FORMATION METHOD OF MAGNETIC SCALE FOR DISPLACEMENT MEASUREMENT OF PISTON ROD USING THIN FIRM

A formation method of magnetic scale for displacement measurement of a piston rod using a thin firm is provided to expand life of the thin film forming magnetic scale by forming a hard chrome layer to protect the thin film. A formation method of magnetic scale for displacement measurement of a piston rod(60) using a thin firm includes the steps of: manufacturing a mask to print magnetic material and non-magnetic material on a thin film repeatedly; printing a ferromagnetic material on the thin film by using a mask for printing ferromagnetic material(40); hardening the printed ferromagnetic material; printing a non-magnetic material(50) on the thin film on which ferromagnetic material is printed by using a mask for printing non-magnetic material; hardening non-magnetic material; forming a groove(61) on the outer peripheral surface of a piston rod with an end mill or a grinding stone; attaching the thin film on which ferromagnetic material and non-magnetic material are printed alternately at a regular interval; coating the thin film with hard chrome to protect magnetic material and to maintain hardness of the surface of the thin film; hardening hard chrome; and grinding and polishing the piston rod to have outer diameter and hardness equal to a conventional piston rod.