During the building of our second printer (you can read more about the process here: http://www.printingin3d.eu/news/second-printer ) we realised we need a simple, but solid filament holder. We wanted something surely won't get stuck. So we created a system to put two bearings and an axis trough the filament roll. And then only a small piece needed to fix it to one of the aluminim profile.The models were created in JavaSCAD, our model generator framework. The models are parametric on the Java side, so you can adjust them to any inner diameter of the roll. The attached file is suitable for a roll which inner diameter is 51mm.