Wire EDM Corner Cleaning: Principles, Settings and Inclined-Cut Machining

During wire EDM, gasification and spark micro-explosions push the wire away from the feed direction. In the cutting zone the wire is therefore slightly bowed, so the actual cutting point is not perfectly synchronized with the table coordinates. This is the wire lag effect. Small as it is, it visibly degrades positional accuracy.

1. The Lag Effect and Where Corner Cleaning Comes From

Typical symptoms:

• Cutting a square hole, the table has already turned at the corner but the wire still lags on the previous line; instead of reaching the exact corner it takes a diagonal shortcut to the next edge, rounding the corner — the measured clearance looks normal yet the part will not assemble
• Cutting a round hole, when the wire completes the circle and returns to the start it cannot reach the true junction, leaving a distinct ridge (“rib”) on the inner wall

Corner cleaning pauses the table at the corner for 1–2 seconds, giving the lagging wire time to catch up, discharge, and flush away the debris before the next edge starts. Note that it mitigates rather than fully eliminates the problem — on circles and complex curves the direction changes constantly and lag causes shape distortion, so only an “approximate” form is possible.

Other ways to reduce lag: lower the wire guide arm, slightly looser tracking, and repeated cutting.

2. Corner Cleaning Settings

1. Corner delay. Set the delay time in the machining parameters (usually 1–2 seconds). In Autocut software, enter the corner delay period and value there
2. Over-cut. After the profile finishes, the wire returns to the origin and leaves a small rib, because the wire is round and the same path has tiny triangular blind areas on either side. Over-cut machining continues a few millimeters past the endpoint to remove the blind area and deliver a complete shape

Beginners should keep corner cleaning enabled — the few seconds “wasted” per corner are nothing compared with the positional accuracy gained.

3. Inclined-Cut Corner Cleaning

Corner cleaning often suffers from unstable discharge, repeated wire retraction, slow feed, high wear and uneven roughness, because the discharge area is small while the depth is large. Inclining the electrode for cutting is a good solution.

Key points:

1. Analyze the feature first — undercuts or reverse tapers that contradict the feed direction rule out inclined cutting; it would change the profile
2. Choose the number of axes — 2- or 3-axis linked motion, depending on shape and openness; use 3-axis wherever possible for better flushing, stability and speed
3. Define the inclined path — the path is the line between the start and end points. The end point is fixed (the final machining position); the start point is defined at programming and should include an angle
4. Choose the start position — the electrode must not interfere with other workpiece areas; set the start a little farther from the end point for lift distance and flushing, but not too far, to avoid long idle travel
5. Adjust parameters — set the lift height large (usually more than twice normal, since it equals the inclined path length), shorten discharge time, and raise lift speed

4. Practical Notes

• HS-WEDM is a “roughing machine” — surface finish and a brittle recast layer are inherent, so leave allowance for follow-up operations
• Hole cutting is the best test of machine accuracy; lead screw precision and reversal backlash make holes slightly elliptical. Multiple skim passes (narrower pulse width, slower wire speed, three sweeps) reach 0.01–0.015mm ellipticity with visibly better finish

Corner cleaning is a necessary setting to ease wire lag and improve corner accuracy — keep it on. For complex features, combine it with inclined-path cutting and tune path definition and electrical parameters for the best result.