Jicheng Bai

Study of Energy-Saving Pulse Power for WEDM Based on Pulse Width Modulation

The energy efficiency of traditional pulse power for wire electrical discharge (WEDM) is less than 25% because of the use of current-limiting resistance. The new type of energy-saving resistor-less pulse power proposed in this paper employs the structure of a dual-arm power amplifier, the strategy of single-arm pulse width modulation (PWM) and the control mode of cutting off long-time short circuit. Heat generated by current-limiting resistance and useless power consumption caused by long-time short circuit is avoided, and therefore the energy efficiency is increased.

A Zero Current Switching Half-Bridge Power Supply for High Speed Drilling Electrical Discharge Machining

High speed drilling electrical discharge machining (HSDEDM) uses controlled electric sparks to erode the metal in a work-piece. Through the years, HSDEDM process has widely been used in high speed drilling and in manufacturing large aspect ratio holes for hard-to-machine material. The power supplies of HSDEDM providing high power applications can have different topologies. In this paper, a HSDEDM power supply prototype has been developed, utilizing the Zero Current Switching (ZCS) Pulsed Width Modulated (PWM) half-bridge topology with a minimal component count and inherent protection under short circuit conditions. This topology has an energy conservation feature and removes the need for output bulk capacitors and resistances. Energy used in the erosion process will be controlled by the switched IGBTs in the half- bridge network and be transferred to the gap between the tool and work-piece. The relative tool wear and machining speed of our proposed topology have been compared with that of a normal power supply with current limiting resistances.

Analysis of Non-limiting Current Resistance and Isopulse Power Supply for WEDM

Wire electrical discharge machine (WEDM) is one of the effective and important methods for machining complex parts and hard cutting materials. The power supply plays an important role in WEDM, which influences the machining precision and cutting speed. The energy efficiency of traditional pulse power for WEDM is less than 25%, because of the use of current-limiting resistance. In the paper, a novel Pulsed width modulated (PWM) half bridge power supply has been developed, eliminating the current-limiting resistance, so the energy efficiency is increased and the energy saving effect is remarkable. Nevertheless, this power supply has adopted a discharge control strategy of breakdown waiting, making the single discharge energy being equal and improving the cutting speed.

A Novel Pulse Power Supply for Insulated Ceramics by HS-WEDM

To and fro wire electrical discharge machining (HS-WEDM) has been employed widely. Currently, there is a new technology that using the assisting electrode method in insulated ceramics HS-WEDM machining. In this paper, a novel current wave pulse power supply is designed to machine the insulated ceramics by HS-WEDM. Aim to the two phases in the insulated ceramics HS-WEDM machining, through the high-low voltage composite method, the half-bridge circuit is designed to realize the abnormity current waveforms in the machining. The conducting layer is formed in the low current and the insulated ceramics is removed in high current for the high temperature. Compared to the normal pulse power supply, the machining speed of the novel pulse power supply is faster then the normal.

A Novel Detecting and Controlling Strategy of the Discharge Status in High Speed Wire Electrical Discharge Machining

There are three discharging statuses-open, discharge and short-in high speed wire electrical discharge machining (HS-WEDM). This paper proposes a novel detecting and controlling strategy of the discharge statuses in HS-WEDM. Floating threshold of voltage which changes with the mode of gap current is proposed in this paper; three basic discharge statuses are detected and controlled by this method. Thus the fine precision and the sensitive of detection will be achieved. Normally, most of the used detecting methods are about fixed voltage threshold detecting technology, these methods can not be used on the range of the current is large and the non-rectangle discharge current waveform. In this paper, the floating threshold of voltage with the mode of gap current following is used to detect the discharge statuses, and the problem about the gap voltage waved with the gap current can be settled effectively. The random gap current wave also can be detected by this method.