Compensating springback in CAD die surfaces

    Achieve enormous time savings in die tryout with global surface morphing

    The elastic properties of the sheet-metal cause springback after the forming of sheet metal parts. This springback is compensated in the sheet-metal die, so that the part is initially formed to an "incorrect" geometry and then springs back to yield the desired geometry. Manually grinding springback in the die is extremely time-consuming in the tryout presses Process reliability is also affected.

    Tebis therefore uses global morphing rules with which individual surfaces can be deformed completely automatically based on FEM analyses, measurements, digitized data or experience – and feedback is compensated, greatly reducing the number of correction loops. The qualitative surface properties such as segmentation, polynomial degree, and transitions are optimally adjusted to the morphing rule in this CAD-based morphing. Analysis functions indicate adherence to the morphing rule and to the quality of the formed surfaces.

    Substantial time savings 
    Less grinding work and fewer corrections cycles in tryout
    High process reliability
    A learning system based on prediction, morphing and subsequent analysis
    High CAD data quality
    The quality of the morphed surfaces meets the requirements of active surface and die design

    Multiple morphing rules

    Tebis offers several options for defining the morphing rule. All morphing rules can be combined together.

    From simulation systems

    FEM systems specializing in the simulation of sheet metal deformation simulate springback and provide compensation rules, such as with two triangular meshes. Tebis uses these and automatically morphs the affected area of the active surface of the die.

    From experience

    If the expert knows how the sheet metal springs back and how it must be deformed, the morphing rule is created in Tebis with a substitute surface pair (visible in the background) that represents the desired morphing. Rules can also be specified with vectors and rotation.

    From measurements

    Tebis takes the measuring points determined on the test part with springback, calculates the distances from the desired part, and automatically compensates the CAD surfaces in the die.

    From digitized data

    The comparison between the scanned sheet-metal part and the CAD surfaces of the die indicates where springback is occurring. The meshes from the scanning process are used to define the morphing rule. Also: Scanned sheet-metal parts can be quickly and easily reverse engineered to surfaces in Tebis (see Tebis reverse engineering).

    Morphing of outer skin surfaces based on results from forming simulations

    The predictions regarding springback are imported in Tebis through interfaces to simulation systems, and the CAD surfaces are automatically morphed. The better the original surfaces are, the better the morphed resulting surfaces will be. Tebis offers an extensive function package for the analysis and optimization of CAD surfaces before and after deformation.

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    Tebis takes the springback compensation data from the simulation system and forms the class-A surfaces of the outer skin part
    The high quality of the deformed surfaces can be seen in the reflection lines

    Morphing sheet-metal parts based on measuring points

    Tebis takes the measuring points determined on the test part with springback, calculates the distances from the desired specified part, and automatically compensates the entire sheet-metal part.

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    Tebis automatically determines the local individual values for compensating springback from the measuring point coordinates and forms the entire sheet-metal part accordingly.
    In the distance analysis, the unchanged areas are shown in green and the deformed areas are shown in blue and red.

    Additional links

    Designing and manufacturing active surfaces to exact specifications

    Tebis offers automated design functions with which active surface designers can include sheet thickness, thinning effects and reliefs in the design of the CAD active surfaces. This results in significant time savings in NC programming, machining and tryout.

    Tebis process solutions at Volkswagen

    "Even if just one pressure area was overlooked in the process, the correction cost us up to 10,000 Euros. Today, for example, we install dies for doors that we previously had to rework directly in the press for roughly 160 hours"

    Roland Schöbel, Head of machining

    Die manufacturing Volkswagen AG, Wolfsburg, Germany

    Read full story
    Using reverse engineering to align the CAD world with the real world

    Reverse engineering is used everywhere that work is performed manually on real objects and in the CAD model. In model manufacturing, design objects and vehicles modeled in clay are scanned and transferred to CAD surfaces. In die manufacturing, manual changes to sheet-metal dies in the tryout phase are scanned and the existing CAD model is updated based on the scanned data.

    Automatically and manually optimize CAD surface quality

    CAD surface quality results from the algorithmic properties of the CAD systems used, from the design history and from conversion processes via interfaces. CAD data with qualitative deficiencies often has to be imported and further processed in order to manufacture molds and dies. Tebis helps optimize surface quality.


    Our new department structure as well as the Tebis solution for morphing and the Tebis analysis and optimization functions enabled us to get correction grinding under control. We scored in all areas: Parts got to the machine faster, CAD data and NC programs could be updated faster, and surface quality was even better.

    Volkswagen AG

    What used to take a week, we can now accomplish in a single day using Tebis Morphing, and the need for manual reworking has gone down.

    Merima Präzisions-Werkzeugbau GmbH, Germany
    Challenges in Sheet Metal Draw Die Manufacturing

    No more visible edges or steps in the die surface: Tebis active surface preparation includes compensation of sheet metal thinning, incorporation of pressure surfaces and free design of negative radii. Specialized functions enable programming without virtual wall thicknesses.

    Read full article
    Tebis white paper: Evolution in sheet-metal forming

    Tebis has developed functioning software-supported processes specifically for die manufacturing to enable the production of top-quality class-A surfaces and to automate manufacturing of small parts. Both processes verifiably reduce manufacturing expenditure, thanks to standardization and the integration of individual manufacturing knowledge. 

    Download white paper