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Demystifying Myths About Non-Contact 3D Scanning

Posted By Thomas Tong on October 27, 2011 at 12:24 PM

We receive inquiries about our products from a wide range of customers, from those well versed in 3D metrology to others who are new to its potential benefits.  We get a lot of questions about non-contact 3D scanning in general and sometimes people have preconceived notiowizardns about this process. Here are some myths that surround the current state of technology in non-contact 3D scanning.

3D scanning is a fully automated “magical” process.  Put the part in front of the scanner, press a button, and out comes a digital model.

While non-contact 3D scanning has come a long way in recent years, it’s far from a magical process that automatically scans the whole object at once. Non-contact scanning allows relatively much faster scan rates by collecting millions of points over an area or region of an object at a time. Building a complete digital model of an object from all angles is a process of scanning multiple sides of an object, aligning the scans, and merging them to create a polygon mesh. From here the data can be used to do either modeling or measurement applications. Creating a CAD model for engineering or analysis requires an additional process in specialty software. Our blog post Common Questions on Reverse Engineering explains more about the process of creating a CAD model from 3D scans.

Non-contact 3D scanning is not as accurate as conventional contact-based CMM’s and portable CMM’s.

With great advances in sensor and projector technologies, today’s optical scanners are achieving accuracies that rival touch-based Coordinate Measurement Machines (CMM).  Depending on the configuration and the implementation, it is reasonable to expect accuracies of 25 micron or better from non-contact systems without sacrificing performance such as scanning speed and density of coverage. In many scenarios, non-contact systems can deliver better accuracy and detail for systems that cost much less than conventional contact-based digitizers.

3D scanners can scan any and all surfaces. They can scan inside and outside at the same time.

Structured-light 3D scanners are based on optical technologies similar to Vision Systems that have been employed for over a half-century now.  They use projectors to overlay fringe patterns or laser lines, and calculate the true shape of the physical object by reading the returned pattern. Surface finishes of the following type are usually non-compliant and difficult to scan if they are a) highly reflective like chrome or glass, b) highly absorbent or flat black like tire rubber or some graphite composites, or c) translucent or transparent like glass or stereo-lithography prototypes.  The best remedy is to apply some acceptable dulling agent to improve scanning results. Dulling agents used in the industry have been from the following list: talcum powder, corn starch powder, tempera paint, welding crack detector, anti-perspirant spray (for PC boards), car polish (for automotive body panels), Drywash (for aircraft skins), and many others. Other than CT or ACSS systems that can see inside the part (non-destructive or otherwise), most optical scanners are limited to what’s visible in the scanner’s field of view.

All non-contact 3D scanners are the same technology and are equal in accuracy.

Non-contact 3D scanning is a wide field with many technologies available today including structured-light (such as white light scanning) and laser point or line. Each comes with it’s own advantages and pitfalls.  And the systems developed on these technologies can vary greatly in the delivered performance such as accuracy, resolution, noise, and speed.  Finding the system that fits their required application means looking at the customer's budget, time-frame, part sizes, working environment, portability requirement, etc.

To investigate 3D scanners, one has to purchase a system to evaluate the benefits.

While purchasing and employing the 3D scanner is the final test of it’s suitability to the work requirements, there are many other ways for customers to mitigate the risk involved.  3D scanner manufacturers are equally interested in demonstrating the capabilities of their product, and parts from a live project scanned for a nominal service fee is the generally the best way to get sample data from the source. There are also many capable independent scanning service bureaus operating today. Finding those who are using the scanner models that suit the customer’s short list of systems and getting service work done will give a very good idea of what’s possible in an end-to-end process with a trained user. Value-added-resellers and system integrators are also subject matter experts in the area of 3D scanning and often times have current experience using 3D scanning systems that are of interest.

Non-contact 3D scanners are very expensive; many cost on the order of $100,000 and up. This is technology only for the Fortune 500 companies.

This myth has a basis in fact since non-contact scanning systems indeed used to cost quite a bit.  To take advantage of the higher speed, full field coverage, and other benefits of non-contact 3D scanners, customers had to be prepared to pay as much or more than the price of a CMM.  They were still ahead when considering 1) simplicity of installation (no large granite slab, no concrete pad to house the machine), 2) annual cost of maintenance (no encoders to get re-certified, mechanical joints to maintain), and 3) portability (scanner could go to part on the shop floor).

But recently, affordability has also entered into the picture to the customer’s advantage. 3D3 Solutions is proud to be part of a new crop of 3D scanner manufacturers that are sourcing the latest in CCD cameras and lenses, consumer-grade projectors, and simple mechanical platforms to make 3D scanners more affordable. As a result, small to medium size companies now have the budget to purchase a 3D scanner to help grow their businesses in innovative ways.

Do you have any questions related to 3D scanning? Please post in the comments section.

This blog post was previously posted on Tue, Oct 27, 2011 on 3D3 Solutions blog. LMI Technologies acquired 3D3 Solutions on May 1, 2013.

Posted by Thomas Tong