Team:TU Darmstadt/Project/Tech/Hardening

Engineering - Hardening and printing results

For testing purposes, a commercial resin called B9R-1-RED (B9Creations USA) was used. As a photoinitiator, IRGACURE 819 (BASF Germany) was chosen as it provided sufficient extinction coefficients at concentrations about 0.1 % at wavelengths about 410 nm. A good mixing was achieved by either solving the photoinitiator in acetone, then adding the colourant Sudan I (Acros Organics USA). After these two substances were completely soluted in acetone, the mixture was put together with the resin and mixed again. Another mixing method which does without acetone requires mixing times of about 1 h. Please note, that other colourants can also be used. Hardening tests were performed using a resin basin with a bottom made of Gorilla glass and a resin basin with a bottom made of Borosilicate glass. In the case of the uncoated Gorilla glass, the commercial resin formed a layer which adhered to the aluminum base plate after lighting for 15 s. It was cured after lighting for 17 s. Long lighting times > 60 s did not lead to a higher hardness. The lowest layer thickness produced were in the range of 120 μm. Layer thicknesses up to 300 μm were found to adhere on the aluminum base plate. Higher thicknesses did not adhere to the base plate but got stuck at the basin bottom. If the Gorilla glass was coated with Teflon, the results did not change.
Using uncoated Borosilicate a high adhesion to the resin bottom was observed. However, this is not intended so the Borosilicate glass was coated with Teflon. Unfortunately this did not lower the adhesion force by a relevant amount. Another test was run by wrapping the resin basin into package tape. This significantly lowered the adhesion of the hardened resin to the basin but strongly lowered the lateral resolution of the printer so this is no sufficient solution. Concerning the layer thicknesses using Borosilicate yielded the same values as Gorilla glass. Therefore, it can be assumed that the transmission of Borosilicate glass is similar to the transmission of Gorilla glass at about 410 nm.