Page 23 - january

METALWORKING EQUIPMENT AND TOOLS

Therefore, we have a work piece installed on the machine tool table (the object table is
not shown in the figure), and a stretched, constantly rewound wire-electrode, which in this case
is a tool. From above and below, the wire passes through special dies installed on the brackets
of the machine. The staples (together with the wire) can move relative to the work piece along
two perpendicular axes X and Y. For simplicity and clarity, all additional elements of the circuit
are omitted (mechanisms of the rewind-tension path, a stage, staples, nozzles, etc.). Due to
electrical pulses from a special generator of technological current passing between the wire-
electrode and the work piece, breaking, crushing, partial evaporation of the material (metal)
of the part (electrical erosion) occurs. Without going into the physical details of the process,
which will be discussed in other articles, we only note that, moving inward, the wire, like a saw
or a jigsaw, cuts a through groove in the work piece of a certain width (slightly larger than the
diameter of the wire itself). The parts processed in this way can be divided into two groups,
which are usually denoted by the terms "punch" and "matrix". The punch is obtained from the
drop-down part of the work piece (see the next figure). In this case, the wire entry (starting
point) is carried out either outside the part (as in the figure), or (for example, in order to avoid
possible leash caused by internal stresses of the material) from an additional internal hole in
the work piece, at some distance from the starting point of the contour.
To obtain a part with an internal contour (matrix), it is necessary to have a preliminary
lead-in hole in the work piece, through which the electrode wire will be threaded before the
start of the machining process. In this case, the central dropping out part is conventionally a
waste.
An important technological factor in
wire cutting is taking into account the width
of the slot to be cut. That is, to obtain a
certain size of the elements of the part, the
point of the center of the wire moves along
a contour that is exactly half the calculated
width of the groove from the original. Thus,
for work pieces with mutually parallel
upper and lower planes (for example, as in
the figures above) with 2-axis wire-cutting
machine, the resulting upper and lower
contours will be the same. You can see
that the process is geometrically similar to
laser beam processing. Now let's turn to
more complex 4-axis machining. As a rule,
Fig. 1.
such a machine has five controlled axes,
but the fifth coordinate (Z - height) performs an exclusively preparatory "setting" function.
Before the start of machining, a certain height (in the following figure - H) is set between the
lower and upper dies of the machine, through which the electrode wire passes. This coordinate
is not directly involved in the cutting process - the distance between the dies, (height) remains

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