Description
Medium-speed Wire cut Electrical Discharge Machining (MS-WEDM)
belongs to the category of reciprocating high-speed WEDM machine
tool. It realizes multiple cutting functions on high-speed
reciprocating WEDM machine, and is commonly known as "medium-speed
WEDM". It is pointed out here that the so-called "mid-traveling"
does not mean that the traveling speed is between high speed and
low speed, but is a composite wire-cutting machine tool. That is to
say, the traveling principle is that high speed (***2m/s) is used
in roughing and low speed (**3m/s) is used in finishing, so that
the work is relatively stable, the jitter is small and smooth. The
errors caused by material deformation and loss of molybdenum wire
are reduced by cutting many times, and the processing quality is
improved relatively. The processing quality can be between
high-speed wire traveling machine and low-speed wire traveling
machine. Therefore, it can be said that what users call
"mid-wire-cutting" is actually a reciprocating wire-cutting
machine, which uses the processing technology of some low-speed
wire-cutting machines for reference, and achieves stripeless
cutting and multiple cutting. In practice, it is concluded that the
first cutting task in multiple cutting is high-speed and stable
cutting. High peak current and long pulse width can be used to
achieve high cutting speed. The second cutting task is to refine,
to ensure the accuracy of processing dimensions. Medium gauge
can be selected to make the roughness Ra between 1.**1.7 um after
the second cutting. In order to achieve the purpose of finishing,
low-speed wire traveling is usually adopted. The wire traveling
speed is **3 m/s, and the tracking feed speed is limited within a
certain range to eliminate the round-trip cutting fringes and
obtain the required dimensional accuracy. The task of the third,
fourth or more cuts (at most seven cuts can be achieved by the
middle wire traveling control software at present) is polishing and
polishing, which can be carried out with the minimum pulse width
(currently the minimum frequency can be divided to 1 ugs). The peak
current varies with the requirements of the surface quality. In
fact, the finishing process is an electrical spark grinding. The
amount of processing is very small, and the size of the workpiece
will not be changed. The wire traveling mode is similar to the
second cutting mode, which adopts the low-speed wire traveling and
speed-limited feed. In the process of mid-wire cutting, attention
should also be paid to deformation treatment, because in the
process of WEDM, with the effect of the original internal stress
and the influence of the thermal stress produced by spark
discharge, irregular deformation will occur, resulting in uneven
thickness of the cutting tool and affecting the processing quality.
Quantity and processing accuracy. Therefore, different machining
allowances should be reserved according to different materials so
that the workpiece can fully release the internal stress and
complete torsional deformation, and there is enough allowance for
finishing in subsequent multiple cutting, so that the final size of
the workpiece can be guaranteed.
