Brief Overview Of The Wire Electrical Discharge Machining (WEDM) Process

I. Selection of Mechanical Parameters
For conventional high-speed WEDM machines, the wire feed speed is generally fixed. Adjusting the feed rate primarily involves regulating the gap between the electrode wire and the workpiece. During cutting, the feed rate and the electro-erosion rate must be well-coordinated to avoid under-tracking or over-tracking. The adjustment of the feed rate is mainly achieved by regulating the frequency conversion feed amount. Under specific machining conditions, there exists only one corresponding optimal feed amount, where the feed speed of the molybdenum wire恰好 equals the maximum possible electro-erosion rate of the workpiece.

Under-tracking often leaves the machining in an open-circuit state, effectively reducing productivity and causing unstable current, which can easily lead to wire breakage. Over-tracking, on the other hand, tends to cause short circuits, also reducing the material removal rate. Generally, adjusting the frequency conversion feed so that the machining current is approximately 0.85 times the short-circuit current (with slight fluctuations of the ammeter pointer) ensures optimal working conditions. This means the frequency conversion feed speed is most reasonable, the machining is most stable, and the cutting speed is highest.

II. Selection of Electrical Parameters
Proper selection of pulse power supply parameters can improve machining performance and stability. During rough machining, higher machining currents and larger pulse energy should be selected to achieve a higher material removal rate (i.e., machining productivity). For finish machining, smaller machining currents and lower single-pulse energy should be chosen to obtain a lower surface roughness of the workpiece.

The machining current refers to the average current passing through the machining area. The single-pulse energy is primarily determined by pulse duration, peak current, and machining amplitude voltage. Pulse duration refers to the duration of the pulse current during discharge, peak current refers to the peak value of the pulse current during discharge machining, and machining amplitude voltage refers to the peak value of the pulse voltage during discharge machining.

The following electrical parameter examples can serve as a reference for use:

(1) Finish Machining:
Select the minimum pulse duration setting, set the voltage amplitude to a low level (approximately 75V), turn on one to two power tubes, adjust the frequency conversion potentiometer to control the machining current between 0.8~1.2A, and achieve a surface roughness of Ra ≤ 2.5 µm.

(2) Maximum Material Removal Rate Machining:
Select pulse duration settings 4~5, set the voltage amplitude to "High" (approximately 100V), turn on all power tubes, adjust the frequency conversion potentiometer to control the machining current between 4~4.5A, and achieve a removal rate of approximately 100 mm²/min (machining productivity). (Applicable for material thickness around 40~60mm).

(3) Machining of Large-Thickness Workpieces (>300mm):
Set the amplitude voltage to "High," select pulse duration settings 5~6, turn on 4~5 power tubes, control the machining current between 2.5~3A, and achieve a material removal rate of >30 mm²/min.

(4) Machining of Moderately Thick Workpieces (60~100mm):
Set the amplitude voltage to "High," select pulse duration setting 5, turn on approximately 4 power tubes, adjust the machining current to 2.5~3A, and achieve a material removal rate of 50~60 mm²/min.

(5) Machining of Thin Workpieces:
Set the amplitude voltage to a low level, select pulse duration setting 1 or 2, turn on 2~3 power tubes, and adjust the machining current to approximately 1A.