3D Scanning techniques | HDI 3D scanners
3D scanning basics | Quality
Scan quality can vary by the following factors:
3D Scanner calibration
The more calibration scans you take, the better the accuracy of the scanner
Environmental conditions
Light and vibration can cause inaccuracies. Ensure the system is stable and the exposure is set to the conditions
Stability of the scanner and the object
If either the scanner or the object move during the scan, the data will be inaccurate. Ensure both are stable and secure
Shape and size of the object
If the part you want to scan has limited features, you must use markers or spheres to align the data. You also must calibrate the scanner with an appropriate lens and calibration board to suit the item
Scan Preparation
When you set up the scanner, you should Understand how the scan data will be used
This determines the mechanics of the scanning process and which features, if any, should be hard probed
This eliminates unnecessary work and potential rescanning.
Scanner positioning
When positioning the scanner to acquire the most accurate data, consider the following items:Scanner position
Positioning the scanner perpendicular to the surface being scanned optimizes the amount data the scanner collects. When the data is at an angle, the light can fade out as it goes farther back and the data becomes less accurate. Also, when you are determining how to position the scanner and object, place the scanner so it can capture as much of the object as possible while remaining perpendicular to the object's surface.
Line of sight. The scanner can capture only what is in its line of sight. If you scan a propeller, for example, it will need to be placed so that the scanner can capture the curve of the blades and in between the blades. If the part needs to be held at a particular location, you must decide the best method for holding the part while scanning. Any solution should allow you to fully capture the part in one setup to minimize the amount of repositioning.
Scanner volume and area. Depending on the lens and calibration board used, the scanner will have a defined area that can be captured. A large part may require several scans to capture all sides and then will be stitched together using Flexscan3D, Leios, or Geomagic. Each scan needs to overlap the previous section to be able to stitch them together or there needs to be common targets on each scan set for alignment. Be sure there are enough features to align the data.
Part preparation
Before scanning there are two steps for part preparation: placing reference targets and coating the part Placing Reference Targets
For parts that have little geometry, place photogrammetric dots on the part in order to use these features during alignment. Refer to Scanning with Markers for more information.
Coating the part. Reflective surfaces scatter the scanner light and create noise artifacts in the final data. Laser and white-light scanners do better when scanning matte, white surfaces. Developer, like Magnaflux Spotcheck Developer, is a powder-based spray commonly used to create a flat white surface for scanning and is available at welding supply stores. Other products you can use include some athlete's foot treatments, spray deodorant with titanium oxide, and tempera paint from a compressor. You can also use white spray paint if it is acceptable to create a more permanent coating. You must spray the part with a uniform, light coat. The thinner the coating, the better. Adding more than a thin coat of developer can impact a part's thickness when scanning. Developer comes off easily and is prone to fingerprints. Mounting an object to a surface (such as a bolt through the center of a threaded section) can provide a hand-hold for moving the part after spraying. You can also spray a portion of the part (leaving a section as a hand-hold), complete the first scan, clean the part, respray the area used as a hand-hold, and then rescan as needed. The following steps are a general procedure for applying developer to a part.
Apply targets before spraying. Otherwise, the targets will slip off the white part
Clean any targets with a cotton swab prior to scanning if necessary
Re-spray any areas that need it
Set the object aside to dry for a few minutes
Hold the can 12 to 18 inches from the part and spray a light first coat
If necessary, mount the part or decide which section to use as a hand-hold
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