Additive Manufacturing

Metrology for Additive Manufacturing 202

Metrology for Additive Manufacturing 202 offers an overview of common inspection tools and methods used in additive manufacturing (AM). Successfully measuring any AM part or process depends on accurate, precise inspection of AM part dimensions, surfaces, and internal structures. This class discusses common hand-held devices, such as calipers and micrometers, as well as other categories of dimensional measuring devices like contact coordinate measuring machines (CMMs), noncontact CMMs, optical comparators, and air gages.

Quality in AM depends on consistent measurement and inspection, which ensures that end-use parts are within tolerance and meet customer expectations. After taking this class, users will be able to describe the general uses and applications of common contact and noncontact inspection instruments and probes, as well as inspection considerations unique to AM and the smart manufacturing environment.

  • Difficulty Intermediate

  • Format Online

  • Number of Lessons 13

  • Language English


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Course Outline
  • The Importance of Metrology in Additive Manufacturing
  • Accuracy and Precision
  • AM Dimensions and Metrology
  • Metrology Tools and AM
  • AM Surface Textures and Metrology
  • Metrology and AM Part Interiors
  • Review: Metrology for AM Forms, Surfaces, and Part Interiors
  • CMMs and Contact Probes
  • Noncontact Probes
  • Metrology Issues for AM Inspection
  • Metrology Considerations for Post-Processing Inspection
  • Metrology and Smart Technology
  • Final Review
  • Describe the importance of metrology in additive manufacturing.
  • Distinguish between accuracy and precision.
  • Describe basic geometric tolerance and dimensioning specifications for metrology.
  • Describe basic metrology tools used with AM.
  • Describe basic metrology for AM surface textures.
  • Describe metrology for AM part interiors.
  • Describe contact probes for CMMs.
  • Describe types of noncontact probes.
  • Describe metrology issues for AM inspection.
  • Describe metrology considerations for post-processing inspection.
  • Describe metrology considerations for advanced technology.
Vocabulary Term


Two-dimensional. Having length and width, but not depth. Flat shapes are two-dimensional.


Three-dimensional. Having a length, depth, and width. Digital twins are generally designed using computer-aided design (CAD) software to make three-dimensional digital models of an asset.

3D scanners

A portable measuring device that uses light and sensors to measure an object's geometric shape. 3D scanners collect large amounts of surface data quickly.


The exactness of a measurement compared to the desired result. Accuracy means less error present in the measurement.

additive manufacturing

AM. The process of joining or solidifying materials to make an object based on a three-dimensional (3D) computer model. Additive manufacturing methods typically build up layers of material to create an object.

air gages

A variable, noncontact instrument that uses pressurized air to pneumatically inspect a hole's inside diameter. Air gages are best for measuring features with tight tolerances.


Additive manufacturing. The process of joining or solidifying materials to make an object based on a three-dimensional (3D) computer model. AM methods typically build up layers of material to create an object.


A fixed jaw against which an object to be measured is placed. On a micrometer, the anvil is an immobile block from which the measurement is taken.

binder jetting

An additive manufacturing (AM) method in which liquid binder is used to join powdered materials to create parts. Binder jetting can create parts out of metal, polymer, or ceramic.


A natural material that composes a part or all of a living structure. Biomaterials, such as living cells and tissues, can be used in some additive manufacturing (AM) methods.

bridge-type CMM

A type of CMM with two vertical supports and a horizontal beam holding the probe. The bridge-type CMM is the most common type.


Computer-aided design. A computer software program that aids in the automated design and technical precision drawing of a part, product, process, or building. CAD software can tell a CMM how to inspect a part.


The comparison and adjustment of a device with unknown accuracy to a device with a known, accurate standard. Calibration eliminates any variation in the device being checked.


A measuring instrument with a pair of jaws on one end and a long beam containing a marked scale of unit divisions. Caliper jaws can measure both internal and external features.


A general category of metalworking processes that involve pouring a liquid material into a hollow mold and allowing the material to cool into a solid shape. Casting includes methods such as investment and sand casting.


Coordinate measuring machines. A sophisticated measuring instrument that uses a suspended probe to measure parts in three-dimensional space. CMMs operate using either contact or noncontact methods.

computer-aided design

CAD. A computer software program that aids in the automated design and technical precision drawing of a part, product, process, or building. Computer-aided design software can tell a CMM how to inspect a part.

contact probe

A type of probe that directly contacts the surface of the part it is measuring. Contact probes are the most common types of probes.

continuous analog scanning

CAS. A method of gathering coordinates that requires a CMM stylus to stay in constant contact with the part's surface. Continuous analog scanning is especially useful for performing reverse engineering.

coordinate measuring machines

CMMs. A sophisticated measuring instrument that uses a suspended probe to measure parts in three-dimensional space. Coordinate measuring machines operate using either contact or noncontact methods.


The process of hardening a material through exposure to heat or another hardening agent, such as ultraviolet (UV) light. Curing is used to harden brittle additively manufactured parts created using powder-based methods and parts made from liquid photopolymer.


An imperfection in a part that prevents it from operating correctly. Defects can lead to reworked or scrapped parts, which increases the cost of a manufacturing operation.

destructive testing

A category of inspection processes that evaluate a part's properties and performance using methods that lead to part failure. Destructive testing renders a part unusable.


The difference between a standard and a result. Deviations can lead to parts that do not meet specifications.

digital thread

An integrated view of all the data and information about a machine or process throughout its lifecycle. The digital thread connects information from all aspects of a product into one seamless network.

digital twin

A virtual representation of a physical asset or part. A digital twin evolves with the asset throughout its product lifecycle.


The desired measurement of a feature on a part. Dimensions are listed on a blueprint as numerical values.

directed energy deposition

DED. An additive manufacturing process in which focused thermal energy is used to melt materials as they are deposited. Directed energy deposition is often used with powdered or wire metal.


A period of time when production stops, often due to mechanical failure or maintenance needs. Downtime reduces the efficiency of a manufacturing operation and should always be limited as much as possible.

eddy current testing

ECT. A nondestructive testing method that uses electromagnetic induction to locate surface and near-surface discontinuities and defects. Eddy current testing is limited to use on electrically conductive materials.


A defining characteristic on a component or part. Features include corners, edges, holes, and grooves.


A final process performed to achieve the specifications required for a part. Sanding, heat treating, and painting are examples of finishing.


A customizable, modular workholding device created by configuring locators, supports, and clamps on a body fixture. Fixtures are common workholding devices for CMM inspection because they allow a part to be accessible while secured in place.


An unintentional irregularity that may be random or repeating. In surface inspection, flaws are random surface defects that are generally not included in the measurement of the surface.

fused deposition modeling

FDM. A material extrusion process that builds parts through extruding successive layers of material. Fused deposition modeling is one of the most accessible and affordable types of additive manufacturing (AM), though it creates parts with poor surface finish and has relatively low build speed.

gaging instruments

A device with an established standard size used to determine whetherthat performs a physical inspection of part features are within specified limits. Gaging instruments provide results in a pass/fail or go/no-go results.

gantry-type CMM

A type of CMM similar to the bridge- type CMM but much larger. Gantry-type CMMs can measure parts the size of a car.

Industrial Internet of Things

IIoT. A network of physical devices used in manufacturing that contain computing systems that allow them to send and receive data. The Industrial Internet of Things allows devices to exchange data and automate processes without any human intervention.


The process of a substance entering a porous material in order to fill any empty spaces or voids. Infiltration is a specialized post-processing step that is sometimes used to harden and strengthen parts produced by binder jetting.


The examination of a part during or after its creation to confirm that it adheres to specifications. During inspection, defects may be identified and corrected.

internal diameter

ID. The interior surface of a spherical or cylindrical object. Internal diameter is also known as inner diameter.

International Organization for Standardization

ISO. An organization based in Switzerland that develops and publishes standards for various aspects of manufacturing and industry. The International Organization for Standardization is responsible for standards across a number of different industries.


A customizable, modular workholding device that supports, locates, and clamps a workpiece and also directs the cutting tool. Jigs are often used to hold irregular parts and generally decrease machine tool setup time as they provide guidance for tools.


A device that generates an intense beam of light that can be precisely aimed and controlled. Laser beams are used to measure and capture surface data.

laser probes

A measuring device that uses a narrow beam of light to take measurements. • Laser probes oOn a CMMs, the project a laser projects onto the part's surface, and a lens on the probe then reads the beam's position.


A repeating, symmetrical pattern of crossing strips of material that leave diamond- or square-shaped gaps between them. Lattices provide excellent strength to a part.

measured surface

The surface that represents the surface after it has been measured. The measured surface determines how much the real surface deviates from the nominal surface.


The act or process of measuring an object. Measurement uses units from either the English or metric system


The science of measurement. Metrology strives for accuracy, precision, and repeatability.


A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are available in numerous types for measuring assorted dimensions and features.


A type of traditional manufacturing process that involves pouring heated liquid into a reusable cavity that shapes the material as it solidifies and cools. Molding processes may use tooling produced through additive manufacturing.

nominal surface

The desired surface that described by a part'srepresents the desired specifications on a part drawing. The nominal surface does not have surface irregularities and is geometrically perfect.

noncontact probe

A type of probe that consists of a laser or scanning system that does not contact the part surface. Noncontact probes are used to inspect small, flexible parts.

nondestructive testing

NDT. A category of inspection processes that evaluate a part's properties and performance using methods that do not damage or permanently alter the part. Nondestructive testing methods can be used to locate discontinuities and defects in parts made by additive manufacturing processes.

optical comparators

A sophisticated measuring instrument that projects an image of a part onto a screen to compare the shape, size, and location of its features to the original. An optical comparator can give an accurate measurement of a profile within the plane of sharpness.

optical projectors

A measuring instrument that projects an image of a part onto a screen to compare the shape, size, and location of its features. Also called an optical comparator.


The smallest piece of information in an digital image. When joined together, pixels form a cohesive image.


A power transmission system that uses gas, such as compressed air, conveyed in a confined conduit under pressure to accomplish work. Powered by pressured gas, such as compressed air, conveyed in a confined conduit.

point cloud

A large collection of data points indicating locations on the surface of a three-dimensional object. Point clouds are typically used to create CAD models of objects.


The amount of small spaces or voids within a solid material. The measure of the open spaces, or voids, in a material. Porosity in athe material can potentially affect the durability of the partmay trap moisture beneath the coating and cause blisters.


A group of procedures that are used to clean, improve, or otherwise finish a part for use by a manufacturer or consumer. Post-processing for additively manufactured parts includes abrasive finishing, heat treatment, and painting.

powder bed fusion

PBF. An additive manufacturing method that uses thermal energy to melt together layers of powdered polymer, metal, ceramic, or other material. Powder bed fusion processes often use either lasers or electron beams as thermal energy sources.


The degree to which an instrument will repeat the same measurement over a period of time. Precision is also called repeatability, as it will show the same results under unchanged conditions.


The shape or outline of a part feature. Profiles generated with an optical comparator can give an accurate measurement within the plane of sharpness.


A stylus-type device that measures surface roughness. A profilometer amplifies its signal to compensate for waviness and indicate only roughness.


The satisfaction of customer requirements. Quality products conform to specifications, are free of defects, and meet the requirements of their anticipated use.

real surface

The actual part surface produced by a manufacturing process. The real surface contains imperfections.


Occurring at the same time or virtually the same time as actual events. Real-time insights are made possible because digital twins monitor the functions of a real-world asset Real-time insights are made possible because digital twins monitor the functions of a real-world asset as they occur.


The ability  of a machine or process to continually deliver consistent and uniform results. Repeatability is crucial for efficiently producing quality, identical parts.


Fine, closely spaced irregularities remaining on a part surface after manufacturing. Roughness is created by the production process.


A gemstone mineral that is wear resistant. A synthetic ruby sphere is often used as the stylus for CMMs.

secondary method

An additive manufacturing (AM) application other than creating a prototype or end-use part. SSecondary methods include using AM to help create a mold, repair a damaged workpiece, or build a model, among other processes.


A material manufacturing process that heats pressed and shaped powdered materials to create a solid shape. Sintering can be used to make both metal and ceramic products.


Able to connect to and send data across the internet.A device that can connect to the internet. Smart devices can track performance without human intervention.


A description of the essential physical and technical properties of a finished part. Specifications outline important information including finished part dimensions and how the part must respond to forces acting upon it.


A spherical portion of a CMM probe that is mounted on the shaft and makes contact with the part. The stylus is usually a synthetic ruby.

support material

Additional material used in the additive manufacturing process to support the product as it is being constructed. Support material is removed from the AM product as part of the additive manufacturing process.

surface finish

The degree of roughness and variation on the surface of a part after it has been manufactured. Due to irregularities created when building a part, surface finish cannot be perfectly smooth.

surface replica block

A surface that contains a specific standard roughness pattern. Surface replica blocks are used in comparison measurements.


A stylus-type device that measures surface roughness. Portable surfometer models can be carried in a pocket on the production floor.


3D. Having length, width, and depth. Three-dimensional models are used to create parts during additive manufacturing processes.


An acceptable deviation from a desired dimension that still meets part specifications. Tolerances indicate the allowable difference between a physical feature and its intended design.

tolerance range

The acceptable range of measurements produced by a given operation. The tolerance range is also known as the tolerance zone.

touch trigger probe

A type of contact probe that detects a feature on a part and generates an electronic signal to record its dimensions. Touch trigger probes are the most accurate and commonly used probes on the CMMs.

traditional manufacturing

A manufacturing process that involves creating a part by shaping or removing material from a workpiece. Traditional manufacturing operations include metal cutting and forming.


2D. Having height and width. Two-dimensional objects are flat and lack depth.

ultrasonic testing

UT. A nondestructive testing method that uses high-frequency ultrasonic waves to detect internal part discontinuities and defects. During ultrasonic testing, reflected sound waves are converted into electrical signals, which technicians then evaluate for any indications.

variable inspection

A type of inspection that reveals the degree of variation from a given standard. Unlike gaging, variable inspection does not result in a pass/fail decision and instead gives the actual measurement of a part feature that can then be compared to its specifications.


Any change or difference from the standard. A variation can signal that an error has occurred.

vat photopolymerization

An additive manufacturing (AM) method that builds a part by curing layers of photopolymer with light. Vat photopolymerization processes include stereolithography (SLA) and digital light processing (DLP).

wall thickness

The amount of material in a flat vertical barrier in a part. Wall thickness must fall within certain parameters for different additive manufacturing (AM) processes.


The repeating, widely-spaced irregularities of surface texture. Waviness can result from factors such as print speed and excess thermal energy.

x-ray computed tomography

x-ray CT. X-ray CT. An advanced radiographic nondestructive testing NDT method that creates a three-dimensional (3D) image of a part’s interior and exterior out of multiple two-dimensional (2D) radiographs. X-ray computed tomography, which is sometimes referred to as micro computed tomography (microCT ), produces high-resolution images that show very fine part details.