*Article* **The Performance of 3D Printed Polymer Tools in Sheet Metal Forming**

**Fabio Tondini, Alberto Basso , Ulfar Arinbjarnar and Chris Valentin Nielsen \***

Department of Mechanical Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark; s192925@student.dtu.dk (F.T.); albass@mek.dtu.dk (A.B.); ulari@mek.dtu.dk (U.A.)

**\*** Correspondence: cvni@mek.dtu.dk

**Abstract:** Additively manufactured polymer tools are evaluated for use in metal forming as prototype tools and in the attempt to make sheet metal more attractive to small production volumes. Printing materials, strategies and accuracies are presented before the tools and tested in V-bending and groove pressing of 1 mm aluminum sheets. The V-bending shows that the tools change surface topography during forming until a steady state is reached at around five strokes. The geometrical accuracy obtained in V-bending is evaluated by the spring-back angle and the resulting bend radius, while bending to 90 ◦ with three different punch nose radii. The spring-back shows additional effects from the elastic deflection of the tools, and the influence from the punch nose radius is found to be influenced by the printing strategy due to the ratio between tool radius and the printed solid shell thickness enclosing the otherwise less dense bulk part of the tool. Groove pressing shows the combined effect of groove heights and angular changes due to spring-back. In all cases, the repeatability is discussed to show the potential of tool corrections for obtaining formed parts closer to nominal values.

**Keywords:** additive manufacturing; rapid prototyping; sheet metal forming; V-bending; groove pressing
