Chamfers

Chamfers are added to precision machined components to:

• limit possible fracture points for components under high stresses
• control air flow over components such as blades and nozzles
• ensure smooth fit, especially for precision fasteners
• reduce the chance of injury from sharp edges.

If your part chamfers are important, you’ll need to measure them accurately, consistently and quantitatively.

Visual inspection of chamfers 

Today, straight edge chamfers are most often* qualified by visual comparison against a known angle wedge. The component is accepted or rejected based on the experienced eye of the inspector.

But visual inspection, while fast and convenient, is subject to variability in alignment, lighting, and many other factors. More importantly, a visual test provides no quantitative data. While qualitative results may be enough for some applications, they are insufficient for controlling critical components such as those used in aircraft, engines, nuclear piping, etc.

*Based on several user surveys by 4D Technology of contacts who evaluate chamfers, conducted 2019-2021.

Stylus profiling is subject to variability

The most common, instrument-based method for assessing chamfers is the 2D stylus profiler. A stylus system may either be workstation-based, or it may be a portable instrument that can be placed directly on the component. While providing a fast measurement method, 2D profilers have several drawbacks:

• Measurement is only a single trace wide, not sufficient to define a plane. Further traces are required to understand the surface.
• Measurement is slow—with transport, set-up, jigging and site selection, often more than 30 minutes to achieve a single high-quality trace, and far longer to acquire multiple traces for sufficient sampling.
• Results are susceptible to variation in the measurement angle relative to the chamfer.
• Limited vertical range prevents measurement of larger chamfers.

These limitations mean multiple measurements—or, in critical applications, multiple inspectors—are required to get enough data to properly assess chamfers.

3D optical measurement provides quantitative production data

Precision machined part manufacturers rely on non-contact, 3D optical metrology to quantify chamfer geometries. 3D optical measurement provides quantitative results, reduces measurement time, and improves accuracy and repeatability. It also eliminates the alignment errors that hamper stylus-based measurements.

Getting chamfers right: calculating chamfer geometries

One major advantage of 3D measurement is the ability to calculate geometries based on best-fit planes, rather than from single traces. This added robustness greatly improves repeatability, by removing alignment variability from the equation. Chamfer size, angles, and other data are rapidly acquired from a single measurement.

The 4D InSpec gauge uses Polarized Structured Light, a measurement technique with vertical resolution better than 2 micrometers  over a 2.5mm vertical range. You get enough resolution for gauge-capable measurement of chamfers on most precision machined parts, which typically require tolerances of 150-300 micrometers.

In this image the 4D InSpec is being used to measure the chamfer at the top of a through hole.

Here is the resulting data as shown in the 4D InSpec software.

4D InSpec XL for larger features

For larger measurements, the 4D InSpec XL provides the same, micrometer-level resolution, portability and ease-of-use but with a larger field of view and higher scan range. Measure features up to 0.6″ x 0.6″ (15mm) across and report results in about a second.