What is a CMM?
A CMM, or Coordinate Measuring Machine, is a precision measurement system used to inspect parts by collecting points in 3D space and comparing them to a drawing or CAD model.
In simple terms: a CMM tells you whether a part is the right size and shape, and whether critical features are in the correct locations.
What a CMM does
A CMM measures the X, Y, and Z coordinates of points on a part. From those points, it can calculate things like:
- dimensions (lengths, diameters, thickness)
- feature locations (hole patterns, datums)
- form (flatness, straightness, roundness)
- GD&T results (position, profile, perpendicularity, etc.)
- pass or fail reports for inspection and quality records
How a CMM measures parts
Most CMMs measure using a probe. Two common methods are:
Touch probing (tactile)
- The probe touches the part at specific points
- Best for feature inspection and tight tolerances
Scanning
- The probe or sensor collects many points along a surface
- Useful for freeform shapes and faster surface coverage
Some systems also use non-contact sensors like laser scanning, but traditional CMM work is still largely tactile probing.
Common types of CMMs
Bridge CMM
- The most common style
- Typically used in a quality lab or controlled area
Shop-floor CMM
- Built to handle harsher environments
- Designed for faster checks closer to production
Why companies use CMMs
CMMs are used because they provide measurement results that are:
- accurate and repeatable
- traceable for customer requirements and audits
- consistent across operators when the process is standardized
- faster than manual measurement for complex parts
They are common in machining, aerospace, automotive, medical, and any industry where tolerances matter.
What you need for a CMM to be useful
A CMM is not just the machine. A complete system usually includes:
- probing hardware (probe head, stylus kits, reference sphere)
- measurement software and reporting tools
- fixturing strategy so parts repeat in the same position
- a stable environment (temperature control helps a lot)
- verification and calibration plan
Bottom line
A CMM is a 3D inspection tool that measures parts with high accuracy, generates quality reports, and helps manufacturers catch problems before parts ship.
If you tell me what kind of parts you measure and where the CMM would live (lab vs shop floor), Made to Measure can recommend the CMM type that fits best and what to budget for beyond the machine itself.