In CNC machining, we often encounter dimensional changes caused by stress release in materials. When a material undergoes milling, drilling, or cutting, internal stress redistributes, potentially leading to shrinkage or expansion of the workpiece, resulting in dimensional instability.
This not only affects machining precision but also impacts assembly compatibility. To ensure product quality, we implement a series of measures to tackle this challenge.
The Impact of Internal Stress in Materials
Metal materials develop residual stress during forging, extrusion, or casting. When these materials undergo CNC machining—especially when split or when a significant amount of material is removed—the internal stress releases, which may lead to:
- Shrinkage or expansion of the workpiece
- Deterioration of flatness or straightness
- Hole position shifts, affecting tolerance accuracy
These issues are particularly common in aluminum alloys, stainless steel, and high-strength steel, so we carefully consider stress release effects before machining.
Our Solutions
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Pre-Treatment and Natural Stress Release
Before actual machining, we allow the material to sit for a period, letting internal stress partially release to reduce the risk of deformation. For example:
- Aluminum alloys: Usually left for 24 hours before re-measuring dimensional changes.
- High-strength steel: May require annealing to reduce internal stress.
- Large workpieces: Often undergo initial rough machining, followed by a resting period of several hours or a full day before precision machining.
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Segmented Machining Strategy
To further minimize the impact of stress release, we adopt a “segmented machining” approach. We first conduct rough machining, leaving a certain margin, and then let the workpiece rest before proceeding with precision machining to ensure final dimensional stability.
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Dynamic Compensation and Measurement
We perform multiple measurements during the machining process to monitor dimensional changes and adjust accordingly. For example:
- For parts with strict tolerance requirements, we predict shrinkage or expansion trends after rough machining and compensate accordingly during precision machining.
- Using high-precision measuring instruments (such as CMMs – Coordinate Measuring Machines) to ensure the workpiece meets specification requirements.
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Heat Treatment and Aging Processes
For certain high-precision parts, we may conduct heat treatment or artificial aging before or after machining to reduce residual stress. Examples include:
- Aluminum alloy parts undergoing aging treatments (such as T6 treatment) to stabilize structure.
- High-carbon steel parts undergoing stress-relief annealing to reduce deformation risks.
Conclusion
Stress release in CNC machining is an unavoidable challenge, but with proper machining strategies, resting periods, precision measurement, and compensation techniques, we can effectively control dimensional changes and ensure high precision and stability.
Our years of experience and technical expertise allow us to provide reliable solutions for our clients, ensuring that every product meets strict quality standards.
If you are experiencing dimensional issues due to stress release in CNC machining, feel free to contact us. We provide professional technical support and solutions!
