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Production industry instruments for measuring dimensions in mechanical engineering

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VIDEO ON THE TOPIC: Sine Bar - Metrology - Mechanical Engineering -

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.

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.

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.

Types and Use of Precision Measuring Instruments

When accuracy greater than or equal to 0. Starrett micrometers are designed and built to the highest standards. Slide calipers provide large measurement range, flexibility and accuracy up to 0. These tools typicall….

Measuring instrument

A gauge or gage , in science and engineering , is a device used to make measurements or in order to display certain dimensional information. A wide variety of tools exist which serve such functions, ranging from simple pieces of material against which sizes can be measured to complex pieces of machinery. Depending on usage, a gauge can be described as "a device for measuring a physical quantity", [1] for example "to determine thickness, gap in space, diameter of materials, or pressure of flow", [2] or "a device that displays the measurement of a monitored system by the use of a needle or pointer that moves along a calibrated scale". The two first basic types are usually easier for the human eyes and brain to interpret, especially if many instrument meters must be read simultaneously. The other two types are only displaying digits, which are more complex for humans to read and interpret. The ultimate example is cockpit instrumentation in aircraft.

December , Cite as.

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. The special branch of science that deals with such instruments is known as metrology. Here we will look at the features and use of certain well known precision measuring instruments used for linear measurement. Vernier Caliper: It is an instrument used to measure internal and external dimensions of an object with a great accuracy. It is provided with inward jaws and outward jaws to facilitate the measurement. A screw clamp is provided that can lock the position of the vernier scale, so that the instrument can be moved without disturbing the reading. A manually operated vernier caliper has a main scale in millimeters or inches and a sliding vernier scale attached to the movable jaw, as shown in the figure.

Industrial Calibration

Ruler and scales : They are used to measure lengths and other geometrical parameters. They can be single steel plate or flexible tape type tool. Calipers : They are normally of two types- inside and outside caliper.

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.

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. For different types of machinery and systems, various measuring tools, instruments and gauges are used on a ship. Measuring instruments and gauges are used to measure various parameters such as clearance, diameter, depth, ovality, trueness, etc. These are critical engineering parameters, which describe the condition of the working machinery. Below, we have compiled a list of mechanical measuring instruments and mechanical gauges which are extensively used on the ship for the recording of different parameters. There are many instruments, tools and gauges which are used on a daily basis onboard ship for measurement, fault finding, wear down etc. They are used to measure lengths and other geometrical parameters. This tool is one of the most famous measuring instruments in mechanical engineering. They can be a single steel plate or a flexible tape type tool. They are usually available in the measuring scale of inch or cm.

Dec 10, - The measuring instruments are the most important part of. recommended the dimensions control of manufacturing products to be made . For the different industry sectors the C Engineering Solutions and Technologies in Manufacturing . Faculty of Mechanical Engineering, Ilmenau University of.

PCE Instruments UK: Test Instruments

Try Lucidchart. It's quick, easy, and completely free. They are typically created by engineers who are designing a manufacturing process for a physical plant. With the record they provide, changes can be planned safely and effectively using Management of Change MOC. They can also be useful in training workers and contractors. Specifications are usually provided in separate documents. But they are incredibly useful in many ways, including:. Instrumentation detail varies with the degree of design complexity.

Types of Gauges - A ThomasNet Buying Guide

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. Measuring instruments, and formal test methods which define the instrument's use, are the means by which these relations of numbers are obtained. All measuring instruments are subject to varying degrees of instrument error and measurement uncertainty. These instruments may range from simple objects such as rulers and stopwatches to electron microscopes and particle accelerators. Virtual instrumentation is widely used in the development of modern measuring instruments. In the past, a common time measuring instrument was the sundial. Today, the usual measuring instruments for time are clocks and watches. For highly accurate measurement of time an atomic clock is used.

Mechanical Engineering Technology

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 Importance of Measurement Accuracy within the Metalworking Industry

Here is some most commonly used mechanical instruments for measurement in industries. Learn all top instruments in our Free Online Course. Highlights of this blog in this Video. Vernier Caliper is a widely used linear measurement instrument with a least count of 0.

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.

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