Simulation methods for multi-axis milling
Patent Information
- Application Number
- TW114108907
- Authority / Receiving Office
- TW · TW
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-11
- Publication Date
- 2026-09-16
- Estimated Expiration
- 2045-03-10
AI Technical Summary
Existing CNC milling simulation methods face inefficiencies due to high computational power requirements for complex intersecting surfaces and significant memory usage, especially when calculating cutting forces, leading to suboptimal machining processes.
A simulation method using a three-dimensional ray model, signed distance function, and ray stepping algorithm to establish tool-workpiece contact areas, optimizing cutting paths and calculating instantaneous cutting forces, enhanced by parallel processing with a graphics processor.
Significantly improves computational efficiency and reduces memory usage, allowing for rapid calculation of cutting paths and instantaneous cutting forces, thereby optimizing machining processes and preventing collisions.
Smart Images
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Abstract
Description
[Technical Field]
[0001] This invention relates to multi-axis machining technology, and in particular to a simulation method for multi-axis milling. [Previous Technology]
[0002] CNC milling is a very common product manufacturing method in the industry. Before actual machining, operators usually use simulation software (such as B-rep Model or Voxel Model) to simulate the machining process to ensure its correctness. Taking the Boundary-Representation Model (B-rep Model) as an example, when calculating the contact area between the tool model and the workpiece model, the extremely complex intersecting surfaces require a huge amount of computational power, resulting in low efficiency. As for the Voxel Model, it uses multiple cube blocks to form the outline of the tool model and the workpiece model. Due to the large number of cube blocks, the amount of memory required during the calculation is also quite large, which also leads to low computational efficiency.
[0003] As can be seen from the above, in the process of simulating actual machining, since the contour of the workpiece model needs to be continuously calculated and updated, choosing any of the aforementioned simulation software will inevitably greatly affect the simulation results and simulation efficiency. Moreover, if further analysis of the machining process is desired (such as calculating instantaneous cutting forces), the insufficient computing power of the hardware is usually encountered. In addition to improving the hardware, finding a more suitable workpiece model and tool model and matching it with a suitable algorithm is the current challenge. [Summary of the Invention]
[0004] The main objective of this invention is to provide a simulation method for multi-axis milling, which can improve simulation efficiency and quickly calculate cutting paths and instantaneous cutting forces to optimize tool paths and feed rates in actual machining processes.
[0005] In order to achieve the above-mentioned main objectives, the simulation method for multi-axis milling provided by the present invention includes the following steps: (a) establishing a workpiece model using a three-dimensional ray model; (b) establishing a tool model using a signed distance function; and (c) obtaining a tool-workpiece contact area using a ray stepping algorithm, and calculating whether a cutting path of the tool model will cause improper collision between the tool model and the workpiece model based on the tool-workpiece contact area.
[0006] As described above, the simulation method of the present invention uses a three-dimensional ray model to establish the workpiece model, which can speed up the calculation compared to the traditional B-rep Model, and reduce the amount of memory used compared to the Voxel Model. Secondly, the simulation method of the present invention uses a signed distance function combined with the ray stepping algorithm to quickly find the tool-workpiece contact area and update the contour of the workpiece model. While updating the contour of the workpiece model, the data of the tool-workpiece contact area can be obtained. The aforementioned data is an important condition for calculating the cutting path. If it is estimated that an improper collision may occur, the cutting path needs to be adjusted to ensure that the two sides do not collide with each other, thereby achieving the effect of optimizing the actual machining process.
[0007] Preferably, in addition to obtaining the cutting path, in step (c), an instantaneous cutting force can be calculated based on the tool-workpiece contact area. This allows the tool model to be simulated to process the workpiece model when it is close to the critical value of the instantaneous cutting force, thereby optimizing the feed efficiency of the actual machining.
[0008] Preferably, in step (c), the light trace stepping algorithm is used in conjunction with a graphics processor to perform parallel calculations to obtain data on the tool-workpiece contact area, which can further improve the calculation efficiency.
[0009] The detailed construction, features, assembly, or usage of the simulation method for multi-axis milling provided by the present invention will be described in the following detailed description of the embodiments. However, those skilled in the art should understand that such detailed descriptions and the specific embodiments listed for implementing the present invention are merely illustrative and not intended to limit the scope of the patent application.
Implementation Method
[0010] The applicant hereby states that throughout this specification, including the embodiments described below and the claims in the claims, all directional terms are based on the directions shown in the drawings. Secondly, in the embodiments and drawings to be described below, the same element reference numerals represent the same or similar elements or their structural features.
[0011] The simulation method of this invention mainly simulates the process of multi-axis milling of the workpiece by the cutting tool before actual machining, in order to ensure the accuracy and correctness of the machining process. The so-called multi-axis can be dual-axis, three-axis, four-axis, or five-axis, and is not limited here. Please refer to Figure 1. The simulation method of this invention includes the following steps:
[0012] (a) As shown in step S1 of Figure 1, a workpiece model 10 is created using a three-dimensional ray model (Tri-Dexel Model).
[0013] The three-dimensional ray model (Tri-Dexel Model) used in this step uses rays emitted from three ray planes in different directions to establish the outline of the workpiece model 10. In this embodiment, as shown in Figure 2, the workpiece model 10 is a tooth model, but it is not limited to this. In other embodiments, it can also be applied to different industry categories such as: manufacturing (aerospace, automotive, electronics, energy equipment, tools, molds or machine tools), medical industry (dental, orthopedics, plastic surgery, medical equipment, surgical planning or guides), academia (mechanical engineering, manufacturing engineering, industrial design, aerospace engineering or materials engineering), etc. The advantages of the three-dimensional ray model (Tri-Dexel Model) are that it is very suitable for parallel algorithms. Compared with the B-rep Model, it can significantly shorten the time required for machining simulation. Moreover, the memory consumed by the three-dimensional ray model (Tri-Dexel Model) is very small compared with the Voxel Model. The endpoint of each ray can carry the physical phenomenon values generated at each instant (such as the cutting area), and therefore has quite good scalability.
[0014] (b) As shown in step S2 of Figure 1, a tool model 20 is established using a Signed Distance Function (SDF).
[0015] The Signed Distance Function (SDF) used in this step is a directly defined mathematical model that calculates the distance from a given coordinate point to the target object in the form of an implicit function. The positive and negative signs indicate whether the object is located inside or outside the object, thereby establishing the outline of the tool model 20 and quickly understanding the positional relationship between it and the workpiece model 10 (as shown in Figure 2).
[0016] (c) As shown in step S3 of Figure 1, a Cutter-Workpiece Engagement (CWE) area 30 is obtained using a Ray Marching algorithm, and an Instantaneous Cutting Force is calculated based on the CWE area 30, and it is calculated whether one of the cutting paths of the tool model 20 will cause improper collision between the tool model 20 and the workpiece model 10.
[0017] The ray Marching algorithm used in this step searches for the closest distance to the object after knowing the origin and direction of the ray. Then, it moves this distance from the origin of the ray towards the direction of the ray, updates the starting position, and repeats the above actions until it contacts the object or determines that the ray is diverging. Since the workpiece model 10 established using the three-dimensional ray model is composed of multiple line segments, it can be regarded as a large number of rays. Therefore, the ray Marching algorithm quickly searches the boundary of the tool model 20 with the original contour of the workpiece model 10 to update the contour of the workpiece model 10. While updating the contour of the workpiece model 10, the data of the cutter-workpiece engagement (CWE) 30 can be obtained (as shown in Figure 2). The aforementioned data is an important condition for calculating the cutting path and instantaneous cutting force. The so-called instantaneous cutting force refers to the instantaneous resistance encountered by the tool when machining the workpiece. If the instantaneous cutting force is too large, it may cause damage to the tool and / or the workpiece. This allows the tool model 20 to be simulated to machine the workpiece model 10 when it is close to the critical value of the instantaneous cutting force, thereby maximizing the feed efficiency of the actual machining. Please refer to Figure 3, which shows the curve relationship between the travel distance of the tool model 20 and the three-axis cutting force in the machining simulation. However, in practice, time can also be used instead of travel distance, that is, to show the magnitude of the three-axis cutting force corresponding to the tool model 20 machining for a specific time (e.g., 10 seconds).
[0018] It is worth mentioning that the Ray Marching algorithm can also be used in conjunction with a Graphics Processing Unit (GPU) for parallel computation, changing from obtaining the starting point and direction of a single ray to obtaining the starting point and direction of multiple rays at the same time, thereby further improving the computation speed of the workpiece model 10 when updating the contour.
[0019] Table 1 below shows the efficiency differences of cutting paths designed using the three-dimensional ray model (Tri-Dexel Model) in combination with the traditional Splits Bounding Volume Hierarchies (SBVH) and the combination of the Signed Distance Function and Ray Marching algorithm used in this invention. Table 1 (0020) frequency SBVH (unit: seconds) SDF+Ray Marching (unit: seconds) 1 15.5336 9.30046 2 15.6123 9.27029 3 15.5674 9.26721 4 15.6874 9.26484 5 15.6036 9.29699 6 15.7078 9.30935 7 15.665 9.29641 8 15.8078 9.32197 9 15.6415 9.29707 10 15.8343 9.28962 11 15.5664 9.31953 12 15.6826 9.2958 13 15.9124 9.29946 14 15.5686 9.30116 15 15.5628 9.30366 Average time 15.6636 9.29559
[0021] As can be seen from the table above, the average computation time of the traditional simulation method is about 15.6636 seconds, and about 702.329 cutter location points can be found per second. The average computation time of the simulation method of the present invention is about 9.29559 seconds, and about 1183.464 cutter location points can be found per second. In comparison, the computation time of the simulation method of the present invention is significantly shortened, and the computation speed can be greatly improved by about 68.51%.
[0022] In summary, the simulation method of the present invention can greatly improve the calculation speed by combining the three-dimensional ray model (Tri-Dexel Model), the signed distance function (Signed Distance Function), and the ray Marching algorithm. The saved calculation time can not only be used to analyze the magnitude of the instantaneous cutting force, but also to calculate whether the cutting path of the tool model 20 will cause improper collision between the tool model 20 and the workpiece model 10. If improper collision is expected, the cutting path needs to be adjusted to ensure that the two do not collide with each other. [Simplified Explanation of the Diagram]
[0023] Figure 1 is a flowchart of the simulation method of the present invention. Figure 2 is a perspective view of the workpiece model and tool model provided by the simulation method of the present invention. Figure 3 is a graph of the travel distance and cutting force provided by the simulation method of the present invention.
Claims
1. A simulation method for multi-axis milling, comprising the following steps: (a) establishing a workpiece model using a three-dimensional ray model; (b) establishing a tool model using a signed distance function; and (c) obtaining a tool-workpiece contact area using a ray stepping algorithm, and calculating whether a cutting path of the tool model will cause improper collision between the tool model and the workpiece model based on the tool-workpiece contact area.
2. The simulation method for multi-axis milling as described in claim 1, in step (c), an instantaneous cutting force is calculated based on the tool-workpiece contact area.
3. The simulation method for multi-axis milling as described in claim 1 or 2, in step (c), uses the trace stepping algorithm in conjunction with a graphics processor to perform parallel calculations to obtain the tool-workpiece contact area.