Understanding the features of a non-contact metrology platform versus a traditional contact coordinate measuring machine (CMM) can help manufacturers choose the right equipment for inspection.

By investing in the right inspection technology, manufacturers can improve product quality while reducing manufacturing costs.
Manufacturers may perform inspection based on a sampling or 100% inspection of the parts. The inspection method may depend on several factors, such as cost of inspection per part, the destructive or non-destructive nature of the test, and the capability of the part creation process. Non-contact metrology platforms and CMMs may be suitable for different applications, depending on the volume and complexity of the parts processed.

Traditional CMMs

Traditional contact CMMs use a mechanical probe to sense discrete points on the surface of the part. Touch probes make contact at various points on the part while scanning probes drag along the surface, taking points at specified intervals. Probe position may be manually or computer controlled.
While traditional CMMs provide highly accurate, precise measurements of part geometries, they usually require extensive setup time that includes specialized programming and training of operators, cutting into the time the machine actually measures parts. Once the machine is setup, data capture can be slow, taking up to 10 minutes to capture 100 points.
For high volume inspection, systems need to rapidly acquire and process data to either reject or accept a part before it proceeds to the next value adding process. In general, contact CMMs work well for sampling and not for 100% inspection of high to medium volume parts.

Non-Contact Metrology Platforms

Non-contact metrology platforms make no physical contact with parts by using an advanced sensor system comprised of lasers, cameras, application specific lighting and software algorithms. Laser triangulation is a 3D measuring technique used to determine the profile of parts. An integrated camera system takes images of the laser stripe. An algorithm then calculates the dimensions of the surface. Multiple parts can be measured in minutes with high accuracy and precision.
In terms of flexibility, non-contact platforms use software to create part measurement plans to quickly setup for inspection of multiple parts. Some platforms can measure specular and reflective surfaces as well. They also preserve part surfaces for manufacturers who use the GD&T callout for roughness for either functional or cosmetic reasons.
Non-contact metrology platforms solve the 100% inspection issue and are ideal for both high value parts, such as medical implants or turbine blades, and for some high volume manufacturing applications. In general, the metrology unit houses several sensors that acquire images from different angles, processing them at a rapid rate. As the most expensive part of the inspection system, it’s important to maximize the sensor use of the unit through high volume manufacturing.

Economic Value

The initial cost of procuring a CMM is usually lower compared to a non-contact metrology platform. However, depending on how frequently the part design changes or a varying product mix, a CMM may have higher operational costs, including probe replacements due to wear, fixture design, hardware costs and operator overhead. A cost-benefit trade-off analysis may help in understanding which system would be most preferred for the application.
While traditional CMMs are prevalent, non-contact metrology platforms are gaining more traction based on the value they add to manufacturing quality with reduced setup time, high accuracy and speed, and high ROI.