious elastic deformation and periodic vibration together with tools and workpieces. Tool chatter marks form regularly on machined surfaces. The workpiece shows ripples, waviness and rough texture, failing to meet surface roughness standards. High-speed milling and fine grinding are particularly affected, and repeated finishing cannot eliminate vibration ripples.
2. Unstable dimensional accuracy and dimensional deviation
Radial cutting force and axial thrust bend the casting structure slightly during processing. The deflection value changes with different cutting depths, feed rates and workpiece weights. The actual cutting dimension drifts up and down, resulting in inconsistent size of batch parts. Even if the parameter setting remains unchanged, finished workpieces will have random dimensional tolerance overshoot.
3. Straightness, flatness and geometric tolerance out of tolerance
For plane milling, long-axis turning and guide rail finishing, insufficient rigidity causes local bending of the machine tool casting. Long workpieces present middle arch or two-end sag errors; machined planes appear concave-convex deformation. Geometric tolerances such as parallelism, perpendicularity and cylindricity cannot reach drawing requirements, which greatly reduces assembly matching precision of subsequent parts.
4. Accelerated wear of guide rails, lead screws and transmission parts
Vibration and micro-displacement generated by weak castings create repeated friction impact between sliding pairs. Guide rail surfaces suffer uneven abrasive wear; lead screw threads and nut pairs bear alternating impact load, leading to rapid clearance increase. Clearance backlash further amplifies vibration and deformation, forming a vicious cycle, greatly shortening the service cycle of precision transmission components.
5. Early fatigue cracks on casting body
Long-term alternating cutting vibration concentrates stress at thin ribs, wall-thickness transition corners and bolt bosses of low-rigidity castings. Microcracks initiate easily under cyclic load. As production time accumulates, tiny cracks expand continuously, evolving into penetrating cracks that scrap the entire machine base or column casting.
6. Weak shock absorption and noise pollution
Gray iron castings rely on rigid integrated structure to absorb cutting vibration. Insufficient rigidity weakens internal vibration damping capacity. Strong high-frequency vibration transmits to workshop ground, producing loud cutting noise that exceeds environmental standards. Vibration also interferes with adjacent precision measuring equipment and other machine tools.
7. Thermal deformation superposition aggravates precision loss
Low-rigidity structures have poor ability to resist thermal stress. Cutting heat causes uneven temperature rise on castings, and the frame bends more significantly under the coupling of thermal expansion and insufficient stiffness. After shutdown cooling, the casting cannot fully rebound to the original geometric state, resulting in permanent dimensional drift after long-term production.
8. Poor heavy-load processing capacity
When clamping large or heavy workpieces, the casting bed sinks and twists obviously under gravity. Deep cutting with large feed will trigger large elastic deflection, making the machine unable to complete heavy-duty rough machining. The equipment is only limited to light cutting, with narrow applicable processing range and low production efficiency.
References
GB/T 7714
Ren G, Zhao Y. Influence of insufficient structural rigidity of machine tool castings on machining performance[J]. Machine Tool & Hydraulics, 2021,49(13):141-145.
MLA
Ren, Gang, and Yan Zhao. "Influence of Insufficient Structural Rigidity of Machine Tool Castings on Machining Performance." Machine Tool & Hydraulics, vol. 49, no. 13, 2021, pp. 141-145.
APA 7th
Ren, G., & Zhao, Y. (2021). Influence of insufficient structural rigidity of machine tool castings on machining performance. Machine Tool & Hydraulics, 49(13), 141–145.
