Simulation is more than Software

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Virtual 3D prints
Using additive manufacturing process simulation to predict and compensate distortions in a 3D printed rolling die

Additive manufacturing process simulation of a rolling die using Ansys Additive Print

Sector: Machinery and plant engineeringSpecialist field: Structural mechanics

Metal powder bed additive manufacturing is a process that can allow for great design freedom. However, rapid heating and cooling cycles during the layer-wise build process lead to distortions, which can cause failed builds and negatively impact part performance. Simulation can help predict and compensate those distortions to save time and cost due to failed prints.

Summary

Task

Distortions of a 3D-printed rolling die shall be simulated with the help of an Ansys Additive Print simulation workflow. A previous print showed larger than permissible warpage, which the simulation shall be used to predict and allow for compensation in order to allow for an in-tolerance print.

Solution

After calibration of the inherent strain simulation approach within Ansys Additive Print using a cantilever calibration part, the current design rolling die was simulated and compared to already printed parts. Predicted distortions matched the real print. These distortions were mapped negatively onto the original CAD geometry and thus compensated. After verification with an additional simulation of the print process, a real print of the part was done. This new part showed significant improvement of the distortions of an order of magnitude lower than before and within tolerance.

Customer benefits

By extending the additive manufacturing process and introducing a virtual print via numerical simulation before the actual print of a part, it will be possible to significantly reduce the number of test prints and potential print failures. The compensation feature allows for a notable reduction of measured iterations. distortions, achieving parts within tolerance without costly manufacturing.

Project Details

Task

Hilti Corporation is a multinational Liechtenstein company that delivers products, services and software for professional construction end-users. In order to produce its differentiating fasteners and metal anchors, high performance tools are needed. Current manufacturing of the tools with subtractive technologies bears some design limitations and could be time consuming and costly. In order to overcome the limitations, additive manufacturing was examined in a project of the Ostschweizer Fachhochschule OST in collaboration with Hilti. Metal powder bed additive manufacturing is a manufacturing process that can allow for virtually unlimited design freedom – complexity for free. However, rapid heating and cooling cycles during the layer-wise build process cause internal stresses and distortions, which can lead to failed builds and negatively impact part tolerances and performance. Numerical simulation of the build can increase process understanding and help develop mitigation strategies to allow for successful first-time-right builds and prevent trial-and-error print failures, which, in turn, significantly reduces cost of production. In this particular project, distortions of a 3D-printed rolling die were simulated with the help of an Ansys Additive Print simulation workflow. A previous print showed larger than permissible warpage, which the simulation helped to successfully compensate in order to allow for an in-tolerance print.


Customer Benefit

A predictive simulation of the selective laser melting additive manufacturing process for a rolling die using Ansys Additive Print was used to evaluate and successfully compensate excessive distortion of the real print. By extending the additive manufacturing process and introducing a virtual print via numerical simulation before the actual print of a part, it will be possible to significantly reduce the number of test prints and potential print failures. The compensation feature allows for a notable reduction of measured distortions, achieving parts within tolerance without costly manufacturing iterations.


Solution

The additive manufacturing process was simulated within ANSYS Additive Print. The simulation method used is based on the inherent strain approach, which assumes a base shrinkage strain during the print process and has to be calibrated to the specific machine settings. For this purpose, a cantilever calibration part was printed with the exact machine setup to be used for the real part, as well as simulated. Measuring the real and virtual part after print and comparing those measurements leads to a scaling factor, which calibrates the simulation to the actual print. Using this calibration factor, the rolling die could be virtually printed in Ansys Additive Print. After verifying that the predicted distortions matched the real print of the die, these distortions could be automatically mapped negatively onto the nominal CAD, and thus compensated. An additional simulation of the pre-compensated geometry was done in order to validate the compensation factor. A final real print of the pre-compensated die showed a significant improvement of the distortions, which were an order of magnitude smaller than before and within tolerance.

Images: © OST


Engineering Services
Dr. sc. ETH Manfred Maurer

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