Multi-sensor measurement of an insulin injection needle

摘要

Insulin injection needles are microparts which are produced in a very high number. Their outer diameter is slightly conical with a mean diameter of approx. 235 μm and the inner diameter is approximately 150 μm. Precise measurements of the geometry of the needles are urgently needed to support their quality assurance which to date is based on flow rate measurements. This contribution describes multi-sensor measurements of the geometry of such a needle. The reference measurement of the part was carried out using a tactile-optical microprobe (3D fibre probe). Due to the high aspect ratio of the inner hole, the use of a custom dual sphere probe was necessary. The uncertainties of the reference measurement are 2.5 μm (outer diameter) and 1 μm (inner diameter). Additionally, the needle was measured using two industrial CT systems (voxel size approximately 3 μm) and a high-resolution CT scan using the synchrotron radiation source at Bessy II in Berlin, Germany (voxel size approximately 0.5 μm). The results of the reference measurement were compared with the results achieved by the three CT systems. In this comparison, the different structural resolutions of the measurements must be taken into account. The investigations were carried out within the European joint research project (EMRP) "Microparts". The needle is one of the workpiece-like reference standards used in the project.