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Injection Molding and Moldmaking
with Surgical Precision

Injection Molding and Moldmaking
with Surgical Precision

Here at Matrix we often manufacture complex plastic components used in surgical devices and other medical applications. These parts can vary greatly in terms of size, material, and design but they all share several characteristics that can make them difficult to inspect using traditional techniques.

Performing first article inspections with these methods can be particularly time consuming and labor intensive. In addition to creating fixtures for each setup, the parts often need to be “sectioned” (sawed, cleaved, ground down) in order to inspect internal dimensions that are not naturally accessible via a touch probe or optical scope.

The associated tasks may require an inspector with a high skill level and/or experience performing similar procedures. It also opens up additional steps where operator bias and other errors can be introduced. Were all cavities saw cut and treated the same? Do different inspectors reproduce the exact same setups?

Above that, the sectioning process itself is inherently flawed. Sawing a plastic part to access a cross section will almost certainly introduce its own level of error, and this error can often exceed the tolerances of the dimension and distort inspection results. Warp, burrs, rolled edges, inaccurate trimming, inaccurate positioning of the section line and melting are all possible byproducts of manual sectioning methods.

And after all is said and done, you end up with first article data that is historically limited to the original points in your inspection layout. If you want to go back later on and inspect any additional dimensions, the setup will have to be recreated with the original parts.

To sum it up, performing a first article inspection (FAI) on complex parts often comes with the following issues:

• Time consuming & labor intensive
• Require highly-skilled technicians
• May introduce operator bias
• Allows for subjectivity in results depending on operator
• Historical reference data is limited to inspection points taken from original sample parts, making any future inspections from those samples very time consuming and possibly inaccurate.
• Requires inherently flawed sectioning process which can introduce error that exceeds dimensional tolerances (warp, burrs, rolled edges, trim marks, melting)

This is where cross-sectional scanning (CSS) comes into play. CSS is a unique process developed by CGI of Eden Prairie, MN. It offers an automated alternative to traditional first article inspection techniques that provides consistent and objective results. Using reverse engineering principles, CSS begins with an actual part and rapidly deconstructs it, cross-section by cross-section, to create a comprehensive set of measurement data capturing every dimension on every surface of the part, both external and internal. This video demonstration of the Cross-sectional scanning process will help clarify the process.

In the end the CSS capability reduces the amount of time and labor required for inspections, nearly eliminates operator bias and human subjectivity from the process, minimizes the dimensional stresses caused by manual sectioning, and leaves you with easily retrievable, electronic historical data that can be interrogated at any point in the future.

Posted by:

Gary Johansson


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