Yuhan Wang

A GPU-based algorithm for generating collision-free and orientation-smooth five-axis finishing tool paths of a ball-end cutter

A graphics process unit (GPU) based approach that generates collision-free and orientation-smooth tool paths for five-axis NC finishing machining of complicated shapes is presented. A new GPU-based method is proposed to compute accessibility cones of cutter location (CL) points for a ball-end cutter and tool orientations are then optimised in the accessibility cones. Three steps in the approach are GPU-based accessibility computation, feasibility map and orientation optimisation. Unlike the existing visibility concept, the diameters of both tools and tool-holders are taken into consideration and the actual accessibility cone is computed directly and efficiently based on occlusion query functionality of the graphics hardware. Next, a feasibility map is used to select feasible orientations due to the limits of collision avoidance and the machine tool. Finally, tool orientations are globally optimised to generate an orientation-smooth tool path. The proposed algorithms allow an acceptable computing time and hardware requirement to generate collision-free and orientation-smooth tool paths for complicated shapes. Examples show the efficiency of computing accessibility cones. The finishing tool paths for machining an impeller are generated as examples and cutting experiments confirm the validity of the proposed approach.

A practical continuous-curvature bézier transition algorithm for high-speed machining of linear tool path

A continuous-curvature smoothing algorithm is developed to approximate the linear tool path for high speed machining. The new tool path composed of cubic Bezier curves and lines, which is everywhere G2 continuous, is obtained to replace the conventional linear tool path. Both the tangency and curvature discontinuities at the segment junctions of the linear tool path are avoided. The feed motion will be more stable since the discontinuities are the most important source of feed fluctuation. The algorithm is based upon the transition cubic Bezier curve that has closed-form expression. The approximation error at the segment junction can be accurately guaranteed. The maximal curvature in the transition curve, which is critical for velocity planning, is analytically computed and optimized. The curvature radii of all transition Bezier curves are also globally optimized to pursue the high feed speed by a linear programm model. Therefore, the algorithm is easy to implement and can be integrated into a post-process system.

An algorithm to generate compact dual NURBS tool path with equal distance for 5-Axis NC machining

A new algorithm is proposed to generate compact dual NURBS tool paths with equal distance (DNTPED) for 5-axis NC machining. The DNTPED has significant advantages over conventional linear tool path in the NC machining of free-form surface since it reduces the tangency discontinuities along the tool path. The discontinuities, the inherent character of the linear interpolation, are the important sources of practical feed-speed fluctuation of the machine tool. The new algorithm is proposed to generate DNTPED based on the theories of rational motion. Here the rational rigid movement of a cutter is represented by a B-spline curve in dual quaternion space. DNTPED is obtained directly from the B-spline dual quaternion curve with the help of the blossom form of the B-spline curve. Comparing with the existing method, the DNTPED consists of less data and each NURBS can be treated as one curve, not as a collection of bezier segments.

Technology solutions for product lifecycle knowledge management: framework and a case study

Information technology has promoted our society gradually into knowledge economy from product economy. Value creation requires more and more knowledge and information to support enterprise activities. Knowledge management (KM) as an activity has already existed, and will make the organisation and individual have stronger competition strength, and make better decisions. In order to respond to the industrial trend towards knowledge management, this paper investigates and proposes a framework for product lifecycle knowledge management that utilises product maintenance data across the lifecycle of the product. A case presented in this paper is a maintenance knowledge service system to prove the framework method.

Dual-Bézier path smoothing and interpolation for five-axis linear tool path in workpiece coordinate system

The tool path composed of consecutive short linear segments (G01 blocks) is still the widespread tool path representation form in five-axis machining. The inherent shortcoming of linear tool path is first-order discontinuity at the corner, which is the bottleneck to achieve high-speed and high-accuracy machining. In this article, a dual-Bézier path smoothing algorithm for five-axis linear tool path in workpiece coordinate system is proposed. There are three steps involved in our method. First, the corner error distribution model is introduced to assign the given tolerance to the smoothing approximation error constraint and the chord error constraint to ensure the interpolation trajectory error within the given tolerance. Second, segment junctions of the linear tool path in workpiece coordinate system are smoothed by double G2 continuous cubic Bézier curves. One cubic Bézier curve is used to round the corner of the tool tip point path, and the other Bézier curve is used to round the corner of the tool axis point path. This algorithm takes the conditions of approximation error constraint, the parameterized synchronization constraint, and continuous curvature constraint into consideration. Hence, the tangency and curvature continuities are both guaranteed in the new path. Third, an adaptive feedrate scheduling method is introduced to interpolate the new path. Simulation and experiment are performed to verify the effectiveness of the proposed method in five-axis tool path smoothing, speed smoothing, and trajectory accuracy controlling.

Research on consecutive micro-line interpolation algorithm with local cubic B-spline fitting for high speed machining

To achieve high-speed and high-accuracy machining, look-ahead scheme and parametric interpolator have shown significant effect on interpolating micro-line blocks. On the one hand, look-ahead schemes have been integrated in many computer numerical control (CNC) systems to alleviate the frequent start/stop motion and achieve a higher feedrate. However, the unsmooth speed at the segment junctions cannot be avoided entirely due to the discontinuous nature of the linearized-segmented contour. On the other hand, parametric interpolator has been proposed to overcome the shortcomings of the linear/circular interpolator. But, it is difficult to fit the blocks into parametric curves on-line. In this paper, a local cubic B-spline fitting algorithm with real-time look-ahead scheme is proposed for consecutive micro-line blocks interpolation. First, the consecutive micro-line blocks, which satisfy the bi-chord error constraint, are fitted into a C1 continuous cubic B-spline curve. Second, machining dynamics and tool path contour constrains are taken into consideration. Third, an optimal look-ahead scheme is proposed to generate the optimal feedrate profile. Simulation and experiment are performed in real-time environment to verify the effectiveness of the proposed method. Compared with the conventional interpolation algorithm, the proposed algorithm reduces the machining time by 70%.

Optimizing tool size and tool path of five-axis flank milling with bounded constraints via normal mapping:

This article presents an approach to generate optimal couples of tool size and tool path for flank milling ruled surface with a conical cutter based on normal mapping, while at the same time keeping this couples within the given bounded constraints. For given initial pairs of taper tool and tool path, tool envelope surface is calculated. Then, the tool axis trajectory surface is related to envelope surface through the normal mapping. On this basis, the correspondence between the surface pair “design ruled surface–envelope surface–tool axis trajectory surface” is established, and it is used to obtain the signed flank milling error. By using this signed error, tool size and tool path optimization for flank milling is formulated as an optimization model subjected to bounds, and the trust-region-reflective least-squares method is used to solve this problem. Numerical example is given to confirm the validity of the proposed method.