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Measuring Replicas

Even though 4D InSpec is a handheld instrument, built with a small-sized business end to permit access to tight spaces, there are locations that remain out of reach. These are narrow holes, and deep recesses. For inspection of those surfaces, a replication is needed.

Replications, made from a rubber-like paste poured or pressed onto the surface, makes a “negative” surface copy—pits become bumps, and raised bits become recesses in the replica. The technique is widely used, and well-accepted, because the material has high fidelity in reproducing surfaces.

For many inspection technicians, the next step is to slice the replica through the defect and view the silhouette of it in a shadowgraph.

We wanted to know:

  • Would 4D InSpec perform good measurements on replication material?
  • Would 4D InSpec results match a profile or shadowgraph measurement of the replica?
  • How much variation would 4D InSpec show between measuring the two materials—the original surface, and the replica?

Did it work?

Jared Wheeler, 4D Technology Application Engineer, conducted several tests to evaluate whether 4D InSpec was suitable for use with replica paste. His methodology, results and conclusions are presented in an Application Note, Measurements of Various Defects and Their Replicas Using the 4D InSpec.”

Spoiler: it’s not disappointing, you’ll like what you’ll see.

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