Abstract:
The present invention comprises a plasma cutting method and a cutting apparatus in which switching can be effected between suitable flow rates of a protective gas at the time of piercing and at the time of cutting, and in which suitable compositions of the protective gas can be set with respect to the time of piercing and the time of cutting, so that it is possible to protect a nozzle favorably from dross and the like, to provide a cut surface high quality and to reduce the operating cost of the protective gas. To achieve this, there are provided a piercing completion detection unit (27, 40) which detects an electric current between an electrode (1) and a workpiece (31) at the time of piercing, and which outputs a signal at the time of the completion of the piercing, and a flow regulator (15) which is provided in a protective gas circuit and which switches, in response to the piercing completion signal, the flow rate of the protective gas from a flow rate at the time of piercing to a flow rate at the time of cutting. Further, on-off valves (51, 53) can be provided in the protective gas circuit to effect switching between the composition of the protective gas at the time of piercing and the composition at the time of cutting.
Abstract:
The present invention relates to a method of machining plate materials with a plasma cutter and plasma torch. This method is one in which the density of a magnetic flux formed in the range between the vicinity of the surface of an electrode material 3 fixed to the front end of the electrode and the vicinity of the nozzle opening 1b of a nozzle 1 is between 10 and 200 gauss. The magnetic flux is generated by a magnetization apparatus 4 disposed in the vicinity of the electrode 2 of a plasma torch 100. A workpiece 26 is cut by a plasma arc emitted from a nozzle, the diameter d of which is 1.5 mm or less. The plasma torch 100 for use in this method is equipped with a magnetization apparatus 4 in the vicinity of the electrode 2 and the nozzle diameter d is 1.5 mm or less. The above magnetization apparatus 4 is disposed on the same axis as the axis center of the nozzle opening 1b. Thus, even if a voltage drop results from the fact that the nozzle diameter of the plasma torch is made very small, the present invention is free from the double-arc phenomenon and the unstable arc phenomenon, thereby enabling a plasma arc to be stabilized. As a result, stable machining quality and a high-precision machined shape can be obtained.
Abstract:
A plasma arc welding for effectively letting gases of low boiling point substances for coating a steel sheet escape, ensuring the escape of a molten metal into gaps between the steel sheets and eventually accomplishing satisfactory plasma arc welding. A hole (31) is first bored in an upper sheet (21)(or both upper and lower sheets (21 and 22)) quickly by using a plasma arc (20) having greater power than an appropriate welding value, and a vapor of coating substances is allowed to escape through the hole (31). Subsequently, power of the plasma arc (20) is lowered to the appropriate welding value, and the upper sheet (21) and the lower sheet (22) are welded together while a filler (9) is being supplied to fill the hole (31) and the gap (23). While boring is made or immediately after boring is finished, the size of the gap (23) is measured on the basis of the plasma arc voltage, and the feed quantity of the filler (9) is controlled in accordance with the size of the gap (23).
Abstract:
The present invention relates to a plasma cutting method and an NC plasma cutting apparatus in which an improvement can be made in the quality of a bore-cut product obtained by using a transferred plasma arc, and the productive efficiency can also be enhanced. In order to achieve the above-described advantages, the transferred plasma arc is switched to a non-transferred plasma arc at a position immediately before a cutting finishing point and in the vicinity of a position at which cutting lines cross each other. Simultaneously with this switching operation, the moving speed of the plasma torch is varied in accordance with a change in the plasma arc current. Additionally, the transferred plasma arc current is reduced at a position immediately before the cutting finishing point and in the vicinity of a position at which cutting lines cross each other. The moving speed of the plasma torch can be varied in accordance with the reduction in the arc current. Further, the above-described voltage detecting function is kept in the off state during a cutting operation, and it is actuated at a position immediately before the cutting finishing point and in the vicinity of a position at which cutting lines cross each other.
Abstract:
There is provided a plasma cutting method using a plasma cutting apparatus which comprises a plasma torch including: an electrode; a confining nozzle so arranged as to surround the electrode with a spacing therefrom that defines a passage for flushing a plasma gas; and an assisting nozzle so arranged as to surround the confining nozzle with a spacing therefrom that defines a passage for flushing a secondary gas, characterized in that a rate of flow of the secondary gas per unit area Vq which is expressed by an equation: Vq=Q/A2 is not less than 250 (m.sup.3 /sec/m.sup.2), where Q is a rate of flow of the secondary gas and A2 is a pinched area of the secondary gas.
Abstract:
A plasma torch for cutting use comprises a torch body, a water-cooled electrode arranged in the torch body, a nozzle arranged outside the electrode so as to cover the electrode through a plasma gas passage formed therebetween, a nozzle cap covering the nozzle, a nozzle protection cap having, on its front end side, an opening opposing to an orifice of the nozzle and being disposed outside the nozzle cap through an annular secondary gas passage communicating with the opening, the nozzle protection cap being arranged in the secondary gas passage in an electrically insulated state from the electrode and the nozzle, and an insulator disposed in the secondary gas passage and formed of an electrically insulating material, the insulator having a rectifying passage for rectifying a gas flow passing the secondary gas passage. The nozzle protection cap is composed of a front end portion and a base end portion secured to the torch body and the front end portion and the base end portion are detachably coupled with each other.