On-machine and in-process surface metrology for precision manufacturing

Nanomanufacturing involves scaled-up, reliable, and cost-effective manufacturing of nanoscale materials, structures, devices, and systems. Nanomanufacturing methods can be classified into top-down and bottom-up approaches, including additive, subtractive, and replication/mass conservation processes. These include a cluster of various techniques such as nanomachining, nanofabrication, and nanometrology to produce nanotechnology components and conduct evaluation. This paper mainly focuses on the manufacturing methods for complex shapes or structures, such as textures on curves and hierarchical structures, and outlines the research perspectives and the current application status of nanomanufacturing fundamentals and key technologies.

https://orbit.dtu.dk/files/138286168/1_s2.0_S0007850617301439_main.pdf

Nanomanufacturing—Perspective and applications

Process chains for high-precision components with micro-scale features

A highly stable motion with orthogonally alternating electric field is established to build the relationship between spatial displacement and time standards. Displacement is measured by counting the time pulses that serve as measurement standards. Thus, a displacement method is called time grating. An orthogonally alternating electric field is generated using two rows of differential capacitive sensing electrodes excited by four sinusoidal voltages. Sine-shaped grating planes rather than hyperfine grating lines are used to pick up the displacement signals. Electrode lead wires are designed below the middle of the electrodes and fabricated using multilayer thin-film technology to suppress the cross-sensitivity effect. A time-grating sensor has been fabricated to evaluate the proposed method. The range of measurement is 200 mm, the width of the electrode is 0.2 mm, the interval between two adjacent electrodes is 20 $\mu \text{m}$ , and the gap for capacitive sensing is 0.3 mm. Experimental results indicate that the measurement accuracy reaches ±200 nm with 1-nm resolution. Nanometer accuracy and resolution are achieved using sensing units with sub-millimeter periods. So, the cost for manufacturing the time-grating sensor can be decreased effectively in comparison to traditional nanometrology displacement sensors, and it may be a suitable low-cost alternative to long-range nanometrology.

A New Capacitive Displacement Sensor With Nanometer Accuracy and Long Range

A grating interferometer, called the “optical encoder,” is a commonly used tool for precise displacement measurements. In contrast to a laser interferometer, a grating interferometer is insensitive to the air refractive index and can be easily applied to multi-degree-of-freedom measurements, which has made it an extensively researched and widely used device. Classified based on the measuring principle and optical configuration, a grating interferometer experiences three distinct stages of development: homodyne, heterodyne, and spatially separated heterodyne. Compared with the former two, the spatially separated heterodyne grating interferometer could achieve a better resolution with a feature of eliminating periodic nonlinear errors. Meanwhile, numerous structures of grating interferometers with a high optical fold factor, a large measurement range, good usability, and multi-degree-of-freedom measurements have been investigated. The development of incremental displacement measuring grating interferometers achieved in recent years is summarized in detail, and studies on error analysis of a grating interferometer are briefly introduced.

Displacement measuring grating interferometer: a review

Precision positioning of an object relative to a reference point is a common task in many activities of production engineering. Sensor technologies for single axis measurement, either linear or rotary, which form the fundamentals of measurement technologies for precision positioning, are reviewed. Multi-axis coordinate measurement methods such as triangulation and multilateration, as well as Cartesian and polar systems for specifying the position in a plane or three-dimensional (3D) space are then presented, followed by a discussion on traceability and standards. Some advanced applications of measurement technologies for precision positioning in manufacturing industries are also demonstrated.

X.D. Lu

Papers

Measurement technologies for precision positioning