1、 Basic idea of section line processing method
Generally, the spherical cutter is used to process the curved surface, and the ring cutter or flat bottom cutter can also be used in some special cases.
Because the spherical cutter is used to process the curved surface, the cutter center actually moves on the equidistant surface of the machined surface. Therefore, the section line method can also be used to machine the surface by constructing the equidistant surface, so that the tool moves along the intersection line of the interface and the equidistant surface of the machining surface to complete the machining of the surface.
The movement of the tool along the intersection of the section and the machining surface is generally in the mode of three-axis linkage movement, and the cutting contact of the tool and the machining surface are in the same section plane. However, due to the rotation of the normal vector of the surface on the section line, the tool center is generally not in the same section, and the movement of the tool along the intersection of the interface and the equidistant surface of the machining surface is in the mode of three-axis linkage movement, and the cutting contact of the tool and the machining surface are generally not in the same section plane, But the deviation from the section is not too far.
For the machining of a single surface, both methods can be used, but the machining effect will be better if the tool moves along the intersection line of the interface and the machined surface, because the cutting contact of the tool and the machined surface is limited to the same section. For the machining of composite surfaces and curved cavities, the calculation method of generating tool path by intersecting the equidistant surface of the cross section and the machining surface is much simpler.
In addition, if the selected CNC machine tool is a three-axis two linkage machine tool, the intersection of the section and the equidistant surface of the machining surface must be used as the tool path to meet the requirements of the coordinate movement of the machine tool.
The section line machining method is very effective for the machining of curved surfaces with uneven grid distribution and multiple curved surfaces, because the cutter and the cutting contact of the machining surface are on the same plane or the same rotating surface, so that the machining path distribution is relatively uniform, the residual height distribution is relatively uniform, and the machining efficiency is relatively high.
2、 Selection of section
The selection of cross-section is very important to improve programming efficiency, machining efficiency and machined surface roughness. The principles of selecting cross-section mainly include the following aspects:
1. The section form should be as simple as possible, such as a group of parallel planes or a group of rotating surfaces around a straight line or a half plane family of an axis.
2. The ruled direction of the section (for the rotating section) is as perpendicular to the machined surface as possible.
3. For the machining of combined curved surface or curved cavity groove, the section generally adopts a group of parallel planes.