The motor mount slides to tension the drive belt, you think a sprung bearing would be better on the drive side too?
This looks interesting, wouldnāt you need a pretty small pinion or pretty beefy stepper though, I guess itās for 1.75mm filament?
If you look at the diameter the mk7 direct drive needs to give enough torque, itās barely bigger than the motor shaft.
Head should be as as light weight as possible, for accuracy of printing. As ppl at Makerbot did as I remember.
Beside that, it looks great.
as to the costs, you can get 10 5x10x4 bearings on the bay for about Ā£2 and a 3mm HTD belt 174mm x 9mm is also just over Ā£2 and a 12 tooth pulley is just over Ā£3. The rest would be odds and sods and printed parts.
@Liam_Jackson with 1.75 a standard Nema 17 should be fine as thatās what is used for direct drive solutions anyway. That assumes the bearings and belt tension donāt provide too much extra friction/resistance.
@Darko_Bednjanec by the looks of the pneufit connector on the top, this is intended for a bowden solution so weight wonāt be a concern.
I made a very similar extruder to this for a delta printer that Iām designing at the moment. Mine is a bit simpler in design but basically the same principle of using two belts to grip the filament. I drive both sides using transfer gears but do not have any tensioners on the belts - the belts are stretched in position. The gap between that belts is also not adjustable itās fixed for 1.75mm filament.
It works really well feeding filament into thin air, you cannot make the filament slip by pulling it with your hands but I still need to get it hooked up to a hot end and see how well it performs against a load.
Only suggestion that I would make with your design is to change the bottom hole so that it has a conical lead-in to make feeding the filament through a lot easier. I had to do this on mine as the filament got caught which made loading it a PITA.