May/June_AMP_Digital

FEATURE A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 0 6 6 10 1 eters are 100% fit, a part will be recognized as OK, Fig. 2. If all tolerance fields are matched, the part will be OK, if only one tolerance field is not matched, the part is sorted as NOK. INSPECTION EXAMPLES The following tests were performed using an eddy-cur- rent system as shown in Fig. 3. Inspection of screws. Screws and other fasteners are extremely important high-security components throughout different industries. The failure of a screwcan lead to produc- tion stoppages or serious accidents. In the fastener industry the permissible error quantity is less than 1 ppm. For this reason, more and more testing machines are equipped with PMFT. Figure 4 shows such a high-speed test- ing system for screws, the test speed is appr. 10-15 parts/sec. This system includes a turntablewith newly developing U-coils, and screws can be checked very sensitively for un- expected various faults, such as strength, structural analysis, carburizing, decarburizing, andmaterial mix. Such testing technology can be adapted at any time to existing testing machines. Inspection of special bolts. These components as shown in Fig. 5 require uniform hardening in a very narrow tolerance band. The drawing tolerance is 260-340 HB, but all parts of a hardening batchmust be in a tolerance of 20HB. A common defect is material-batchmixing that leads to different hardness within the drawing tolerance. In this ex- ample, there are two mixed material batches from the same material, batch 1, with 275-285 HB, and batch 2, with 315-330 HB. Both batches are in the drawing tolerance but the spread in the heat treat batch is too high. The PMFT established a save test system, which made sure that no batch mixing or other faults are in production. SUMMARY The test against unknown heat treatment faults and material mingling by means of preventive PMFT eddy-cur- rent testing gives the heat treatment department a safe test method with the highest possible safety. Due to the inte- gration in production lines, low test costs are possible, with enormous security. In addition to high test sensitivity for microstructural changes, hardness faults, and case depth changes, PMFT provides a very high level of test safety for unexpected heat treatment defects andmaterialmingling. Thus, the eddy-cur- rent test is well suited to 100% testing of medium and large quantities in order to ensure production quality. ~HTPro For more information: Arnold Horsch, Arnold Horsch e.K., Berghauser Str. 62, 42859 Remscheid, Germany, +49 (0) 2191 7912021, info@arnold-horsch.de. Fig. 2 — Examples of OK and NOK distance pin parts. Fig. 3 — The eddyvisor eddy-current test system. Fig. 4 — Bolt test machine, rotating table. Fig. 5 — Tested special bolts.