A method for processing precision cover parts
By using the mesh surface function in NX software to generate tool paths bypassing the convex island area, the problems of hollow cutting areas and over-cutting in precision cover parts processing are solved, and efficient and stable processing processes and good part quality are achieved.
Patent Information
- Application Number
- CN202411843313.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-04-08
AI Technical Summary
The existing processing methods have problems such as empty cutting areas, overcutting, and constant feeding speed when processing precision cover parts, resulting in low machining efficiency, unstable quality and serious tool loss.
Through the surface modeling function of NX software, the required flow surface is constructed using the mesh surface function, a tool path bypassing the convex island area is generated, and the raised sides are avoided along the cutting path through the tool axis control, realizing the machining scheme of five-axis equipment and four-axis equipment.
Eliminates the empty cutting stroke and overcut phenomenon, improves feed speed and processing efficiency, ensures cutting surface quality, extends the tool service life, and realizes continuous production and processing.
Smart Images
Figure CN119772237A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a processing method, in particular to a processing method for precision cover body parts. Background Art
[0002] Engine cover parts are very common in the components of special equipment production and scientific research. Most of them are thin-walled structures containing one or two groups of pressure measuring nozzles or ignition nozzles. According to the usage and design requirements, the overall finishing size requirements are relatively high.
[0003] The parts studied so far are all precision cover parts made of TC4 or TC11 high-strength, high-toughness titanium alloys that are difficult to process. The two parts have similar structures, except for the different shapes of the nozzles where the curved surfaces are raised. Figure 1 As shown. Current processing methods: The CNC programming method for curved surfaces is generally computer software-assisted programming. This programming method is simple and efficient, and has low requirements for programmers. Taking NX software as an example, parts processing is completed through the surface drive method and tool axis control (different solutions may be available depending on the equipment). This programming method is simple and can directly obtain a tool path with high neatness. The tool avoidance effect can be obtained by slightly enlarging the size of the model at the nozzle, such as Figure 2 When the protrusion is magnified, it can be seen that the tool axis bypasses the protrusion from the top of the part, as shown in the figure. Figure 3 shown.
[0004] When processing such parts with the current processing method, there is an empty cutting area above the nozzle of the tool, which will cause a certain amount of processing time loss. The feed speed during cutting is the same as the feed speed around the raised area, so the feed speed setting value is the global feed value, and the speed on the bypass path cannot be increased; from the time the tool leaves the cutting area to the time it re-contacts the cutting area, the tool will produce an instantaneous torque change, so when it re-contacts the cutting area, it will "stab" into the cutting area, resulting in overcutting. Due to the particularity of such parts and the large demand, this type of solution cannot achieve efficient and continuous processing, and the yield rate is also low, so it is necessary to study its processing method.
[0005] During the surface finishing milling process of this type of high-precision cover parts, general computer-aided manufacturing software cannot automatically generate a tool path that bypasses the convex island area. This is because the principle mechanism of most computer-aided manufacturing software to generate tool paths based on surfaces is consistent, that is, to generate tool paths based on the UV direction of the surface. In NX software, the deep principle of the tool path generated by the surface as a driver is to control the flow direction of the surface UV. In the surface analysis view, we can get a complete UV wireframe. Figure 4As shown in the figure, it can be clearly seen from the UV wireframe of the surface that the driving line of the tool path is blocked at the nozzle. In this case, the tool path will inevitably wrap around the top of the nozzle.
[0006] After analyzing the above processing methods, the following main problems can be found:
[0007] (1) There is an empty cutting area above the nozzle of the tool, which will cause a certain loss of processing time.
[0008] (2) When the tool leaves the cutting area and re-enters the cutting area, the tool will produce an instantaneous torque change, so when it re-enters the cutting area, it will "stab" into the cutting area, resulting in overcutting.
[0009] (3) The feed speed during cutting is consistent with the feed speed for bypassing the raised area, so the feed speed setting value is the global feed value, and the speed on the bypass path cannot be increased.
[0010] (4) To obtain better dimensional accuracy and surface quality, the cutting direction needs to remain consistent, and down milling is optimal.
[0011] (5) Due to the tool sticking phenomenon in the raised area, an instantaneous torque change will occur during cutting, and the tool is prone to chipping or even breaking, resulting in serious wear and tear.
[0012] The above factors have resulted in problems such as unstable parts processing quality, low human-machine efficiency, and high tool costs, which have been seriously restricting the product output of such parts. Summary of the invention
[0013] The purpose of the present invention is to provide a new processing method for the surface finishing of precision cover parts. According to actual needs, the surface modeling function of NX software is used to construct the required flow surface using the mesh surface function, so as to generate a tool path that bypasses the convex island area. The tool path driven in this way can achieve detours, avoid tool jams, and have the advantages of constant feed speed. At the same time, it also takes into account quality safety and processing efficiency, and has strong machinability. Continuous production and processing are realized, which provides good support for the establishment of an automatic production line for tight cover parts.
[0014] The present invention is achieved by the following technical solutions:
[0015] A method for processing precision cover parts uses the surface modeling function of NX software and the mesh surface function to construct the required flow surface. In the island area, concentric curves are used to split and re-converge, so that the driven tool path bypasses the island area. Then, the tool axis is controlled to avoid the raised side along the cutting path.
[0016] Five-axis equipment processing solution:
[0017] In the island area, the fourth axis is locked at a tilt angle of 20°, and the forward milling is performed on the curved surface close to the center of the part. The fourth axis is locked at a tilt angle of 25°, and the forward milling is performed on the curved surface far from the center of the part. In the remaining processing areas, the forward milling is performed using the five-axis linkage method.
[0018] Four-axis equipment processing solution:
[0019] For island areas with inconsistent nozzle sizes, the nozzles are bypassed along the wide area, and the cutting path always remains in the forward milling direction. For island areas with consistent nozzle sizes, the nozzles are bypassed in half from the side, and the cutting path always remains in the forward milling direction.
[0020] Combining the above two solutions, the present invention is suitable for most types of machine tools to complete the processing of such parts. Both solutions can realize the cutting path of the tool bypassing the island area and automatically diverting according to needs.
[0021] Compared with the previous solutions, these two solutions have the following advantages:
[0022] 1. There is no empty cutting stroke in the tool path;
[0023] 2. Eliminate the situation of overcutting parts such as "knife stab" to ensure the quality of parts;
[0024] 3. The feed speed has been greatly improved compared with the previous method, and the processing efficiency has been improved;
[0025] 4. The tool path ensures down milling, and the cutting surface quality is greatly improved;
[0026] 5. The cutting speed is constant, the cutting force is uniform, and the tool life is greatly improved.
[0027] 6. In the five-axis equipment processing solution, the tool installation length is significantly reduced, the tool rigidity is good, and the processing stability is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 Comparison diagram of two parts structures;
[0029] Figure 2 Enlarged schematic diagram of the model at the nozzle;
[0030] Figure 3 A partial enlargement of the schematic diagram of the tool axis passing over the protrusion from the top of the part;
[0031] Figure 4 UV wireframes generated by NX software for current parts;
[0032] Figure 5 Use the mesh surface function to construct the required flow surface diagram;
[0033] Figure 6Schematic diagram of the upper part of the surface processed by the five-axis equipment;
[0034] Figure 7 Schematic diagram of the lower half of the surface processed by the five-axis equipment;
[0035] Figure 8 Schematic diagram of the corner area of the surface processed by the five-axis equipment;
[0036] Fig. 9 Schematic diagram of island areas with inconsistent nozzle sizes when machining curved surfaces with four-axis equipment;
[0037] Fig.10 Schematic diagram of island areas with uniform size when processing curved surface nozzles using a four-axis machine;
[0038] Fig.11 Use VERICUT simulation software to simulate and verify the processing quality;
[0039] Fig.12 Use VERICUT simulation software for collision detection. DETAILED DESCRIPTION
[0040] In the automatic processing of curved surfaces, the direction of the curved surface tool path is actually controlled by the concentric lines of the curved surface. Changing the direction of the guide rail can only optimize the UV flow direction of the curved surface. In order to achieve the purpose of the present invention, the required flow direction curved surface can be constructed by using the surface modeling function of NX software and the mesh surface function. Figure 5 As shown in the figure, it can be seen that in the island area, the concentric curves are divided and re-converged, so that the tool path driven by this method can be bypassed. Then, through the tool axis control, the tool side along the cutting path can avoid the raised side.
[0041] By solving the core problem, the required tool path can be obtained, and the actual application must have sufficient machinability for the existing equipment, while also taking into account quality safety and processing efficiency.
[0042] Combined with NX and other software, different processing solutions can be provided for five-axis equipment, vertical machining centers (with four-axis rotary tables), horizontal machining centers, etc., as follows:
[0043] Five-axis equipment processing solution:
[0044] Lock the fourth axis at a 20° tilt angle and perform down milling on the upper half of the curved surface. This allows for a shorter tool length and more stable tool axis control. Figure 6 shown.
[0045] Locking the fourth axis at a 25° tilt angle and milling the lower half of the curved surface can smoothly avoid island areas and annular surfaces and obtain stable processing quality. Figure 7 shown.
[0046] Taking advantage of the equipment, the five-axis linkage method can be used to obtain a sufficiently neat machining path in the corner area, with consistent tool direction and optimal tool cutting rigidity. Figure 8 shown.
[0047] Four-axis equipment processing solutions (including horizontal machining centers or vertical machining centers with fourth-axis rotary tables):
[0048] The island area with inconsistent nozzle size can be bypassed along the wide area. The tool path is neat, the cutting feed speed can be increased compared with the original solution, and the cutting path always maintains down milling. Fig. 9 shown.
[0049] For island areas with the same nozzle size, the nozzle can be bypassed in half from the side. The tool path is neat, the step distance is uniform, the cutting feed speed can be increased compared with the original solution, and the cutting path can always be milled forward. Fig.10 shown.
[0050] VERICUT simulation software was used to simulate and verify the safety and quality of this machining method using the same virtual machine tool and the same tool:
[0051] Check surface quality, such as Fig.11 shown.
[0052] Collision detection is performed to ensure cutting safety, such as Fig.12 shown.
[0053] Through the simulation of NC code, the safety of tool cutting can be fully verified. The change of color area can be used to observe whether there is overcutting. The simulated appearance of the cutting area can be observed in the local magnified view. The simulation results confirm that these two solutions are machinable.
[0054] The present invention has the following advantages:
[0055] 1. Before this, all computer-aided programming software on the market could not rely on the software's own strategy to automatically output bypass tool paths for surfaces with island areas, and the particularity of high-precision cover parts in the military industry led to the lack of similar or applicable cases for reference in the civilian industry. In order to meet the high requirements for the quality and appearance of military products, there must be sufficient verification and theoretical basis when trying new processing methods. The study of this method has obtained an ideal tool cutting path, eliminated most of the unfavorable factors in the original processing process, and provided a reasonable solution for improving the quality and efficiency of actual production.
[0056] 2. Through the study of the method of finishing the surface of the common precision cover parts of engine components, under the premise of ensuring the quality of parts, cutting efficiency, equipment safety and stability, and the universal adaptability of the processing method, the present invention proposes a programming method that can realize the automatic diversion and re-convergence of the tool path around the convex area of the curved surface parts with convex island shape, and provides two processing schemes for four-axis and five-axis equipment. The simulation analysis is carried out through VERICUT, and the results show that the automatic diversion and avoidance programming method around the curved surface island area is feasible.
Claims
1. A method for processing precision cover parts, characterized by: Through the surface modeling function of NX software, the required flow direction surface is constructed using the mesh surface function. In the island area, concentric curves are used to divert and re-converge, so that the driven tool path bypasses the island area. Then, through tool axis control, the raised side is avoided along the cutting path.
2. According to claim 1, a method for processing precision cover parts is characterized by: After generating the tool path, the five-axis equipment processing plan: In the island area, the fourth axis is locked at a tilt angle of 20°, and the forward milling is performed on the curved surface close to the center of the part. The fourth axis is locked at a tilt angle of 25°, and the forward milling is performed on the curved surface far from the center of the part. In the remaining processing areas, the forward milling is performed using the five-axis linkage method.
3. The method for processing precision cover parts according to claim 1 is characterized in that: After generating the tool path, the four-axis equipment processing plan: For island areas with inconsistent nozzle sizes, the nozzles are bypassed along the wide area, and the cutting path always remains in the forward milling direction. For island areas with consistent nozzle sizes, the nozzles are bypassed in half from the side, and the cutting path always remains in the forward milling direction.