How to reduce chip sticking to the tool during stainless steel CNC turning?
Release Time : 2025-11-20
In stainless steel CNC turning, chip adhesion to the tool is a common problem, affecting not only the surface finish but also accelerating tool wear and reducing production efficiency. Its causes are mainly related to the characteristics of stainless steel, cutting parameter settings, tool geometry, and cooling/lubrication methods, requiring a comprehensive approach involving tool selection parameter optimization, cooling improvements, process adjustments, and operational procedures.
The selection of tool material and coating is fundamental. Stainless steel cutting easily generates high temperatures, causing chips to adhere to the tool rake face. Therefore, the tool material must possess high red hardness and anti-adhesion properties. Among cemented carbide tools, grades with lower cobalt content (such as YG6) are more suitable for stainless steel machining due to their high hardness and good wear resistance. For higher performance, cermet tools can be selected, as their anti-adhesion and high-temperature resistance are superior to ordinary cemented carbide. Furthermore, tool surface coatings can significantly improve anti-adhesion performance. TiAlN coatings can form an alumina protective layer at high temperatures, reducing direct contact between chips and the tool; DLC (diamond-like carbon) coatings, with their low coefficient of friction, effectively reduce chip adhesion, making them particularly suitable for finishing applications.
Optimizing cutting parameters requires balancing efficiency and quality. Excessive cutting speed intensifies friction between the chip and the tool rake face, easily leading to tool sticking; conversely, insufficient speed increases cutting force, also potentially causing sticking. Therefore, a suitable speed range must be selected based on the stainless steel material (e.g., austenitic, martensitic) and the machining stage (roughing, finishing). Insufficient feed rate results in thinner chips, making them prone to curling and sticking; excessive feed rate causes a sudden increase in cutting force, potentially causing vibration. In actual machining, the optimal parameter combination can be gradually determined through a "trial cut, then adjustment" approach. For example, during roughing, appropriately increasing the feed rate reduces the contact time between the chip and the tool; during finishing, reducing the cutting speed improves surface quality.
Adjusting the tool geometry is crucial. While an excessively large rake angle reduces cutting force, it weakens the tool and easily leads to chipping; an excessively small rake angle increases cutting deformation, making chips prone to sticking. Generally, a rake angle of 5°-15° is suitable for stainless steel turning. While a large clearance angle reduces friction between the tool face and the workpiece, it also decreases the tool's heat dissipation capacity; conversely, a small clearance angle increases friction and easily leads to built-up edge. Generally, a clearance angle of 8°-12° is chosen. Furthermore, the selection of the principal and secondary cutting edge angles must be considered in conjunction with the workpiece shape and rigidity. Increasing the principal cutting edge angle reduces cutting vibration but decreases the cutting edge strength; decreasing the secondary cutting edge angle improves surface finish but may increase friction. In actual machining, adjustments must be made flexibly based on specific circumstances.
Improvements in cooling and lubrication methods are crucial. The high temperatures generated during stainless steel cutting accelerate tool wear and chip adhesion; therefore, a cutting fluid with both cooling and lubricating properties must be selected. Water-based cutting fluids are suitable for high-speed machining due to their rapid heat dissipation and low cost; oil-based cutting fluids, with their excellent lubrication, reduce tool-chip friction and suppress tool sticking. For difficult-to-machine stainless steel, synthetic cutting fluids containing extreme pressure additives can be used, as they form a lubricating film at high temperatures, significantly improving anti-sticking properties. In addition, the coolant spraying method also needs optimization. High-pressure internal cooling technology directly sprays cutting fluid into the cutting area through internal channels in the tool, providing a significantly better cooling effect than traditional external cooling methods, especially suitable for deep hole machining or thin-walled part machining.
Adjusting the process method can indirectly reduce tool sticking. Segmented cutting breaks down a long cutting process into multiple short cutting segments, reducing the continuous contact time between chips and the tool and lowering the risk of sticking. Stepped cutting gradually changes the depth of cut, avoiding sudden changes in cutting force and improving machining stability. For stainless steel parts prone to tool sticking, a semi-finishing process can be added after roughing to reduce the tendency for chip adhesion by decreasing the cutting parameters. Strict adherence to operating procedures is crucial. Before machining, check that the tool is securely installed to avoid tool sticking caused by vibration; during machining, regularly clean chips to prevent them from entangled in the tool or scratching the workpiece surface; after machining, clean the tool and machine tool promptly to prevent residual cutting fluid from causing corrosion.
Furthermore, operators must be familiar with the machining characteristics of stainless steel and flexibly adjust parameters according to the machining conditions to avoid tool sticking problems caused by improper operation. Reducing chip sticking during stainless steel CNC turning requires coordinated optimization of multiple aspects, including cutting tools, parameters, geometry, cooling, processes, and operations. Through appropriate material selection, precise parameter adjustment, scientific design, improved cooling, process adjustments, and standardized operations, machining quality and efficiency can be significantly improved, while production costs can be reduced.