Clothing Steamers Manufacturing Defect
EDT was asked to examine clothing steamers with damaged internal components and determine the cause of the damage.
EDT Analysis and Findings:
After a clothing steamer manufacturer changed suppliers for its appliance power cords, consumers began to return steamers to the factory for repairs at a higher than expected rate. An investigation into the cause of the returns revealed heat damage to internal components of the steamers. A disagreement arose between the manufacturer of the steamers and the supplier of the cords, over the cause of the damage to the units.
EDT received two damaged steamers, several damaged power cords, and two exemplar steamers for examination and testing. Examination of the damaged steamers revealed that the ON/OFF power switches had experienced melting that resulted in displacement of the metallic contacts within the switch body. As a result of the contact displacement, the switches would not permit electricity to flow into the steamer. The damaged power cords exhibited heat damage (melting and discoloration) near the crimp connector for the connection to the ON/OFF power switch.
EDT conducted operational tests of the exemplar steamers. During the operational tests, temperature measurements were made using an infrared camera and thermocouple devices. The measurements indicated that the maximum temperature within the interior of the steamers was near the connection between the cord and the ON/OFF power switch of the steamers.
Because the maximum temperatures were found near the crimp connector of the power cords, poor electrical contact between the crimp connector body and the copper conductors was suspected. Poor electrical contact would have resulted in resistive heating, which could have damaged the switches. To confirm this hypothesis, EDT mounted, in an epoxy base, crimp connectors from power cords manufactured by both the current supplier and the previous supplier. The connectors were cross-sectioned near the center of the crimp area and photographed. Figure 1 below shows a crimp connection from the previous supplier.
The crimp connection in Figure 1 resulted in a compressed connection, with good contact between the individual conductors and between the conductors and the connector body. Photographic image analysis revealed that the copper-filled area inside the crimp body was 92%, resulting in about 8% air space within the crimp area. In contrast, the crimp connection in Figure 2 had a fill rate of 78%, resulting in 22% air space between individual copper conductors and between the conductors and the connector body. The air space resulted in less contact surface area between conductors, and, therefore, higher resistance. The air space also would have allowed oxygen from the air to oxidize the copper conductors, which, in turn, would have resulted in higher resistance for the connection. A proper crimp connection would result in good surface contact between the conductors and the connector body. The failure by the new power cord supplier to make a proper crimp connection was a manufacturing defect that resulted in a high resistance connection in the power cord.
In summary, the investigation by EDT showed that the heat damage observed inside the clothing steamers was attributable to defective crimp connectors on the power cords from the new power cord supplier.