The fillet radius of the round nose knife is a parameter that needs to be considered in path planning. Due to its unique fillet structure, it is easy to produce undercutting when machining convex surfaces, and overcutting may occur when machining concave surfaces. To solve this problem, it is necessary to offset the theoretical path according to the fillet radius of the tool. Use CAM software to offset the design contour along the normal direction by a tool fillet radius value to generate a compensated safe path to ensure that the tool cutting point fits the design surface accurately and eliminate the machining error caused by the tool geometry from the source.
Layered milling is a common processing method for surface milling. By reducing the single cutting depth, the deformation risk caused by cutting force fluctuations can be reduced. The cutting depth of each layer needs to be reasonably set in combination with the tool rigidity, workpiece material and machine tool performance, and is usually controlled at 5% - 15% of the tool diameter. At the same time, optimizing the step distance is the key to avoiding undercutting residues. During fine machining, the step distance should be less than 2 times the tool fillet radius to ensure that adjacent tool paths overlap and cover the fillet area. In addition, using spiral cutting or ramp cutting instead of vertical cutting can effectively alleviate the instantaneous force on the tool and prevent overcutting.
Contour milling and projection milling are the core strategies for surface machining. Contour milling cuts layer by layer along the contour of the surface, which is suitable for steep surfaces, but it is easy to produce empty cuts or undercuts in the gentle area; projection milling projects the tool path onto the surface, which has a higher fit. In actual machining, contour milling can be used to quickly remove the excess, and then projection milling can be used to refine the gentle area. The two strategies complement each other, which can not only ensure machining efficiency, but also avoid overcutting or undercutting problems caused by improper path planning in different surface areas.
With the help of the path simulation function of modern CAM software, the tool movement trajectory can be simulated to intuitively find potential overcutting or undercutting areas. After the path is generated, the dynamic interference between the tool and the workpiece needs to be checked from multiple perspectives, especially the parts with large changes in surface curvature. The software will mark the abnormal contact between the tool radius and the surface, and the operator can adjust the path parameters accordingly, such as changing the cutting direction, adding auxiliary support surfaces or adjusting the tool posture. At the same time, the error analysis function is used to quantitatively predict the residual height and machining deviation, optimize the path in advance, and ensure machining accuracy.
Adaptive cutting technology can dynamically adjust the path according to the real-time cutting load. The round nose knife monitors parameters such as cutting force and vibration through sensors. When it detects that the local cutting force is too large (possibly overcutting) or too small (possibly undercutting), the system automatically adjusts the feed speed, cutting depth or tool path trajectory. For example, at the point where the curvature of the surface changes suddenly, the system automatically reduces the feed speed and increases the number of cuts; in the area where the material hardness is uneven, the cutting parameters are dynamically adjusted. This intelligent adjustment mechanism can effectively deal with the uncertainty in processing and improve the surface processing accuracy.
In five-axis processing, reasonable adjustment of the tool posture can reduce the risk of overcutting. By changing the angle between the tool axis and the surface normal vector, the tool fillet and the surface are avoided from interfering. For example, when using the side milling method to process deep cavity surfaces, tilting the tool at a certain angle can disperse the cutting force and reduce the radial force. At the same time, precise multi-axis linkage control can ensure the positioning accuracy of the tool under complex paths. Using the RTCP function of the machine tool, the tool center point always moves along the planned path. Even if the tool posture changes, the cutting point position can be guaranteed to be accurate, avoiding overcutting or undercutting caused by axis linkage errors.
After the round nose knife is processed, the surface is accurately inspected using a three-dimensional coordinate measuring machine or optical inspection equipment, and the actual measurement data is compared with the design model to analyze the specific location and degree of overcutting or undercutting. If the error exceeds the allowable range, it is necessary to re-evaluate the path planning parameters, such as adjusting the step length, cutting depth, or tool path type. For example, for the undercut area, a local finishing path can be added or the step length correction can be refined. Through the closed-loop process of "detection - analysis - optimization", the path planning strategy is continuously improved to ensure the quality of surface milling.
