the extruders currently being used have undergone many evolutions or are based on the more evolved setups to get to the reliability that we are finally getting after many of us went through long and frustrating periods of extruders working for a while and then jamming or breaking...
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reprap.org]
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hydraraptor.blogspot.com]
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reprap.org]
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www.thingiverse.com]
i say don't bother, stand on the shoulders of others because it's definetely the hardest part of making a FDM/FFF machine.
if you're making another derivative, the only way you can improve it is to cut down on parts, part size and cost, add a ptfe or silicone or some high temp plastic hot end tip around the nozzle like nopheads so plastic doesn't catch onto the nozzle.
anyway 30 pounds is pretty cheap for everything for an extruder, the motor alone would be around 10, then you have a few different materials that have to be machined, the nozzle tip very precisely.
but maybe you will surprise us all and give us all something that takes reprap in a completely different direction and i will regret not sending my 30 pounds asap.
