METHOD FOR MANUFACTURING GLOW PLUG FOR DIESEL ENGINES WITHOUT LOSS OF WORK COMPARED WITH CONVENTIONAL METHOD BY FORMING EXTERNAL SHAPE AND HOLE FOR HOT WIRE COIL BY PRESSING WORK

摘要

PURPOSE: To provide a method capable of continuously mass-producing glow plug for diesel engines while minimizing unnecessary loss of a work. CONSTITUTION: The manufacturing method of glow plug for diesel engines comprises a cutting process(P0) of cutting a work supplied to a cutting dies to a certain length by a cutting knife; a hardening process(P1) of flatly hardening both fractured surfaces of the work by inserting the cut work into a first dies and pressing the cut work by a punch part; a preforming process(P2) of enlarging an upper portion of the work to a large diameter so that a head portion of the glow plug is formed by inserting the work into a second dies and pressing the work by a punch part, and forming a central seat surface on a lower central portion of the work so that a hole is formed on the central seat surface; an upset and forward extrusion process(P3) of forming the head portion in a hexagonal shape by upset by inserting the work into a third dies and pressing the work by a punch part, and forming a lower preliminary hole with a certain depth on a lower central portion of the work along the central seat surface by extrusion; second extrusion process(P4) of forming an upper preliminary hole connected to the head portion hole while forming a head portion hole with a certain depth on an inner central region of the head portion by extrusion by inserting the work into a fourth dies and pressing the work by a punch part; third extrusion process(P5) of forming the lower preliminary hole deeper by extrusion by inserting the work into a fifth dies and pressing the work by a punch part; fourth extrusion process(P6) of forming the upper preliminary hole in the head portion deeper by inserting the work into a sixth dies and pressing the work by a punch part; and blanking process(P7) of forming a through hole by pressing the work by a dies pin and removing the work between the lower preliminary hole and the upper preliminary hole formed in the above processes in the state that the work is inserted into a seventh dies and held by a punch part.