Views: 0 Author: Site Editor Publish Time: 2026-07-13 Origin: Site
From a mechanical engineering perspective, rotary draw bending is a complex balancing act between plastic and elastic deformation. When a CNC machine forces a tube around a bend die, the outer wall undergoes tensile stress while the inner wall experiences compression. The zone neutral to these forces shifts, and when the tooling unclamps, the internal residual stresses relax. This relaxation is elastic recovery, universally known as springback.
Predicting this behavior mathematically requires factoring in the material's Young's Modulus, its yield strength, the bend radius ($CLR$), and the tube's structural geometry. Wonsten Group's proprietary CNC control software integrates these variables into a live, closed-loop processing system to handle this material variance automatically.
The magnitude of springback is directly proportional to the material's yield strength and inversely proportional to its elastic modulus. Highly elastic materials with high yield strength (like specific titanium or high-tensile stainless steel grades) exhibit severe springback compared to mild carbon steels.
$$Angle_{\text{Bending}} = Angle_{\text{Target}} + Angle_{\text{Springback}}$$
Calculating $Angle_{\text{Springback}}$ isn't linear. It changes if the tube wall thins slightly during tight radius bends ($CLK \le 1.5 \times OD$). Wonsten’s software uses predictive modeling based on empirical stress-strain curves, allowing the CNC system to adapt to these non-linear variables without requiring the operator to run manual calculations or stress tests.
Instead of relying solely on post-bend measurements, Wonsten's software integrates directly with the machine’s servo-drive system to monitor resistance and angular displacement through a precise execution sequence:
The operator enters the basic CAD layout data ($YBC$ or $LRA$ coordinates). The software imports these vector points and automatically references the designated material profile, identifying the expected springback coefficient based on historical and engineered baselines.
For critical tolerance work, the software activates a dual-stage bending logic:
Stage 1: The machine performs the primary bend to roughly $95\%$ of the calculated overbend target.
Stage 2: The pressure die backs off slightly, allowing the sensors to read the immediate elastic release of the tube while it is still loaded on the mandrel. The software analyzes this localized data point, calculates the exact remaining angle required, and applies the final stroke.
Every completed bend feeds data back into the active control system. If a batch of raw material is slightly harder than the previous lot, the software detects the higher springback trend and automatically offsets subsequent bends within the program, keeping parts uniform throughout a high-volume production run.
When a machine compensates correctly through software logic rather than brute mechanical force, tool wear drops sharply. Correctly calculated overbending ensures that pressure dies, mandrels, and wiper dies experience uniform friction profiles, minimizing the risk of localized overheating or premature galling. For manufacturing facilities integrating CNC tube benders into broader automated cells, Wonsten’s automated compensation software provides the baseline consistency needed to ensure downstream welding robots receive perfectly fitting components every single time.
