Challenges with Difficult Surface Finishes

Laser line scanning relies on the reflection of a laser line projected on a parts surface to generate point cloud data. Certain surface characteristics can affect data quality:

Dark surfaces. These absorb laser energy, resulting in low intensity reflections that can be difficult for the sensor to detect. Marco Torsello, product manager at Faro Creaform, told Vision Systems Design: “The way you solve this is by increasing laser intensity and camera gain, but it sounds simpler than it actually is.”

Reflective or shiny surfaces. High reflectivity produces complex reflective patterns where the laser line can be mistaken for reflections, leading to noisy or incomplete scans. Orcello noted that advanced image processing algorithms analyze intensity patterns, multiple image redundancies, and use laser wavelengths optimized for different materials to differentiate actual laser lines from reflections.

High-contrast surfaces. Surfaces with rapid alternation between dark and bright regions challenge camera exposure settings. Torsello pointed out that enhanced HDR and auto-exposure techniques are used to handle these conditions, allowing the sensor to adjust exposure dynamically during scanning.

The DTEX pipeline update Incorporates these improved image-processing techniques to reduce operator intervention for parameter tuning and enhance automatic handling of variable finishes.

Effect on Workflow Efficiency

Testing on representative challenging parts demonstrated up to a 60% reduction in time to usable scan data. Torsello explained that “the reduction in scan time was measured on a part that was definitely challenging to scan before the release of the new set of algorithms,” and that for ideal surfaces, improvements are more related to set-up automation than actual scan speed. These efficiency gains can reduce cycle time and manual overhead in workflows requiring inspection or reverse engineering of complex surfaces.

DTEX Pipeline, Rotary Table Integration

The DTEX processing pipeline combines multiple filtering and adaptive image-processing tools to distinguish true laser line signals from noise and reflections. “While users may have needed to go through some part preparation (mattening/whitening) on very challenging parts with previous methodologies, that is not the case anymore,” he said. This positions the Faro LLP lineup among the more capable systems for portable CMM scanning of difficult surfaces, he added.

The 8-axis Max Rotary table extends the effective measurement volume of the FaroArm systems by enabling continuous measurement as the part rotates. Torsello illustrated this with an example of measuring a 1m x 1m part. Repositioning the arm without the rotary table adds error and time, whereas the 8-axis Max allows rotation of the part while keeping the arm fixed in the same coordinate system. The system reduces operator moves and maintains reference accuracy during complex scans, benefiting applications involving larger parts across industries, he says.

Upgrade Consideration, Future Scope

The update is firmware-based and can be installed quickly via a simple download process tied to a device serial number. Torsello confirmed that “measurement integrity remains inherently preserved after the update and follows strict ISO certification/traceability standards.” Automation of acquisition parameters reduces the need for operator training, he adds. The update package runs almost automatically once the arm is connected to the PC, and training materials are available to support users.

Currently, DTEX development focuses on the laser line probe product line, given its specific optical configuration. Torsello said that while some lessons from DTEX development may be applicable to other Faro products, the integration of such algorithms on other systems requires deeper evaluation due to metrological and accuracy considerations.