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Glossary M thru R
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Glossary Terms M thru R
machine  (n) A combination of interrelated parts used for applying, storing, or transforming energy to do work. Machines consist of one or more assemblies, which are analyzed using techniques such as kinematics and dynamics.
machine control  n) A process that directs the machine tools necessary to transform raw materials into a finished product. Machine control has evolved from human control to machine automation using numerical control (NC) and then computer numerical control (CNC).
machine screw  (n) A mechanical fastening device with a slotted head on one end and threads on the other. The threaded end can screw into either a mating part or a nut. A machine screw is similar to a slotted head cap screw but is normally smaller.
machine tool  (n) A production device used to change the shape, finish, or size of a piece of material, typically using some type of cutting edge.
major axis  (n) The long axis of an ellipse. In a pictorial projection, this axis represents the true diameter of the circle being projected.
major diameter  (n) A threading term referring to the largest diameter on an internal or external thread.
manifold models  (n) Models that unambiguously define a boundary between the inside and outside of an object. Solid modelers are usually restricted to manifold objects, whereas surface modelers often define unclosed, nonmanifold objects with no clear division between inside and outside.
manufacturing automation protocol  (n) See MAP.
manufacturing processing  (v) An activity concerned with the scheduling, forming, treating, shaping, joining, and cutting of raw material in the production of goods.
MAP  (n) An acronym for manufacturing automation protocol, a communications standard being developed for compatibility between different automated manufacturing systems. The goal of MAP is the total integration of islands of automation in manufacturing, regardless of the type of hardware and software used in each system.
marketing  (n) The division of a business involved with convincing customers to purchase the product or service provided by the company. In order to sell the product more effectively, marketing will gather information on potential customers, both directly and indirectly, and will use these data to influence the design of the product so that it more closely matches the customer’s needs.
marks  (n) The fundamental graphic elements used to encode data in a visualization. Marks can be thought of as graphic primitives and are typically classified as either simple or complex. Simple marks include points, lines, areas, and volumes. Complex marks are also called glyphs. All marks interrelate closely with the dimension of the data type.
mass properties analysis  (n) Analytic techniques directly related to the geometric properties of an object. Typical calculations are the mass, centroids (center of gravity), and inertial properties of the object. In order to successfully use these techniques, the model must be able to unambiguously define the volume the object occupies and the density of the material within the volume.
material control  (n) A term describing the management of the flow of materials through the production process. Just-in time (JIT) techniques are used to recognize which raw materials are needed and when.
material requirement planning  (n) See MRP.
materials engineering  (n) A field of engineering that comprises a wide spectrum of activities directed toward the design, development, and production of metals, alloys, ceramics, semiconductors, and other materials for engineering applications.
mathematics  (n) An abstract symbol-based communications system based on formal logic. Geometry is one of the oldest fields of mathematics and underlies most of the principles used in technical graphics and CAD.
matrix charts  (n) A visualization technique that uses grids to show relationships between at least two, often qualitative, variables. Each variable is represented along a scale, and the interior grid cells represent possible combinations of variable values. Marks are placed in the grid cells, representing the relationship between variable values.
maximum material condition (MMC)  (n) A tolerancing term defining the condition of a part when it contains the most amount of material. The MMC of an external feature, such as a shaft, is the upper limit. The MMC of an internal feature, such as a hole, is the lower limit.
mean  (n) A statistical interpretation of a data set. Calculated by dividing the sum of a set of terms by the number of terms. Also referred to as an arithmetic mean.
mechanical engineering  (n) A field of engineering comprising a wide range of activities, including research, design, development, manufacturing, management, and control for engineering systems and their components. Mechanical engineers work in such fields as transportation, power generation, energy conversion, environmental control, aeronautics, marine science, and manufacturing.
mechanical fastening  (v) A process that uses a manufactured device added to an assembly to hold parts together. Mechanical fasteners include threaded and nonthreaded fasteners, such as rivets, keys, pins, snap rings, and clips.
mechanics  (n) An area of applied physics which, at a macro level, deals with the response of bodies (parts) to the action of forces, and, at the micro level, with the response of materials.
mechanism  (n) A mechanical system made of rigid structures, such as shafts, housings, and pillow blocks, and connected by various linkages, such as gears, cams, and cranks. A mechanism is activated by applying a load or force at one or more points in the mechanism.
mechanism analysis  (n) An analytic technique that determines the motions and loads associated with mechanical systems made of rigid bodies (links) connected by joints. The two most common types of mechanism analysis are kinematic and dynamic.
Media  (n) A means of conveying information, both graphic and textual. Traditionally, this refers to the types of paper used in drafting; more recently, it has also come to refer to the types of information storage and playback technology, such as video, audio, CD-ROM, etc.
memory device  (n) Computer hardware used to store information, such as CAD data. Transient storage is random access memory (RAM); more permanent storage includes floppy disks, CD-ROMs, magnetic tape, etc.
midpoint  (n) A singular location that is equidistant between two locations. The midpoint of a line divides the line in half.
minor axis  (n) The short axis of an ellipse. In a pictorial projection, the length of this axis varies with the relationship of the view direction to the surface of the circle the ellipse represents.
minor diameter  (n) A threading term referring to the smallest diameter on an internal or external thread.
mirror  (v) To duplicate geometric elements across a line or plane such that they would be duplicated but inverted as they would be seen in a mirror.
miter line  (n) A special construction line used to share the depth dimension between the top and right side views of a multiview drawing. The line is drawn at a 45-degree angle and is used as a point of intersection for lines coming to and from the right side and top views.
MMC  (n) See maximum material condition.
model solid  (n) In a modeling system, the solid object being manipulated by tool solids during the course of creating the final model. Whereas the tool solids are transient in nature, the model solid defines the state of the object as it evolves into the final model.
modeling  (v and n) Often referred to as geometric modeling, which is both a process and a product. Modeling is used to analyze preliminary and final design solutions, as well as provide input to the production process in the form of a computer database. Modeling is a product since it is a result of the design process, which uses graphics as a tool to visualize possible solutions and to document the design for communications purposes.
modem  (n) A computer hardware device that uses standard telecommunications lines (phone lines) to send computer data from one computer to another. Modems are used to connect computers at remote sites not connected by local area networks. The speed in which modems can transfer information is measured in bits per second, or baud.
motion  (n) The movement of a part, either linearly or angularly, over time and space.
mouse  (n) A small, hand-held computer input device that rests on a work surface and is moved in two dimensions to correspond to locations on the computer monitor. A cursor on the screen indicates the current location of the mouse and buttons on the top of the mouse are used to indicate the action to be performed at that location.
MRP  n) An acronym for material requirement planning, a process used to calculate the amount of raw materials necessary to manufacture a specified number of products. MRP uses the bill of materials from the engineering drawings or CAD techniques such as attribute assignments. MRP has evolved into material resource planning, which includes both materials and financing.
multimedia  (n or adj.) A term used to refer to the systems or methods that convey information in more than one media form and often through more than one sense. The integration of text and graphics could be thought of as a simple multimedia system.
multiple-line graph  (n) A visualization technique similar to a regular line graph, except that an additional independent variable is mapped. The second independent variable typically has only a few discrete values, each of which is mapped as a separate line on the graph. Color or symbol coding is used to distinguish between the lines on the graph.
multiview drawing/sketch  (n) A type of orthographic drawing based on multiview projection techniques in which two or more views of an object are arranged in a single drawing. Each view shows only two dimensions of the object and is chosen to depict specific features of the object clearly and distinctly.
multiview projection  (n) A special type of orthographic projection that places the object in a unique position behind a projection plane such that a view is produced that shows only two dimensions of the object. The outline of the features of the part shows where the parallel lines of sight pierce the projection plane.
mutually perpendicular  (adj.) Two or more lines or planes that are at 90 degrees (right angles) to each other, that is, orthogonal.
NC  (n) Acronym for numeric control, a form of programmable automation of a machine tool, using numbers, letters, and symbols. unlike on an engineering drawing, the part geometry must be defined using coordinates instead of graphics. All NC systems today use computers and are called computer numerical control (CNC) machine tools.
nesting  (v) The process of fitting multiple patterns of material to be cut from a single continuous piece. This can be thought of like a jigsaw puzzle problem.
networked hierarchy  (n) A hierarchical parts structure used by modeling systems. In a networked hierarchy, parts can be shared across assemblies by means of software links set up external to any one file. These parts structures are often managed by special database software networked across workstations within an organization.
node  (n) A singular location in space. A node of a spline curve is used to control the location or curvature of the spline.
nominal scale  (n) A qualitative data scale that has no inherent order to it (e.g., New York, Boston, and Houston).
nominal size  (n) A dimension used to describe the general size of an object, usually expressed in common fractions. For example, a bolt might have a nominal size of 1/2".
nonhierarchical  (n) A structure in which elements may be sorted into separate groups, but there is no defined linkage or ordering of the groups. Layering in CAD systems is often defined as being nonhierarchical.
nonisometric line/plane  (n) A line or plane that is not parallel to one of the principal isometric axes or to two adjacent isometric axes, respectively. In an isometric drawing, nonisometric lines and planes are typically more difficult to draw than isometric elements.
nonuniform rational B-spline  (n) See NURBS.
normal  (adj. or n) A term describing a direction perpendicular to a planar surface, or a vector representing a perpendicular direction. Normals are used to calculate the orientation of a surface with respect to a light source or view point.
normal edge/line  (n) An edge of a face parallel to a plane of projection and perpendicular to the adjacent orthogonal planes. The edge appears as an orthogonal, true-length line in two of the principal views and as a point in the third view.
normal face  (n) A planar surface of an object that is parallel to one of the principal image planes. A normal face is seen in its true size and shape in the image plane to which it is parallel and is seen as an edge in the other two principal image planes. The normal face is named for the image plane to which it is parallel.
nuclear engineering  (n) A field of engineering that includes all areas of research, development, and application of nuclear energy. Areas of specialty include reactor engineering, reactor control, nuclear materials, reactor physics, controlled thermonuclear fusion, reactor safety, fuel management, and shielding.
numeric control  (n) See NC.
NURBS  (n) Acronym for nonuniform rational B-spline, a type of free-form curve that uses rational B-splines and allows for a weighting value at each point on the surface. Because NURBS can also precisely describe conic surfaces, they are gaining popularity in tasks previously done with other types of 3-D modelers.
nut  (n) An internally threaded device used on the ends of threaded fasteners to join materials. Nuts are an alternative to threading the part itself and are often paired with a washer to assist in distributing the pressure and/or securing the nut.
oblique  (adj.) A direction that is neither parallel nor perpendicular to a plane.
oblique edge/line  (n) An edge of a face that is not parallel to any of the three primary orthogonal planes. The edge appears foreshortened in all three principal views of a multiview drawing.
oblique face  (n) A planar surface of an object that has been rotated about two axes from one of the principal image planes. An oblique face will appear foreshortened in all three of the principal views. Unlike inclined and normal faces, an oblique face is not seen as an edge in any of the principal image planes.
oblique projection  (n) A form of parallel projection used to create oblique pictorials. Oblique projection results when the projectors are parallel to each other but at some angle other than perpendicular to the projection plane. Typically the most descriptive face of an object is placed parallel to the frontal plane.
offset coordinate method  (n) A construction method used to construct non-normal views of cylinders, circles, arcs, and other curved or irregular features. The feature is first drawn in an orthographic view, and then regularly spaced coordinate points are transferred to the foreshortened view space, where they are connected using an irregular curve.
offset section  (n) A full section view generated by multiple, connected cutting planes that are parallel but not coplanar. This technique is used to allow the cutting planes to pass through a series of features that do not all lie in the same plane.
ogee curve  (n) A curve that connects two parallel lines with two arcs, forming a smooth curve. Such curves are often seen in architectural details.
open gaging  (v) The inspection of parts without any dedicated fixtures, using standard inspection devices, such as surface plates, calipers, coordinate measuring machines (CMMs), etc.
open loop  (n) A set of edges in a CAD model that does not connect end to end, creating a closed loop. Solid modelers differ as to whether open loops can be used as profiles for feature generation. Open loops cannot be used to define faces on a solid model.
operating system  (n) The software controls the basic functions of a computer system, such as reading and writing files to the disk, communicating with the printer, etc. Common operating systems include UNIX, MS-DOS, and Macintosh OS.
ordinal scale  (n) A qualitative data scale that has an inherent order. Even though ordinal data has an order, the order is not quantitative because the individual data elements are symbolic and have no inherent magnitude.
origin  (n) The intersection point of the X, Y, and Z axes.
orthographic projection  (n) A parallel projection technique that creates a 2-D image of 3-D objects or structures on an image plane perpendicular to the lines of sight. The orthographic projection technique can produce pictorial drawings, such as isometric or oblique, that show the three dimensions of an object or multiviews that only show two dimensions of an object in a single view.
outline assembly  (n) A general graphic description of the exterior shape of an assembly. Outline assemblies are used for parts catalogs and installation manuals or for production when the assembly is simple enough to be visualized without the use of other drawing techniques, such as sectioning. Hidden lines are omitted except for clarity.
output device  (n) A peripheral hardware device linked to a computer that allows information in the computer to be accessible to the human senses. Common types of output devices include computer monitors and printers.
overconstrained  (adj.) Typically used in reference to geometry contained in a 3-D model. In an overconstrained model or feature of a model, the relationship and location of geometric elements is redundantly defined in one or more instances.
painter’s algorithm  (n) A rendering technique used to perform hidden surface removal. All of the polygons are sorted and then drawn on the screen from back to front. Both the computer and a painter use this technique to ensure that elements in the background are covered by those in the front.
parabola  (n) A single-curved surface primitive, defined as the curve of intersection created when a plane intersects a right circular cone parallel to one of the cone’s elements.
parallelepiped  (n) A prism with a rectangular or parallelogram as a base.
parallel lines  (n) Two lines in a plane that stay equidistant from each other along their entire logical length. The lines can be straight or curved. Circular curved parallel lines share the same center point and are referred to as concentric.
parallel planes  (n) Two planes that are equidistant from each other over their entire surfaces. Two planes are considered parallel when intersecting lines in one plane are parallel to intersecting lines in the second plane. Also, seen in edge view, the two planes appear as parallel lines.
parallel projection  (n) A projection technique in which all the projectors are parallel to each other, eliminating convergence. All major projection techniques, except perspective, use parallel projection.
parallelism  (n) In geometric dimensioning and tolerancing an orientation control that is flatness at a distance or straightness of an axis at a distance.
parallelogram  (n) A quadrilateral (four-sided polygon) in which opposite sides are parallel. The square, rectangle, rhombus, and rhomboid are all parallelograms.
parametric  (adj.) A term used to classify curves for which the path is described by a mathematical function rather than a set of coordinates. A parameter within the function (often specified as u or v) is varied from 0 to 1 to define all the coordinate points along the curve.
parent-child  (n) Describes the relationship between features in a model. The parent is created first and the child feature is dependent on the parent feature for its definition in some way. An example would be that workplane might be the parent of a swept feature if the workplane was used in part to define the feature profile of the sweep.
partial view  (n) A view that shows only what is necessary to completely describe the object. Partial views are used for symmetrical objects, for some types of auxiliary views, and for some types of multiview drawings. A break line or center line may be used to limit the partial view.
patch  (n) A closed series of parametric curves that describe a surface region. Series of patches are usually combined together in surface modeling systems to describe an object.
patent  (n) The “right to exclude others from making, using, or selling . . .” a product, granted by the federal government for a period of 17 years. The patenting process was developed to encourage the free and prompt disclosure of technical advances. Patents often require specialized graphics as supporting documentation.
PCB  (n) Acronym for printed circuit board, a rigid board typically made from fiberglass, approximately .060” thick, and used for mounting electronics components as part of a larger assembly. This board, also called a printed wiring board (PWB), has wiring patterns formed by traces of a conductor, such as copper, fused to the board. The wiring pattern is created either by depositing the conductor on the board or by starting with a solid film of the conductor and etching away what is not needed.
PDES  (n) An acronym for product data exchange using STEP, a new data exchange standard that attempts to incorporate information for the complete life cycle of the product. The type of information covered includes shape, design, manufacturing, quality assurance, testing, support, etc. As indicated by its name, PDES incorporates the evolving STEP standard.
PDM  (n) An acronym for Product Data Management. This refers to the digital management of all data needed to manage the complete lifecycle of a manufactured product. APDM system is the computer system and network used to manage this database.
perception  (n) The mental image or knowledge of the environment received through the senses. Real objects can be perceived through viewing or touching, whereas graphic representations are perceived through viewing alone.
perfect form  (n) A term used in geometric dimensioning and tolerancing to describe the ideal shape of a feature. Form controls on a feature are defined relative to the perfect form. For example, the cylindricity tolerance zone is defined as a perfect cylindrical shape.
perimeter loop  (n) A closed set of edges and vertices that constitute the outer boundary of a face. The perimeter loop is a variable in the Euler–Poincaré formula used as part of the process of validating the topology of a model.
perpendicular lines  (n) Two or more lines that intersect once at a right angle (90 degrees), sometimes referred to as normal.
perpendicular planes  (n) Two planes oriented at right angles (90 degrees) to each other. Two planes each containing a line that is perpendicular to a line in the other plane, are also perpendicular to each other. Multiviews are generated by mutually perpendicular image planes.
perpendicularity  (adj.) An orientation control for geometric dimensioning and tolerancing. Perpendicularity is the condition of a surface, center plane, or axis that is at a right angle to a datum plane or datum axis, respectively.
perspective projection  (n) A projection technique in which some or all of the projectors converge at predefined points. This pictorial projection technique is used to replicate closely how humans perceive objects in the real world.
PERT chart  (n) This type of diagram shows the relationship between a set of activities or processes taking place in an organization. These linked relationships define paths through the process and identifies the order, likely length of time, and critical steps that need to be completed. PERT stands for Program Evaluation and Review Technique which was derived by the U.S. Navy in the 1950’s from the Critical Path Method.
phantom line  (n) A line used to represent a movable feature in its different positions as well as a repeating pattern, such as screw threads on a shaft.
Phong shading  (v) A rendering method that uniformly adjusts the value of a surface color based on the relationship of the light source to normals calculated along each edge of the model. Unlike Gouraud shading, Phong shading allows the representation of highlights arising from specular reflection.
photorealistic  (adj.) A term describing a rendered object that attempts to match the perceptual effects of color, texture, lighting, etc., of a real object. This type of rendering is used by industrial designers, marketing executives, and others interested in gaging the effects of its visual appearance.
physical prototypes  (n) Physical models of a proposed design. These are used in the evaluation and testing of a product before going into full production. Increasingly, simulated or virtual prototypes created with CAD/CAM tools are used for analysis.
pictorial assembly  (n) A pictorial drawing (normally an axonometric view) of a partially or fully disassembled assembly. Center lines, called flow lines in this application, are used to show how each part is assembled. The pictorial assembly is commonly used in installation and maintenance manuals.
pictorial drawing/sketch  (n) A drawing in which all three of the primary dimensions of an object are seen in a single view. These drawings are used to give a holistic view and are not used to depict specific features on the object. Axonometric and perspective pictorials are the two main types.
picture plane  (n) An alternate name for the plane of projection. The plane upon which the object is projected in a perspective projection.
piercing point  (n) The intersection of a line and plane.
pin  (n) A mechanical fastener, typically cylindrical in shape, used to keep parts in position or to prevent slippage after assembly. Some of the more common types of pins are dowel, straight, tapered, groove, spring, and cotter.
pinion  (n) The smaller of two gears in a meshed pair of gears. The larger of the two gears is simply called the gear. A gear and pinion pair is used to change the speed of shaft rotation, with the pinion shaft rotating at a higher rate than the gear shaft.
piping  (n) A specialized engineering field for the design of fluid and gas-carrying piping systems for process plants and other industrial and commercial structures.
piping drawing  (n) A specialized drawing used in the design and maintenance of piping systems. The piping systems are shown in an orthographic plan view or in a pictorial view such as isometric. The drawing can be done as a single-line drawing in which the components are represented as a single line or as a doubleline drawing for a more realistic spatial layout of the components. Specialized graphic symbols are used to represent the pipes, fittings, and valves used in the system.
pitch  (n) A thread term used to describe the distance measured parallel to the axis between corresponding points on adjacent thread forms. The pitch is equal to 1 divided by the number of threads per inch.
pixel  (n) A single point on a display device, such as a computer monitor. Pixels are arranged in horizontal and vertical rows. On a CRT type monitor, a pixel is an electronically charged point on the screen. Pixel is often used in describing the minimal unit of resolution of any bitmapped graphic output.
planar surface  (n) A flat, two-dimensional bounded surface.
plan drawing  (n) A type of drawing commonly used in civil, architectural, or engineering projects involving large structural layouts. A plan drawing (sometimes called a plan view) is an orthographic view taken from the top and looking down parallel to the line of gravity. These drawings are useful in planning the flow of vehicles, people, or material through constructed spaces or along the terrain.
plane  (n) A region of space defined by a minimum of three noncoincident points in space. For the simplest type of plane surface, all points can be described by two coordinate axes; that is, the plane has no curvature.
plane geometry  (n) The geometry of planar figures, such as circles and triangles, and their relationships. This mathematical field is an important part of traditional engineering and technical graphics.
plane of projection  (n) An imaginary plane in space upon which an object is projected. The plane can be imagined as a pane of glass on which lines of sight from the object form an outline of the object. This plane is also referred to as a picture plane.
plastics  (n) A material made from natural or synthetic resins that can be formed or shaped. Common industrial plastics include polystyrene, acrylics, polycarbonate, ABS, PVC, acetals, nylon, polypropylene, polyethylene, epoxy, and phenolics. PLM (n) Product lifecycle management is a term that addresses the management of the key data from a product’s conception through its production life.
PLM  (n) Product lifecycle management is a term that addresses the management of the key data from a product’s conception through its production life.
plumbing  (n) The piping used to transport water, waste, and gaseous fuels, especially in residences.
plus and minus dimensioning  (n) A tolerancing specification that gives the allowable positive and negative variance from the dimension specified. Sometimes, the plus and minus values will be equal; at other times, they will be different.
point  (n) A singular location in space, usually defined by coordinate values (i.e., X,Y,Z).
point light source  (n) A light source located at a specified point in space. In rendering, the point light source is usually close to the model. Because the light radiates omnidirectionally from the point source, no two rays hit a planar surface at the same angle. An uncovered incandescent light bulb is analogous to a point light source.
point view  (n) The direction of view of a line or axis that projects as a single point on the plane of projection. That is, the line of sight in a parallel projection is parallel with the line or axis.
point-to-point diagram  (n) See wiring diagram.
polar coordinates  (n) A 2-D coordinate system used to locate a point in a plane by specifying a distance and an angle from the coordinate origin. When another distance normal to the coordinate origin is added, cylindrical coordinates can be specified.
polygon  (n) A plane figure bounded by straight lines. If the sides are of equal length and form equal angles with each other, the polygon is considered a regular polygon (e.g., a square or hexagon).
polygonal prism  (n) A geometric solid consisting of two equivalent polygonal bases parallel to each other. Each equivalent edge of the bases is connected to form a series of parallelograms, bounding the sides of the solid.
polyhedron  (n) A geometric solid bounded by polygons. If the polygons are equal, regular polygons, the solid is called a regular polyhedron.
port  (n) In 3-D modeling systems, a defined region on the computer screen, used for displaying a single view of an object. Typically, a different set of view parameters is assigned to each port.
position  (n) A control for geometric dimensioning and tolerancing. Position specifies the total zone specification for a feature, such as a diameter or the total height.
precedence of lines  (n) A convention describing the order of priority of different linestyles. For example, if a visible and hidden line coincide, the visible line is the one drawn.
presentation graphics  (n) Graphics intended for a wide audience and used to communicate information about a proposed product or design to other individuals within the company, to clients, or to the potential end user.
pressure angle  (n) A term used in the design of gears and defined as the angle between the tangent to the pitch circles and the line drawn normal to the surface of a gear tooth. The pressure angle has been standardized by gear manufacturers and by ANSI (14 1/2 degrees being the most common), and it determines the shape of the involute curve used to design the gear tooth.
primary auxiliary view  (n) A single auxiliary view projected from one of the six standard views. Primary auxiliary views are used to show inclined surfaces in their true size and shape. Secondary auxiliary views are used for oblique surfaces and are derived from primary auxiliary views.
primary axes  (n) Three mutually perpendicular axes representing the primary dimensions of an object. Each of these axes is normal (perpendicular) to one of the primary image planes.
primitive  (n or adj.) A term used primarily to describe the fundamental geometric forms used for building 3-D CAD models. Primitives are typically defined parametrically or with single sweep operations. Primitives are used as tool solids in Boolean operations.
principal plane  (n) A plane that is seen in its true size and shape in two of the six principal views and as an edge in the other four. The three principal planes are frontal, profile, and horizontal. For example, the frontal plane is seen in its true size and shape in the front and rear views and as an edge in the other four views.
principal (standard) view  (n) One of the six mutually perpendicular views of an object, produced after an object’s position is selected. The six views can be created by positioning the object inside a glass box and viewing the box with parallel lines of sight perpendicular to the glass planes. These views are the cornerstone of multiview drawings.
printed circuit board  (n) See PCB.
printed wiring board  (n) See PWB.
problem identification  (n) A process used by the design team during the ideation process to set the parameters of the design project before attempting to find a solution to the design. This process includes such stages as objectives, limitations, and scheduling.
procedural  (adj.) A term used to describe the process by which a model is constructed. Procedural information can be thought of as actions, such as creating a face on the cube by following the path made by edges 1 through 4.
process control  (n) The measurement, analysis, and adjustment of manufacturing processes, such as drilling, milling, and turning. The quality of a product relies heavily on process control techniques used to check the variability of machined parts and to detect defects. The use of statistical techniques is an important component of process control.
process piping  (n) The piping used to transport liquid and gaseous chemicals for industrial processes.
process planning  (n) The stage in the manufacturing process in which the most efficient way of producing the product is determined. In this stage, industrial engineers determine how parts will be fabricated and in what sequence.
product data exchange using STEP  (n) See PDES.
product data management  (n) See PDM.
product (industrial) design  (n) A complex activity that includes function analysis, market analysis, production, sales, and service. The goal of product design is to produce a product that will meet the wants and needs of the consumer, can be economically produced, is safe for the consumer and the environment, and will be profitable.
production drawing  (n) See working drawing.
production process  (n) The planned action used to convert raw materials into finished products. The production process is sometimes referred to as the manufacturing process. However, production is a more global term that includes both the manufacturing of products and the construction of structures.
profile  (n) A form control for geometric dimensioning and tolerancing. A profile is the outline of a feature projected onto a plane. They usually consist of combinations of contiguous lines, arcs, and other curves. The profile tolerance zone may be made of a combination of straightness, roundness, parallelism, etc.
profile line  (n) A line seen in its true length in the profile plane, either the right or left side view.
profile plane  (n) A principal orthographic plane of projection. This plane is used to define both the right and left side orthographic views.
profile sketch  (n) Typically a closed loop of lines drawn on a workplane as part of the feature definition process in 3-D modeling. In a constraint-based modeler, the profile sketch is constrained with dimensions and other geometric relations and then swept out to form a 3-D solid model feature.
profile view  (n) A principal orthographic view created by a projection onto the profile plane. This term includes both the right and left side views.
projection line  (n) A construction line drawn between views in a multiview drawing to align 3-D space dimensions. This term is sometimes used in a more general sense to refer to lines representing the transference of spatial information between objects, or between an object and an image plane. The relationship of the projection lines to each other and to the image plane defines whether the projection technique is perspective, parallel, or oblique.
projection theory  (n) The principles used to represent objects and structures graphically on 2-D media. Some of the primary projection methods include orthographic, oblique, and perspective.
proportion  (n) The comparative relation, or ratio, between dimensions of a feature or object.
prototyping  (n or v) A term used to describe the process by which physical mockups are made of proposed designs. Increasingly, prototyping is done using the databases associated with 3-D computer models. Because of the speed and efficiency, this technique is often referred to as rapid prototyping.
PWB (printed wiring board)  See PCB.
pyramid  (n) A geometric solid consisting of a polygonal base and a series of triangular lateral faces. The triangular faces each share one side with the polygonal base and the other two sides with the neighboring triangular faces. The triangular faces all meet at a common point called the vertex.
quadrilaterals  (n) Four-sided polygons of any shape. The sum of the angles inside a quadrilateral always equals 360 degrees. Quadrilaterals are classified by the characteristics of their sides. If opposite sides of the quadrilateral are parallel, the shape is a parallelogram.
qualitative  (adj.) A type of data used as a method of labeling and identifying. Qualitative data are classified as being either nominal or ordinal.
quality  (adj.) The capacity of a product or service to consistently meet or exceed customer needs and expectations. Quality includes performance, special features, reliability, durability, and service after sale.
quantitative  (adj.) A type of data that has numerical value. Quantitative data are further classified by the number of components and by the scales of values used (e.g., scalar, vector, or tensor).
radial line  (n) One of a set of lines radiating from or converging to a common center. A line that is directed along a radius of a circular arc or circle.
radiosity  (n) A rendering technique, based on thermal principles, in which there is a conservation of light energy in a closed environment. With radiosity methods, any size or shape surface is capable of both radiating and absorbing light energy. The rate at which energy leaves a surface is its radiosity, and is the result of all light energy received, absorbed, and then transmitted by the surface.
radius symbol  (n) A symbol that precedes a numerical value, indicating that the associated dimension shows the radius of a circular arc. The radius symbol is the capital letter R.
range bars  (n) Line or bar marks, such as those used in bar charts, that indicate an interval of variable values. For example, range bars could be used to indicate the period of time that a product is in transit between machining stations on a manufacturing line.
rapid prototyping  (n) A broad term used to describe several related processes that create physical models directly from a CAD database. Prototyping systems use a variety of techniques, including stereolithography and fused deposition modeling (FDM). Rapid prototyping is used to create prototypes for concept modeling, injection molds, and investment casting.
ratio scale  (n) A data scale that has a natural zero point but is insensitive to the units used. Ratio values are often generated by dividing two values that have either similar or dissimilar units.
rats nest  (n) The drawing representing straightline connections between all of the electronic components on a printed circuit board. Once the components are located on the board, the rats nest is generated, using the component connection list. The rats nest drawing is part of the iterative design process to optimize placement of components.
ray  (n) An entity of unspecified length, but no depth or breadth, that extends into infinity from a specified point. In computer graphics, ray is a common term used, when rendering a scene, to describe the path a light ray follows.
ray tracing  (n) A rendering technique that calculates the path of all rays of (a) theoretical light source(s) within a model scene. The technique includes tracing the path from the light source, between all objects which may reflect and pass the light, to the viewer’s eye.
reach envelope  (n) A volume of space representing all possible locations in space that a human operator’s limbs could occupy. Reach envelopes are used to analyze the locations of controls, such as in the design of workstations, tools, cockpits, etc.
rear view  (n) A principal view of an object, created by rotating the object 180 degrees about the vertical axis from the front view. This view is not typically included in a standard multiview drawing.
redlining  (n) Corrections and comments made on a document. Traditionally, these were made with a red pencil on paper working drawings, but they may refer to any additional notations made on paper or electronic documents. Redlining is a way in which individuals in an organization other than the individual who produced the document can provide input into either the design represented in the document or the correctness of the document itself.
reference dimension  (n) A numerical value, enclosed in parentheses, provided for information only and not used in the fabrication of the part. A reference dimension is a calculated size used to show the intended design size of a part. Drawings made to older standards may use REF placed next to a reference dimension, instead of using parentheses.
reference lines  (n) Lines used to correlate scale values with data markers in a visualization. Because reference lines are not the central focus of a visualization, they tend to be thin and sometimes dotted or dashed.
reference plane  (n) An imaginary plane placed in multiviews to facilitate the solving of descriptive geometry problems.
reference point  (n) A point from which measurements or comparison can be made. Also called the origin or measurement.
refinement  (v) A repetitive process (iterative or cyclical) used to test the preliminary design, make changes if necessary, and determine if the design meets the goals of the project. Models are used to analyze and visualize the design. Refinement drawings are used to analyze the design in its current stage of the design process.
regression line  (n) A line mark used in conjunction with point marks to represent data trends in a visualization. Although this line, either linear or curved, can be drawn freehand, it is usually calculated using statistical techniques.
regular curve  (n) A bent line composed of constant-radius arcs generated around a single centerpoint. With traditional tools, regular curves are drawn using a compass or circle template; with CAD, they are constructed with the CIRCLE and ARC commands.
regular isometric  (n) An isometric pictorial drawn as if the viewer is looking down on the object from the top. In a regular isometric, the 30-degree axes are drawn upward from the horizontal. The regular method is the most common type of isometric drawing.
regular polygon  (n) A two-dimensional shape whose sides are equal in length.
regular polyhedra  (n) A three-dimensional surface or solid that has regular polygons for faces.
relative coordinates  (n) Coordinate locations specified in reference to a previously defined location other than the origin. Relative coordinates are sometimes referred to as delta coordinates, meaning changed coordinates.
removed section  (n) A section view that does not follow the standard alignment of views practiced in multiview drawing. This technique is used to show multiple section views generated from parallel cutting planes and views placed on separate drawings or using different scales.
removed view  (n) A complete or partial orthographic view that is not aligned with any of the principal views. Removed views are often shown on a different drawing sheet or at a different scale.
reprographics  (n) The process of storing, retrieving, and copying engineering drawings. Often, specialized service bureaus are used to provide these services to small firms.
reverse engineering  (v) A method of accurately evaluating existing products, then inputting the information into a CAD database. Often a coordinate measuring machine (CMM), an electromechanical device with a probe on one end that accurately measures objects, is used to input the 3-D data into the CAD system.
reversed axis isometric  (n) A variation of the regular isometric pictorial. Whereas in a regular isometric, it appears as though the viewer is looking down from the top of the object, in the reversed axis isometric, it appears as if the viewer is looking up from the bottom of the object. The 30-degree axes are drawn downward from the horizontal.
revision block  (n) An area located next to the title block, listing the version, or revision, of the drawing depicted.
revolution  (v) The rotation of a point, line, plane, or entire object about an axis parallel to a plane or projection. The revolution method is one of the standard techniques used in descriptive geometry.
revolved section  (n) A section view made by revolving the cross-section view of the part 90 degrees and placing the section view on the part. Visible lines adjacent to the revolved view can be either drawn or broken out using conventional breaks.
RGB color model  (n) A color model based on the three additive primaries: (R)ed, (G)reen, and (B)lue. This color model is used extensively because of its close correlation to the hardware implementation of color on a computer monitor.
rib (web)  (n) A thin, flat feature of an object that acts as a structural support. Ribs, webs, spokes, lugs, and other thin features are not section lined if a cutting plane passes parallel to the feature.
right side view  (n) A principal view of an object, created by rotating the line of sight 90 degrees about the vertical axis to the right of the front view. This view is typically included in a standard multiview drawing.
rigid-body transformations  (n) Transformations applied to geometric forms. Such transformations affect the location or orientation in space but not the shape. Examples are translation and rotation.
rivet  n) A permanent mechanical fastener, consisting of a smooth metal shaft with a head. Rivets are placed in the part and held in place by spreading the tip protruding through the material.
robot  (n) A computer-controlled device used in manufacturing for many purposes, such as assembly, painting, and material movement. Robotics is an important component of CAD/CAM and in the automation of production facilities.
root  (n) A threading term used to describe the bottom of a screw thread cut into a cylinder.
roulette  (n) The curve generated by the rolling contact of one curve or line on another. Any point attached to the rolling curve will describe a roulette curve. The moving point is called the generating point. The roulette is constructed by moving the rolling curve to a number of new positions and plotting the corresponding positions of the generating point.
round  (n) A round is an exterior corner normally found on cast, forged, or molded parts. Like a fillet, a round can indicate that a surface is not machine finished. Around is indicated on engineering drawings as a small arc.
roundness  (n) See circularity.
rule 1  (n) A central principle to geometric dimensioning and tolerancing (ANSI Y14.5– 1982). It stated that, where only a tolerance of size is specified, the limits of size of an individual feature prescribe the extent to which variations in its geometric form, as well as its size, are allowed.
ruled surface  (n) A surface produced by the movement of a straight-line generatrix controlled by a directrix to form a plane, a single curved surface, or a warped surface.
runout  (n) A filleted surface that runs tangent to a cylindrical one. A runout is drawn on multiview drawings starting at the point of tangency, using a radius equal to that of the filleted surface, with a curvature of approximately one-eighth of a circle.





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