{"id":53,"date":"2026-11-11T01:28:41","date_gmt":"2026-11-11T01:28:41","guid":{"rendered":"https:\/\/mcadauthority.com\/?p=53"},"modified":"2026-11-11T01:28:41","modified_gmt":"2026-11-11T01:28:41","slug":"mechanical-cad-terminology","status":"publish","type":"post","link":"https:\/\/mcadauthority.com\/?p=53","title":{"rendered":"Essential Mechanical CAD Terminology Every Designer Should Know"},"content":{"rendered":"<p>In my first week on any new team, I run a small, slightly mischievous experiment. I ask three people the same question: &#8220;What is the difference between a version and a revision?&#8221; It is rare to get three identical answers. In one case, a design manager and a senior designer spent ten minutes arguing about it while the junior who had asked the original question quietly took notes. The argument ended only when we looked at a drawing that had been manufactured twice, to two different &#8220;latest versions&#8221;.<\/p>\n<p>Words matter in engineering. A misunderstood term becomes a misunderstood requirement, and a misunderstood requirement becomes a scrapped part. <strong>Learning the vocabulary of Mechanical CAD is not academic work; it is risk management.<\/strong> It also makes you faster, because you can read documentation, follow tutorials, talk to suppliers and ask for help without constantly stopping to decode jargon.<\/p>\n<p>This guide gives you the essential vocabulary of MCAD, grouped by subject, with short definitions and, where useful, my own practical comment. I have included the terms you will meet daily, the ones that cause confusion, and a table showing how the same idea is named in different software systems. If you are new to the field, start with <em><a href=\"https:\/\/mcadauthority.com\/?p=46\">What Is Mechanical CAD (MCAD)? A Complete Beginner&#8217;s Guide<\/a><\/em>, then keep this page open as a reference.<\/p>\n<hr \/>\n<h2>How to Use This Glossary<\/h2>\n<p>You do not need to memorize it. Read it once through, to get a feel for the landscape, then return to a section when you need it. Terms are grouped as follows:<\/p>\n<ol>\n<li>The big acronyms<\/li>\n<li>Sketching<\/li>\n<li>Features and modeling<\/li>\n<li>Geometry and data representation<\/li>\n<li>Assemblies<\/li>\n<li>Drawings and documentation<\/li>\n<li>Tolerances and fits<\/li>\n<li>Manufacturing terms<\/li>\n<li>Simulation terms<\/li>\n<li>Files, data and change management<\/li>\n<\/ol>\n<p>At the end you will find a comparison of terms across popular systems, and a short list of the confusions I see most often.<\/p>\n<hr \/>\n<h2>1. The Big Acronyms<\/h2>\n<ul>\n<li><strong>CAD (Computer-Aided Design):<\/strong> using software to create and document designs. The umbrella term.<\/li>\n<li><strong>MCAD (Mechanical CAD):<\/strong> CAD for mechanical products: parts, machines, mechanisms and tools. See <em><a href=\"https:\/\/mcadauthority.com\/?p=47\">Mechanical CAD vs. General-Purpose CAD: Key Differences Explained<\/a><\/em>.<\/li>\n<li><strong>ECAD (Electronic or Electrical CAD):<\/strong> CAD for circuits, boards and wiring.<\/li>\n<li><strong>AEC \/ BIM (Architecture, Engineering, Construction \/ Building Information Modeling):<\/strong> CAD and data modeling for buildings and infrastructure.<\/li>\n<li><strong>CAM (Computer-Aided Manufacturing):<\/strong> software that generates machine instructions, such as CNC toolpaths, from a CAD model. See <em>CAD to CAM: Understanding the Complete Manufacturing Workflow<\/em>.<\/li>\n<li><strong>CAE (Computer-Aided Engineering):<\/strong> analysis and simulation tools: stress, heat, flow, vibration, motion. See <em>Computer-Aided Engineering (CAE): A Complete Beginner&#8217;s Guide<\/em>.<\/li>\n<li><strong>PDM (Product Data Management):<\/strong> controlled storage, versioning and release of engineering files. See <em>Product Data Management (PDM): A Complete Guide<\/em>.<\/li>\n<li><strong>PLM (Product Lifecycle Management):<\/strong> the broader management of product information across its whole life: requirements, design, manufacturing, service. See <em>PDM vs. PLM: Understanding the Key Differences<\/em>.<\/li>\n<li><strong>BOM (Bill of Materials):<\/strong> the structured list of parts, quantities and materials that make up a product. See <em><a href=\"https:\/\/mcadauthority.com\/?p=54\">Understanding Parts, Assemblies, Drawings, and BOMs in MCAD<\/a><\/em>.<\/li>\n<li><strong>DFM \/ DFA (Design for Manufacturing \/ Design for Assembly):<\/strong> design principles that make parts easy to produce and assemble. See <em>Design for Manufacturing (DFM) and Design for Assembly (DFA): A Complete Guide<\/em>.<\/li>\n<li><strong>MBD (Model-Based Definition):<\/strong> defining a product&#8217;s requirements directly in the 3D model, with annotations, instead of relying only on drawings.<\/li>\n<li><strong>PMI (Product Manufacturing Information):<\/strong> the dimensions, tolerances, notes and symbols attached to a 3D model. See <em>Model-Based Definition (MBD) and 3D Product Manufacturing Information (PMI)<\/em>.<\/li>\n<li><strong>GD&amp;T (Geometric Dimensioning and Tolerancing):<\/strong> a symbolic language for defining the allowed variation of form, orientation and position. See <em>Geometric Dimensioning and Tolerancing (GD&amp;T): A Complete Guide<\/em>.<\/li>\n<li><strong>FEA (Finite Element Analysis):<\/strong> a numerical method for predicting how a part behaves under load, heat or vibration.<\/li>\n<li><strong>CFD (Computational Fluid Dynamics):<\/strong> simulation of liquid and gas flow.<\/li>\n<li><strong>ECR \/ ECO (Engineering Change Request \/ Order):<\/strong> the formal documents requesting and authorizing a change to a released design. See <em>Engineering Change Requests (ECR) and Engineering Change Orders (ECO)<\/em>.<\/li>\n<\/ul>\n<hr \/>\n<h2>2. Sketching<\/h2>\n<p>Nearly every 3D shape starts here.<\/p>\n<ul>\n<li><strong>Sketch:<\/strong> a 2D drawing made on a plane or face, used as the basis for a feature.<\/li>\n<li><strong>Profile:<\/strong> a closed outline in a sketch, used to create a solid. A sketch with gaps will not produce a solid.<\/li>\n<li><strong>Sketch plane:<\/strong> the flat surface on which a sketch is drawn.<\/li>\n<li><strong>Geometry (sketch entities):<\/strong> the lines, arcs, circles, splines and points in a sketch.<\/li>\n<li><strong>Construction geometry:<\/strong> helper elements, such as centerlines, that guide the sketch but do not create material.<\/li>\n<li><strong>Dimension:<\/strong> a numerical size or position that controls geometry.<\/li>\n<li><strong>Driving dimension:<\/strong> a dimension that controls the geometry. Change the number, the shape changes.<\/li>\n<li><strong>Driven (reference) dimension:<\/strong> a dimension that only reports a value and cannot be edited. Useful for checking.<\/li>\n<li><strong>Constraint (geometric relation):<\/strong> a rule linking geometry: horizontal, vertical, parallel, perpendicular, tangent, concentric, coincident, equal, symmetric, fixed.<\/li>\n<li><strong>Degrees of freedom (DOF):<\/strong> the ways a sketch element can still move. A fully constrained element has none left.<\/li>\n<li><strong>Fully defined (fully constrained) sketch:<\/strong> nothing can move without changing a dimension. This is the professional standard.<\/li>\n<li><strong>Under-defined sketch:<\/strong> some geometry is still free to move. Risky, because it may shift when edited.<\/li>\n<li><strong>Over-defined sketch:<\/strong> too many dimensions or constraints, some conflicting. The software warns you.<\/li>\n<li><strong>Projected geometry:<\/strong> edges or sketches from other features, projected into the current sketch as references.<\/li>\n<li><strong>Solver:<\/strong> the engine that calculates sketch geometry from dimensions and constraints.<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"\/wp-content\/uploads\/mcad-guides\/mcad-terminology-01-sketch-anatomy.png\" alt=\"Annotated fully defined sketch with dimensions and constraint symbols\" \/><\/p>\n<p><em>Figure 1. Anatomy of a fully defined sketch.<\/em><\/p>\n<p><strong>My comment:<\/strong> the habit of making every sketch fully defined is the cheapest quality improvement I know. For help when it goes wrong, see <em>Resolving Overdefined and Underdefined Sketches<\/em>.<\/p>\n<hr \/>\n<h2>3. Features and Modeling<\/h2>\n<ul>\n<li><strong>Feature:<\/strong> a single modeling operation that adds or removes material, or modifies a shape.<\/li>\n<li><strong>Base feature:<\/strong> the first feature in a part, from which everything else grows.<\/li>\n<li><strong>Extrude:<\/strong> pushes a sketch profile straight, giving it thickness. Can add (boss) or remove (cut) material.<\/li>\n<li><strong>Revolve:<\/strong> spins a profile around an axis. Used for shafts, pulleys, bottles and any round part.<\/li>\n<li><strong>Sweep:<\/strong> moves a profile along a path, producing tubes, rails or pipes.<\/li>\n<li><strong>Loft:<\/strong> blends between two or more profiles, producing transitions and organic shapes.<\/li>\n<li><strong>Hole (hole feature):<\/strong> a purpose-built operation that creates a hole with defined diameter, depth, thread and type. Better than a plain cut because it carries meaning.<\/li>\n<li><strong>Fillet:<\/strong> rounds an edge. <strong>Chamfer:<\/strong> bevels an edge.<\/li>\n<li><strong>Shell:<\/strong> hollows a solid, leaving walls of a chosen thickness. Common in castings, molded parts and enclosures.<\/li>\n<li><strong>Draft:<\/strong> a small taper applied to faces so a molded or cast part can be released from its mold.<\/li>\n<li><strong>Rib and boss:<\/strong> reinforcing and mounting features common in plastic and cast parts.<\/li>\n<li><strong>Pattern:<\/strong> repeats a feature: linear, circular or along a path.<\/li>\n<li><strong>Mirror:<\/strong> copies a feature or body across a plane.<\/li>\n<li><strong>Boolean operations:<\/strong> combining solids by <strong>joining<\/strong> (union), <strong>cutting<\/strong> (subtraction) or <strong>intersecting<\/strong>.<\/li>\n<li><strong>Body:<\/strong> a distinct solid within a part file. A part may contain several (multi-body modeling).<\/li>\n<li><strong>Parametric modeling:<\/strong> a method where geometry is driven by dimensions, constraints and a history of features. See <em>Parametric 3D Modeling: A Complete Practical Guide<\/em>.<\/li>\n<li><strong>Direct modeling:<\/strong> editing the geometry itself, by pushing and pulling faces, without relying on history. See <em><a href=\"https:\/\/mcadauthority.com\/?p=50\">Parametric vs. Direct Modeling: Which Approach Is Better?<\/a><\/em><\/li>\n<li><strong>Feature tree (model tree, browser, timeline):<\/strong> the ordered list of features that built a part. Different software names it differently.<\/li>\n<li><strong>History:<\/strong> the recorded sequence of operations. Reading it tells you how a part was made.<\/li>\n<li><strong>Parent-child relationship:<\/strong> a dependency between features. A fillet is the child of the edge it rounds. Delete the parent and the child may fail.<\/li>\n<li><strong>Rollback:<\/strong> temporarily returning the model to an earlier point in its history, to edit or insert a feature.<\/li>\n<li><strong>Suppress:<\/strong> temporarily switching a feature off, without deleting it.<\/li>\n<li><strong>Rebuild (regeneration, update):<\/strong> recalculating the model after an edit.<\/li>\n<li><strong>Failed feature:<\/strong> a feature that cannot be rebuilt because its references are missing or its geometry is invalid. See <em>How to Fix Failed Features in Parametric CAD Models<\/em>.<\/li>\n<li><strong>Design intent:<\/strong> the rules and reasoning that define how the model should behave when changed. See <em><a href=\"https:\/\/mcadauthority.com\/?p=51\">Understanding Design Intent in 3D Mechanical Modeling<\/a><\/em>.<\/li>\n<li><strong>Parameter:<\/strong> a named value, such as a length or count, that controls a model.<\/li>\n<li><strong>Equation (formula):<\/strong> a relationship between parameters, such as a boss diameter equal to the hole diameter plus twice the wall thickness.<\/li>\n<li><strong>Configuration \/ family table \/ design table:<\/strong> a method of defining multiple variants of a part or assembly in a single file. Autodesk Inventor uses <em>iParts<\/em> and <em>iAssemblies<\/em> for similar purposes. See <em>Design Tables and Parameter-Driven CAD Models<\/em>.<\/li>\n<li><strong>Template:<\/strong> a starting file with preset units, materials, standards and layouts.<\/li>\n<li><strong>Origin:<\/strong> the point where the model&#8217;s coordinate axes meet. Good models are anchored to it.<\/li>\n<li><strong>Reference geometry (work features, datum features):<\/strong> planes, axes and points used to position other features. In Autodesk Inventor, these are called <em>work planes, work axes and work points<\/em>.<\/li>\n<li><strong>Coordinate system:<\/strong> a set of axes used to locate geometry, often needed for manufacturing and analysis.<\/li>\n<\/ul>\n<hr \/>\n<h2>4. Geometry and Data Representation<\/h2>\n<p>This is the &#8220;what&#8217;s under the hood&#8221; section. You can design for years without knowing it, but understanding it explains many strange behaviors.<\/p>\n<ul>\n<li><strong>Wireframe model:<\/strong> edges only, no surfaces or volume.<\/li>\n<li><strong>Surface model:<\/strong> infinitely thin skins describing the outside of an object. See <em>Surface Modeling in Mechanical CAD: A Complete Guide<\/em>.<\/li>\n<li><strong>Solid model:<\/strong> a closed volume with an inside and an outside, which therefore has mass and can be cut, assembled and analyzed.<\/li>\n<li><strong>Mesh model:<\/strong> a shape made of many small triangles or polygons, typical of 3D scans and STL files. See <em>B-Rep vs. Mesh Geometry: Understanding the Differences<\/em>.<\/li>\n<li><strong>B-rep (boundary representation):<\/strong> the way most solid modelers store geometry: as a collection of faces, edges and vertices that bound a volume.<\/li>\n<li><strong>Face, edge, vertex:<\/strong> the surfaces, curves and points that make up a B-rep solid.<\/li>\n<li><strong>NURBS (Non-Uniform Rational B-Splines):<\/strong> the mathematical curves and surfaces used to describe free-form shapes.<\/li>\n<li><strong>Geometry kernel:<\/strong> the mathematical engine that creates and manipulates solids. Well-known kernels include <strong>Parasolid<\/strong> and <strong>ACIS<\/strong>. Autodesk&#8217;s products use a kernel called <strong>ShapeManager<\/strong>, which evolved from ACIS. See <em>Parasolid vs. ACIS: Understanding 3D Geometry Kernels<\/em>.<\/li>\n<li><strong>Manifold \/ watertight:<\/strong> a valid solid with no gaps, no overlapping faces and a well-defined inside. Non-manifold geometry is a common cause of import and printing problems.<\/li>\n<li><strong>Tessellation:<\/strong> converting smooth geometry into a mesh of triangles for display, printing or analysis.<\/li>\n<li><strong>Tangent continuity (G1) and curvature continuity (G2):<\/strong> descriptions of how smoothly two surfaces meet. G0 means they simply touch; G1 means no visible crease; G2 means the curvature also matches. See <em>Understanding Curvature Continuity: G0, G1, G2, and G3<\/em>.<\/li>\n<li><strong>Dumb solid:<\/strong> a solid with no feature history, typically imported from another system. It can be edited directly, but its original intent is lost.<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"\/wp-content\/uploads\/mcad-guides\/mcad-terminology-03-brep-vs-mesh.png\" alt=\"Comparison of B-rep geometry with faces, edges and vertices against a triangle mesh\" \/><\/p>\n<p><em>Figure 2. B-rep stores exact boundaries; a mesh approximates shapes with triangles.<\/em><\/p>\n<hr \/>\n<h2>5. Assemblies<\/h2>\n<ul>\n<li><strong>Part:<\/strong> a single component, typically a single manufactured item.<\/li>\n<li><strong>Subassembly:<\/strong> an assembly that is itself used inside a larger assembly.<\/li>\n<li><strong>Assembly:<\/strong> a collection of parts and subassemblies positioned relative to each other.<\/li>\n<li><strong>Component:<\/strong> any part or subassembly placed in an assembly. Also called an <em>occurrence<\/em> or <em>instance<\/em> in some systems.<\/li>\n<li><strong>Constraint (mate, joint):<\/strong> a relationship between two components that defines how they are positioned. In Inventor and Creo, the term is <em>constraint<\/em>; in SOLIDWORKS, <em>mate<\/em>; in Fusion, <em>joint<\/em>. A <em>joint<\/em> may also include motion. See <em>Understanding Assembly Constraints, Mates, and Joints<\/em>.<\/li>\n<li><strong>Grounded (fixed) component:<\/strong> a component locked in space, used as the reference for the rest of the assembly.<\/li>\n<li><strong>Degrees of freedom (assembly):<\/strong> the motions a component can still make. Free components have six: three translations and three rotations. See <em>Degrees of Freedom in Mechanical Assemblies Explained<\/em>.<\/li>\n<li><strong>Interference:<\/strong> two components occupy the same space. Interference checking finds them automatically. See <em>Interference Detection and Clearance Analysis in MCAD<\/em>.<\/li>\n<li><strong>Clearance:<\/strong> the gap between components. Too little causes collisions; too much causes looseness.<\/li>\n<li><strong>Bottom-up design:<\/strong> creating parts individually, then assembling them.<\/li>\n<li><strong>Top-down design:<\/strong> defining the overall layout first, and creating or driving parts from it. See <em>Bottom-Up vs. Top-Down Assembly Design<\/em>.<\/li>\n<li><strong>Skeleton (master layout):<\/strong> a sketch or simple model that controls the positions and sizes of many parts. See <em>Skeleton Modeling and Master Layout Techniques<\/em>.<\/li>\n<li><strong>In-context design (external reference):<\/strong> a part created or driven using the geometry of other parts within an assembly.<\/li>\n<li><strong>Exploded view:<\/strong> an image or animation showing components separated along their assembly paths.<\/li>\n<li><strong>Representation (display state, configuration of view):<\/strong> a saved way of displaying an assembly, for example with some parts hidden or simplified. Large assemblies use <strong>simplified<\/strong> or <strong>lightweight<\/strong> representations to remain responsive. See <em>How to Create and Manage Large CAD Assemblies<\/em>.<\/li>\n<li><strong>Envelope:<\/strong> a simplified volume representing the maximum space a part or module may occupy.<\/li>\n<li><strong>Standard (library) component:<\/strong> a purchased or standardized item such as a screw, bearing or pin. See <em>Managing Standard Parts and CAD Component Libraries<\/em>.<\/li>\n<\/ul>\n<hr \/>\n<h2>6. Drawings and Documentation<\/h2>\n<ul>\n<li><strong>Engineering drawing:<\/strong> the formal 2D document describing a part or assembly for manufacturing or assembly. See <em>Mechanical Engineering Drawings: A Complete Guide<\/em>.<\/li>\n<li><strong>Orthographic projection:<\/strong> representing a 3D object with flat views (front, top, side) taken along perpendicular directions.<\/li>\n<li><strong>First-angle and third-angle projection:<\/strong> two conventions for arranging those views. First-angle is common in Europe and much of the world; third-angle in North America. See <em>Orthographic Projection and Engineering Drawing Views Explained<\/em>.<\/li>\n<li><strong>Base view \/ projected view:<\/strong> the first view you place, and the views derived from it.<\/li>\n<li><strong>Section view:<\/strong> a view showing the inside of a part, as if it had been cut open.<\/li>\n<li><strong>Detail view:<\/strong> an enlarged view of a small area.<\/li>\n<li><strong>Auxiliary view:<\/strong> a view taken perpendicular to an inclined face, to show its true shape.<\/li>\n<li><strong>Broken view:<\/strong> a view with the middle removed, to shorten long parts.<\/li>\n<li><strong>Associative:<\/strong> a drawing is associative when it updates automatically with changes to the model.<\/li>\n<li><strong>Title block:<\/strong> the box on a drawing that holds part number, title, material, scale, author, date and revision.<\/li>\n<li><strong>Revision block (revision table):<\/strong> the record of each approved change on the drawing.<\/li>\n<li><strong>Balloon (item number):<\/strong> a numbered callout linking a component in the drawing to its row in the parts list.<\/li>\n<li><strong>Parts list:<\/strong> the table on an assembly drawing listing the components. Generated from the BOM.<\/li>\n<li><strong>Scale:<\/strong> the ratio between drawing size and actual size.<\/li>\n<li><strong>Annotation:<\/strong> any note, symbol, dimension or text added to a view.<\/li>\n<li><strong>Dimensioning:<\/strong> the practice of specifying sizes and positions. See <em>Engineering Dimensioning: Rules and Best Practices<\/em>.<\/li>\n<li><strong>Hole table:<\/strong> a table listing sizes and positions of holes, often used on plates.<\/li>\n<li><strong>Datum (drawing):<\/strong> a reference surface, axis or point that dimensions and tolerances are measured from.<\/li>\n<\/ul>\n<hr \/>\n<h2>7. Tolerances and Fits<\/h2>\n<ul>\n<li><strong>Nominal size:<\/strong> the theoretical size of a feature, such as 25 mm.<\/li>\n<li><strong>Tolerance:<\/strong> the permitted variation from nominal. A dimension of 25 plus or minus 0.1 mm may range from 24.9 to 25.1.<\/li>\n<li><strong>Limits:<\/strong> the maximum and minimum permitted sizes.<\/li>\n<li><strong>Fit:<\/strong> the relationship between two mating parts, such as a shaft in a hole. It may be a <strong>clearance fit<\/strong> (always a gap), an <strong>interference fit<\/strong> (always tight) or a <strong>transition fit<\/strong> (either). See <em>Fits and Tolerances: Clearance, Transition, and Interference Fits<\/em>.<\/li>\n<li><strong>Tolerance stack-up:<\/strong> the accumulation of tolerances across several parts or features, affecting whether an assembly fits. See <em>Tolerance Stack-Up Analysis for Mechanical Assemblies<\/em>.<\/li>\n<li><strong>General tolerances:<\/strong> default tolerances stated in a note or title block for dimensions without specific ones.<\/li>\n<li><strong>Datum (GD&amp;T):<\/strong> a theoretical reference defined by a real feature, used as the starting point for geometric tolerances. See <em>Datums and Datum Reference Frames in Mechanical Design<\/em>.<\/li>\n<li><strong>Feature control frame:<\/strong> the rectangular symbol that states a geometric tolerance, its value and its datum references. See <em>Understanding GD&amp;T Symbols and Feature Control Frames<\/em>.<\/li>\n<li><strong>Surface finish (roughness):<\/strong> the texture of a surface, specified by symbols and values. See <em>Surface Finish and Surface Roughness Symbols Explained<\/em>.<\/li>\n<li><strong>ASME Y14.5 and ISO GPS:<\/strong> the main standards families for dimensioning and tolerancing. See <em>ASME Y14.5 vs. ISO GPS: Understanding the Differences<\/em>.<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"\/wp-content\/uploads\/mcad-guides\/mcad-terminology-02-fit-types.png\" alt=\"Tolerance zones for clearance, transition and interference fits using H7 g6, k6 and p6 examples\" \/><\/p>\n<p><em>Figure 3. Clearance, transition and interference fits compared.<\/em><\/p>\n<hr \/>\n<h2>8. Manufacturing Terms<\/h2>\n<ul>\n<li><strong>CNC (Computer Numerical Control):<\/strong> machine tools controlled by programmed instructions, such as milling machines and lathes.<\/li>\n<li><strong>Toolpath:<\/strong> the path a cutting tool follows to machine a part.<\/li>\n<li><strong>Post-processor:<\/strong> software that translates toolpaths into the specific code format of a particular machine.<\/li>\n<li><strong>Milling and turning:<\/strong> machining by rotating cutters over a stationary part, and by rotating the part against a stationary tool.<\/li>\n<li><strong>Sheet metal:<\/strong> parts made from flat metal sheet, cut and bent.<\/li>\n<li><strong>Flat pattern:<\/strong> the unfolded shape of a bent sheet metal part, used for cutting.<\/li>\n<li><strong>Bend allowance and K-factor:<\/strong> values used to compute how much material a bend consumes. The K-factor describes where the neutral line sits within the thickness. See <em>Understanding Bend Allowance, Bend Deduction, and K-Factor<\/em>.<\/li>\n<li><strong>Weldment:<\/strong> an assembly of parts joined by welding, typically frames and structures. See <em>Weldment Design and Modeling in Mechanical CAD<\/em>.<\/li>\n<li><strong>Casting and injection molding:<\/strong> forming parts by pouring or injecting material into a mold.<\/li>\n<li><strong>Parting line:<\/strong> the line where mold halves meet.<\/li>\n<li><strong>Undercut:<\/strong> a feature that prevents a part from being released from a simple two-part mold or accessed by a cutter.<\/li>\n<li><strong>Wall thickness:<\/strong> the thickness of the walls of a molded, cast or hollow part. Uniformity is usually the goal.<\/li>\n<li><strong>Additive manufacturing (3D printing):<\/strong> building parts layer by layer. See <em>Design for Additive Manufacturing (DfAM): A Complete Guide<\/em>.<\/li>\n<li><strong>Jig and fixture:<\/strong> devices that hold or guide a workpiece during manufacturing or inspection. See <em>Designing Jigs, Fixtures, and Manufacturing Tooling<\/em>.<\/li>\n<li><strong>Prototype:<\/strong> an early physical version, used to test form, fit or function.<\/li>\n<li><strong>First article:<\/strong> the first production part, inspected in detail against the drawing.<\/li>\n<\/ul>\n<hr \/>\n<h2>9. Simulation Terms<\/h2>\n<ul>\n<li><strong>Mesh:<\/strong> the network of small elements into which a model is divided for analysis.<\/li>\n<li><strong>Element:<\/strong> a small piece of the mesh, such as a tetrahedron or hexahedron.<\/li>\n<li><strong>Mesh convergence:<\/strong> refining the mesh until the results stop changing significantly. See <em>Understanding Mesh Generation and Mesh Convergence in FEA<\/em>.<\/li>\n<li><strong>Load:<\/strong> a force, pressure, torque, temperature or other action applied to a model.<\/li>\n<li><strong>Constraint (fixture, support) in simulation:<\/strong> a condition that holds the model in place. Note that this word means something different from an assembly constraint.<\/li>\n<li><strong>Boundary conditions:<\/strong> the full set of loads and supports. See <em>Loads, Constraints, and Boundary Conditions in Mechanical Simulation<\/em>.<\/li>\n<li><strong>Stress:<\/strong> internal force per unit area.<\/li>\n<li><strong>Von Mises stress:<\/strong> a combined stress value commonly used to judge whether ductile materials will yield.<\/li>\n<li><strong>Strain and deformation (displacement):<\/strong> how much a part stretches or moves under load.<\/li>\n<li><strong>Factor of safety:<\/strong> the ratio between material strength and applied stress.<\/li>\n<li><strong>Modal analysis:<\/strong> finding the natural frequencies and shapes of vibration of a structure.<\/li>\n<li><strong>Kinematics:<\/strong> studying motion without considering forces. <strong>Dynamics<\/strong> includes forces.<\/li>\n<li><strong>Topology optimization and generative design:<\/strong> methods that propose shapes by removing material that carries little load. See <em>Topology Optimization and Generative Design in Mechanical Engineering<\/em>.<\/li>\n<\/ul>\n<hr \/>\n<h2>10. Files, Data and Change Management<\/h2>\n<ul>\n<li><strong>Native file:<\/strong> a file in the software&#8217;s own format, such as <code>.ipt<\/code> and <code>.iam<\/code> in Autodesk Inventor, or <code>.sldprt<\/code> and <code>.sldasm<\/code> in SOLIDWORKS.<\/li>\n<li><strong>Neutral file:<\/strong> a file in a vendor-independent format, such as <strong>STEP<\/strong>, <strong>IGES<\/strong>, <strong>STL<\/strong>, <strong>DXF<\/strong> or <strong>3MF<\/strong>. See <em>Native vs. Neutral CAD File Formats: Advantages and Risks<\/em>.<\/li>\n<li><strong>STEP:<\/strong> a widely used international standard for exchanging 3D product data. See <em>STEP Files Explained: Uses, Advantages, and Limitations<\/em>.<\/li>\n<li><strong>STL:<\/strong> a mesh format used mainly for 3D printing. See <em>STL vs. STEP vs. 3MF: Choosing the Right 3D File Format<\/em>.<\/li>\n<li><strong>DWG and DXF:<\/strong> drawing file formats, originating in AutoCAD and widely supported.<\/li>\n<li><strong>Metadata (properties):<\/strong> information attached to a file: part number, description, material, author, revision.<\/li>\n<li><strong>Part number and item number:<\/strong> the part number identifies the part uniquely across the company. The item number is the line position in one particular BOM. They are not the same.<\/li>\n<li><strong>Check-in \/ check-out:<\/strong> taking a file from the vault to edit and returning it. Prevents two people from overwriting each other.<\/li>\n<li><strong>Vault:<\/strong> the secure repository managed by a PDM system. Autodesk Vault is a well-known example.<\/li>\n<li><strong>Version:<\/strong> one saved state of a file. Versions accumulate during work.<\/li>\n<li><strong>Revision:<\/strong> a formally released and approved state, usually labeled A, B, C or 1, 2, 3. See <em>CAD Version Control vs. Revision Control Explained<\/em>.<\/li>\n<li><strong>Released \/ in work \/ obsolete:<\/strong> common lifecycle states for documents.<\/li>\n<li><strong>Where used \/ contains:<\/strong> relationships showing which assemblies use a part, or which parts an assembly includes.<\/li>\n<li><strong>Engineering BOM and Manufacturing BOM (EBOM and MBOM):<\/strong> the BOM as the designer sees it, versus the BOM as production builds it. See <em>Engineering BOM vs. Manufacturing BOM: Key Differences<\/em>.<\/li>\n<li><strong>Digital thread:<\/strong> the continuous link of data from design through manufacturing and service. See <em>Building a Digital Thread from Mechanical CAD to Manufacturing<\/em>.<\/li>\n<\/ul>\n<hr \/>\n<h2>Same Idea, Different Names: A Cross-Software Table<\/h2>\n<p>Moving between systems is easier when you realize that the concepts are shared and only the labels change. Here is a quick comparison for popular systems. Exact names can differ between versions, so treat this as an orientation.<\/p>\n<div style=\"overflow-x:auto\">\n<table class=\"mcadai-table\">\n<thead>\n<tr>\n<th>Concept<\/th>\n<th>Autodesk Inventor<\/th>\n<th>Autodesk Fusion<\/th>\n<th>SOLIDWORKS<\/th>\n<th>PTC Creo<\/th>\n<th>Siemens NX<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><strong>History list<\/strong><\/td>\n<td>Model browser<\/td>\n<td>Browser and timeline<\/td>\n<td>FeatureManager design tree<\/td>\n<td>Model tree<\/td>\n<td>Part navigator<\/td>\n<\/tr>\n<tr>\n<td><strong>Part file<\/strong><\/td>\n<td><code>.ipt<\/code><\/td>\n<td>Design in the cloud (<code>.f3d<\/code>)<\/td>\n<td><code>.sldprt<\/code><\/td>\n<td><code>.prt<\/code><\/td>\n<td><code>.prt<\/code><\/td>\n<\/tr>\n<tr>\n<td><strong>Assembly file<\/strong><\/td>\n<td><code>.iam<\/code><\/td>\n<td>Design with components<\/td>\n<td><code>.sldasm<\/code><\/td>\n<td><code>.asm<\/code><\/td>\n<td><code>.prt<\/code> (assembly)<\/td>\n<\/tr>\n<tr>\n<td><strong>Drawing file<\/strong><\/td>\n<td><code>.idw<\/code> or <code>.dwg<\/code><\/td>\n<td>Drawing<\/td>\n<td><code>.slddrw<\/code><\/td>\n<td><code>.drw<\/code><\/td>\n<td>Drawing in <code>.prt<\/code><\/td>\n<\/tr>\n<tr>\n<td><strong>Assembly relationship<\/strong><\/td>\n<td>Constraint, joint<\/td>\n<td>Joint<\/td>\n<td>Mate<\/td>\n<td>Constraint<\/td>\n<td>Assembly constraint<\/td>\n<\/tr>\n<tr>\n<td><strong>Variants<\/strong><\/td>\n<td>iPart, iAssembly, parameters<\/td>\n<td>Parameters, configurations<\/td>\n<td>Configurations, design tables<\/td>\n<td>Family tables<\/td>\n<td>Part families, expressions<\/td>\n<\/tr>\n<tr>\n<td><strong>Reference geometry<\/strong><\/td>\n<td>Work plane, axis, point<\/td>\n<td>Construction plane, axis, point<\/td>\n<td>Reference plane, axis, point<\/td>\n<td>Datum plane, axis, point<\/td>\n<td>Datum plane, axis, point<\/td>\n<\/tr>\n<tr>\n<td><strong>Sheet metal<\/strong><\/td>\n<td>Sheet Metal environment<\/td>\n<td>Sheet metal<\/td>\n<td>Sheet metal<\/td>\n<td>Sheet metal<\/td>\n<td>Sheet metal<\/td>\n<\/tr>\n<tr>\n<td><strong>Welded structures<\/strong><\/td>\n<td>Frame Generator, weldment<\/td>\n<td>Limited, via add-ons<\/td>\n<td>Weldments<\/td>\n<td>Frame and weld tools<\/td>\n<td>Structural and weld tools<\/td>\n<\/tr>\n<tr>\n<td><strong>Data management<\/strong><\/td>\n<td>Autodesk Vault<\/td>\n<td>Cloud-based project and data management<\/td>\n<td>SOLIDWORKS PDM<\/td>\n<td>Windchill<\/td>\n<td>Teamcenter<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<p>If you are choosing or comparing systems, see <em>Best Mechanical CAD Software for Professional Engineers<\/em> and <em>How to Migrate from One Mechanical CAD System to Another<\/em>.<\/p>\n<hr \/>\n<h2>The Confusions I See Most Often<\/h2>\n<p>Having trained many classes, I can predict which pairs of terms will cause trouble.<\/p>\n<ol>\n<li><strong>Version vs. revision.<\/strong> A version is a save. A revision is a formal, approved issue. A part may have forty versions and be on revision B.<\/li>\n<li><strong>Part number vs. item number.<\/strong> One identifies the part, the other the row in a BOM.<\/li>\n<li><strong>Constraint (sketch) vs. constraint (assembly) vs. constraint (simulation).<\/strong> Same word, three meanings: a geometric rule in a sketch, a positional relationship between components, and a support in an analysis.<\/li>\n<li><strong>Datum (CAD reference) vs. datum (GD&amp;T).<\/strong> One is a plane or axis used for modeling; the other is a reference on the real part used for tolerancing.<\/li>\n<li><strong>Assembly vs. subassembly.<\/strong> Often the same file type, only the role differs.<\/li>\n<li><strong>Parametric vs. direct.<\/strong> Not opposites. Many systems use both.<\/li>\n<li><strong>Model vs. drawing.<\/strong> The model is the master. The drawing is a report derived from it, and also the contractual document in many industries.<\/li>\n<li><strong>Tolerance vs. fit.<\/strong> A tolerance is for one feature. A fit is the relationship between two features.<\/li>\n<li><strong>Native vs. neutral.<\/strong> Neutral formats lose some information, particularly history and intent.<\/li>\n<li><strong>Configuration vs. revision.<\/strong> A configuration is a variant that coexists. A revision is a replacement over time.<\/li>\n<\/ol>\n<p><img decoding=\"async\" src=\"\/wp-content\/uploads\/mcad-guides\/mcad-terminology-04-version-vs-revision.png\" alt=\"Timeline showing many saved versions and three released revisions A, B and C\" \/><\/p>\n<p><em>Figure 4. Versions track your work; revisions are the formal releases.<\/em><\/p>\n<hr \/>\n<h2>A Short Learning Strategy for Vocabulary<\/h2>\n<p>If you want the terminology to stick, here is what has worked for my students.<\/p>\n<ul>\n<li><strong>Learn terms in context.<\/strong> When you build your first part, name each concept as you use it.<\/li>\n<li><strong>Read real drawings.<\/strong> Ask a machinist or a supplier to show you drawings from the shop floor.<\/li>\n<li><strong>Keep a personal glossary.<\/strong> Add terms as you meet them, with an example from your own work.<\/li>\n<li><strong>Ask what the term means in your company.<\/strong> Many teams use local variants of words. Write the local definition down.<\/li>\n<li><strong>Teach someone else.<\/strong> Explaining a term is the best test of whether you understand it.<\/li>\n<li><strong>Respect the standards.<\/strong> Where a term is defined in ASME or ISO documents, the standard is the authority. See <em>Mechanical CAD Standards: A Complete Guide<\/em>.<\/li>\n<\/ul>\n<hr \/>\n<h2>Final Thoughts<\/h2>\n<p>I sometimes tell my trainees that CAD is two languages at once. One is the language of the software: buttons, menus and commands that change every year. The other is the language of engineering: features, tolerances, fits, datums and revisions that have barely changed in decades. <strong>Learn the second one deeply, and the first one will always be learnable.<\/strong><\/p>\n<p>Use this glossary as a map, not a test. Return to it whenever a term trips you up. And when someone on your team uses a word differently from you, do not argue; write the definition down and agree on it. That small act will prevent more errors than any software feature.<\/p>\n<p><strong>Where to go next:<\/strong> continue with <em><a href=\"https:\/\/mcadauthority.com\/?p=54\">Understanding Parts, Assemblies, Drawings, and BOMs in MCAD<\/a><\/em>, which shows how the four core deliverables relate, and then <em><a href=\"https:\/\/mcadauthority.com\/?p=52\">The Complete Mechanical CAD Workflow: From Concept to Manufacturing<\/a><\/em> to see these terms in a real project sequence.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In my first week on any new team, I run a small, slightly mischievous experiment. I ask three people the same question: &#8220;What is the difference between a version and a revision?&#8221; It is rare to get three identical answers.\u2026<\/p>\n","protected":false},"author":1,"featured_media":101,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[37,19,36],"class_list":["post-53","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-fundamentals","tag-glossary","tag-mcad-basics","tag-terminology"],"_links":{"self":[{"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/posts\/53","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=53"}],"version-history":[{"count":1,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/posts\/53\/revisions"}],"predecessor-version":[{"id":57,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/posts\/53\/revisions\/57"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=\/wp\/v2\/media\/101"}],"wp:attachment":[{"href":"https:\/\/mcadauthority.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=53"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=53"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mcadauthority.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=53"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}