Introduction to CMM Arms 362

“Introduction to CMM Arms” provides an overview of the components and functions of a portable coordinate measuring machine arm, or CMM arm. Portable CMM arms are used to measure workpiece features and record their coordinate locations with software. CMM arms measure using either contact or noncontact methods and can be used in most environments on the production floor.

CMM arms are used for many applications in manufacturing, including inspection, rapid prototyping, and reverse engineering processes. After taking this class, users will be able to describe CMM arms and best practices for using them.

Class Details

Class Name:
Introduction to CMM Arms 362
Difficulty:
Advanced
Number of Lessons:
13

Class Outline

  • Coordinate Measuring Machines
  • Portable CMMs
  • CMM Arms
  • CMM Arm Applications
  • Review: CMM Arm Introduction
  • Parts of a CMM Arm
  • CMM Coordinate Systems
  • Alignment
  • Workholding
  • Review: CMM Parts and Setup
  • CMM Arm Operation
  • Data Collection and Output
  • Final Review

Objectives

  • Describe CMMs.
  • Distinguish between types of portable CMMs.
  • Describe CMM arms.
  • Describe CMM arm applications.
  • Identify the components of a CMM arm.
  • Describe CMM coordinate systems.
  • Describe CMM arm alignment.
  • Describe part workholding when using a CMM arm.
  • Describe CMM arm operation.
  • Describe CMM arm data.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
3D Three-dimensional. Having or appearing to have length, breadth, and depth. 3D models show an object's shape better than two-dimensional drawings.
adhesives A chemical material used to bond two objects together. Adhesives are often used to stabilize smaller parts during inspection.
alignment The process of arranging components so that they are lined up. Alignment of a CMM arm occurs when the part coordinate system matches the machine coordinate system.
articulated Consisting of segments connected by joints. Articulated CMM arms move in many directions.
automated Controlled by machines or computers with little human interaction. Automated CMMs can measure parts once programed.
axes An imaginary line or circle that is used to define the position of an object in space. The linear axes are X, Y, and Z.
base The foundation of a machine that supports all other machine components. The base stabilizes the machine and provides it with rigidity.
bridge A machine part that provides support and allows movement. On a CMM, the bridge is a horizontal beam that provides a stable area for movement of the probe.
CAD 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 arm how to inspect a part.
climate-controlled Having artificially regulated air temperature, humidity, and movement. Climate-controlled environments are not necessary for portable CMMs.
CMM arms A portable measuring device consisting of segments connected by joints. CMM arms operate using either contact or noncontact methods.
CMMs 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 arm how to inspect a part.
contact probes A type of probe consisting of a synthetic ruby-tipped stylus that makes physical contact with a workpiece. A contact probe records one single point each time it touches a part's surface.
control system A manual or automatic mechanism used to manage dynamic processes. Control systems in CMM arms power and operate the measuring device and record data for inspection.
coordinate measuring machines CMM. 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.
coordinate system A system that uses three linear axes to describe the location of an object in three-dimensional space. A coordinate system expresses the location of any point as the distance from it to the origin, or the fixed intersection of axes.
counterbalanced Weighted so as to stabilize opposing force. Counterbalanced linkage arms in a CMM arm increase its stability and ease of operation.
datum A point of reference for machine tools, programs, and fixtures from which measurements are taken. A datum acts as the origin of the part coordinate system.
deviations The difference between a standard and a result. Deviations can lead to parts that do not meet specifications.
distance meter An instrument that uses a laser to accurately determine the distance of an object without contacting it. Distance meters are highly accurate and can measure far distances.
distortion Warpage in a workpiece due to stresses caused by exposure to pressure and other manufacturing forces. Distortion can be prevented through proper use of workholding devices.
fixed CMMs A stationary coordinate measuring machine. Fixed CMMs have a large base with a suspended probe and are operated in a controlled environment.
fixtures 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.
geometry The measurement, properties, and relationships of the lines and points of an object that make up its shape. Geometry is used when measuring and designing parts.
home position The central point from which a machine begins an operation. The home position acts as the origin of the machine coordinate system.
in-process Currently being produced by manufacturing. In-process parts are found throughout the process of turning raw material into finished products.
inspection 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.
joints A place where two things or parts are connected. The joints in a CMM arm allow the device to move freely and to measure several different kinds of parts.
laser A device that generates an intense beam of light that can be precisely aimed and controlled. Lasers are projected on a part's surface to scan position coordinates.
laser scanner A portable measuring device that uses a beam of light to measure an object's geometric shape. Laser scanners are noncontact probes.
laser trackers A portable measuring device that projects a beam of light at a retroreflective target to measure large objects. Laser trackers require a person to hold a target on the object being measured.
linkage arms Separate segments of an articulated arm connected by joints. Linkage arms are lightweight and rotate on the CMM arm's axes.
machine coordinate system A fixed coordinate system that has the machine's home position as its origin. The machine coordinate system's X, Y, and Z axes are mapped to the components of the machine and remain the same for every part.
metrology The science of measurement. Metrology strives for accuracy, precision, and repeatability.
modular wrist A handheld, movable grip at the end of a CMM arm that holds probes. A modular wrist can fully rotate on an axis.
nominal A stated measurement that may not correlate exactly with a physical part. Nominal measurements for a part indicate the size specified in the blueprint, which may differ from the size of the actual part.
noncontact probe A type of probe that consists of a laser or scanning system that does not physically contact the part surface. Noncontact probes are used to streamline surface inspection.
on-machine Relating to or being on a machine. On-machine parts can easily be measured with a CMM arm.
orientation Position in three-dimensional space. Orientation is determined by the vectors in a coordinate system.
origin The fixed, central point in a coordinate system where the axes meet. The origin has a numerical value of zero.
part coordinate system A unique coordinate system that has a feature or datum of a specific workpiece as its origin. A part coordinate system's X, Y, and Z axes are mapped to the features of the specific workpiece.
pistol grip handle A handheld, movable handle with an extra rotating axis at the end of a CMM arm that holds probes. A pistol grip handle can provide better accuracy when scanning an object with a laser scanner.
portable CMMs A coordinate measuring machine that can be easily carried or moved. Portable CMMs can be used on the factory floor.
prints A document that contains the instructions necessary to manufacture and/or assemble a part. Prints include the degree of tolerance necessary for the part to function as intended.
probe A device that gathers measurement data from the workpiece. The probe on the CMM arm is attached to the modular wrist or handle and uses either contact or noncontact methods to measure a part.
quality control A system of managing quality by inspecting finished products to make sure they meet specifications. Quality control relies on error detection and correction.
quality report A document of measurement data used for inspection. Quality reports provide the information needed to determine the dimensional accuracy of parts.
rapid prototyping A product development technique that uses additive manufacturing (AM) to create prototypes for a traditional manufacturing operation. Rapid prototyping allows engineers to quickly create a number of prototypes in a short time period.
restrained Securely held in place so as to limit mobility. Restrained parts are held by fixtures or other workholding to keep them in place during inspection.
retroreflective Reflecting light back in the direction from where it came. Retroreflective targets are used with laser trackers.
reverse engineering A process that captures geometric data of an existing object to convert it to a three-dimensional (3D) computer-aided design (CAD) model. Reverse engineering can be used to create a reproduction based on a part's composition.
rotary encoders A device that translates angular position or motion into a digital signal. Rotary encoders in the joints of a CMM arm detect the incremental lines on a scale to determine positioning.
stylus A precision tip that records measurements. The stylus on the CMM arm is the spherical portion of the contact probe that is mounted to the wrist and makes contact with the part.
three-dimensional 3D. Having or appearing to have length, breadth, and depth. Three-dimensional models show an object's shape better than two-dimensional drawings.
tolerances An unwanted but acceptable variation or deviation from a desired dimension of a part. A part within tolerances will meet specifications and pass inspection.
unrestrained Free of external force or restrictions that would limit movement. Unrestrained parts are large enough or heavy enough to not need workholding during inspection.
vacuum Any device that uses suction. Vacuum-powered stands draw air rapidly, providing a portable CMM with a stable, rigid base.
vectors A set of numbers specifying a direction in 3D space. Vectors are used when determining the exact orientation of a part.
white light scanners A portable measuring device that projects a grid of light on an object and scans an image of it to record 3D surface measurements. White light scanners may take several scans before gathering all the dimensional data.
workholding A device used to secure, support, and locate a workpiece during a manufacturing operation. Workholding helps to ensure that parts are created accurately and with good repeatability.
X axis The linear axis representing side-to-side movement in a device, relative to the origin. A CMM arm uses the X, Y, and Z axes as reference.
Y axis The linear axis representing back-and-forth movement in a device, relative to the origin. A CMM arm uses the X, Y, and Z axes as reference.
Z axis The linear axis that represents up-and-down movement in a device, relative to the origin. A CMM arm uses the X, Y, and Z axes as reference.