Making the Most of Laser Scanning

Complex measurement can be done quickly and accurately

Photo of laser measuring a complex part.

An integrated scanner allows switching between tactile probe and laser scanning for accurate measurement.

In the digital manufacturing age, quality and production process stakeholders must choose and implement metrology equipment that helps build closed-loop manufacturing systems. When it comes to 3D laser scanners and portable coordinate measuring machines (PCMMs), the stakes are high. In today’s advanced manufacturing environment, controlling production costs and delivering high-quality parts are critical to maintaining a competitive advantage in the marketplace.

Astute organizations must look for versatile scanning options that can meet their needs today and in the future. Scanners suited for applications like point cloud inspection, product benchmarking, reverse engineering, rapid prototyping, virtual assembly, and CNC milling help meet those needs. In addition to these work functions, the operator’s experience with the scanner is important. A scanner should travel smoothly and easily with the operator, providing natural ergonomic motions that complement the way the human body moves with little fatigue.

A guiding principle to keep in mind when reviewing a scanner is this: Can anyone use it and get good results?

Production Cycle Time Savings

You’ve likely read statistics that the cost of a typical manufacturing design cycle can be reduced by 75 per cent when using 3-D scanning. This is a repeated refrain that can be found in Metrology News1 and Future Market Insights2. Potential savings like this have complex part manufacturers seriously evaluating the 3-D technologies.

Today’s laser scanners are robust tools engineered to deliver scanning speed and productivity. Selecting a laser scanner with a wide line greatly enhances productivity, but not all wide-line scanners are created equal. Some powerful scanners offer a 150-mm scanning line that scans more surface, reducing the time spent to perform the scan. The analogy of a paint roller works here, a perfect tool for painting a large area quickly. By selecting a scanner with a wide laser line, the operator can scan objects much faster.

Some scanners offer a laser line up to 150 mm but when it comes to delivering accuracy, the actual working area of that line can drop to as little as 50 per cent of the claimed scan width. That is because some scanners require the operator to use the high-definition scanning mode, which can drop the working scan line to 75 mm or less to get an accurate representation. When the necessary scan overlap is factored in, what could be considered a job completed by a paint roller has been effectively reduced to something more akin to finish work done with a paint brush.

A built-in scanner can help optimize cycle times because the scanner is attached and does not need to be calibrated each time it is used. All that is necessary is to turn it on and go.

Speed and Accuracy

Speed on the factory floor requires a scanner that allows the operator to accurately provide measurements with the least number of laser passes. Again, some devices with narrow scanning lines fall short because they require numerous passes to gather the information.

Today’s laser scanners are up to 60 per cent faster than their predecessors. Coupled with the wider scanning line and higher point resolution, a scanning session provides greater point cloud detail in significantly less time. Knowing the actual width of the scanning line being used is vital for selecting a truly fast scanner.

Operators face a built-in compromise when using the high-definition setting with many scanners. The scanning line can drop to a width as narrow as 75 mm. When the 25-mm scanning overlap on either side of the line is achieved, the operation might obtain accurate scanning data as limited as 75 mm. Scanners that do not require use of the high-definition mode to obtain a part’s rich point cloud offer more speed and accuracy.

Phot oof laser measuring a drone.

Laser scanning can provide rapid, accurate measurements of curved surfaces and holes or crevices.

The need for part surface preparation is another shortcoming of some scanners. Typically, laser scanners require the application of a spray or powder to ensure that the scanner can accurately read the surfaces. In addition, highly reflective or dark-colored parts can require additional preparations that can include the application of dots to the part surface to assist the reading process. Not all scanners require these elaborate and time-consuming steps.

When evaluating a laser scanner’s speed and accuracy, a shop should consider time spent calibrating the scanner; applying targets; spraying or powdering the part surface; the actual scanning; and cleaning up, which could include removing targets. Scanners with flying-dot technology can accurately read shiny or reflective surfaces without added targets and automatically adjust for low or bright light, saving time.

More Data Points, More Efficiency

Manufacturers in advanced markets like automotive and aerospace require high-precision components. These parts and finished products often have complex geometries. Consequently, PCMM laser scanners must be able to adapt to the physical parameters of the product being scanned.

The scanner’s ability to penetrate deep crevices requires a sufficient standoff distance. That distance is predetermined based on the accuracy and the power and configuration of the laser. The greater the standoff, the deeper the scanner line can penetrate a hole or cavity.

Consequently, a short standoff means there is the possibility of not being able to scan to the bottom of tight spaces, which can lead to inaccurate information. This can slow the production cycle and allow for potential inaccuracies that increase defects and scrap.

A modern scanner with completely new optics and electronics allows for 60 per cent faster scans than its predecessors.

Truly fast scanning requires the highest number of data points achievable in a single line. Some laser scanners top out at around 2,000 points per line at low accuracy and just 1,300 at high accuracy.

Market research shows that some scanning technologies offer a capability of 7,520 points per line and an astronomical 752,000 points per second versus the average of 2,000 points per line.

Simplifying the Scanning Process

Today’s advanced manufacturers work with materials that present challenges to traditional scanning technologies, specifically carbon fibre and machined steel surfaces. In many cases, surfaces include contoured details that create difficult-to-scan shapes.

If a company is working with complex components with holes or surface cavities, being able to employ tactile and non-contact dimensional measurements in the same session simplifies and accelerates the process. Using an easily mounted touch probe can simplify the work flow. Hard probing into a part that has a complex terrain structure can save time, especially if the probe offers a self-centring capability.

Photo of laser scanning part inspection.

A laser scanner can provide detailed measurements of cast, metal, and composite parts.

A touch probe is also the proper tool to measure parts with surface details that enable other parts to sit on or connect with them. Technicians can change from tactile to non-contact measurement as needed to obtain accurate scanning data even when confronted with challenging material surfaces.

A laser scanning system must be able to interface with software that provides a full range of filter management scanning functionalities. These include features like point smoothing and removal, noise reduction, and other management functions to intelligently reduce file sizes and processing time without sacrificing accuracy or part integrity.

What It All Means

As advanced manufacturers craft their strategies for staying competitive, portable laser scanner measurement capabilities become necessary to achieving productivity and quality goals. Equipment with an integrated scanner, combined with a RS4 scanner, enables manufacturers to achieve this target. Such scanners are ergonomically designed for comfortable use in metrology and inspection, production, design, and engineering departments, where geometric properties such as lengths, thicknesses, and angles need to be measured and verified.

With touchless scanning, manufacturers can use a CAD comparison process that quickly shows deviations from the theoretical part produced against the theoretical or original one.

A portable laser scanner provides a way to accomplish multiple tasks on the manufacturing floor, including 100 per cent part verification and reverse engineering of complex parts. Those parts can be cast or produced from metal or plastic. When carefully selected, a laser scanner automatically provides rich point cloud data sets without warmup time. Operators using a portable measuring arm can switch seamlessly between tactile probe measurements and laser scanning to acquire 3-D point data from a variety of surface types.

Today’s laser scanners join other technologies to create a holistic process in the modern manufacturing environment. This cohesive environment is the foundation for turning data into action for manufacturing processes to save time and money while increasing quality.

Photos courtesy of Hexagon Manufacturing Intelligence.

Gene Daniell is ROMER Absolute Arms product manager, North America, for Hexagon Manufacturing Intelligence, 800-955-5200, www.hexagonmi.com.

Notes

  1. http://metrology.news/global-3d-scanner-market-predicts-continued-uptake-manufacturing-industry
  2. www.futuremarketinsights.com/reports/3d-scanner-market