Abstract: A process for drilling chamfered holes includes the steps of directing noncontact energy onto the outer surface of the part to form a recessed crater-like entrance with chamfered walls and thereafter directing a small diameter wire electrode adjacent the substrate and spark eroding the base without removing material from the chamfered walls so as to produce a combined passage through the part with a chamfered entrance leading to a smaller outlet. In one embodiment the part has a ceramic coating which is initially removed from the part by either focusing a laser beam to a penetration depth which removes the ceramic coating while forming the entrance and in another embodiment the coating is initially removed by imposing a high voltage pulse thereagainst from a spark erosion electrode of electrical discharge machining equipment.

Abstract: Apparatus and a process for trimming the tip of a spark erosion electrode includes a mirror system for selectively diverting a hole drilling laser beam through a path which intersects the tip of an electrode used to finish laser holes by spark erosion of the walls of the laser formed hole. The apparatus includes one mirror unit which is selectively positioned to intercept the hole drilling laser beam for diverting it for electrode trimming.

Abstract: Electric discharge machining of workpieces on a mass production basis is accomplished with adaptive feedback control to achieve accurate machining of a feature to a specified size. After machining a feature, it is measured to obtain a value which represents its size. An EDM process parameter is adjusted in accordance with the measurement value so that the next feature will be machined with the size closer to the specified size. Multiple features are machined in succession and the measurement values of successive features are analyzed to determine the trend of change of the values with respect to the specified size. The parameter, such as spark energy, is adjusted in a sense which tends to cause the succeeding features to machined more accurately to the specified size.

Abstract: An EDM head has a single servo-controlled electric motor and a high ratio gear system that drives a wire electrode during both an EDM machining operation and a wire erosion compensation operation. An associated control system can be programmed to selectively drive the electrode to compensate for wire erosion and to control blind hole breakout.

Abstract: EDM apparatus has a servo drive under the control of a main control system for advancing a machining electrode toward a conductive workpiece. When the electrode arrives at a surface of the workpiece to commence EDM machining, the main control system causes a sudden deceleration of the servo. The depth controller detects this sudden deceleration by means of a sensor and sets a zero reference plane from which machining depth is measured. The depth controller can also detect electrode breakthrough by detecting servo acceleration occurring when the electrode breaks through a surface of the workpiece.

Abstract: An electronic depth controller is associated with EDM apparatus for controlling the depth of holes which are machined in workpieces by the EDM apparatus. The electronic depth controller comprises its own microprocessor which acts upon selectable input data from a control panel to provide signals relating to hole depth control to the main control system of the EDM apparatus. The electronic depth controller is selectively operable to one or the other or both of two operating modes. Data relating to each mode is input to the system via switches on the control panel.

Abstract: A process control system for electrical discharge machining apparatus to control automatically the machining of a workpiece. The process control system is operable to receive and retain a plurality of operation instructions regarding electrical discharge machining parameters and transmit operation commands to the electrical discharge machining apparatus to execute the operation instructions in controlling the complete machining of a workpiece. The process control means includes a storage unit operable to store a plurality of operation instructions enabling absolute repeatability of the machining process defined by the operation instructions in the storage unit for a plurality of workpieces. The process control system also includes a digitally controlled servo system to regulate the movement of the electrode toward and away from the workpiece.

Abstract: A steady rest follower for a workpiece comprising a frame supporting a slide which is movable in directions toward and away from the workpiece. A pair of vertically spaced support wheels are mounted on the slide for engagement with the workpiece. A pair of springs yieldably urge the slide rearwardly away from the workpiece and into engagement with the peripheral surface of an eccentrically configured roller member that is mounted on the frame. During the machining of the workpiece, the eccentric roller member is rotated to move the slide against the pressure of the springs toward the workpiece so that the support roller members are maintained in continuous engagement with the workpiece as the size of the workpiece is reduced.

Abstract: Electrical discharge machining apparatus in which a plurality of generally parallel electrodes are moved during machining and during refeed in generally parallel paths. A drive roller assembly is provided for refeeding the electrodes after each machining cycle to compensate for erosion of the electrodes that occurred during the preceding machining cycle. The drive roller assembly consists of a plurality of rollers arranged on opposite sides of the electrodes so that the electrodes are drivingly engaged between the rollers. The apparatus is further equipped with a movable gage member having an electrode engaging surface. After each machining cycle, the gage member is moved to a predetermined position between the location of the workpiece and the electrodes. The electrodes are refed into engagement with the electrode engaging surface which defines a reference surface between the workpiece and the electrodes. Refeed of the electrodes is terminated when the electrodes engage the gage member.

Abstract: Electrical discharge machining apparatus in which a plurality of generally parallel electrodes are moved during machining and during refeed in generally parallel paths. A drive roller assembly is provided for refeeding the electrodes after each machining cycle to compensate for erosion of the electrodes that occurred during the preceding machining cycle. The drive roller assembly consists of a plurality of rollers arranged on opposite sides of the electrodes so that the electrodes are drivingly engaged between the rollers. In one embodiment of the invention, the rollers slip on the electrodes after the electrodes have been moved to positions engaging the work until all of the electrodes have been moved into engagement with the work. In another embodiment of the invention, each electrode is independently driven and engagement of each electrode with the work is electrically sensed and in response to such sensing, the drive for that electrode is discontinued.

Abstract: Electrical discharge machining apparatus having means to sense the position of the electrode at the start of EDM machining of a workpiece. The apparatus includes means to measure the forward movement of the electrode during each machining cycle and regulate the backward retracting movement of the electrode to a preselected distance so as to compensate for erosion of the electrode during the machining cycle to thereby facilitate positioning of the electrode in the correct location for the next machining cycle. The apparatus includes a sensing device operable to transmit electrical pulses corresponding to incremental movements of the electrode and control circuitry which receives the pulses and controls subsequent movement of the electrode.