Thermal rectifiers using linear nanostructures as core thermal conductors have been fabricated. A high mass density material is added preferentially to one end of the nanostructures to produce an axially non-uniform mass distribution. The resulting nanoscale system conducts heat asymmetrically with greatest heat flow in the direction of decreasing mass density. Thermal rectification has been demonstrated for linear nanostructures that are electrical insulators, such as boron nitride nanotubes, and for nanostructures that are conductive, such as carbon nanotubes.

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Solid state thermal rectifier

For measuring machines and machine tools, geometrical accuracy is a key performance criterion. While numerical compensation is well established for CMMs, it is increasingly used on machine tools in addition to mechanical accuracy. This paper is an update on the CIRP keynote paper by Sartori and Zhang from 1995 [Sartori S, Zhang GX (1995) Geometric error measurement and compensation of machines, Annals of the CIRP 44(2):599–609]. Since then, numerical error compensation has gained immense importance for precision machining. This paper reviews the fundamentals of numerical error compensation and the available methods for measuring the geometrical errors of a machine. It discusses the uncertainties involved in different mapping methods and their application characteristics. Furthermore, the challenges for the use of numerical compensation for manufacturing machines are specified. Based on technology and market development, this work aims at giving a perspective for the role of numerical compensation in the future.

Geometric error measurement and compensation of machines : an update

The miniaturization of machine components is perceived by many as a requirement for the future technological development of a broad spectrum of products. Miniature components can provide smaller footprints, lower power consumption and higher heat transfer, since their surface-to-volume ratio is very high. To create these components, micro-meso-scale fabrication using miniaturized mechanical material removal processes has a unique advantage in creating 3D components using a variety of engineering materials. The motivation for micro-mechanical cutting stems from the translation of the knowledge obtained from the macro-machining domain to the micro-domain. However, there are challenges and limitations to micro-machining, and simple scaling cannot be used to model the phenomena of micro-machining operations. This paper surveys the current efforts in mechanical micro-machining research and applications, especially for micro-milling operations, and suggests areas from macro-machining that should be examined and researched for application to the improvement of micro-machining processes.

Investigation of micro-cutting operations

Ultra-precision grinding is primarily used to generate high quality and functional parts usually made from hard and difficult to machine materials. The objective of ultra-precision grinding is to generate parts with high surface finish, high form accuracy and surface integrity for the electronic and optical industries as well as for astronomical applications. This keynote paper introduces general aspects of ultra-precision grinding techniques and point out the essential features of ultra-precision grinding. In particular, the keynote paper reviews the state-of-the-art regarding applied grinding tools, ultra-precision machine tools and grinding processes. Finally, selected examples of advanced ultra-precision grinding processes are presented.

Ultra-precision grinding

Micro and Nano Machining by Electro-Physical and Chemical Processes

Brittle materials are difficult to mechanically micro machine due to damage resulting from material removal by brittle fracture, cutting force-induced tool deflection or breakage and tool wear. This paper demonstrates the feasibility of micro machining glass materials with polycrystalline diamond (PCD) micro tools that are prepared in a variety of shapes using non-contact micro electro discharge machining. The PCD tools contain randomly distributed sharp protrusions of diamond with dimensions around 1 µm that serve as cutting edges for micro machining grooves in soda-lime glass and pockets in ultra-low expansion glass. Results indicate that smooth surfaces are obtained with process conditions allowing material removal by ductile regime cutting instead of brittle fractures, and the PCD tools show very little wear. With further improvements in material removal rate, micro machining with PCD tools is a promising approach for producing micro molds and micro fluidic devices in glass materials.

https://iopscience.iop.org/article/10.1088/0960-1317/14/12/013/pdf

Micro machining glass with polycrystalline diamond tools shaped by micro electro discharge machining

An interconnection circuit includes a plated through hole having a plurality of electrically isolated segments with at least one of the plurality of electrically isolated segments coupled to a signal path and at least one of the electrically isolated segments coupled to ground With this arrangement, the circuit provides a signal path between a first and a second different layers of a multilayer By providing one segment as a signal segment and another segment as a ground segment the size and shape of the electrically isolated segments can be selected to provide the interconnection circuit having a predetermined impedance characteristic The interconnection circuit can thus be impedance matched to circuit board circuits, devices and transmission lines, such as striplines, microstrips and co-planar waveguides This results in an interconnection circuit which maintains the integrity of relatively high-frequency signals propagating through the interconnection circuit from the first layer to the second layer The interconnect circuits can be formed by creating distinct conductor paths within the cylindrical plated through-holes using variety of manufacturing techniques including, but not limited to, broaching techniques, electrical discharge milling (EDM) techniques and laser etching techniques

Split via surface mount connector and related techniques

Elastic pivots are commonly used in precision machines and instruments as bearings for guiding small displacements or rotations. They provide accurate and frictionless motion with little hysteresis. Elastic pivots are frequently designed with either straight beams or notches shaped as conic sections with circular, elliptical, parabolic, or hyperbolic profiles. The compliance of a pivot is typically predicted by analytical expressions derived from implicit equations for the pivot’s profile. This article describes a more general geometric model suited to representing the entire family of conic section shapes using quadratic rational Bezier curves. This general representation of the geometry is suitable for computer aided design and analysis, especially with finite element methods that yield compliances and stress distributions. The utility of this formulation is demonstrated by optimizing an elastic pivot to meet compliance and stress requirements.

A unified geometric model for designing elastic pivots

This paper provides an overview of several approaches to micro-machining by mechanical and electro-discharge means of material removal. Two steps are required in machining micro features. Firstly, a custom-shaped tool is created from suitable stock. In many cases, this is carried out using a small-scale version of wire Electro-Discharge Machining (EDM) in tool materials such as sintered PolyCrystalline Diamond (PCD) or tungsten carbide. Then the micro-tool can be used as a miniature end mill, drill or abrasive wheel. Each of these mechanical machining methods can be combined with EDM to achieve a customisable surface finish and feature accuracy. Trade-offs such as tool wear, Material Removal Rate (MRR) and machining time are discussed in this paper within the context of several examples.

Micro-machining and micro-grinding with tools fabricated by micro electro-discharge machining

Metrology applications commonly require non-contact, capacitive sensors for displacement measurements due to their nanometer resolution. In some metrology applications, for example, the measurement of roundness and spindle error motion, the displacements of stationary and rotating cylindrical artifacts are measured. Error from using a conventionally calibrated sensor with a non-flat (e.g., cylindrical) target is typically neglected, but these errors cannot be ignored for nanometer-level accuracy. The capacitance between a sensor and a cylindrical target is less than that of a sensor with a flat target, which causes four effects. As the diameter of the target shrinks, the sensitivity of the sensor increases, the sensing range decreases, the sensing range shifts towards the target, and the nonlinearity increases. These errors can be greatly reduced by either calibrating sensors with the correct target surface or by determining corrections for post-processing data. This paper quantifies and experimentally verifies these errors for a commonly used sensor, and a simulation of a nanometer-level measurement of out-of-roundness and spindle error motion demonstrates that measurement accuracy is improved with corrected sensitivities.

R. Ryan Vallance

Papers

Micro machining glass with polycrystalline diamond tools shaped by micro electro discharge machining

Split via surface mount connector and related techniques

A unified geometric model for designing elastic pivots

Micro-machining and micro-grinding with tools fabricated by micro electro-discharge machining

Correcting capacitive displacement measurements in metrology applications with cylindrical artifacts