Bertelsen, J. G.

Davoudinejad, A.

Li, D.

M. Ribo, M.

Regi, F.

Thorn, S.

Tosello, G.

Zhang, Y.

Mask projection vat-photopolymerisation (MPVP) technology provides a method for additive manufacturing (AM) of high resolution surface features. In the present project, the technology is used to generate injection moulding inserts containing a double-curved freeform surface with bi-directional reflectance patterns (Fig. 1 &amp; 2). Orienting the anisotropic patterns by 0° and 90° relative to the viewing direction generates surface contrast with “dark” and “bright” areas (Fig. 5). This allows for incorporation of information barcodes in the polymer insert which subsequently replicates into every injection moulded part, e.g. enhanced product traceability, B2B information or end-user interaction

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G. ; Thorn, S. ; Mendez Ribo, Macarena; Li, D. ; Regi, Francesco; Davoudinejad, Ali; Zhang,Yang; Tosello, GuidoPublication date:2018Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Bertelsen, J. G., Thorn, S., M. Ribo, M., Li, D., Regi, F., Davoudinejad, A., ... Tosello, G. (2018). DimensionalAccuracy and Repeatability of Mould Inserts Manufactured by Mask Projection Vat-Photopolymerization. Postersession presented at Euspen Special Interest Group Meeting 2018: Structured & Freeform Surfaces, Cachan,France.Mask projection vat-photopolymerisation (MPVP) technology provides a method for additive manufacturing (AM) of high resolution surface features. In the present project, the technology is used to generate injection moulding inserts containing a double-curved freeform surface with bi-directional reflec-tance patterns (Fig. 1 & 2). Orienting the anisotropic patterns by 0° and 90° rela-tive to the viewing direction generates surface contrast with “dark” and “bright” areas (Fig. 5). This allows for incorporation of information barcodes in the pol-ymer insert which subsequently replicates into every injection moulded part, e.g. enhanced product traceability, B2B information or end-user interaction.CAD part and printed features were in close concordance at E = 11.83 mJ/cm2, however areas from midline to peak were not printed correctly due to overex-posure. Using E = 1.94 mJ/cm2 generates a uniformly covered reflectance sur-face with fewer defects (Fig. 6). Metrological assessment of parts created with 1 µm and 0.625 µm layer thickness yield low surface roughness with Ra val-ues ~10-50 nm (Fig. 7 & Tab. 1). The process generally yields more defects at layer thickness below 4 μm. This instability could be be due to oxygen inhibi-tion, insufficient stirring due to capillary forces and varying detachment area.A study of optimal parameters has been conducted with a “working curve ex-periment”. Cure depth Cd is plotted as a function of radiant exposure E with a logarithmic behavior (Fig. 3 & 4) - in full accordance with the Beer-Lambert Law. The slope is the penetration depth Dp (the depth at which the irradiance is reduced to 1/e (~37 %) of the surface irradiance) and the intersection with the x-axis is the critical exposure Ec that causes gelation/cross-linking. The results from the working curves were used in a subsequent full-factorial, two-level DoE to reveal specific parameters to achieve best replication of surface features.Surface Rougness - ISO 4287VerticalMean RaStd. RaMean RzStd. RzHorizontalMean RaStd. RaMean RzStd. Rz4404321632223537157[nm][nm][nm][nm][nm][nm][nm][nm]Dimensional Accuracy and Repeatability of Mould Inserts Manufactured by Mask Projection Vat-PhotopolymerizationJ.G. Bertelsen†1, S. Thorn†1, M.M. Ribo1, D. Li1, F. Regi1, A. Davoudinejad1, Y. Zhang1, G. Tosello1MotivationResults & Findings†These authours contributed equally to this work. 1Technical University of Denmark (DTU)Resulting surfacesThis paper reports work undetaken in the context of project 5163-00001B funded by Innovation Fund DenmarkIntroductionParameter optimisationFig. 1. Initial CAD model of double curved free-form surface without reflectance elements. Ren-der from SolidWorks 2018 Photoview 360. Fig. 2. Final CAD model including reflectance el-ements. The viewing angle is identical to Fig. 1.  Render from SolidWorks 2018 Photoview 360.Fig. 5. CAD render of final insert with reflec-tance elements and mounting flanges on top and bottom. Viewed 10° to light source angle.Fig. 6. Confocal microscope image of printed insert with reflectance elements. Notice the ring-formed defects as well as the gashes outward from the four central valleys.Fig. 7. Top: CLSM zoom-in on the triangu-lar prism reflectance elements. Bottom: Pro-filometry image generated by SPIP 6.7.5. Tab. 1:  Mean roughness values for the surface depicted in Fig. 7 by either horizontal or vertical measurement. Fig. 3. Working curve for FunToDo Industrial Blend Red. Dp = 176.61 µm & Ec = 1.037 mJ/cm2.Fig. 4. Working curve for Formlabs High Temper-ature Resin. Dp = 306.71 µm & Ec = 7.92 mJ/cm2.20xAcknowledgements  

Dimensional Accuracy and Repeatability of Mould Inserts Manufactured by Mask Projection Vat-Photopolymerization

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Dimensional Accuracy and Repeatability of Mould Inserts Manufactured by Mask Projection Vat-Photopolymerization

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