Part Scanning 101
The idea behind part scanning is that you want to take a part in the real world, and get an accurate model in a computer. To do this you somehow measure the part with a computer, getting a three dimensional representation of the parts surface. Today, there are six basic ways to do this:
Measure points on the part relative to some reference. This is great for measure simple geometry where you can reconstruct it by knowing key dimensions.
This process shines a laser on an object and measures the distance to the object. It does this thousands of times to build up a point array of the surface
This process puts down a series of parallel lines, or a grid of lines, and measures how far they distort from a flat pattern. With this information it can create a massive amount of points on the objects surface.
If you need to see inside, light based scanning does not work. In cross sectional scanning you machine away thin slices of an object and take an accurate picture of each layer as you go. This can then be turned in to an accurate representation of both the inside and outside of the object.
Another way around the fact that light can not penetrate an object is to use various types of radiation, like X-Rays, that go inside an object. Although new for industrial applications this method is growing for complex parts with internal geometry.
If accuracy is not critical, then software can take pictures taken from dozens of views and reconstruct a 3D shape. This is used most often for art and entertainment, but is not precise enough for engineering yet.
PADT offers Structured Light and Cross Sectional Scanning
The Point cloud can them be turned in to a faceted representation of the object. For many people, this is all they need. This faceted representation can be rendered on a computer screen or 3D Printed. It can also be used with inspection software to determine the accuracy of the part relative to its original specification as well as variations across multiple copies of the same geometry.
To do accurate part scanning you need:
- A precision scanning device
- Software to take the measured data and create an accurate point cloud. This includes repair and cleanup tools.
- Software to convert the point cloud into a usable 3D CAD model
- or, Software to conduct accurate inspection on the measured geometry.
All of these tools require some training and practice to use efficiently. It is fairly easy to get ball park computer models using consumer level tools. But to get accurate, engineering quality results the right tools and processes must be applied.
Why does Part Scanning Take so Long and Cost So Much?
When people ask for their first part scanning quote, they can often be surprised by the cost. The scanning process doesn’t look that hard. And to be honest, the amount of time you actually spend scanning most parts is pretty short. The time is spent on the preparation, scanning hard-to-reach areas, the clean up, and then converting the data in to usable formats.
If we are using cross sectional scanning, the part needs to be cast inside a rigid material, so the part we are scanning does not distort as we remove layers. In addition, if the part is not a solid light or dark color, it may need to be died to provide contrast for the camera.
Both processes also require some study to determine the orientation of the part relative to the scanner and how the scanning process will take place. Once all this is worked out, the scanning often goes very fast. If there are nasty little parts that are hard to get to or that confuse the device, the engineer may have to modify things, do some special localized scanning, or even make castings that are then scanned. As is usual with technical processes, a very small portion of the surface being scanned may take up the vast majority of the scanning time.
Once the scanning is done, the real hard work begins. Although software is much better than it was in the past, the resulting point cloud needs to be massaged and cleaned. Stray data is removed, and points from different scans need to be positioned and combined. Then everything must be checked. If a CAD solid model is needed, then the engineer must spend considerable time dealing with complex features and transition areas. As with the scanning, the bulk of the time spent creating a CAD model is spent on a relatively small percentage of the geometry.
All of this adds up. Plus, to be honest, things rarely go as planned and unexpected issues arise that need to be dealt with.
Part Scanning Services at PADT
Our primary scanner is a Zeiss Comet L3D 5M STructured light scanner. It used to be called a Steinbichler, till Zeiss bought them in 2015. Although it is portable and easy to manipulate, the Comet L3D 5M is highly accurate. It allows us to scan everything from small medical devices to the front end of acar, and to know that the resulting geometry will be accurate and usable. This is the best option for inspection and reverse engineering of high-precision parts.
If parts have internal features, and are made of plastic, we use our Cross Sectional Scanners. These high precision devices do a fantastic job and are really the best way to capture inside surfaces. Our customers love it to see how injection molded parts are coming out on well used molds.
If anything else is needed, our experts can outsource to a niche supplier.
Want to do it Yourself?
If you need to do your own scanning, no worries. PADT also sells all the tools we use inhouse to customers that need the capability internally.
Next Steps
Download our brochure here.
Either way, you can email rp@padtinc.com or call 480.813.4884 and ask to talk about Part Scanning. We also have some information on our website at www.padtinc.com/scanning.
