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When people talk about accuracy in EDM, the focus usually goes straight to the controller, the software, or the power supply parameters. These are important, but they are not the full picture. In fact, many accuracy problems that show up in production have nothing to do with programming or discharge settings. The wire system itself is often overlooked.

Wire Condition Matters

Imagine you have already accounted for machine feed, linear guide precision, and process parameters, etc. What remains is the true state of the wire during discharge. This state is measurable and controllable, but only if you focus on the right elements:

a. The wire must run without abnormal vibration;

b. The wire must maintain constant tension dynamically;

c. The wire must start from the correct initial tension baseline.

a. Stability

Nothing destroys accuracy faster than vibration. If the wire shakes while running, vertical surfaces lose straightness, leaving wavy lines instead of flat planes. Horizontal profiles lose dimension, with shapes drifting unpredictably. Surface finish becomes chaotic, with random ripples and rough feel. (Random ripple marks and rough feel.)

Stability depends on the smooth passage of the wire through every contact point: guide wheels, conductive blocks (or power feeders), etc. Any dirt, wear, or imbalance introduces periodic vibration that amplifies into accuracy loss.

b. Constant Tension

Even a stable wire cannot hold its path if tension varies during cutting. Vertical surfaces distort into a “barrel shape,” wider in the middle than at the ends. Horizontal profiles round off at corners or drift away from programmed paths. Surface finish shows repeating stripe patterns that are difficult to polish out. (Bulging sides, rounded corners, or repeating stripes.)

Constant tension acts like a suspension system, absorbing the forces of sparks and coolant flow. Without it, shape accuracy is lost no matter how perfect the program is.

c. The Right Baseline

Every control system needs a reference, and in wire EDM that reference is the initial tension you set.

If this is not right, vertical surfaces cannot achieve full straightness, even with stable running. Horizontal profiles shift consistently off-size, either too big or too small. Surface finish fails to reach the optimum quality, and cutting efficiency drops. (Systematic size errors.)

In summary, the part itself can become your diagnostic tool. You can confirm stability first by listening, feeling, and watching the wire path, and then verify constant tension response during corners and thick cuts, or check the baseline tension with measurement tools. A healthy wire system protects part quality, reduces downtime, and raises machine value.