Tool path generation for the point-pressing-based 5-axis CNC incremental forming

The existing studies on the CNC incremental sheet metal forming technology are all for the sheet metal parts with either concave peaks or convex peaks, and rarely involve the sheet metal parts with both concave peaks and convex peaks. However, with the deepening of the research for the CNC incremental sheet metal forming technology, the forming of the multi-peak sheet metal parts with both concave peaks and convex peaks will become a hot research topic. Compared to 3-axis CNC incremental forming, 5-axis CNC incremental forming can extrude the blank in any desired direction because its extruding tool has even more freedom and is more suitable for the forming of the multi-peaks sheet metal parts. In this paper, 5-axis CNC incremental forming path planning and generation method based on STL model has been proposed for the sheet metal parts with both concave peaks and convex peaks. The forming path planning scheme and the algorithms for the cutter location point calculation, forming path planning and extruding tool posture calculation are also given, which are necessary for 5-axis CNC incremental forming path generation for the sheet metal part with both concave peaks and convex peaks. The case study shows that the proposed method can automatically generate smooth and continuous 5-axis CNC incremental toolpath and runs steadily and reliably.

Tool path generation framework for accurate manufacture of complex 3D sheet metal parts using single point incremental forming

Incremental forming of sheet metal is a new sheet forming process. He has shown a variety of applications ranging from the automotive field to the biomedical field. However, sheet metal parts cannot be made in a one-step incremental forming process because the maximum profile angle of the wall that can be formed is limited for a given sheet material and for a given thickness. This limitation can be overcome with the multi-step incremental forming process (MSIF). In the framework of this study, it is proposed to analyze by experimental techniques the thickness and the profile of a truncated cone obtained by several steps forming an incremental MSIF. The study has been carried by forming a conical cup with 85° wall angle in four stages. Experimental tests were performed for specific conditions such as forming strategy, tool path, increment and cutting parameters. ABAQUS numerical simulations were performed to validate the experimental results at the end of each incremental forming step. The numerical and experimental results of the profile sheet metal are the subject of a comparative study between the theoretical, simulated and experimental models.

Spiral tool path optimization method for fast/slow tool servo-assisted diamond turning of freeform surfaces with highly form accuracy

Introduction: With the development of computer technology and data modeling, the use of point cloud models to generate tool paths is particularly important for improving productivity and accuracy.Methods: This study proposes a new method that first preprocesses the point cloud data using four-point denoising and octree methods to improve processing efficiency. Subsequently, roughing tool paths were analyzed using the layer slicing method and finishing paths using the residual height method.Results and Discussion: The experimental results show that the layer slicing method has a minimum error close to 10% on the roughing path generation and the computation time is reduced to 35 s, while the residual height method has an error rate of 10.17% on the finishing path and the computation time is only 11.82 s, which reflects a high trajectory smoothness and accuracy. The above results show that the study not only optimizes the tool path generation process and improves the machining efficiency and accuracy, but also demonstrates the potential application of point cloud models in the machining of complex parts.Conclusion: The novel tool roughing and finishing methods provide more reliable path planning for actual machining operations, and future research will be devoted to further improving the performance of the data processing algorithms and exploring more efficient path planning strategies to facilitate automated production.

Tool path generation is an important task in end milling. In the existing literature, the tool path pattern/style is determined based on geometric analysis. However, there is little analysis from the viewpoint of machining dynamics/cutting force, which is more related to the final manufacturing performance. Although there are many types of tool paths (e.g., zigzag, spiral, and ISO-scallop tool path), they can be decomposed into a number of circular tool paths with various path radii and cutting angles. Firstly, by investigating chip formation mechanism, the effect of tool path radius on uncut chip thickness is obtained. Analysis shows that tool path radius has a significant influence on uncut chip thickness, thus affecting the cutting force, especially when the tool path radius is small. Then, the effect of cutting angle on cutting force distribution is analyzed. It is found that the feed direction could vary the distribution of cutting force in X and Y direction in 3-axis end milling. Based on such analysis, the cutting force prediction model considering tool path effect is established. To validate the proposed model, various experiments have been carried out based on well-designed tool paths. The comparative results show that (1) tool path has great effect on cutting force through the tool path radius, rotation direction, and start/end point, and (2) the proposed model is capable of providing accurate cutting force prediction considering tool path effect. From a physical viewpoint, the proposed method provides huge potential in automated/intelligent tool path optimization towards better surface quality via minimizing cutting force, which significantly contributes to the state of the art in tool path generation.

Blisk is an essential component in aero engines. To maintain good aero-dynamic performance, one critical machining requirement for blades on blisk is that the generated five-axis tool path should be boundary-conformed. For a blade discretely modeled as a point cloud or mesh, most existing popular tool path generation methods are unable to meet this requirement. To address this issue, a novel five-axis tool path generation method for a discretized blade on blisk is presented in this paper. An idea called Linear Morphing Cone (LMC) is first proposed, which sets the boundary of the blade as the constraint. Based on this LMC, a CC curve generation and expansion method is then proposed with the specified machining accuracy upheld. Using the proposed tool path generation method, experiments on discretized blades are carried out, whose results show that the generated tool paths are both uniform and boundary-conformed. Highlights Five-axis finishing tool path based on Linear Morphing Cone (LMC) is presented. The method is implemented on a mesh model. Tool path generated from the proposed method is boundary-conforming. Boundaries of the machining region can be arbitrarily assigned. Experiments are carried out on two mesh blades.

Robot based incremental sheet metal forming (Roboforming) is an innovative die less forming process, which is developed by the Chair of Production Systems at Ruhr-University Bochum. Suitable for rapid prototyping and manufacture of small batch sizes with low costs, this forming process is based on flexible shaping through the synchronous movement of two tools hold by two industrial robots. Since there is no existing solution to quickly and accurately generate two synchronized tool paths according to the will of users, the research of this method should first be focused on the tool path generation. In this paper, different forming strategies and their algorithms of generating synchronized path points are explained at first. Based on these established algorithms, three approaches to create CAM-interfaces for the generation of robot programs are introduced thereafter. Depending on different users, they are individually based on postprocessors, Application Program Interface (API) and a stand-alone program. Each introduced approach for Roboforming is validated by forming experiments and they also give a good reference to the third-party development of a CAD/CAM-system.

Unified 2D polygon-based CAM framework integrating tool path generation, machinability evaluation, and cutting-force simulation

A residual height trajectory algorithm of complex surface plane envelope is proposed for NC grinding of complex surface. Firstly, based on the differential geometric relationship between the grinding wheel end plane and the workpiece surface, the properties of the plane enveloping surface are analyzed; secondly, the residual height based on the space vector is calculated; Secondly, the algorithm is proposed by using the tangent characteristics of the contour line of the equal residual height; Finally, the tool path of the ellipsoid convex surface is calculated, and the characteristics of the two different tool paths are compared and analyzed, and it is proved that the proposed method is effective The tool path has higher machining efficiency at the residual height.

Tool Path Generation, for Complex Surface Machining, Using Point Cloud Data

One of the variants and simplest form of incremental sheet metal forming process is single-point incremental forming in which a spherical ended tool is used to form features on one side of the initial plane of the sheet. Dimensional deviation is observed in the region of component opening (due to sheet bending) and at the wall as well as base regions. This article presents a methodology to minimize the dimensional deviation in the wall and base regions of single-point incremental forming formed components. The authors observed that the sheet deflection due to axial force and tool deflection due to radial force are the two main factors leading to the geometric deviation in wall as well as base regions. An analytical model has been developed for estimating these two deflections. These deflection values are incorporated in the tool path generation, and the components formed using the compensated tool path resulted in acceptable dimensional accuracy in the wall region. Force predictions carried out by force equilibrium method are used to calculate the deflection compensations as its predictions are in reasonably good agreement with the force predictions of finite element analysis and experimental measurements. Significant improvement in accuracy is achieved by using the deflection compensated tool paths.

CAM software is generally used to generate tool paths for 5-axis controlled machining. However, adjusting its several parameters and settings is difficult. We propose a system for tool path generation to be applied to 5-axis controlled machining. The system allows machining movements to be established by manipulating haptic devices in a virtual environment. Therefore, the cutter location for 5-axis machining can be easily controlled by operating a virtual cutting tool. The contact between the cutting tool and the target shape is reflected to the user through the haptic device. The generated path can be converted into a numerical control program for the actual machining of the target object. We detail the implementation of the proposed interface using two haptic devices and a method of tool path generation that improves rough cutting by smoothing the generated cutting points and simplifying the tool postures. The effectiveness of the developed system is confirmed through machining simulations.

A tool path generation strategy for three-axis ball-end milling of free-form surfaces

In recent years, trochoidal milling has become greatly widespread since it provides high productivity and long tool life, especially when cutting difficult-to-machine materials. Numerous studies have dealt with the analytical description and the experimental investigation of the evolution of cutting force, temperature, tool wear, chatter stability, etc. However, most of these analyses are focusing on the conventional circular and cycloid-shape trajectories. Only a few studies address the potential of improving the efficiency by modifying the tool path shape, leaving significant reserves untapped. If the mathematical formulation of the trajectory cannot be described easily, then a sophisticated optimisation algorithm is needed to determine the appropriate tool path shape. To overcome these difficulties at trochoidal milling of straight slots, the present work proposes a new tool path generation algorithm that can maximize the average material removal rate (MRR) while controlling the tool load. In this approach, the tool path is modelled by a B-spline curve whose control points are optimised using a differential evolution algorithm. The developed tool path generation strategy was compared through simulations and experiments with two widely used solutions viz the traditional cycloid-shaped tool path and a modern approach used in computer-aided manufacturing (CAM) systems. The results reveal that the developed method is able to control the tool load and the smoothness of the tool path, and most importantly, also exceeds the existing methods in terms of productivity.