Flatness (manufacturing)
Encyclopedia
In manufacturing
and mechanical engineering
, flatness is an important geometric condition for workpieces and tools.
In the manufacture of precision parts and assemblies, especially where parts will be required to be connected across a surface area in an air-tight or liquid-tight manner, flatness is a critical quality of the manufactured surfaces. Such surfaces are usually machined or ground
to achieve the required degree of flatness. High-definition metrology
, such as digital holographic interferometry, of such a surface to confirm and ensure that the required degree of flatness has been achieved is a key step in such manufacturing processes. Flatness may be defined in terms of least squares fit to a plane ("statistical flatness"), worst-case or overall flatness (the distance between the two closest parallel planes within.
Two parts that are flat to about 1 helium light band (HLB) can be "wrung" together, which means they will cling to each other when placed in contact. This phenomenon is commonly used with gage blocks.
Geometric dimensioning and tolerancing
has provided geometrically defined, quantitative ways of defining flatness operationally
.
popularized the first practical method of making accurate flat surfaces during the 1830s, using engineer's blue
and scraping
techniques on three trial surfaces. By testing all three in pairs against each other, it is ensured that the surfaces become flat. Using two surfaces would result in a concave surface and a convex surface. Eventually a point is reached when many points of contact are visible within each square inch, at which time the three surfaces are uniformly flat to a very close tolerance.http://journals.iranscience.net:800/www.newscientist.com/www.newscientist.com/lastword/article.jsp@id=lw801
Up until his introduction of the scraping technique, the same three plate method was employed using polishing techniques, giving less accurate results. This led to an explosion of development of precision instrument
s using these flat surface generation techniques as a basis for further construction of precise shapes.
Manufacturing
Manufacturing is the use of machines, tools and labor to produce goods for use or sale. The term may refer to a range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale...
and mechanical engineering
Mechanical engineering
Mechanical engineering is a discipline of engineering that applies the principles of physics and materials science for analysis, design, manufacturing, and maintenance of mechanical systems. It is the branch of engineering that involves the production and usage of heat and mechanical power for the...
, flatness is an important geometric condition for workpieces and tools.
In the manufacture of precision parts and assemblies, especially where parts will be required to be connected across a surface area in an air-tight or liquid-tight manner, flatness is a critical quality of the manufactured surfaces. Such surfaces are usually machined or ground
Grinding operations
Grinding is an abrasive machining process that uses a grinding wheel as the cutting tool.A wide variety of machines are used for grinding:* Hand-cranked knife-sharpening stones * Handheld power tools such as angle grinders and die grinders...
to achieve the required degree of flatness. High-definition metrology
High-definition metrology
High-definition metrology refers to measurement of dimensional or other attributes of a surface or an object in which measurements are made densely across the observable extent of that surface or object, so that the measured attribute of the surface or object can be portrayed with high-definition...
, such as digital holographic interferometry, of such a surface to confirm and ensure that the required degree of flatness has been achieved is a key step in such manufacturing processes. Flatness may be defined in terms of least squares fit to a plane ("statistical flatness"), worst-case or overall flatness (the distance between the two closest parallel planes within.
Two parts that are flat to about 1 helium light band (HLB) can be "wrung" together, which means they will cling to each other when placed in contact. This phenomenon is commonly used with gage blocks.
Geometric dimensioning and tolerancing
Geometric dimensioning and tolerancing
Geometric dimensioning and tolerancing is a system for defining and communicating engineering tolerances. It uses a symbolic language on engineering drawings and computer-generated three-dimensional solid models for explicitly describing nominal geometry and its allowable variation...
has provided geometrically defined, quantitative ways of defining flatness operationally
Operational definition
An operational definition defines something in terms of the specific process or set of validation tests used to determine its presence and quantity. That is, one defines something in terms of the operations that count as measuring it. The term was coined by Percy Williams Bridgman and is a part of...
.
History
Joseph WhitworthJoseph Whitworth
Sir Joseph Whitworth, 1st Baronet was an English engineer, entrepreneur, inventor and philanthropist. In 1841, he devised the British Standard Whitworth system, which created an accepted standard for screw threads...
popularized the first practical method of making accurate flat surfaces during the 1830s, using engineer's blue
Engineer's blue
Engineer's blue is a highly pigmented paste used to assist in the mating of two or more components.Joseph Whitworth popularized the first practical method of making accurate flat surfaces, during the 1830s, by using engineer's blue and scraping techniques on three trial surfaces...
and scraping
Hand scraper
A hand scraper is a single-edged tool used to scrape metal from a surface. This may be required where a surface needs to be trued, corrected for fit to a mating part, needs to retain oil , or even to give a decorative finish.Surface plates were traditionally made by scraping...
techniques on three trial surfaces. By testing all three in pairs against each other, it is ensured that the surfaces become flat. Using two surfaces would result in a concave surface and a convex surface. Eventually a point is reached when many points of contact are visible within each square inch, at which time the three surfaces are uniformly flat to a very close tolerance.http://journals.iranscience.net:800/www.newscientist.com/www.newscientist.com/lastword/article.jsp@id=lw801
Up until his introduction of the scraping technique, the same three plate method was employed using polishing techniques, giving less accurate results. This led to an explosion of development of precision instrument
Measuring instrument
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...
s using these flat surface generation techniques as a basis for further construction of precise shapes.