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Method of automatically feeding wire to an electric discharge machine

  • US 5,077,457 A
  • Filed: 11/24/1989
  • Issued: 12/31/1991
  • Est. Priority Date: 11/28/1988
  • Status: Expired due to Term
First Claim
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1. In an electric discharge machine which develops electric discharge by applying a voltage across a work fastened to a work table and a wire electrode that is successively delivered from a wire feeding port of a wire head via a wire electrode feeding system, in order to machine said work into a predetermined machining profile utilizing the energy of electric discharge, a method of automatically feeding the wire to the electric discharge machine to insert said wire electrode in a start hole that has been perforated in advance in said work via a feed pipe mounted on a holder that reciprocally moves on guide rods provided in the head of said electric discharge machine, comprising:

  • a step for detecting the breakage of said wire electrode during the electric discharge machining using a breakage sensor that is provided in said wire electrode feeding system and that detects the condition of feeding said wire electrode;

    a step for stopping the relative movement of said work table and said wire head in response to the breakage of said wire electrode that is detected by said breakage sensor during the electric discharge machining;

    a step for taking up and removing said wire electrode of the broken side;

    a step for annealing said wire electrode of the feeding side by causing an electric current to flow therethrough to extend said wire electrode straight by eliminating internal stresses which cause curving and curling;

    a step for cutting and removing the tip of said wire electrode annealed in order to trim the tip of said wire electrode by causing the tip to hang down vertically;

    a step for moving down the tip of said feed pipe to said wire head and for moving down said annealed wire electrode while feeding said wire electrode thus annealed to meet the descending speed of said feed pipe;

    a step for delivering said wire electrode to thread said wire electrode in said worked slit of said work at a point where the wire electrode was broken;

    a step for drawing said wire electrode that has passed through said worked slit to extend said wire electrode under the tensed condition;

    a step for upwardly moving said feed pipe to return said feed pipe to the initial position; and

    a step for developing electric discharge by applying a voltage across said wire electrode and said work in order to discharge-machine said work again into a predetermined machining profile using the energy of electric discharge.

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