Creating Features In Scanned Data Without A CAD - Scan To Scan Comparison In Polyworks

Published by CMMXYZ on December 8, 2021

PolyWorks Tech Tip: This video demonstrates different methods to create geometrical features in a scanned data without a CAD model. After creating the features, using the scan as a reference/master we'll be comparing it with another scan.

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Welcome to Tech Tips from CMMXYZ. On today's topic, let's check how to create features in scan data without a CAD model and also use that scan data as a reference object or master part to compare it with other scans.

In PolyWorks, scan the reference part first using the scanning device. I have a scan part on which I'm going to create features and use it as my reference part. There are different ways to create features on the scan data. One of the methods is by using extract, using polygonal model. Select the Extract Using Polygonal Model icon. In the dialogue zone, you can use Automatic, letting the software guess the feature on the scan, or choose the feature that you want to create.

I'll select Plain and click on the surface where I want my paint to be created. Then click on Confirm to create the plane, and close. Next method is by using Create Features. I'll hide the plane to make easy to create the circle. Go to Create Features icon and select the feature that you want to create. Select the Method as Fit, then select Pick, then Fit for sub-method.

Use space bar to manipulate the 3D scene and pick three points inside to hole to create a circle feature. Then close the Create Features dialogue zone. Another method is by going to Create Features icon, select the feature that you want to create. Then select Fit as Method. And, this time, select Fit Element as sub-method.

Use Select Elements icon, which can also be enabled by space bar, highlight all the scan data points for creating circle feature using Select Elements. Use space bar to manipulate the 3D scene.

After highlighting the scan points, click on Create to create the feature. And then close the Create Features dialogue zone. Sometimes the circle feature created will be an external feature and not an internal hole. In this case, circle 1 is an external feature even though it's a hole.

The features can be differentiated by the symbols. To change the feature type from external to internal, highlight the feature, right click, Edit, Invert Orientation, then check on Invert and Space Orientation, and click on OK. This will change the feature to an internal feature or an external feature.

Next, to use one scanned data of a part as a reference and to compare it with other scanned data, create all required features on the reference scan data. After creating all the features, highlight all the features in the preview, right click, Edit, and select Swap Nominal to Measured Value. This will change the measured values as the nominal values of the feature. Then, to convert the scan data, as a reference object, highlight the scan in preview, right click, Edit, and select Convert Data to Reference Object.

Next, scan the second part that has to be compared with the reference scan, or import the scan data if you've already scanned it in another project. I have a second scan saved as an STL file which I'll be importing into the project. After importing the second scan, do a best fit data-to-reference alignment to align the two-scan data. Then highlight all the features, right click, and extract the measured value from the second scan. This will give us the deviation of the second scan from the reference scan. This was a video on how to create a feature on scan data and how to do a scan-to-scan comparison. Thank you for watching the video.

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