Metal Cutting Theory and Practice

David A. Stephenson, John S. Agapiou

• Editorial: CRC Press
• Año: 2018
• ISBN:
  9781315360317
• Edición: 3
• Categoría: Tecnologia e ingegneria
• Categoría: Ingegneria industriale

A Complete Reference Covering the Latest Technology in Metal Cutting Tools, Processes, and Equipment

Metal Cutting Theory and Practice, Third Edition shapes the future of material removal in new and lasting ways. Centered on metallic work materials and traditional chip-forming cutting methods, the book provides a physical understanding of conventional and high-speed machining processes applied to metallic work pieces, and serves as a basis for effective process design and troubleshooting. This latest edition of a well-known reference highlights recent developments, covers the latest research results, and reflects current areas of emphasis in industrial practice. Based on the authors' extensive automotive production experience, it covers several structural changes, and includes an extensive review of computer aided engineering (CAE) methods for process analysis and design. Providing updated material throughout, it offers insight and understanding to engineers looking to design, operate, troubleshoot, and improve high quality, cost effective metal cutting operations.

The book contains extensive up-to-date references to both scientific and trade literature, and provides a description of error mapping and compensation strategies for CNC machines based on recently issued international standards, and includes chapters on cutting fluids and gear machining. The authors also offer updated information on tooling grades and practices for machining compacted graphite iron, nickel alloys, and other hard-to-machine materials, as well as a full description of minimum quantity lubrication systems, tooling, and processing practices. In addition, updated topics include machine tool types and structures, cutting tool materials and coatings, cutting mechanics and temperatures, process simulation and analysis, and tool wear from both chemical and mechanical viewpoints.

Comprised of 17 chapters, this detailed study:

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• Describes the common machining operations used to produce specific shapes or surface characteristics
• Contains conventional and advanced cutting tool technologies
• Explains the properties and characteristics of tools which influence tool design or selection
• Clarifies the physical mechanisms which lead to tool failure and identifies general strategies for reducing failure rates and increasing tool life
• Includes common machinability criteria, tests, and indices
• Breaks down the economics of machining operations
• Offers an overview of the engineering aspects of MQL machining
• Summarizes gear machining and finishing methods for common gear types, and more

Metal Cutting Theory and Practice, Third Edition

emphasizes the physical understanding and analysis for robust process design, troubleshooting, and improvement, and aids manufacturing engineering professionals, and engineering students in manufacturing engineering and machining processes programs.

1 Introduction

1.1 SCOPE OF THE SUBJECT

Metal cutting processes are industrial processes in which metal parts are shaped by the removal of unwanted material. In this book, we will primarily consider traditional chip-forming processes such as turning, boring, drilling, and milling. In these operations, metal is removed as a plastically deformed chip of appreciable dimensions, and a fairly unified physical analysis can be carried out using basic orthogonal and oblique cutting models (Figure 1.1).

Related metal removal processes include abrasive processes, such as grinding and honing, and nontraditional machining processes, such as electrodischarge, ultrasonic, electrochemical, and laser machining. In abrasive processes, metal is removed in the form of small chips produced by a combination of cutting, plowing, and friction mechanisms; in nontraditional processes, metal is removed on a much smaller scale by mechanical, thermal, electrical, or chemical means. In all cases, the physical mechanisms of removal differ considerably from those of chip formation, so different physical analyses are required. Basic information on abrasive processes, tools, and surface finish capabilities is included in Chapters 2, 4, and 10. Physical analyses of abrasive and nontraditional machining processes are not considered in this book but are available in the literature [1–6].

Metal cutting processes can also be applied to nonmetallic work materials such as polymers, wood, and ceramics. When these applications are considered, the subject is more commonly called machining. Because of differences in thermomechanical properties, the analyses of metal cutting discussed in this book provide only limited insight into the machining of nonmetals. More relevant information can be found in the literature on the machining of specific classes of materials [7,8].

The objective in this book is to provide a physical understanding of conventional and high-speed cutting processes applied to metallic workpieces. The mechanics of chip formation, temperature generation, tribology, dynamics, and material interactions are emphasized. We also include significant descriptive information on modern machinery, tooling, and coolant systems. Hopefully this information, summarized with reference to the large research and trade literature on this subject, will provide the reader with sufficient physical insight and understanding to design, operate, troubleshoot, and improve high-quality, cost-effective metal cutting operations.

1.2 HISTORICAL DEVELOPMENT

1.2.1 ANCIENT AND MEDIEVAL PREDECESSORS

Metalworking is an old human activity. Native metals, especially copper, and meteoric iron were worked wherever they were encountered by Neolithic peoples, and the mining and smelting of metal ores dates to preliterate times [9–12]. The techniques used to process metals during this period would today be classified as casting and forming processes. Casting has been practiced since at least 5000 BCE [11], and many ancient peoples, notably the Egyptians and the Chinese, were expert metal founders. Forging by hammer (an open die operation) was the chief activity of the smiths and goldbeaters of antiquity and was the basis for deformation processes such as coining, wire drawing, and rolling, all of which were developed in ancient or early medieval times [13–16].

Metal-cutting operations have a more modest pedigree. Ancient peoples certainly ground and filed metals but did not machine them. (Vitruvius and Philo of Byzantium both report that Ktesibios of Alexandria, who lived in about c. 300 BCE, bored the brass or bronze cylinders of pump-like machines [17,18]. but the engineering details of their descriptions are not credible.) As will be shown, with the isolated exception of canon boring, metal cutting as contemporary engineers would understand it was not practiced until the Industrial Revolution of the late eighteenth century, and no machine resembling a contemporary machine tool was developed until around the year 1800.

FIGURE 1.1 Orthogonal (a) and oblique (b) culling of a flat workpiece by a wedge-shaped tool.

Most contemporary machining operations, however, were based on analogous earlier methods for shaping wood and stone. Grinding and drilling both have prehistoric roots. Prehistoric peoples shaped stone objects such as querns and axe heads by abrasion with harder stones (especially sand-stones), and sharpened axes and other tools by similar methods [19,20]. Drilling was carried out in Neolithic times by rotating as stick in an abrasive, generally sand, to bore holes in stone objects [19]; trepanning was also practiced by substituting a hollow bone tube for a solid stick. In later practice, both Egyptian and Roman artisans sharpened tools with whetstones [21,22] and drilled holes in wood using bow drills [23,24]. Holes in stone were trepanned as before by rotating a bronze tube in abrasives [25]. Copper or iron saws with loose abrasives were also used to cut stone [21,22]. The first known representation of a cord lathe, similar to those used in contemporary nonindustrial societies, is from a Ptolemaic Egyptian tomb [26], although earlier stone and wooden objects that were clearly turned have been recovered [27]. Medieval European craftsmen developed a variety of pole and crank-driven lathes as described by Theophilus and in other contemporary manuscripts [15,27,28]. The cylindrical grinding stone and the brace and bit for drilling were medieval innovations [24,29]. Flat surface were machined in ancient times by grinding, filing, and planing using hand planes [24,30]. Early metal planers and shapers are similar in concept to hand planes. Face milling of flat surfaces, which has no ancient precedent, is a nineteenth-century invention, and surface broaching, which is broadly similar to filing, was not introduced until the 1930s [31].

Before proceeding to more modern tunes, it is interesting to note four ancient and medieval manufacturing methods, which bear similarities to later practice:

1. Ancient Egyptian multispindle drilling: The ancient Egyptians used large quantities of beads to decorate mummies and made them in high volumes in specialized workshops [32,33]. The final step in bead production was the drilling of mounting holes using a copper-tipped bow drill. Not surprisingly, this holemaking operation was the production bottleneck, and at least some craftsmen developed methods of driving multiple drills from a single bow to increase throughput (Figure 1.2) [32]. Stocks [33] describes several depictions of this practice from Theban tombs, including three-, four-, and five-spindle applications. Similar multi spindle drilling methods found widespread later use in the railroad and automotive industries.

2. Philistine tool-sharpening service: The Hebrew Bible reports that the Philistines, having at one point conquered the Israelites, forbade them from sharpening their own tools, recognizing that this skill would also be useful in making weapons [34]. Instead, the Israelites were required to send dull tools to Philistine artisans, who charged by the piece for sharpening (a pim for a plowshare, a third of a shekel for axe, etc.). Following this biblical prototype, contemporary tool-sharpening businesses still typically use a per-piece fee structure. The Philistines did not charge for programming or setup.

3. Da Vinci’s machine tools: Leonardo Da Vinci drew designs for a number of machine tools in his notebooks. including lathes, thread-cutting machines, boring mills, and grinding machines [27,29,31,35–38]. None of these machines was apparently ever built, but many contain design details independently developed and used in later ...