Along with the development of several kinds of automatic systems and consolidated processing systems, Seidensha developed the Computer-Controlled Fully Automatic Metal Chain Welding System and the Computer-Controlled Waterproof Sheet Welder in 1989.

In 1994, Seidensha expanded its business to such fields as welding monitoring equipment and image-applied measuring equipment.

In 1996, Seidensha developed the digital-ultrasonic welder, the SIGMA Series, a machine representing the concept of the next generation, which united their enormous knowledge and know-how with modern sensor and computer technology. Seidensha accomplished innovative high quality and precise welding machines, which had never been realized before.

Seidensha continued to break new ground by developing the SONOPET 300S series of light weight, high-energy portable welders in 2003. The 300S series is a vast improvement on older, portable welder designs and has continued to evolve with the release of the 303S models in 2007. Seidensha has also begun mass production of their new SIGMA 630 B units, which break further boundaries beyond the 300S series.