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So I just had this idea like 10 minutes ago and I want to make a video about it so it's
prior art and nobody can patent it, in case somebody could.
So ... in a normal 3D printer, on your X carriage, typically, you have a stepper motor, your
extruder stepper motor, that turns a ( hobbed ) gear, that pushes filament into the hotend
and you have plastic coming out of the hotend. That's what makes it 3D print.
If you want to have a system with two hotends, so you can do dual extrusion, you need to
have two stepper motors, one like this ... and one like this, with a second hotend. Problem
is, as you add extruders, you get more weight, and the more weight you have, the more inertia
you have, the slower you have to go, and the less acceleration you need to have, so your
machine doesn't shake too much. One idea I had, and this is not just me, I
found a video on Youtube from somebody that did this too, is you use a hex shaft, a hexagonal
shaft, the guy on youtube used a square shaft, and you have a part like this, this is just
like this ( hobbed ) gear, here, except instead of having it attached directly to the stepper
motor, what you have is, you have a hexagonal hole in it, and it slides on this shaft, so
it's still attached to the hotend, it's still attached to the your X carriage, but instead
of having your stepper motors turn directly the gear, what you have is the stepper motor
is at the other side ( of the shaft ), and it turns the shaft, and with the shaft turning,
it turns the gear. It still moves left to right ( with the carriage ) and it pushes
filament into the hotend. What this gives you is basically you don't
have to move the stepper motor ( left and right ), so it's much more lightweight.
It's much more lightweight like this. The problem I had was, I wanted to use this
system for dual extrusion, or triple extrusion, whatever ... and then you have to have multiple
shafts, ( one two three ), or you have to have, just one shaft, but selonoids, on each
of the gears, to push or pull the filament against the gear, so like if you have three
hotends, you have three solonoids, and each one pushes or pulls the filament against it's
gear. Oops. The problem with that is, selonoids, are quite heavy too, so you loose part of
your advantage. One other system that exists, if you don't
want to have a lot of weight on your X carriage, is instead of having the stepper motor directly
here, you have the stepper motor fixed, and the hotend still moves, and you have a bowden
tube in between the two. The stepper motor pushes the filament into the bowden tube,
it goes all the way into it like this, the motor doesn't move, the hotend moves, like
this, and it's quite great because you don't have any weight here, the problem is, this
acts kind of like a spring, and you don't get exactly the same output here as you requested
here. So that's not ideal. So I thought of a solution that combines the
two. Basically what you have is, you have this, with the gear here that turns with the
shaft, the stepper motor is still fixed, and you have a bowden tube. And you -also- have
a stepper motor here, that pushes or pulls the filament ( into the tube ).
So, the idea here is. So the problem if you did it just like that, is here you have two
( hobbed ) gears, and they necessarily push ... if you have two hotends, they necessarily
push in the two hotends at the same time. But the idea here would be to use the second
stepper motor, to pull the filament out in one of the hotends, so you pull the filament
out, meaning, when the ( hobbed ) gear turns, it doesn't touch the filament, so it can't
push/pull it, but it still pushes the filament in the hotend it which you -left- the filament.
And if you want to change hotends, all you have to do is, pull the filament, from the
hotend you used, and then use the stepper motor for the second hotend at the other end,
to push the filament back in here, and then you are using the second hotend.
If you want to change you just pull again, you pull all the filament, nothing is touching
the gears here, you use the stepper motor for the first hotend to push ( the filament
) back into it, and then, when you are extruding, you basically have the two stepper motors
synchronized so they push at the same time. So, what's great about this. Also. Yeah. So,
it's a bit more complex, you have to have multiple stepper motor drivers, and stuff
... but what's great is, you have multiple hotends here, you can have three or four,
whatever, and you have very very little weight, because all the stepper motors are outside,
they don't move, they are fixed. There is one way to simplify this, even further,
instead of having one stepper motor ... one fixed stepper motor per hotend, to push into
the bowden tube, what you have is, you don't have any of the externals, you just have one
stepper motor, here ( attached to the shaft ). And this is where it gets a little bit
crazy, so ... to control this side, the fixed side, you still have the shaft, but it doesn't
move, so you also have ( hobbed ) gears here, but they don't move. So you have three here
and three here, and so they all turn at the same time, but to control whether one of gears
is going to push filament or not, you use, like I explained before, you use a solenoid
to push the filament against the gear. So basically that's the idea.
You get a very lightweight system, where mostly, all the weight is just small gear that's very
lightweight, and the hotend. And it's very lightweight, so you can have two, three, four,
whatever you want. One of the problems I can forsee with this,
is you have to pull the filament entirely out of the hotend,
where in other systems you just pull it just a little bit.
So here you have to pull it entirely out of the hotend, and then re-enter it entirely,
but you can do that very fast, because you can use a big stepper motor here ( for the
shaft ), that's fast, that's strong. And you can just, when you have pulled it
all in, you just waste a bit of filament, and you clean it up on the side or something.
So yeah ... that's the idea basically, I just wanted to like ... make a small video about
it, and make sure nobody can patent it. And I'm going to be prototyping this in the near
future, when I'm done with these babies. Ok, see you later.