| 摘要 |
<p>A method of controlling wire tension of a wire-cut discharge machining apparatus to avoid break in the wire by preventing the wire tension from changing excessively because of abnormal operation of an electromagnetic powder brake when the tension to the wire is applied, removed or is changed. When it is judged that the practical wire tension may change excessively based on the comparison of the presently instructed wire tension and a newly instructed wire tension, the processing is repeated to add or subtract the upper-limit change quantity (Δt), which has been set in advance to a value that will not excessively change the wire tension, to or from a present desired wire tension (tO) at a predetermined period (U) until the desired wire tension reaches the instructed wire tension (tn). The electromagnetic powder brake undergoes the braking operation with an operation voltage corresponding to a desired wire tension that gradually changes, and the practical wire tension gradually changes until the instructed wire tension is reached.</p> |
