Company History

How It Began

We were first established as Seidensha Seisakujo in 1924, producing and selling both cable and wireless communication machines.

About Us

In response to the rapid development of the plastic industry in early 1950s, Seidensha started producing high frequency welders and high frequency sewing machines and developing and applying electromagnetic energy to plastic processing. Due to their success in the plastics market, Seidensha Electronic Co., LTD was created in July 1956 and built a new factory in preparation of production systems. 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.

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    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.

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Our Foundation

We have been working as a reliable consultant and unique manufacturer that can generally provide welding and joining equipment and applied processing technology for plastic materials. The foundation of the company is based on their many patents and accumulated know-how developed from their research and development system and collaborative development based on their close relationships with public universities across Japan.