Teaching Good, Catching Bad: Inside ibg NDT's iPMFT and Good-Part-Teaching

In this interview, Dr. Eddy explains why good-part teaching, combined with ibg NDT Technology's iPMFT, delivers the most reliable results for heat treatment verification and mix-up detection.

What advantage does ibg NDT Technology’s Preventive Multi-Frequency Testing (iPMFT) offer for heat treatment verification and material mix-up detection, given that both are ultimately aiming to test microstructure?

Dr. Eddy: In the past, digital electronics were slow and multi-frequency testing was a speed issue. Therefore, many instruments, even today, run only on one or a few base frequencies. But the one or the few frequencies allow only to detect defined NOK parts/mix-ups, mostly sampled by artificially created parts. The set-up of the test is directed towards these bad parts (bad-part-teaching, single-frequency testing).

The drawbacks of bad-part teaching on only one or a few frequencies are multifold:

1. There is no way to validate that the bad part(s) created cover the full range of heat treatment-, material- and mix-up mistakes and errors that might occur in practice.
2. Every new part requires a range of reproduceable bad parts, which need to cover the universe of possible deviations from OK microstructure, not just hardness.
3. Experts are required to perform the set-up. If the number of base frequencies and harmonics is limited, you need to find the right combination of them; a task, which can range from complicated to impossible. We call that the “barista style” of testing.
4. Most critically: Other variations of the microstructure, other than the expected ones of the NOK master, are not detectable without good-part teaching, combined with preventive multi frequency testing and simultaneous harmonics as by ibg (iPMFT and iSHA).

These drawbacks of conventional ET/ECT structure testing, rooted in lower performing instrumentation, pose a serious risk to the quality of the final product. This risk is not abstract: it translates directly into potential harm to people, as well as financial penalties and other claims.

Dr. Eddy: Modern, digital high-speed eddy current solutions use eight base frequencies (preventive multi frequency, PMFT), and, as with ibg, simultaneously appply two sets of harmonics of these base frequencies (Simultaneous Harmonics Analysis by ibg, iSHA). The combination is called iPMFT and provides detailed fingerprints of the microstructure. It allows the prevention of bad parts leaving the factory. Even more importantly, it also detects those defects, which differ from the expected defect patterns in subtle yet critical ways, as well as mix-ups between visually identical components.

This truly preventive thinking and solution design has guided the quality philosophy of ibg NDT's founder Mr. Baumgartner for over 40 years and continues to do so today.

Dr. Eddy: ibg NDT technology uses good-part teaching, because it allows sorting out everything which deviates from OK parts. It also makes the set-up of a new part type or material as easy and reliable as possible, even for non-NDT experts. Internally, we call our instrumentation the “automated coffee machine with coffee-type-selector and integrated bean recognition.” That also means a master NOK part(s), as used in bad-part-teaching, may always be used for verification purposes, like a “bad bean”😊. 

Dr. Eddy: iPMFT and good-part teaching by ibg require only a few parts that are homogenous in their eddy current footprints, usually eight or thirteen parts. The visualization of the fingerprints of these parts as bars and ellipses on the screen is intuitive and shows the homogeneity of the microstructures. If everything is unknown, the outlier parts should be analyzed with conventional, destructive methods. With the remaining OK parts, the system defines the thresholds automatically (tolerance zones) for sorting across all base frequencies and their harmonics (teaching, deterministic machine learning). The multitude of 24 thresholds allows a very fine distinction between OK and NOK parts and a very fine classification of parts. And, if a NOK master is available, we recommend verifying the sorting with it. The eddy current fingerprints of the NOK master are also stored in the system for reference.

ibg NDT Technology is a German manufacturer of eddy current testing and NDT solutions, headquartered in Ebermannstadt. Founded in 1983 by Herbert Baumgartner, it's now a world leader in eddy current NDT. Its product line includes test controllers (eddyvisor, eddyliner, eddyguard, eddyQlab), automated inline systems, and AVIKO ball inspection machines—made in Ebermannstadt, with ball inspection systems built via Sorting Solutions s.r.o. in Bílina, Czech Republic. Key technologies: PMFT, iSHA, iTAS, and AI/ML evaluation via the ibg Ai Cube CDP.

ibg NDT serves aerospace, automotive supply, bearing manufacturing, renewable energy, and defense/ammunition sectors through 30+ global distribution partners. Services span consulting, integration, training, calibration, and repairs. ISO 9001 certified since 1995, with 40+ years of NDT expertise.