Every Feature, Internal and External in a Single Scan
Advancements in industrial CT have enabled the ability to produce dimensional metrology results for component parts with increasingly tight tolerances. CT is an ideal method for gathering data on component parts with small features, especially internal features.
Advanced Inspection Services (AIS), located in Minneapolis, has a twenty-year history of supporting med tech organizations with dimensional metrology services. A common product they see are Lure Fittings.
“Luer fittings are used extensively in medical and life sciences applications. At its most basic level, a Luer fitting is defined as a small-bore, friction based, leak-proof connector. Its prominent use is to connect tubing and equipment for the transfer of fluids and gases.”
Because of the need for leak proof connections between components and devices from different manufacturers, ISO standards have been developed to insure interchangeability. The original ISO 594 standard has now been updated through the ISO 80369 Series standard.
Lure fittings are an ideal CT application because of very small internal features that can only be measured through mechanical sectioning or CT.
Like many med tech applications, the ability to validate measurement capability is critical to accepting the measured results. National and International standards for determining the measuring performance of industrial CT systems are now just being released, these standards are most useful for establishing installation standards and comparing the performance of one system vs. another. They are not as useful for proving a valid measurement, traceable to an accepted standard.
AIS Uses a process that first qualifies key features with a traceable measuring system like a contact CMM or multi-sensor CMM and then measures the same features with CT and compares the results. Because the CMM will gather hundreds of measured points and the CT will gather millions of points on the same surface correlation issues will often result between the two systems.
AIS Uses SmartProfile software from Kotem Technologies to solve this issue. The first step is to gather a medium density point cloud on the Lure Fitting key features with the CMM system:
The highlighted pink points in the image above can then be used to extract equivalent points from the millions of points in the CT point cloud and determine measurement results from both systems. For this part, three test features were chosen, Dimensions 7 and 8 above, internal diameters and Dimension 6 the major diameter of the thread. The results were:
These results show the worst-case difference between CM and CT results to be .012 mm, or 12% of the total tolerance allowed. The stated uncertainty of the CMM for this task is .0012 mm. The final combined uncertainty for the CT measurement of these features is under .015 mm or 15% of tolerance, meeting the customer requirements of 25% or less in a validated and traceable measurement process.
To learn more about this application and other AIS services, please visit: