The inherent nature of sand blasting produces a taper angle of about 15°, which for some applications, i.e.: sound attenuation, is a distinct advantage. Because of the taper, the process is limited to a maximum of a 2:1 thickness to hole diameter ratio. The result is the entry hole opening will be larger than the exit hole opening. This can be mitigated by sand blasting from both sides. The graphic below illustrates this phenomenon:
The photoresist mask has a nite life before degradation occurs, limiting the depth of machining. This limitation can also be affected by the composite materials used, the type of epoxy-resins used, and the feature being machined. In sum, this process is well suited to thinner composites (up to 5mm).
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