Basics of Precision Engineering

Richard Leach, Stuart T. Smith, Richard Leach, Stuart T. Smith

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9780429887437
• Edition: 1
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie civile

Advances in engineering precision have tracked with technological progress for hundreds of years. Over the last few decades, precision engineering has been the specific focus of research on an international scale. The outcome of this effort has been the establishment of a broad range of engineering principles and techniques that form the foundation of precision design.

Today's precision manufacturing machines and measuring instruments represent highly specialised processes that combine deterministic engineering with metrology. Spanning a broad range of technology applications, precision engineering principles frequently bring together scientific ideas drawn from mechanics, materials, optics, electronics, control, thermo-mechanics, dynamics, and software engineering. This book provides a collection of these principles in a single source. Each topic is presented at a level suitable for both undergraduate students and precision engineers in the field. Also included is a wealth of references and example problems to consolidate ideas, and help guide the interested reader to more advanced literature on specific implementations.

1Introduction to Precision

Richard Leach and Stuart T. Smith

1.1Introduction

1.2Foundational Concepts for Precision Process Design and Evaluation

1.2.1Analysis Is Not Design Synthesis

1.2.2Design Specifications and Other Requirements

1.2.3Symmetry

1.2.4Identify and Eliminate, Where Possible, Bending Moments

1.2.5Loops

1.2.6Stiffness

1.2.7Compensation

1.2.8Null Control

1.2.9Error Separation

1.2.10Self-Correction/Calibration

1.2.11Kinematic Design

1.2.12Psuedo-Kinematic Design

1.2.13Elastic Design and Elastic Averaging

1.2.14Plastic Design

1.2.15Reduction

1.2.16Cosine and Abbe Errors

1.2.17Design Inversion

1.2.18Energy Dissipation

1.2.19Test and Verify

1.2.20Occam’s Razor

1.3Performance Measures

1.4Development of Precision Processes

1.4.1Ishikawa Diagrams for Precision

1.4.2Introduction to Project Management and System Engineering

1.5Limits of Precision

References

Ultimately, the goal of precision engineering design is to create a process for which the outcomes are deterministic and controllable over a range of operation, with unpredictable deviations from a desired result being as small as is physically and economically possible. This book outlines concepts that might be considered good practice in precision engineering, concentrating on the basic principles and how to use them as part of the design, development and characterisation of the precision process in question. Many conceptual tools are discussed throughout the book and have been collected in this introductory chapter. Because these ideas are only briefly explained here, it is recommended that this be reviewed both before and after reading the rest of this book. To introduce this topic, this chapter discusses some general ideas of what constitutes precision engineering as a field of study and concludes with an outline of fundamental limits to precision.

1.1Introduction

Precision engineering has been, and continues to be, one of the disciplines needed to enable future technological progress. Being always at the edge of technological capability and pushing towards the limits imposed by physical laws, the drive for increased precision is, and always will be, an intellectually demanding pursuit, and brings with it the benefit of being pivotally involved in some of the most exciting of human endeavours.

It is clear that technology is changing the world in many ways, but both its impact and progress is difficult to summarise into a single equation, chart or graph. However, it is readily apparent that the advent of the transistor has played a large part in recent technological advances. Gordon Moore (1965) ably illustrated progress in this field by plotting the number of transistors on a chip as a function of time, showing that this number was doubling every two or so years, a relation now called Moore’s law. Over time, the quoted number of components on a chip has changed, but the overall trend has stayed relatively consistent for more than six decades, although it appears to have slowed a little over the last decade or so to a doubling every two and a half years. However, Moore’s plot does not contain the effect of increasing clock speeds, and newer roadmaps of this technology now incorporate this to reflect the rate at which information can be transferred and processed, typically plotting a measure of the number of calculations per second over time (see also Chapter 2, Section 2.2). Notwithstanding these details, a simplified and modified Moore’s law plot is shown in Figure 1.1. As usual, time is shown as the horizontal axis, while there are two lines showing the number of components on a chip as the primary vertical axis and component size (assuming that the chip is square and 20 mm on a side). Typically, for a chip consisting of an array of transistors, the features on this component will be around one quarter of the size. A glance at this plot shows the number of components increasing exponentially, with the size of components correspondingly reducing. For example, with a component size of 100 nm, the individual feature dimensions will be of the order 25 nm. A reduction in component size to 10 nm in the mid-2020s indicates features to have dimensions of the order of only a few nanometres. Interestingly, when the dimensions of electrical circuits approach atomic scales, quantum effects will significantly influence the nature of conduction and place constraints on the motion of electrons. Fundamentally, a wire must comprise a conductor surrounded by an insulating barrier. However, on a quantum level, the barrier only affects the probability of the electron being located in the re...