Quality Scan: Selecting Next-Generation Laser-Scanning Technology
By Alex Lucas
Business Development Manager/Scanning Products
Nikon Metrology Inc.
New product development is a powerful force in expanding manufacturing’s impact on economies around the world. The focus on improving production efficiency and part quality while meeting stringent production schedules is unrelenting. Measurement and inspection is one vital area being marked for improvement by advances in laser-scanning technology. Retrofitting coordinate-measuring machines (CMMs) or articulated arms with new laser scanners is one affordable option many manufacturers are considering.
Given the right choices in scanning and software technology, many advances are possible:
- Measurement coverage. Where many touch probes might achieve input rates of one point per second, laser-scanning stripes can range from 50 to 200 mm in width and scan tens of thousands of data points per second.
- Speed. With laser scanning, even complex 3D castings, production dies, turbine blades, cell phones, or plastic parts can be scanned in a matter of minutes.
- Offline reporting. Reserving your CMM or articulated arm for measuring and inspection, and transferring data to PC-based reporting software can significantly reduce inspection time and speed time to market.
- Quick and simple retrofits. A range of laser-scanning options are compatible with many existing CMM and articulated arm setups. Often retrofits can be accomplished in a matter of hours.
- Ability to automate. Integrated software packages are available that can handle gathering data, measuring, comparing scanned data to CAD models, and generating reports with both visual representations and tabular data into a single automated process.
- Latest technology. New technologies such as cross-scanning combine multiple scanners and digital cameras for scanning complex parts and features without reorientation.
Many choices in CMM based laser-scanning technology are available. On the entry level, numerous companies make single-stripe laser scanners that provide approximately a 50-mm stripe width, generate 20–25 stripes per second, and input something in the ballpark of 20,000 points per second while maintaining an error tolerance of 20–25 µm. For more demanding inspection tasks, Nikon Metrology manufactures a laser scanner featuring a 60-mm stripe width while scanning at a blazing 75 stripes-per-second scan rate that can maintain an error tolerance of 9 µm. Scanners are also available with smaller fields of view for digitizing small, detailed objects with higher point densities and tolerances down to 4 µm.
For scanning large objects, laser scanners are available in hand-held models or for attaching to articulated arms, making walk-around scanning easier. Depending on the type of scanner, stripe widths can vary between 50 and 200 mm, and digital cameras capture more than a thousand points per stripe. This provides optimum resolution for efficiently scanning freeform surfaces and features. Cross-scanners are also available, that incorporate multiple scanners and multiple cameras for measuring or reverse-engineering large parts.
A former hurdle with laser scanning was difficulty scanning highly reflective surfaces. This would necessitate spraying the object with a matte spray coating to eliminate obtaining reflective data and other extraneous noise. Today’s laser scanners feature automatic real-time adjustment of sensor settings for each individual point along the laser stripe, effectively handling highly reflective surfaces or those with varying colors.
Software compatibility is another important point to keep in mind. Nikon Metrology maintains partnerships with a number of inspection software providers and also provides its own point-cloud-processing solution. Laser scanning can input tens of thousands of points per second, so effective inspection software should be able to handle a large volume of inspection data (up to 100 million points) and provide a variety of analysis tools, such as geometric dimensioning and tolerancing (GDT).
With the right laser-scanning technology, measurement and inspection can be simple, fast and get better products to market faster. ME
This article was first published in the February 2014 edition of Manufacturing Engineering magazine. Click here for PDF.
Published Date : 2/1/2014