What Is a CMM Machine? Coordinate Measuring Machine Guide

A Coordinate Measuring Machine (CMM) is a device used to measure the geometry of physical objects. It employs a probing system to detect discrete points on the surface of an object, providing precise measurements.

The first CMM appeared in the early 1960s. Originally developed by the Ferranti Company in Scotland in the 1950s, this two-axis machine used a 3D tracing device with a basic digital readout to display XYZ positions. Ferranti utilized the CMM to measure components for military products. By the late 1960s, three-axis models were introduced.

CMMs are primarily used to test parts and assemblies, ensuring they meet the original design specifications. Integrated into quality assurance (QA) or quality control (QC) workflows, CMMs help inspect the dimensions of manufactured components, identifying or preventing quality issues.

CMMs offer significant advantages over manual inspections using traditional tools like micrometers and height gauges, including increased accuracy, speed, and a reduction in human error.

There are various types of CMMs, typically categorized by their structures, with each offering specific advantages and drawbacks. Let’s explore the different CMM types in more detail.

Types of CMMs

1. Bridge CMM

Bridge CMMs use a probing system that moves along three orthogonal axes (X, Y, and Z) in a Cartesian coordinate system. The machine detects points on an object’s surface, creating a point cloud that represents the area of interest. Bridge CMMs are often divided into two sub-types: moveable-table and moveable-bridge systems.

Pros of Bridge CMMs

  • Extremely accurate
  • Ideal for measuring parts with high precision tolerances
  • Great for small to medium-sized components
  • Capable of multi-sensor measurements, such as probing and scanning

Cons of Bridge CMMs

  • Expensive
  • Fixed measurement volume
  • Lack of portability (the part must be brought to the machine or moved with machinery)
  • Sensitive to vibrations, requiring use in a metrology lab
  • Complex to operate and requiring skilled operators
  • Requires rigid setups for each inspected part

2. Gantry CMM

Similar to bridge CMMs, gantry CMMs are typically much larger and designed to handle heavier or larger parts. They are mounted on a solid foundation, directly on the floor.

Pros of Gantry CMMs

  • High accuracy
  • Large measurement volume, suitable for large or heavy parts
  • Easier to load and unload components compared to bridge CMMs

Cons of Gantry CMMs

  • Expensive
  • Fixed measurement volume
  • Lack of portability
  • Large footprint and takes up significant floor space
  • Sensitive to vibrations and needs to be used in a metrology lab
  • Complex operation requiring skilled operators

3. Cantilever CMM

Cantilever CMMs differ from bridge CMMs by having a measuring head attached only to one side of a rigid base, providing easier access for operators on all three sides.

Pros of Cantilever CMMs

  • High accuracy
  • Ideal for smaller parts
  • Open access on three sides makes loading/unloading easier

Cons of Cantilever CMMs

  • Expensive
  • Fixed measurement volume
  • Lack of portability
  • Sensitive to vibrations and must be used in a controlled environment
  • Requires rigid setups for each part
  • Complex operation requiring skilled personnel

4. Horizontal Arm CMM

Horizontal arm CMMs feature horizontally mounted probes, designed to measure long and thin objects, such as sheet metal. These are useful for geometries that are challenging to access with vertical CMMs.

Pros of Horizontal Arm CMMs

  • Suitable for long, thin parts
  • Good for parts with low tolerances
  • Does not require an extensive foundation system
  • Easy to install with a smaller footprint

Cons of Horizontal Arm CMMs

  • Less accurate than other CMMs
  • Fixed measurement volume
  • Lack of portability
  • Sensitive to vibrations and should be used in a metrology lab
  • Requires rigid setups and skilled operators

5. Portable Measuring Arm CMM

Portable measuring arm CMMs are designed for on-site measurement, allowing inspectors to take measurements on the shop floor, providing quick, real-time data. These CMMs can be articulated (6- or 7-axis systems) to measure components directly in their assemblies.

Pros of Portable Measuring Arm CMMs

  • Portable and lightweight
  • Can measure parts wherever they are located
  • Extendable measurement volume
  • Multi-sensor capabilities (probing and scanning)
  • Cost-effective and easy to operate

Cons of Portable Measuring Arm CMMs

  • Less accurate than other CMM types
  • Sensitive to environmental vibrations
  • Requires rigid setups

6. Optical CMM

Optical CMMs are non-contact devices that use optical triangulation methods to scan and obtain 3D measurements of objects. They are fast and provide metrology-grade accuracy, making them suitable for Industry 4.0 manufacturing.

Pros of Optical CMMs

  • Portable and lightweight
  • Can measure components directly at their location
  • Extendable measurement volume
  • Quick measurement acquisition times
  • Cost-effective and easy to operate

Cons of Optical CMMs

  • Slightly less accurate compared to conventional CMMs, depending on the application

Why CMM Speed Matters

In today’s manufacturing environment, speed and efficiency are critical to meeting tight delivery schedules, increasing throughput, and reducing costs. When bottlenecks occur at CMMs, inspection times extend, driving up costs.

The need for faster CMMs has become apparent due to the high volume of work managed by a limited number of qualified metrologists. Traditional CMMs with probes tend to be slow, especially when measuring complex shapes. Meanwhile, newer CMMs, equipped with sensors, accelerate the process but still require expert handling.

Manufacturers are increasingly turning to advanced technologies like optical CMMs, which can keep pace with demanding production environments while meeting rigorous QA and QC standards. These systems help streamline inspections and ensure faster, more efficient workflows.

What Does CMM Stand For?

CMM stands for Coordinate Measuring Machine. A CMM measures the coordinates of points on a physical part and uses those points to evaluate dimensions, geometry, and GD&T requirements against a drawing or CAD model.

How Does a CMM Machine Work?

A CMM establishes a three-dimensional coordinate system and records points as a probe or sensor interacts with the part. CMM software then uses those points to construct and evaluate features such as planes, circles, cylinders, slots, holes, and surfaces. The resulting data can be compared with nominal dimensions and geometric tolerances and reported for quality decisions.

Modern CMM systems can use touch-trigger probes, continuous scanning probes, optical sensors, and other measurement technologies. The best configuration depends on the part size, tolerance, geometry, throughput requirement, and environment.

What Is a CMM Used For?

Manufacturers use CMMs for first article inspection, production inspection, incoming inspection, tooling and fixture verification, process development, reverse engineering, capability studies, and complex GD&T verification. Companies that do not have enough internal CMM capacity can also outsource work to a dimensional inspection and CMM service provider.

New vs Used CMM Machines

A new CMM can make sense when you need a specific measuring volume, accuracy, sensor package, warranty, or long-term platform. A properly evaluated and recertified used CMM can provide substantial value when the mechanical structure is sound and the controls, probing, software, and calibration strategy support the application.

Explore CMM equipment and used CMM machines, or talk with Made to Measure about matching a machine to your actual parts and tolerances.

CMM Software and Programming

The physical machine is only one part of a CMM system. Software controls programming, alignments, feature construction, GD&T evaluation, reporting, and automation. Different shops may prioritize ease of use, DMIS compatibility, offline programming, reporting, or an open-platform approach. See our CMM software options for more information.

CMM Calibration, Service and Support

A CMM must remain capable of producing trustworthy measurements throughout its life. Installation, relocation, calibration, preventative maintenance, controller and probing upgrades, and repair all affect uptime and measurement performance. Made to Measure provides CMM calibration, service, relocation, retrofit and repair support.

CMM and GD&T Training

Good hardware cannot compensate for weak measurement strategy. CMM programmers and inspectors need to understand alignments, probing strategy, drawing interpretation, and GD&T. Made to Measure offers metrology training, including AUKOM and GD&T training.

Frequently Asked Questions About CMM Machines

How accurate is a CMM?

CMM accuracy varies by machine design, measuring volume, probing configuration, environment, and calibration condition. The correct question is whether the complete measurement system is sufficiently capable for the tolerances you need to verify.

What is the difference between a CMM and a 3D scanner?

A traditional CMM commonly uses tactile probing to measure selected features with high accuracy and repeatability. A 3D laser scanner captures much denser surface data quickly. Each has advantages, and many inspection workflows use both technologies.

Can a CMM measure GD&T?

Yes. With appropriate software, programming, datum alignment, probing strategy, and operator knowledge, a CMM can evaluate many GD&T requirements including position, profile, flatness, perpendicularity, parallelism, runout, and others.

Should I buy a new or used CMM?

That depends on required accuracy, measuring volume, software, sensors, budget, serviceability, and expected throughput. A recertified used machine can be an effective option when its condition and configuration are properly verified.

Can Made to Measure inspect parts if I do not own a CMM?

Yes. Made to Measure provides contract dimensional inspection for manufacturers that need first article work, overflow capacity, complex measurement, or an independent inspection resource.

Need a CMM, CMM Support, or Inspection Capacity?

Made to Measure supports the full CMM lifecycle, from selecting new and recertified CMM equipment and software to service, calibration and contract inspection and training. Contact Made to Measure and tell us about your parts, tolerances, current equipment, and inspection goals.

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