AN-000158
Document Number: AN-000158
Page 12 of 22
Revision: 1.2
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Layer thickness of 0.025
mm (0.001”)
For critical dimensions, the tolerance of printed samples should be within 0.1 mm of nominal.
Chirp DOES NOT recommend using
FDM (filament based) 3D printers for making horn Acoustic Interfaces.
FDM 3D printing does not have the required resolution,
accuracy, and surface finish to produce Acoustic Interfaces with good acoustic performance.
For mass production, Chirp has the following recommendations for the tooling of Acoustic Interfaces:
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Unless specified otherwise, the tolerance of critical dimensions should be ± 0.05 mm or better. Critical dimensions include
the internal geometry of the Acoustic Interface and the alignment features that will align it to the sensor’s port hole.
For
non-critical dimensions, a tolerance of ± 0.1 mm is acceptable.
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The sensor-contacting surface of the Acoustic Interface should be flat to 0.025 mm or better.
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The minimum surface finish for all critical Acoustic Interface surfaces (sensor contact surface, tube/horn internal profile
surface, exterior top surface) should be equivalent to SPI-B2 or better, with SPI-A3 or better recommended.
Figure 10. Critical surfaces on Acoustic Interfaces are highlighted in red.
The inside pocket surface of the Acoustic Interface needs to be smooth to ensure good and gapless contact with the sensor. The highlighted
exterior-facing surfaces (in red) interact with the ultrasound wave. To minimize unwanted interference (constructive or destructive), these
surfaces should also be tightly controlled to ensure a smooth finish.
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For straight tubes, the tube interior edges must be as sharp as possible for optimal acoustic performance. The maximum
allowable edge fillet radius is 0.025 mm.
Figure 11. The exterior edge of a tube Acoustic Interface (highlighted blue) should be as sharp as possible to maintain a wide FoV.
