A lathe-type machine for electrochemical discharge machining (ECDM) has been developed for machining cylindrical parts made from insulating materials. In this paper, the removal mechanism of glass was experimentally investigated by measuring the machining forces with a two-axis force sensor during ECDM. The tangential force at an applied voltage of 40 V was larger than that at 0 V while the normal force was controlled. The amplitude of the tangential force was increased and the cycle lengthened during ECDM. Soluble and sticky sodium silicate was generated by the chemical reaction of silica glass with sodium ion. This removal process mainly caused dissolution of the sodium silicate into electrolyte.
This paper deals with an electrode feeding device based on AZARASHI mechanism for microhole electrical discharge machining. This device has a controlled friction device, a friction device for applying a constant friction and an extension device for changing the distance between the friction devices. To adjust the friction easily, a stacked piezoelectric actuator was embedded in a displacement magnification system for the controlled friction device, and a constant friction was applied with a coil spring. The performance of the concurrent machining in the case of using two devices was compared with that in the case of using a single device. The two devices were concurrently controlled with a digital signal processor. The piercing of each tool electrode was detected by the electric contact between the tool electrode and a target plate in the concurrent machining. The machining time and accuracy were the same in the both cases.
This paper deals with the monitoring of the current during electrochemical discharge machining (ECDM) with multiple electrodes. A gravity-feed-type unit with six electrodes for ECDM was fabricated. The polarity of the electrodes was set to be negative. While some holes were machined by ECDM on glass, the discharge current was forced to disperse by switching the electrodes to decrease the number of cracks (divided power). The current in the divided power was observed during the machining process and compared with those in the cases of multiple electrodes connected electrically in parallel (equipotential) and of a single electrode. Bubbles were generated by current pulses with a duration of several milliseconds when the voltage was applied. However, they disappeared during pulse intervals. A current pulse with a duration of two to five milliseconds preceded a series of sharp pulses below 200 μs in the single-electrode and divided power methods. Long and low-peak-current pulses frequently occurred, and the current pulses were concentrated at the electrodes at the two ends with equipotential power.
In this study, separation forces between molded epoxy resin and EDM finished surfaces were measured by using a tensile tester in order to quantitatively evaluate mold releasability. Based on the releasability test results, factors affecting the releasability of molded resin were discussed. Experimental results clarified that the separation force of molded epoxy resin from the EDM finished surface with kerosene type working fluid decreased with an increase of the surface roughness. The separation forces from the EDM finished surfaces with silicon powder mixed fluid and aluminum power one were higher than that with kerosene type working fluid. Furthermore, EDM finishing using nickel powder mixed fluid was tried to form thin surface layer containing nickel which would have high releasability. By using nickel powder mixed fluid, nickel could be included into the EDM finished surface, which led to lower separation force of molded resin.
Difficult-to-machine materials, like titanium alloy, have many advantages such as high hardness and strength. On the other hand, these advantages become obstacle because of the tool wear in the case of mechanical machining, such as cutting and grinding. ECM is effective method for hard materials. However, such as titanium, passivity occurs and machining stops immediately. Electrochemical mechanical polishing (ECMP) is effective for materials that easily become passivated. In this paper, the machining characteristics of difficult-to-machine materials with ECMP are investigated.
A little longer pulse duration more than several hundred nanoseconds is the middle region between ablation and melting removal of material, and effective removal of material can be expected. However, influence of these phenomena on material removal characteristics has not been clarified sufficiently. Therefore, influence of pulse duration and laser intensity on plasma was investigated by measurements of transmittance of laser energy through the plasma. Finally, effective energy to material removal characteristics was discussed with calculated laser energy relating to removal volume of mild steel as a commonly used steel by using several hundred nanoseconds pulsed laser. Transmittance ratio of laser energy was high at long pulse duration in several hundred nanoseconds range under the same pulse energy condition, because there was low reduction rate of laser energy by laser induced plasma. A little long pulse duration could perform efficient processing of mild steel under the same pulse energy condition by using several hundred nanoseconds pulsed laser.
In a large-area electron beam (EB) method developed recently, the EB of 60mm in a diameter can be used for melting or evaporating of metal surface instantly. Thus, smoothing of metal surface could be performed efficiently by preferential melting of convex parts with the surface roughness of several μmRz. It was also confirmed that edge of convex parts was rounded by the EB irradiation, since the material removal remarkably progressed due to the electron concentration and heat accumulation at the edge. It is highly expected that micro burrs can be instantly and preferentially removed by the EB irradiation. In this study, micro-deburring of rollover burr is experimentally investigated by using the preferential edge removal effect in the large-area EB irradiation. In addition, variations of burr height for each number of shot are analyzed and predicted by unsteady heat conduction analysis.