Freeform surfaces, also called sculptured surfaces, have been widely used in various engineering applications. Freeform surfaces are primarily manufactured by CNC machining, especially 5-axis CNC machining. Various methodologies and computer tools have been developed in the past to improve efficiency and quality of freeform surface machining. This paper aims at providing a state-of-the-art review on recent research development in CNC machining of freeform surfaces. This review primarily focuses on three aspects in freeform surface machining: tool path generation, tool orientation identification, and tool geometry selection. For each aspect, first concepts, requirements and fundamental research methods are briefly introduced. The major research methodologies developed in the past decade in each aspect are presented with details. Problems and future research directions are also discussed.

Review: Recent development in CNC machining of freeform surfaces: A state-of-the-art review

This paper presents a novel “layer jamming” mechanism that can achieve variable stiffness. The layer jamming mechanism exploits the friction present between layers of thin material, which can be controlled by a confining pressure. Due to the mechanism's hollow geometry, compact size, and light weight, it is well suited for various minimally invasive surgery applications, where stiffness change is required. This paper describes the concept, the mathematical model, and a tubular snake-like manipulator prototype. Various characteristics of layer jamming, such as stiffness and yield strength, are studied both theoretically and experimentally.

A Novel Layer Jamming Mechanism With Tunable Stiffness Capability for Minimally Invasive Surgery

Techniques are provided for searching on three dimensional (3D) objects across large, distributed repositories of 3D models. 3D shapes are created for input to a search system; optionally user-defined similarity criterion is used, and search results are interactively navigated and feedback received for modifying the accuracy of the search results. Search input can also be given by picking 3D models from a cluster map or by providing the orthographic views for the 3D model. Feedback can be given by a searcher as to which models are similar and which are not. Various techniques adjust the search results according to the feedback given by the searcher and present the new search results to the searcher.

Methods, systems, and data structures for performing searches on three dimensional objects

This paper presents a methodology and algorithms of optimizing and smoothing the tool orientation control for 5-axis sculptured surface machining. A searching method in the machining configuration space (C-space) is proposed to find the optimal tool orientation by considering the local gouging, rear gouging and global tool collision in machining. Based on the machined surface error analysis, a boundary search method is developed first to find a set of feasible tool orientations in the C-space to eliminate gouging and collision. By using the minimum cusp height as the objective function, we first determine the locally optimal tool orientation in the C-space to minimize the machined surface error. Considering the adjacent part geometry and the alternative feasible tool orientations in the C-space, tool orientations are then globally optimized and smoothed to minimize the dramatic change of tool orientation during machining. The developed method can be used to automate the planning and programming of tool path generation for high performance 5-axis sculptured surface machining. Computer implementation and examples are also provided in the paper.

Optimizing tool orientations for 5-axis machining by configuration-space search method

An energy harvesting system for use with a vehicle including an RF transmitter positionable in a vehicle and a key fob having an antenna configured to receive an RF signal from the RF transmitter and convert the RF signal to electrical energy, a power management circuit configured to distribute the electrical energy in the key fob, and an energy storage device configured to store at least some of the electrical energy converted from the RF signal.

Energy harvesting system

We describe a system that generates 5-axis roughing tool paths directly from a tessellated representation of a body. Instead of decomposing the shape into manufacturing primitives, we generate tool paths directly from the shape of the workpiece using measures of accessibility avoid collisions. There are three stages in our approach: visibility computation, posture definition and path interpolation. In the first stage, we use the concept of visibility to determine the directions from which a point in the delta-volume is likely to be accessible to an observer located outside the convex envelope of the object and describe a technique to compute this information rapidly using graphics hardware. However, visibility does not ensure accessibility because visibility cannot account for the diameter of the tool, the tool-holder or the spindle. In the posture definition stage, a local search is performed in the neighborhood of the visibility direction using rapid collision avoidance. The output of this step is a set of valid tool postures for every sample point in the delta-volume. Finally, all that remains to be done is to connect the valid postures into a valid continuous tool path. This is not a trivial task because the tool must not interfere with the part while interpolating between valid postures. In the third stage of our approach we interpolate collision free tool paths by performing NC simulation and path correction within the loop of path generation using rapid collision detection algorithms.

Generating 5-axis NC roughing paths directly from a tessellated representation

We present a series of algorithms and heuristics for generating collision-free 5-axis CNC finishing toolpaths automatically. These algorithms are based on the core concept of visibility, which can be generated in high resolution by discretizing the part and using graphics hardware as described in earlier papers by the authors. Using this visibility data for finish machining is a challenge, and we show how it can be used to generate globally collision-free 5-axis finishing toolpaths while also considering machine limits, tool tilt, cusp height limits, tool pitch limits and the need to keep toolpaths continuous. We then show how the toolpath can be verified during the path generation process, how collision-free interpolation can be carried out and how the sampling can be adjusted to ensure that the finishing toolpaths are accurate. We end with examples of 5-axis toolpaths generated for complex parts.

Collision-free finishing toolpaths from visibility data

A fiber optic sensor is provided. The fiber optic sensor includes a fiber core having a plurality of Bragg grating elements wherein, the grating elements comprise a periodic or a quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral structure and a cladding disposed about the fiber core.

Fiber optic sensor for detecting multiple parameters in a harsh environment

An energy harvesting device, system and method are described. The energy harvester collects acoustic energy and transforms it into electrical energy for use by a sensor. The energy harvester utilizes a piezoelectric device, which may be encased, either wholly or partially, within an acoustic chamber. Alternatively, the piezoelectric device may be entirely exterior to the acoustic chamber, which acts to amplify the collected acoustic energy.

Energy harvesting system, apparatus and method

An intuitive man–machine interface for generating 5-axis tool paths is described in the paper. The system is based on a 5 degree-of-freedom force feedback haptic system, which is used to interface a human with an impenetrable 3D part. In the process of feeling the object, the user ‘teaches’ a milling machine to machine a virtual 3D object. The tool path generation has two phases: recording of access directions at the surface of the object and the post-processing phase. During the recording phase, three functions are carried out simultaneously: first, a fast collision detection algorithm, using hierarchical object representation, to drive the haptic system; second, visual feedback to show the regions that have been accessed by the tool; and third, a system to capture the access directions of the tool as the user touches the object. The post-processing phase involves the use of information generated in the recording phase to generate 5-axis tool paths. First, the access directions at the surface of the part are interpolated; and second, any residual collisions are detected and eliminated. We show the results of the tool path generation for two parts. The system can help an expert user generate, correct and tweak tool paths.

Mahadevan Balasubramaniam

Papers

Generating 5-axis NC roughing paths directly from a tessellated representation

Collision-free finishing toolpaths from visibility data

Fiber optic sensor for detecting multiple parameters in a harsh environment

Energy harvesting system, apparatus and method

Generation of collision-free 5-axis tool paths using a haptic surface