The Impact of Wire Electrical Discharge Machining (WEDM) on Material Deformation and Stress

The Impact of Wire Electrical Discharge Machining (WEDM) on Material Deformation and Stress

I. Causes of Material Deformation in WEDM

1. Release of Internal Stresses
   Materials inherently possess residual stresses, which are disrupted during the machining process, leading to deformation as the material seeks a new equilibrium. For example, materials that have undergone quenching have significant internal stresses. Directly cutting these materials over a large area can break this stress balance and cause noticeable deformation.
2. Influence of Workpiece Shape and Structure
   Workpieces with narrow and elongated shapes (such as dies and punches) and those with thin walls are more prone to deformation during cutting. This is because these shapes are more susceptible to stress concentration and thermal effects during the process.
3. Impact of Machining Processes
• Cutting Path Selection: An unreasonable cutting path can lead to localized stress concentration, triggering deformation.
• Heat Treatment Processes: Quenching and tempering significantly affect the internal stresses of materials. Materials with high residual stresses after quenching are more likely to deform if not treated to release these stresses before cutting.
• Clamping Methods: Improper clamping can cause uneven forces on the workpiece during machining, leading to deformation.
4. Influence of Machining Parameters
• Discharge Gap: An excessively small or large discharge gap can affect machining stability and surface quality, thereby influencing workpiece deformation.
• Machining Current: Higher machining currents increase the energy per pulse, which, while improving cutting speed, also increase surface roughness and the likelihood of deformation.

II. Measures to Prevent Material Deformation

1. Optimizing Machining Processes
• Rational Machining Sequence: Perform mechanical rough machining before quenching to remove most of the material, reducing the stress after quenching.
• Improving Heat Treatment Processes: Optimize tempering processes to reduce internal residual stresses in workpieces.
2. Stress-Relief Cutting
• Rough Machining: Before large-area cutting, perform rough machining to release most of the internal stresses.
• Two-Stage Main Cutting: For large dies, conduct two stages of main cutting. The first stage uses a larger offset (0.1-0.2 mm) to release stress, followed by a second stage with the standard offset.
3. Optimizing Cutting Paths
• Stress-Relief Path Cutting: For narrow and elongated profiles, first cut an internal stress-relief path before machining the outer profile.
• Piercing Holes: Create piercing holes for closed-contour machining to reduce deformation caused by unbalanced stresses.
4. Selecting Appropriate Machining Parameters
• Optimizing Discharge Gap: Choose an appropriate discharge gap to ensure machining stability and surface quality.
• Controlling Machining Current: Select the machining current based on the material and machining requirements to avoid excessive current that can cause deformation.

III. Conclusion