3D Model Laser Scanning Multiple Times

3D Model Laser Scanning Multiple Times

Scanning a part multiple times can significantly increase the accuracy of the finished model.

A customer needed to reproduce some inserts for an automotive injection mold. Attempts to build them using their customer's CAD models failed because the inserts didn't match the models.

The inserts had advanced surfaces that had to match exactly with neighboring surfaces in the mold. This made the project ideal for laser scanning except that the accuracy required was about twice that of what my laser was typically capable of using a single scan. By scanning the inserts four times each and then averaging the scans, we were able to achieve the desired accuracy.

In a measuring system, if the measurement error is randomly distributed about zero, measurement uncertainty can be reduced as a function of the square root of the number of measurements made and averaged. In other words, if you measure something four times, the average of those measurements will have half of the uncertainty of any one measurement.

As part of Reverse Austin's monitoring of laser performance, I periodically scan and measure a CMM training standard. From the many measurements I've done, I can see that the measurement error is random and fairly well distributed about zero. If I chart the error from the averages of any four consecutive scans, I get errors that are a little less than half of the errors from individual scans.

If you've done your homework and you know the uncertainty of your scanning system, you can significantly improve accuracy (reduce uncertainty) by scanning multiple times and averaging the scan data.