The present invention relates to a method for evaluating a welded part on production. More particularly, the present invention relates to a method for evaluating whether the welded part has a strength more than a desired strength.
In a manufacturing process for electrical products, for example, there is a process of electrically connecting conductive members with each other through a welded part. Here, the producing order of such a welded part is described by one example of electrical wires as the conductive members, in brief.
For instance, it is carried out to arrange respective cores of plural wires between an ultrasonic horn and an anvil and further carried out to apply a compression and ultrasonic vibrations on the cores of the wires pinched between the ultrasonic horn and the anvil. Then, the resulting ultrasonic energy allows the cores to be molten thereby producing a welded part among the cores. FIGS. 1A, 1B and 1C shows various welded forms each obtained by connecting a plurality of wires W with each other through a welded part (or welded part) 105 in accordance with the above-mentioned welding order. As for the welded part 105 by ultrasonic welding etc., it is subsequently carried out to inspect whether the welded part 105 is in an appropriate welded condition or not in order to prevent shipment of defective products.
FIGS. 2A, 2B and 2C show one conventional method for evaluating such a welded part. According to the conventional evaluation method, on condition of fixing one wire W, a predetermined tensile force f1 is applied on the other wire W. Thus, by acting the tensile force f1 on the welded part 105, it is estimated whether the welded condition is proper or not. In detail, if the welded part 105 is not broken in spite of the application of the tensile force f1, then it is judged that the welded part 105 is nondefective. While, if the structure 105 is broken, it is judged that the structure 105 is defective.
As the other conventional evaluation method for such a welded part, FIGS. 3, 4 and 5 show one evaluation method disclosed in U.S. Pat. Publication No. 6,393,924. According to this evaluation method, as shown in FIG. 3, a welded part 105 is pinched between holding parts 106a, 107a of a pair of arm members 106, 107. In this state, a compressive force f2 is applied on the welded part 105 in order to judge whether such a welded condition is proper or not. In detail, on the application of the compressive force f2 on the welded part 105, it is judged that a product with the structure is 105 is nondefective unless it is broken as shown in FIG. 4. While, if the welded part 105 is broken as shown in FIG. 5, then it is judged that the product is defective.
In the conventional evaluation methods mentioned above, however, it is noted that the welded part 105 is subjected to such a tensile or compressive force that the part 105 might be broken. That is, a product on completion of the above inspection is not worthy of being a good product even if the welded part is not broken. Therefore, since the above evaluation methods require some evaluation samples to be picked up from a flow of products, an amount of production is influenced due to the presence of evaluation samples.