The object of the invention is a method for continuous machining of a surface and a tool for continuous machining of a surface, related in particular to curved surfaces.

Surface machining involves removing (shearing) small fragments (i.e. chips) of a machined material. Surface machining can be categorized as chip machining, with a defined geometry and amount of the shearing blade, or a second group, abrasive machining, wherein these parameters are not defined.

Chip machining of a surface is carried out, for example, by drilling, turning, milling, broaching, push broaching, planing or slotting. Due to the nature of the machining, these processes can be divided into continuous processes, such as planing, slotting, turning, drilling, and non-continuous processes, such as milling.

Continuous machining is characterised in that in order to produce a desired surface, the blade, once plunged into the material, moves along a cutting trajectory to the very end, thereby obtaining the shape of the surface. In state of the art machine tools, trajectories are straight, spiral or helical. This limits the surfaces that can be obtained by the continuous method to surfaces having a flat, cylindrical, helical or any other profiled shape (any cross- section usually drawn along a straight line). Arbitrary shapes, such as curved surfaces, can be currently obtained by machining on milling machines (typically numerical controlled). This machining method also involves leading the tool along a set trajectory, but it uses a rotating tool, namely a milling cutter placed in a rotary spindle. The blades of the milling cutter continuously plunge into the material and come out of it, thereby shaping the surface in a non-continuous manner. This non-continuity results in roughness of the surface obtained by the machining process. It can only be improved by reducing the tool feed, which increases the machining time, and by increasing the rotational speed of the tool, which has limitations in the form of maximum rotational speed of machine spindle or in the form of permissible machining speed, beyond which the tool blade undergoes rapid wear. Initially, the milling machines were machines which used rotating tools - i.e. tools based on non-continuous machining. Later on, structures and special tool holders were created, which made it possible to mount non-rotating tools, such as a turning tool or a chisel, to the milling machines, which made it possible to perform continuous machining operations on these machines, such as turning, slotting, planing, with the use of standard tools, such as chisels, turning tools, boring bars, etc. The surfaces machined in this way could only be simple surfaces, for example a plane, a cylinder, because this machining method implies applying existing machining operations, such as turning or slotting, to the milling machine. The main limitation to the introduction, to the milling machine, of continuous cutting of any surface, for example curved surfaces, is geometry of the blade and its orientation in relation to the workpiece.

According to the invention, the method of continuous surface machining consists in that in the spindle axis of a milling machine, in particular a six-axis milling machine with a smoothly controlled position of the spindle axis, programmed in the CAM system, a cutting tool is placed, the cutting edge of which is placed in the virtual axis of the spindle, and then a tool path with smooth maintenance of a preferably constant relief angle and of a direction of rake face to the tool path, the direction corresponding to the construction of a particular blade, is run on the milling machine.

Preferably, the cutting edge of the tool is placed in the spindle axis.

The tool for continuous surface machining is characterised in that the cutting edge of the cutting blade is set in a tool shaft by means of which the tool is mounted in the spindle, coaxially with the virtual axis of the spindle.

Preferably, the cutting edge of the cutting blade is set in the tool shaft in the spindle axis.

As a cutting blade, a turning or milling plate is used, which is set in the tool shaft by means of which the tool is mounted in the spindle so that the cutting edge is located on the virtual axis of the spindle.

Preferably, as a cutting blade, a turning or milling plate is used which is set in the tool shaft by means of which the tool is mounted in the spindle so that the cutting edge is placed in the spindle axis.

The method of machining according to the invention and the tool for machining with this method make it possible to obtain very good roughness, because during machining, there is no component from the rotating tool. Due to the use of large feeds, the time of surface machining is reduced several times. It is possible to use tools with corners of a small radius, of the order of a few hundredths of a millimetre, while maintaining very high rigidity of the tool. This increases durability of the spindle, due to the zero rotational speed during machining. Ready turning or milling plates are used for machining, which are much cheaper than rotary milling cutters. The durability of the blades is significantly increased due to machining with a low cutting speed which is equal to the feed. In some cases, a feed being several times higher is obtained, while reducing the machining speed by several times compared to the classic milling. The method and the tool for continuous machining according to the invention are schematically shown in the drawing in which Fig. 1 shows a workpiece set on a milling table, Fig. 2 shows an example embodiment of a tool according to the invention, set in a milling spindle, Fig. 3 shows surface shaping by means of a standard turning boring bar, Fig. 4 shows an example of a strategy for machining a curved surface with the use of a six-axis machine, and Fig. 5 explains the principle of programming the milling machine spindle movement along a specific path of the tool.

As shown in Fig. 1, the widest application of the method of continuous machining according to the invention is obtained on six-axis machines with kinematics of three linear axes XYZ, a tilt axis for example A, a rotary axis for example C, a smoothly controlled spindle axis S, all being programmed in a CAM system, wherein, of course, all configurations are possible, for example XYZ, AB, S. This allows running, on the milling machine, any tool paths with smooth maintenance of a constant relief angle a (controlled by the axes, for example A and C) and of a direction of a rake face which is perpendicular to the direction and sense of the velocity vector in the tool path.

This direction is controlled for example by the spindle axis S in 6-axis machining or for example by rotary axis C in 5-axis or 4-axis machining. These angles are not necessary for precise maintenance but are the most optimal due to the machining process itself for a specific blade. A workpiece 1 is set on the table, and a tool 2, in this example a turning tool, in a shaft 3 of which a plate 4 of a cemented carbide, is mounted in a spindle 5 of the milling machine. The axis of the spindle is controlled so that the machining is conducted without idle return movements, which is shown in Fig. 4. As shown in Fig. 2, the plate is mounted in the shaft 3 of the turning tool so that the cutting edge is located in the axis of the spindle 5 - in this case, the cutting edge is placed in the spindle axis. In the example of machining strategy shown in Fig. 3, the tool is a standard turning boring bar - here the cutting edge of the tool is not located in the spindle axis, it is offset thereto, is placed in the virtual axis of the spindle, indicated by a dashed line. The offset is taken into account when programming the spindle movement. As shown in Fig. 5, to ensure the best machining conditions for any designed blade, it should be maintained as close as possible to the nominal value of the relief angle. Therefore, for continuous machining of any surface, including curved surfaces, the spindle setting must change smoothly during machining - a tool path with smooth maintenance of a most optimal, constant relief angle and of a direction of rake face which is perpendicular to the tool path is run on the milling machine.