Method of making an injection molding nozzle with tip insert

In a method of making an integral heated injection molding nozzle comprising the steps of:

• (a) making an elongated inner portion having a rear end, a front end, a melt bore extending therethrough from the rear end to the front end, and a general cylindrical outer surface with a spiral groove extending therearound,
• (b) making an outer collar portion to fit around the inner portion adjacent the rear end of the inner portion, the outer collar portion having a radial opening therethrough,
• (c) winding an electrical heating element into the spiral groove extending around the outer surface of the inner portion, mounting the outer collar portion in place around the inner portion with at least one terminal portion of the heating element extending outwardly through the radial opening through the outer collar portion, and closing in the radial opening around the at least one terminal portion,
• (d) applying a first brazing material having a predetermined melting temperature between the inner portion and the surrounding outer collar portion,
• (e) integrally brazing the inner portion, the outer collar portion, and the electrical heating element together by heating them in a substantially oxygen free atmosphere in a vacuum furnace to a temperature above the melting temperature of the first brazing material, and
• (f) machining the integral nozzle to provide a desired outer shape and finish, the improvement comprising the further steps of:
• (g) making a seat extending around the melt bore at the front end of the inner portion of the nozzle,
• (h) making a tip insert having a rear end, a rear portion extending forwardly from the rear end, at least one tip portion extending forwardly from the rear portion, and a melt bore extending forwardly therethrough from the rear end, the rear portion being made to fit in the seat at the front end of the inner portion of the nozzle with the melt bore through the tip insert extending from the melt bore through the inner portion of the nozzle,
• (i) inserting the tip insert into the matching seat at the front end of the inner portion of the nozzle,
• (j) applying a second brazing material where the tip insert and the inner portion of the nozzle join, the second brazing material having a predetermined melting temperature substantially lower than the melting temperature of the first brazing material, and
• (k) integrally brazing the tip insert in place in the inner portion by heating them to a temperature above the melting temperature of the second brazing material and below the melting temperature of the first brazing material.