Toolpath Planning and Generation for Multi-Stage Incremental Forming Based on Stretching Angle

To solve the problems that exist in the multi-stage forming of the straight wall parts, such as the sheet fracture, uneven thickness distribution, and the stepped feature sinking, a new forming toolpath planning and generation method for the multi-stage incremental forming was proposed based on the stretching angle. In this method, the parallel planes that were used for forming toolpath generation were constructed by using the stretching angle so that the distances between the parallel planes and the forming angles were gradually reduced. This makes the sheet material flow become changed and the thickness thinning is relieved. The software system for the toolpath generation was developed by using C++, VC++, and OpenGL library. In order to verify the feasibility of the proposed method, numerical simulation and forming experiments were carried out for the single stage forming, the traditional multi-stage forming, and multi-stage forming based on the proposed forming toolpath, using 1060 aluminum sheets. The comparative analysis of the thickness distribution, profile curve, strain curve, and sheet material flow shows that the proposed method is feasible, and the profile dimension accuracy is better, the thickness distribution is more uniform, and the sinking and bulging are significantly reduced. The formed sheet part with the stretching angle of 15° has higher dimensional accuracy, smaller bottom subsidence, and larger thickness than that of the stretching angle 5°.

An Augmented-Reality Based Human-Robot Interface for Robotics Programming in the Complex Environment

To solve the problems of complex robot programming tasks, we propose an Augmented Reality (AR) based human-robot interface for planning a collision-free path in a complex environment. Current robot programming methods usually require a high level of experience in robot programming (online programming), the time-consuming 3D modeling of the working environment for collision detection (offline programming), and a tedious and inefficient re-planing to adapt environment or task changes (both online and offline programming). In order to address these problems, an end-to-end AR human-robot interface is proposed, which provides a new affordance to users by enabling them to plan the path in the AR environment. A set of user-interactive tools allow users to define and edit waypoints as the high-level guidance and the direct inputs for the toolpath planning package, Kinematics and Dynamics Library (KDL). With the fast sensing of the workspace and accurate rendering, an in-situ simulation module is utilized for collision check and verification by the users’ perception. Users will repeat the process of 1) waypoints definition and editing, and 2) the collision checking and path feasibility verification, until a satisfactory path is obtained. A preliminary testing is conducted in a use case with complex obstacles to verified the effectiveness and the efficiency of the proposed interface.

Voxel-Based Adaptive Toolpath Planning using GPU for Freeform Surface Machining

Today freeform surfaces are widely used on products in automobile, aerospace, and die/molds industries, which are generally manufactured using multi-axis CNC machines. Frequent changes in the design of products necessitate creation of CNC part programs which need fast and accurate toolpath generation methods. Traditional toolpath generation methods involve complex computations and are unable to consider multiple surface patches together. The voxel-based CAD model provides the ability to represent the multi-patch surfaces in a discretized manner which can be processed using an advanced parallel computing framework for accurate tool path planning. This paper presents a new method to generate an adaptive Iso-planar toolpath for a 3-axis CNC machine using the voxel-based part model. The algorithm is designed to work on a Graphics Processing Unit (GPU) that allows parallel processing for faster toolpath generation. The proposed approach consists of two main steps, an algorithm to generate gouge free cutter location points from the voxel-based CAD model and an algorithm to find out sidestep and forward step from those cutter location points to create the final CNC tool path. A new image-processing technique has been proposed to identify gouge by detecting the shadow surface voxels and their intersection with the cutting tool. The developed system was extensively tested and compared with the various reported toolpath planning strategies for machining complex freeform surface parts. The results show that the developed method is computationally efficient, robust, and accurate in generating adaptive planar toolpath.

3D Printing of Objects with Continuous Spatial Paths by A Multi-Axis Robotic FFF Platform

Conventional Fused Filament Fabrication (FFF) equipment can only deposit materials in a single direction, limiting the strength of printed products. Robotic 3D printing provides more degrees of freedom (DOF) to control the material deposition and has become a trend in additive manufacturing. However, there is little discussion on the strength effect of multi-DOF printing. This paper presents an efficient process framework for multi-axis 3D printing based on the robot to improve the strength. A multi-DOF continuous toolpath planning method is designed to promote the printed part’s strength and surface quality. We generate curve layers along the model surfaces and fill Fermat spiral in the layers. The method makes it possible to take full advantage of the multi-axis robot arm to achieve smooth printing on surfaces with high curvature and avoid the staircase effect and collision in the process. To further improve print quality, a control strategy is provided to synchronize the material extrusion and robot arm movement. Experiments show that the tensile strength increases by 22–167% compared with the conventional flat slicing method for curved-surface parts. The surface quality is improved by eliminating the staircase effect. The continuous toolpath planning also supports continuous fiber-reinforced printing without a cutting device. Finally, we compared with other multi-DOF printing, the application scenarios, and limitations are given.