Slice-Based Automated Support Generation for Additive Manufacturing

Multi-free-surface mirror integrated system is the development trend of optical system, but its ultra-precision machining is very difficult, this paper mainly studies the tool path generation problem of multi-free-surface reflector integrated system. In this paper, two tool path generation methods for the off-axis four-mirror group machining with SPDT are presented, one tool path generation method is separate machining and the other is integrated machining. Both methods are based on cylindrical spiral and generate tool path by projecting points onto surfaces. For the tool path generation method of integrated machining, the linear transition is used to realize the smooth transition of the mirror surfaces. By comparing the simulation machining of two kinds of tool path generating methods, it is found that the integrated tool path generating method is more suitable for off-axis four-mirror group machining and has higher machining efficiency.

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.

Fast/slow tool servo (FTS/STS) technology plays an important role in machining freeform surfaces for the modern optics industry. The accuracies of these surfaces not only depend on the performance of the FTS/STS but also on the methods of tool path generation (TPG). Current methods of pre-compensating tool nose radius and control dynamics still do not address the inherent profile errors arise from the methods of TPG. Furthermore, it is also not efficient to characterize a freeform surface in the post-machining stage, giving a high risk of failing to meet the accuracy requirements. In this paper, a profile error analysis (PEA) is introduced into the pre-machining stage to address this inherent profile error. PEA is carried out to compare two methods of TPG, namely the constant angle and constant arc methods and optimizes the number of cutting points in the TPG. Thus, the profile accuracy can be pre-determined to meet accuracy requirements by determining the appropriate TPG method with a least number of the cutting points. In the experiments, sinusoidal wave grid and micro-lens array surfaces are fabricated and their profiles successfully achieve the accuracy tolerance of 1 μm. These further credit the capability of PEA as an effective and accurate tool in improving profile accuracies and meeting accuracy requirements.

A new approach to CNC tool path generation

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

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

Integrated steepest-directed and iso-cusped toolpath generation for three-axis CNC machining of sculptured parts

Flat-end cutter orientation on a quadric in five-axis machining

With the increasing market demand for optical complex surface parts, the application of multi-axis ultra-precision single-point diamond turning is increasing. A tool path generation method is very important to decrease manufacturing time, enhance surface quality, and reduce cost. Compared with the tool path generation of the traditional multi-axis milling, that of the ultra-precision single-point diamond turning requires higher calculation accuracy and efficiency. This paper reviews the tool path generation of ultra-precision diamond turning, considering several key issues: cutter location (CL) points calculation, the topological form of tool path, interpolation mode, and G code optimization.

Iso-planar piecewise linear NC tool path generation from discrete measured data points

The frequent change in tool attitude makes the quality of machined surface worse. In the study, the influence of the change in tool attitude is evaluated, based on the experiment. Then, an evaluation formula is proposed, considering the influence of both the tool attitude and the change in tool attitude against the machined surface. Machining experiments are performed to confirm the validity. Moreover, the method that generates appropriate tool path for finish machining is devised by utilizing the evaluation formula. It is confirmed that the tool path generation method is useful to improve the quality of machined surface.

In this chapter, we address various issues related to data processing for rapid prototyping. In contrast to traditional material removal processes, rapid prototyping techniques build a part by incrementally adding materials layer by layer (Kruth 1991, Barequet and Kaplan 1998), so they are also called layer-based manufacturing or layered manufacturing. The processes are fully automatic and offer a number of competitive advantages over traditional manufacturing processes. Hence, they are particularly useful for rapid product development. The entire process for model prototyping is illustrated in Figure 5-1 and can be summarized as follows: CAD modeling: The first step in rapid prototyping is to prepare a computer-aided design (CAD) model of the object to be fabricated using layer based manufacturing processes. For most of the available RP technologies, a solid model with complete topological and geometric information is required. STL interfacing: STL is the de-facto standard for the rapid prototyping industry. It is a file format for approximately defining an object using triangular facets. When a CAD model is available, the entire part geometry is converted into STL format based on a tolerance for accuracy control. Part orientation: Before processing for prototyping, a RP engineer needs to figure out the specific orientation in which the prototype model will be produced. Part accuracy, the amount of supporting material required and ease of post-processing are important factors influencing part orientation determination. Support generation: Depending on the specific RP process to be used, one may need to further define support structures for supporting down-facing areas during part build-up. Support generation can be done on the basis of a STL model or the original CAD model. Model slicing and tool path generation: In contrast to material removal manufacturing technologies, rapid prototyping technologies refer to a class of layer-based material increase manufacturing processes. The digital model of the object and related support structures need to be sliced layer by layer. For each layer, a set of surface contours is obtained and a tool path is defined within the material area for model production in a layer-wise fashion. Model production on a RP machine: The produced tool path is sent to a RP machine for building up the prototype model, including support, layer by layer. Post-processing: Depending on the RP process involved, a post-processing step might be needed for post-curing in the case of stereolithography, for infiltration and furnace sintering in the case of SLS, and/or for removing the support structures and surface polishing in the cases of most other RP processes.

The complicated surface part generally possesses exceptional properties, then the developments of high-end equipment and the precision physics experiment are in pressing demand of it. To accurately manufacture the complicated surface part, this study presents a toolpath generation strategy for slow tool servo (STS) turning with position-velocity-time (PVT) interpolation under the constraint of the specified interpolation error. Based on the mathematical principle of PVT interpolation, the interpolation point is calculated. With the anticipant curve represented with a spatially circular arc, the cutter contact point (CCP) of the toolpath with PVT interpolation is derived under the constraint of the specified interpolation error by way of the presented bisection algorithm. Then the cutter location point (CLP) of the toolpath is calculated through the tool nose radius compensation for STS turning. The validated experiment shows that the workpiece machined with the toolpath with PVT interpolation generated through the proposed scheme satisfies the constraint of the specified interpolation error. The peak to valley (PV) value of the form error of the surface is 8.2 μm, besides the root mean square (RMS) value of the form error is 1.9 μm. The volume of CLPs of the toolpath is reduced by 51.7% compared with the toolpath discretized by an equal angle. The achievement of this study provides guidance for the STS precision turning with PVT interpolation for the complicated surface.

Considering the residual height of the sheet metal part surface formed by the point-pressing incremental forming method and the efficiency of the forming process, the candidate terminal cutter location points based on the latitudinal/longitudinal residual height were calculated firstly, and then adjusts the candidate terminal cutter location points that are beyond the maximum residual height. Finally, all the terminal cutter location points are obtained. Thus, while satisfying the maximum residual height, the pressing points are sparse as much as possible, which improves the forming efficiency. In addition, for the problem that the ordinary 3-axis CNC incremental forming cannot press the sheet in the different directions according to the surface features, a method for determining the spatial posture of the 5-axis pressing tool by adjusting the front angle and side dip angle was proposed so that the sheet metal can be pressed in different extrusion directions. According to the proposed 5-axis point-pressing incremental forming tool path generation method, the actual forming experiment was carried out, and the sheet metal part was successfully formed, which meets the residual height requirements and shows that the methods for the tool path generation and the spatial posture determination of the forming tool are feasible. In addition, a comparative experiment was conducted with the 5-axis consecutive incremental forming tool path under the same residual height conditions. Through the measurement and analysis of the experimental parts, it is concluded that the profiles of the sheet metal parts obtained under the two forming methods have a good geometrical agreement with the designed parts. However, the profile of the sheet metal part formed by the 5-axis point-pressing incremental forming tool path is closer to the designed part as a whole, and the thickness in the forming region is also slightly higher than that of the sheet metal part formed by the 5-axis consecutive incremental forming tool path.