Giraffe - Voronoi Style, model by roman_hegglin - Voronoi models are great for testing the ability of a hot end to print fine structures without ooze.
I decided to make this a general overview of the different hot-ends and give you some feedback from my real-world use of these. Because I have used them to print real parts on a lot of different machines and over a period of a year, so many things have also changed, even the hot-ends themselves, based on user feedback have been further tweaked and refined by the developers.
I also had different filament sized, both 1.75 and 3mm and a wide range of nozzles, so I’ll make the specification clear in the below and in a future article these differences will also be compared.
So for this overview if seemed fair to provide general feedback and observations rather than going into exact scientific measurements for this article. But now that things are starting to settle down with lots of these newer designs, with a few of the top performers I do plan to test different aspects like force to extrude, maximum flow and ooze characteristics at various temperatures, in a more controlled and repeatable way. Some general tests you can perform on any hot-end - It almost goes without saying, but be careful these things get extremly hot and molten plastic is not something you want to get on your skin.
The two finger extrusion test (2finger) You need to do this one ‘hot’ (at material temperature) and after auto-calibration (M303) has been completed and settings added to firmware. I always like to see how well a filament can be extruded by only using two fingers to push the filament directly down into the hot-end manually. This can tell you a lot about the hot-ends ability to melt material and the pressure required to extrude. It’s worth doing this test at various temperatures going up in 5 degree steps, both with and without cooling fans. I find this especially useful for 3mm hot-ends, depending on how the nozzle has been drilled and the taper, gaps and seals etc. this simple test
The third issue of RepRap Magazine. Interview with Nicholas Seward, Paste Extrusion, Hot-Ends, and much more.