For the "V" shaped rough machining process, first use UG CAM for preliminary process planning, and then post-processing planning. Adapt the initial code output by UG based on MATLAB compiler software. For the finishing process, use UG CAM to directly plan the path for the ultrasonic disc cutter and generate a CNC program that can be used for machining.
3.1 Second arrangement of CLs
In the "V" -shaped machining process, to obtain a tool path with a small cutting depth and uniform chip formation, forming a diamond-shaped cross section, the tool path between the odd and even layers can be misaligned by 0.5f.
In the second layout process, the tool path of the odd or even layer is translated in the Y direction to form the odd and even layer cutting, then the single cutting can only realize one of the "V" shaped edges in the "V" shaped processing technology. One side, and the other side needs to be cut on one side of the layer after changing, change the straight blade cutter swing angle and cut again along the same tool path, as shown in Fig. 5-b, Fig. 5-c; there will be a Y-empty situation.
The step distance is set to 0.5f, as shown in Fig. 6-a. In the second layout process, the CL of the odd and even layers are re-arranged respectively, and the tool path with the step distance of f is deleted. In a single-line tool path After cutting, change the tool angle and return along the original tool path. The order of the parity layer passes is shown in Fig. 6-b and Fig. 6-c respectively. Increased cutting efficiency. First set a step size of 0.5f. After cutting and editing the tool path, all tool paths have not been translated, and it is still based on the precise tool path formed by the original surface to improve processing efficiency.
The technical route of the CL sequence of the initial code is adapted, as shown in Fig. 7.
(1) Read the code line by line. The general idea of adapting the code is to use the "fopen" function to open the initial code document, and use the "fgetl" function to read each line of code line by line and form a string group, and then identify, judge, and adapt the content of each line of string.
(2) Distinguish between odd and even layers. The order of the CL of the odd and even layers must be adapted separately, so how to distinguish the odd and even layers is an important preparatory link. "EngageMove" represents the infeed. The Z coordinate of the infeed first appears in the next line of this mark. This coordinate represents the height of the current cutting layer in the Z direction, so it is feasible to distinguish the parity layer by the change of the Z coordinate value.
(3) Record the cutter counting location(CCL). As shown in Fig. 8, under the premise that the X axis direction is the cutting direction, if only the X coordinate appears in the current CL, it means that a new cutting tool path has appeared in the cutting order, and this CL is recorded as CCL ". Due to the complex surface problem, not every tool path is a straight line along the X axis. When the tool path is close to the curved surface, there will be more than one CL with only X coordinates in the same tool path, such as x6 ,At this time, the CCL previously recorded in this tool path should be discarded and updated to the current CCL. As the turning mark of tool path, CCL is mainly used to delete and adjust the order of CL.
(4) Delete and adjust the order of CL. The odd-numbered toolpaths in the odd-numbered layers are reserved, and the odd-numbered toolpaths in the even-numbered layers are deleted, but the deletion method is the same. In odd-numbered layers, odd-numbered toolpaths need to be retained, and after the end of the toolpath, return along the original toolpath and enter the next toolpath, so start when the number of CCL is odd, record the point behind the CLs, and write in reverse order when the CCL is even.
(5) Delete the duplicate CL. After the adjustment of the CL sequence is completed, there will be a situation where the information of the current CL and the previous CL are overlapped, and the current one should be identified and deleted.
3.2 Research on information planning of lifting and lowering cutter
The code generated by the preliminary planning based on the cavity milling process using UG contains only three-axis CNC information, so there is no change in the angle of the rotation axis when the tool changes the tool path inside the part, resulting in no lifting of the tool path turning point within the lifting CL. Therefore, it is necessary to add the information of lifting and lowering the cutter, and the places where the cutter needs to be lifted include but not limited to the above situations. The main situations that need to lift the cutter are as follows, as shown in Fig. 9.
(1) the situation of continuous cutter lift. Fig. 10 is a schematic diagram of the tool lifting situation. The process from the CL P1 to P2 is the non-cutting process that the tool needs to lift. This kind of situation usually occurs when the tool path turns to the edge of the convex curved surface area. Point P1 contains only X coordinate information and its absolute value is less than Xmax, and the moving distance in the Y direction from the point P1 to P2 is greater than the moving distance in the X direction (that is, the angle φ between the stepping direction and the X axis direction is greater than the straight blade cutter, The limit value of the rotation angle of the surface in the workpiece φmax). In this case, it is recognized at point P1 that the cutter needs to be lifted. The CL lift should be added after P1, and the position of the lower cutter should be added after P2 (The next CL outside the blank should be added with the next cutter information), while adding the tool lifting information, since the process from the CL P1 to P2 is a non-cutting process, the rotation angle information of the rotary axis before the point P2 should be deleted to improve work efficiency.
(2) The situation of area jump type cutter lifting. As shown in Fig. 10, the CL P3 to P4 are the process from the normal complete cutting area to the incomplete cutting area with convex curved surface. This process does not require cutting, and the tool needs to be lifted after the point P3 to move to the point P4. The judgment method in this case is that the point P4 contains both X and Y coordinate information, the absolute value of the X coordinate is less than Xmax, and the amount of movement in the Y direction is greater than 0.5f. This situation is different from the situation (1). Situation 2 recognizes the need to lift the cutter at point P4. The position of the cutter lifting position should be added before P4, and the position of the lower cutter position is added to P4. After adding the tool lifting information At the same time, delete the rotation angle information before P4 to improve work efficiency.
(3) The tool path changes too much. As shown in the CLs P5, P6, and P7 in Fig. 10, when a convex curved surface affects the tool path planning of the current layer but does not completely block the tool path, a single tool path will detour. There will be a situation where the angle between the small tool path and the X axis φ changes too much, as shown in the tool path of the point P5 to P6. The judgment method in this case is that the absolute value of the X coordinate of the point P5 is less than Xmax, and the angle between P5P6 and the upper tool path exceeds φmax. The solution for lifting the cutter in this case is the same as the case (1). Because the surface of aerospace parts is very smooth, and the rough machining process has a large margin, the amount of overcut generated by deleting the curved section in this tool path is very small (about 0.5mm), and will not affect the finishing process and the final part surface integrity.
Among them, Xmax is the half of the maximum blank size in the X direction of the blank set in UG, and φmax is the limit value of the rotation angle of the straight blade cutter face in the workpiece.
3.3 Research on planning of chip breaking toolpath
In the cutting process of "V" shape with ultrasonic straight blade cutter as the processing tool, when the entire tool path does not encounter the inclined surface, the straight blade cutter needs to complete the cutting twice to complete the chip removal; In the case of inclined planes, the chips can’t fall off after the straight blade cutter has been cut back and forth along this path, as shown in Fig. 11. This section will identify this phenomenon and add a chip breaking tool path. The key steps are as follows:
(1) Record the cutter location of chip breaker(CLCB). The position of the tool path that needs to be added with chip breaking is located at the tool lifting and lower CL studied in Section 3.2. Therefore, the CL with Z coordinate information can be found and recognized by identifying the CL coordinate information Determine the X and Y coordinate information of the current CL. If x <xmax is met and the Y coordinate difference with the previous CLCB is less than 0.5f, record the current X and Y coordinate information and save as The CLCB is used for subsequent connection to become a chip breaker tool path.
(2) Supplement the command angle for the CLCB. The blade posture of the straight blade cutter for cutting chips is different from that of the "V" -shaped machining process. When cutting, the straight blade cutter only needs to include the forward inclination angle.
(3) Insert the CLCB. The chip breaking tool path is formed by adding the information of each CL to the code in sequence. The specific method is: if the CLCB appears in the current layer, the CLCB will be added after the "DepartureMove" sign appears at the end of the layer, The chip location forms a chip breaking tool path.
(4) Raise the tool path to avoid interference of the tool tip. Tool tip interference can be avoided by raising the overall tool path.