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Product manufacture instruments for measuring dimensions in mechanical engineering

Product manufacture instruments for measuring dimensions in mechanical engineering

This involves quality assurance, quality control and metrology. We use quality assurance to gain confidence that quality requirements will be fulfilled. Quality control is used to check that requirements have been fulfilled. This is a subtle difference and in practice the terms are sometimes used interchangeably. Metrology is the science of measurement.

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Coordinate-measuring machine

Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. The ability to produce quality products hinges on four key competencies: modeling of process form and precision levels, design tolerancing of parts and products, selecting production processes that match part specifications, and applying quantitative measurement methods for inspection and process control.

The first two—process modeling and design tolerancing—are of primary importance and drive the second two; however, both are surprisingly ill-understood in a scientific sense. Mathematical models for predicting process precision, and quantitative precision and inspection data for actual processes, are scarce and often proprietary.

Tolerancing today is based on informal definitions and on tolerance-assignment and inspection procedures of limited generality and validity. As a result, tolerancing; process selection and control; and, to some extent, metrology and nondestructive evaluation still rely largely on tradition.

Process modeling is discussed in Chapter This chapter deals with process precision, a crucial but often overlooked component of quality technology. This chapter reviews the current research status and needs of process precision and metrology. It concludes with recommended research opportunities.

It can be divided into two areas: 1 precision and metrology and 2 nondestructive evaluation. The emphasis thus far in this report has been on processes and on the knowledge and technologies needed to implement them.

An alternative approach is to shift the focus to parts and products and view unit manufacturing processes merely as the means to make quality parts and products.

This approach exposes new issues that strongly influence the usefulness of unit processes and an overall ability to make quality goods. These issues arise, because manufacturing and assembly processes produce parts and products that vary. Variations in part geometry, as graphically illustrated in Figure , could result from inherently imprecise processes, or from variations in process control.

Control variations could be due to a lack of knowledge concerning the process variables, inadequate means of process control, indifference to process control, etc. Distinguishing between the imprecise execution of a process and the execution of an imprecise process is at the heart of precision engineering. Most processes underlying. Consequently, mechanisms that accommodate and control variability are woven throughout the entire manufacturing system. When parts and products are designed, dimensional tolerances are assigned to specify allowable variations.

Parts are then manufactured and products assembled by selecting processes that are repeatable and precise enough to meet the specified tolerances.

Thus three key producibility themes emerge: design to accommodate variability arising from the control process design, design to ensure that the realized process variations do not exceed the design tolerance, and design to minimize the dispersion of variations within the allowed ranges of variability through careful control of manufacturing and assembly processes.

The nominal design of products, subassemblies, and parts is driven mainly by functionalism—that is, by what the items must do. The main tools are parametric modeling e. The next stage of design, detailed design, supplies the details that were ignored in nominal design and accommodates manufacturing and assembly variability by specifying allowable variations in spatial forms and relations.

Interchangeable assembly usually becomes the dominant constraint. The main working tool is tolerancing i. Current tolerancing standards prohibit specification by process and by reference to other artifacts. As a result, parts must be specified as free-standing geometric entities, rather than by procedures for making them or by requirements that they mate with other parts.

These restrictions were motivated by procurement problems; they have the intent of preserving full manufacturing freedom and facilitating competitive ''out-sourcing.

Manufacturing and assembly planning can be simplistically viewed as a mix-and-match exercise in which processes of adequate precision are selected to produce the various features of a part or to mate parts in assembly and then are sequenced to meet process, functional, and cost constraints.

In physical manufacturing, parts are made using unit processes. The processes must be controlled passively or actively for predictable results, and every form of control uses some form of process model. Physical assembly is analogous to physical manufacturing in that unit assembly processes e. Assembly processes must be controlled passively or actively for predictable results, and every form of control uses some form of assembly process model.

The conformance testing i. The main techniques are conventional parametric measurements and binary i. Testing strategies vary from percent inspection of all toleranced features of all parts through statistical sampling of small lots of parts to no inspection at all when the manufacturing processes are very tightly controlled.

Statistical design of experiments during the process development phase could guide the establishment of a statistical process control system that will lead to the minimum inspection program required to assure high quality Taguchi et al. Performance testing of the final product is the analog to part conformance testing. Thus, as one moves downstream from nominal design, the control of variability becomes the major production concern.

Variability arises from the physical processes used to make and assemble parts. Four central factors are involved:. Tolerancing and process modeling dominate, because they influence, or provide critical data to, the other two factors. Some of the current topics in process precision and metrology are discussed below. They include issues in dimensional scale and precision in manufacturing, dimensional tolerances and metrology, process planning, and process modeling.

Table indicates that typical manufactured products vary greatly in scale and in their requirements for precision. In the table, dimension, D, is a normal size parameter and tolerance, T, is a typical limit on the allowable variation in D.

The tools and methods used for performance testing are highly dependent on the nature of the product.

However, most components of conventional products e. Conventional parts and products are a main focus, since they constitute well over half of all discrete goods by dollar value and contribute close to 10 percent of the gross national product, and they are produced using the unit processes discussed earlier.

Unit processes for the most part have been designed to operate in the scale and precision ranges spanned by these products. Figure distinguishes "precision" and "ultraprecision" machining from "normal" machining in terms of dimensional scale and tolerance. Precise and ultraprecise manufacturing and measurement processes are quite specialized and limited in applicability, but the volume, value, and technical importance of the products requiring processing in these regimes are growing. Obviously, this requires improvements in existing processes, either by implementing the practices of the next higher quality level or by improving the existing process.

In either case, a cultural change is often necessary to institutionalize the higher quality level. A similar plot can be made for other unit processes, such as those listed in Table ; the trends for those unit processes are directly analogous to the case of machining.

Parts are specified in terms of their nominal ideal shapes and nominal material properties, with allowable variations on both. Assemblies are specified in terms of part associations and performance specifications, again with allowable variations on both. The trend toward tighter tolerances is being motivated by a desire for longer life, faster but quieter operation, greater efficiency, and simplified assembly operations.

For example, sorting piston pins for proper match into the piston was once a common practice. It is now considered obsolete, because accurate machining is currently inexpensive enough to enable all parts to match. By contrast, the fit required for diesel fuel injector plungers is so critical that current technology does not allow for economical manufacture of parts for universal assembly.

The conformance of parts and assemblies to geometrical specifications is assessed by physical measurements. The term "dimensional metrology" covers the various instruments and techniques used for making such measurements. Contact technologies are relatively precise and robust, but they are inherently slow and therefore expensive. They are likely to be replaced gradually with faster noncontacting technologies based on wave phenomena.

The standard is best viewed as a collection of sensible principles, defined mainly through examples cast in prose and graphics. There is no companion standard to specify how pans are to be measured to assess conformance to the definitions in Y The informal definitions of Y When CMMs arrived, however, inspectors found that CMM results did not always agree with traditional inspection results.

This is called "methods divergence," and its recognition triggered increasingly strident warnings in the s about a "metrology crisis. The major recommendations are as follows Tipnis, The standards community responded vigorously to the recommendations by establishing new committees in to mathematize Y A new standard, "Y The advent of these new standards, in which mathematics is the defining medium, probably marks the end of the year era in which tolerancing and metrology evolved as industrial practices without strong theoretical underpinnings.

It is important to note that while a new era with a precise language mathematics for defining tolerances has begun, there is no proper mathematical theory to govern the use and interaction of tolerances. A theory can be expected, however, because research in tolerancing and metrology is growing Menon and Voelcker, ; Menon and Robinson, Unfortunately there has been little progress in introducing these topics into engineering curricula.

It is worth noting that there is a movement in Europe advocating the adoption of vectorial tolerancing as a replacement for, or at least a co-equal alternative to, the International Standards Organization brand of geometric tolerancing. Vectorial tolerancing was formulated by Adolph Wirtz of Switzerland Wirtz, ; Figure conveys some of its essential elements.

The basic concept is to cast tolerances in terms of parameters that are important in manufacturing and inspection, with the current formulation oriented toward machine tools and CMMs.

This has the advantage of removing the language mismatch noted later in this chapter, but it does so only for one or two families of processes. It is a retrograde step in the sense that it re-establishes the coupling between design specifications and manufacturing methods that was deemed harmful in the early days of geometric tolerancing.

Process planning directly links manufacturing to design. Process planning can be described using the simple example of machining the bracket described in Figure Observe that the plan shown as output in Figure is influenced strongly by the hole tolerances. Specifically, the central hole D should be generated first, because it serves as a position datum for the four-hole pattern.

Drilling is an imprecise hole-making process. Boring and reaming are hole-finishing operations that have different form and positional accuracies. Finally, note that the plan shown in the figure does not require special tooling. However, if a different process family had been used—molding, for example—then tooling e. Experienced machinists can easily construct plans such as that shown in Figure , because they possess a wealth of experiential data and subtle reasoning powers.

To date, researchers have tried to codify, or to replace, this data and logic with automated process planning systems with little success. An experienced machinist knows semiquantitatively, for example, that boring is positionally and orientationally more accurate then reaming but less accurate in terms of cylindrical form.

To understand why, observe that the study of process planning raises two basic issues: what knowledge e. The first issue will receive focus here, because it is the sine qua non for understanding and automating planning and deficiencies in this area almost surely are responsible for the lack of progress just noted.

Measuring instrument

However, as manufacturers attempt to grow their trade in the global business environment, the need for measurement accuracy has become an even higher priority due to the time- and cost-savings that businesses can potentially achieve. Some common applications that make use of these advanced technologies include Parts Inspection, Alignment, Reverse Engineering, and Dimensional Measurement. All four categories are similar in the way that their need for measurement and documentation accuracy is tightly woven into each of their core activities. To elaborate, measurement accuracy is widely agreed to be a most important aspect in mechanical parts inspections.

A coordinate measuring machine CMM is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. Various types of probes are used in CMMs, including mechanical, optical, laser, and white light.

Sitemap Contact Us. Although dimensional inspection hand tools are frequently a simple and elegant solution, they still must be treated with the same care as a machine that uses more advanced technology. Some devices must be calibrated or regularly cleaned to ensure that they provide consistent, accurate results. It is also important that the operator is appropriately trained to prevent human error. Whether you have a simple measuring problem or a complex quality control requirement, come to Q-PLUS Labs for all of your dimensional inspection needs.

Manufacturing metrology

Mechanical gauges are instruments that measure pressure, dimensions, levels, etc. They can be mechanical or electro-mechanical devices and offer displays ranging from direct-reading rules to digital LCDs. Gauges which measure pressure are classified as analog or digital depending on their readouts. Dimensional gauges are classified by what they measure, be it bore diameter, depth, or height, and are specific to machining processes. Level gauges measure the level of fluid in tanks and pressure vessels. Other gauges are used in very specific measuring applications from spark plug gaps to screw threads. Below we list the different types of gauges used in industries. Analog Pressure Gauges are mechanical instruments which measure the force that a contained liquid or gas exerts on a unit area. An analog gauge often relies on a coiled tube attached to a pointer to directly display pressure against a dial face.

Types and Use of Precision Measuring Instruments

Mikell P. The fourth edition introduces more modern topics, including new materials, processes and systems. End of chapter problems are also thoroughly revised to make the material more relevant. Several figures have been enhanced to significantly improve the quality of artwork. All of these changes will help engineers better understand the topic and how to apply it in the field.

Machinery onboard ships require regular care and maintenance so that their working life and efficiency can be increased, and the cost of operation, which includes unnecessary breakdowns and spares, can be reduced.

A multidisciplinary reference of engineering measurement tools, techniques, and applications—Volume 1. Measurement falls at the heart of any engineering discipline and job function. Whether engineers are attempting to state requirements quantitatively and demonstrate compliance; to track progress and predict results; or to analyze costs and benefits, they must use the right tools and techniques to produce meaningful, useful data. The Handbook of Measurement in Science and Engineering is the most comprehensive, up-to-date reference set on engineering measurements—beyond anything on the market today.

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Main research topics are: a surface metrology, b coordinate metrology, and c process metrology. The latest research in surface metrology deals with traceability, modelling and characterization of polished surfaces and multifunctional surfaces obtained through hard machining followed by Robot Assisted Polishing. The latest research in coordinate metrology encompasses traceability of optical 3D scanning, traceability of 3D SEM, and traceability of CT scanning for coordinate metrology. A separate research topic of increasing importance deals with accurate dimensional measurements in a production environment.

SEE VIDEO BY TOPIC: Top-10 Mechanical Measuring Instruments(Every Mechanical Engineer should know))

Calibration is a comparison between a known measurement the standard and the measurement using your instrument. Typically, the accuracy of the standard should be ten times the accuracy of the measuring device being tested. However, accuracy ratio of is acceptable by most standards organizations. Calibration of your measuring instruments has two objectives. It checks the accuracy of the instrument and it determines the traceability of the measurement.

PCE Instruments UK: Test Instruments

Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. The ability to produce quality products hinges on four key competencies: modeling of process form and precision levels, design tolerancing of parts and products, selecting production processes that match part specifications, and applying quantitative measurement methods for inspection and process control. The first two—process modeling and design tolerancing—are of primary importance and drive the second two; however, both are surprisingly ill-understood in a scientific sense. Mathematical models for predicting process precision, and quantitative precision and inspection data for actual processes, are scarce and often proprietary. Tolerancing today is based on informal definitions and on tolerance-assignment and inspection procedures of limited generality and validity. As a result, tolerancing; process selection and control; and, to some extent, metrology and nondestructive evaluation still rely largely on tradition. Process modeling is discussed in Chapter

Dimensions, Tolerances, and Related Attributes Dimensions and Other Geometric Attributes Conventional Measuring Instruments and Effect of Manufacturing Processes In addition to mechanical and physical properties a manufactured product include the dimensions and surfaces ofits components.

PCE Instruments PCE is an international supplier of test instruments, tools and equipment for measuring, weighing and control systems. Founded by German engineers nearly two decades ago, PCE offers more than test instruments with applications in industrial engineering and process control, manufacturing quality assurance, scientific research, trade industries and beyond. In addition, PCE can provide custom test instruments on demand. PCE serves customers from government, industry and academia in diverse fields such as acoustical engineering, aerospace, agriculture, archaeology, architecture, automotive, aviation, bioengineering, building inspection, chemistry, civil engineering, computer science, construction, data acquisition, education, electrical engineering, energy, environmental science, food processing, forensics, forestry, geology, government, horticulture, HVAC, hydrology, industrial hygiene, law enforcement, library science, logistics, machining, maintenance, manufacturing, materials science, mechanical engineering, metal working, meteorology, military, mining, nondestructive testing NDT , occupational health and safety, oil and gas, pharmaceuticals, property management, pulp and paper, physics, robotics, structural engineering, supply chain, transportation, tribology, veterinary science, water treatment, welding, woodworking and more. Test instruments can be found in research laboratories as well as in places like automobile repair shops, construction job sites and manufacturing facilities.

The Importance of Measurement Accuracy within the Metalworking Industry

A measuring instrument is a device for measuring a physical quantity. In the physical sciences , quality assurance , and engineering , measurement is the activity of obtaining and comparing physical quantities of real-world objects and events. Established standard objects and events are used as units , and the process of measurement gives a number relating the item under study and the referenced unit of measurement.

Why Calibration of Your Measuring Instruments is Important

Account Options Anmelden. Meine Mediathek Hilfe Erweiterte Buchsuche. Occupational Outlook Handbook Department of Labor.

With a need to make quality products which meet design specified tolerances, a large number of firms, research and development centers, and school and college laboratories use measuring instruments that have high accuracy and precision.

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Types of Gauges - A ThomasNet Buying Guide

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