Characterising Devices: Measurement of Components

When it comes to the reverse engineering/measurement of the existing components in a device there are many methods to go for. Some of the options available for accurately replicating the critical features of components can sometimes overcomplicate the process and result in a lot of time being wasted pursuing one method. In our experience its proven to be more efficient to just keep it simple, manually measuring with a calibrated Vernier!

We’ve worked on projects where 3D scanning has been the chosen method of measurement for replicating components. However, this process brought with it a lot more issues than expected. Initially, anyone would think having a 3D scan of a component would tick all the replication boxes quickly and easily, job done! Unfortunately, there are a few pitfalls that crop up along the way that can blow all the resulting data out of the water. The main issue is most 3D scanning processes produce STL files, which, as designers, we know are not the best and wouldn’t be the first file format we’d choose, especially when trying to accurately replicate components. The low resolution and unstructured triangulated surfaces of the STL files make it difficult to establish clear datum points to measure between when trying to replicate certain features.

In addition to this, it is difficult to ensure the components that are being scanned haven’t been damaged or distorted during disassembly. This can be especially difficult if the components were previously glued or ultrasonically welded together within the device. Something to bear in mind during this process, if measuring just one set of 3D scan data from one device, it’s impossible to know if those plastic injected moulded parts that were scanned were at the upper or lower moulded tolerance limit. This would mean that ideally a sample group of components would all have to be scanned and compared against each other to gauge an average dimension across various features. This could be seen as a bit of a drain on project time, especially over some more conventional measuring techniques.

Manually measuring components with a calibrated Vernier step by step, feature by feature, building up an engineered 3D CAD model, is often the most time efficient and accurate solution. At HD its proven to be useful to have built up the CAD model this way. Following an efficient CAD modelling method allows any members of the team who join later in the project to pick up where the previous designer left off. They can see all the previous CAD design history and can easily adjust specific component features without the worry of the CAD models imploding!

In the next blog post we will talk more about the importance of efficient CAD modelling especially when readying the components for manufacture, as well as the creation of some very useful documents that really get to the heart of medical device characterisation…

For all other Characterisation articles, please click the below links:

• Chemical & Material Characterisation
• Tolerance Analysis & Manufacturing Data
• Interactions Matrix & Essential Functions Documents