Ever since the founding of Marujo Seisakusho in 1906, we have been committed to better craftsmanship. For the last 55 years since 1945, we have been particularly meticulous in the making of springs.
Marujo's unique technical resources and creativity, always looking ahead to the next generation, have always opened a new epoch, and attracted the note of fellow traders.
■Features
・Grinding of Materials
The company has two peeling machines capable of grinding wires of 12 to 50 mm in diameter. Spring materials are cleared of harmful scars on the surface by grinding, resulting in enhanced accuracy and durability of large springs, which are vital components of drive systems.
Also, as we can machine wires in 0.1 mm units in terms of diameter, loads and stresses can be finely adjusted when designing springs.
Ground wires are less susceptible to scars due to machining on the surface than drawn wires, and accordingly are safer to use.
While the use of a peeling machine for grinding spring materials is a common practice in the industry now, Marujo was the pioneer in the development of this technique, and is still unparalleled by others in this expertise.
・Manufacture of Precision Springs
The company has at its disposal a wealth of technical resources for the manufacture of springs which require compactness and a particularly high level of precision for use in fuel injection valves and safety valves among other things. Our products are delivered to all major engine builders in Japan, who produce B&W and/or Sulzer models.
The springs we produce for valves which require a low D/d ratio (ratio between the PCD and the material diameter of the spring) and load accuracy when operating in 0.1 mm units are highly appreciated as evidenced by their large delivered volume, reflecting the manufacturer's long experience and accumulated technical know-how.
・Production of Large Springs
Our special equipment for large spring production, including a large coiling machine and a long heating furnace enables us to meet orders for all kinds of large springs up to 80 mm in material diameter.
Centralized control of the temperature in the furnace prevents overheating and completely eliminates decarbonization on the spring surface to which hotmolded coil springs are otherwise susceptible, resulting in high grade products in which we take pride.
・Surface Treatment for Springs
Shot peening which serves to increase the resistance of springs to permanent strain or deformation is a standard part of our manufacturing process, which also includes all features of Marujo's technical know-how for improved product durability such as double peening, hot setting and creep forming, resulting in highly durable products irrespective of size.
・Quality Control and Inspection Facilities
Marujo's is the only factory in Japan that is authorized to label itself with a Japanese Industrial Standards mark for coil springs for use in marine engine rooms, and its products are under thorough quality control in accordance with quality control agreements with major Japanese shipbuilders.
The company is further equipped for complete product quality assurance with various inspection systems including magnetic defect detectors and load testers for the load range of 0.5 kilogram to 150 tons.
