Not sure if this is the correct forum... but...
It looks like a lot of people love Bowden extruder for the speedy printing. But as we all know, it has an inherent drawback of high hysteria.
So, I was thinking... what if we put a small stepper motor on the extruder? You know, it's like one of those direct drive extruder, but using much smaller stepper motor, like this one?
We will still keep the main motor and let it do the most of "pushing" (typical Bowden extruder setup), but this small additional motor will be right at the top of the hot end, not to push and pull the filament, but just to eliminate the hysteria.
So, it's like hybrid of Bowden and direct drive extruder, but it's more of Bowden principal...
Even with a mini stepper, it will add some weight to the extruder, but it will probably be still a lot lighter than typical direct drive extruders, so we may be able to achieve very good speed...
For this to be possible, two motors will need to work in perfect unison. I searched the internet a little bit, but the one I showed in the picture was the only stepper motor that was small (well, there were really really miniature ones, but I think they are actually too small), and this guy has a different step angle - 7.5 degree instead of 1.8 degree which typical NEMA 17 motors have. So, it may get tricky to make these two motors push and pull the filament the exact same length at the exact same speed...
I thought about using NEMA 8 motor instead of mini stepper motor, but I am not sure how light they are - I know they will most likely be lighter, but the question is if that's light "enough" - and also NEMA 8 motors seem to be quite expensive.. like around 200 USD.
Is there some extruder like this out there already? If not, what do you guys think? Do you think it would be feasible, or at least worth a try? Those mini stepper motors are actually pretty cheap, like 6-7 USD.
And if you know what you are doing (I don't) maybe it won't take that much effort to modify the firmware to take one E motor instruction and translate that to two separate drive signals...
Or, maybe you can create two sets of instructions for two E motors during slicing - I would guess you would either need a new or modified version of a slicing software or modify the g code instructions which were generated for a single E motor. The latter may not be too hard, since these two motors always have to work in unison, you probably can figure out the E step values for the second motor by multiplying certain ratio (if they need to move different steps) or simply by duplicating the same value (if they move the same steps).
Edited 2 time(s). Last edit at 08/24/2013 02:45AM by Yamster.
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