Part Scanning – An Update

Did you know that PADT does scanning of parts?  No? You are not alone. We recently ran into several customers who were sending their scanning out of state and didn’t know that they could have it done by PADT, someone who is already a trusted partner. So we thought it would be a good time to do an update on our Scanning services and provide some additional background on what it is.

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:

Physical Measurement (CMM)
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.

Laser Scanning
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

Structured Light Scanning
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.

Cross Sectional Scanning
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.

Volumetric Scanning
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.

Photometric Scanning
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

All of these methods create points in space.  The more sophisticated the software, the more automatic the process of assembling the points to define the surfaces of the full object. These points are sometimes called a “point cloud.”

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.

If users need more, like a full CAD model, that can be created from the point cloud using specialized software.  PADT uses Geomagic DesignX.  This tool not only creates usable geometry, but it can export in the customer’s native CAD format.

To do accurate part scanning you need:

1. A precision scanning device
2. Software to take the measured data and create an accurate point cloud. This includes repair and cleanup tools.
3. Software to convert the point cloud into a usable 3D CAD model
4. 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 working with a light based scanner, we have to prepare the parts so that they reflect the light properly. Sometimes we have to cover the part with a find powder, sometimes we may even have to paint it.  What we need is for the reflection and color of the part to not interfere with the scanning.

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

Now we get to the important part of this post: hiring PADT to do your scanning.  We added this capability to support our 3D Printing customers that wanted copies of physical parts.  But as we looked at it, we found that we also had customers who needed inspection and reverse engineering of legacy parts. We studied the problem for some time and found the right tools and people to make it happen.

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.

We also have a Geomagic Capture scanner. Although less accurate it is more portable and simpler to operate. It is ideal or taking to a customer and getting geometry for reverse engineering or part copying.

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

Hopefully this posting has answered most of your questions and you are eager to try 3D Part Scanning.  The best place to start is to get a quote from PADT.  However, if you still have questions then feel free to contact us and fire away. We are passionate bout this capability and love talking about it.

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.