Plastic Fantastic CT Scan
To accurately print a mouth-blown musical instrument, you have to get information about both the outside and the inside. This is different from printing a solid object, where measurements or methods such as photogrammetry can be used to generate printable files. The only method which can give the information we needed to print an accurate 3D version of a recorder is CT-scanning, which uses X-rays to show internal details.
We have scanned an eighteenth-century ivory recorder from the Bate Collection (http://www.bate.ox.ac.uk) at Cranfield University. The micro-CT scanner (a Nikon XT H225) is capable of high-resolution scanning, the X-ray source and detector remaining fixed while the stage on which the object is mounted rotates slowly through 360o. Many images of the object are taken as it rotates in the X-ray source. The longer sections of recorder needed to be scanned in two parts, the sections being joined digitally during image processing afterwards. Processing converts the data from the CT scanner into .stl files ready for printing.
One thing that we weren’t expecting was that the wooden block inside the mouthpiece of the recorder (the block forms the shape of the windway in the mouthpiece and is important in determining sound quality) had been eaten by wood boring beetle. There are clearly channels inside the block where the larvae have eaten through it. This results in quite a lot of extra data to print – we are hoping that the wood-worm holes can be ‘filled in’ digitally before printing.