Australian based startup BrainyDeep has just launched the first true dual pinch wheel extruder for 3D Printers on crowdfunding platform IndieGoGo.
Billed as the world's first dual pinch wheel extruder and also the smallest dual nozzle extruder, the Kraken, is two extruders in one, requiring only a single tool and a few minutes to reconfigure.
Dual Pinch Wheel Configuration
In the dual pinch wheel configuration, both motors on the Kraken are used to drive a single filament, one from each side. This means filament drive forces are greatly increased, allowing for radically increased print speeds and printing at lower temperatures. The Kraken has been tested to close to 900mm/s burst extrusion rates.
The dual pinch wheel also means that stripping filament, a fault found on many existing extruders where the drive grinds away the material, is eliminated, as both drive wheels would have to slip for this to occur.
Dual Nozzle Configuration
The Kraken is the smallest dual nozzle extruder available, at only just over 40mm wide. This means you can have 4 nozzles in less than the size of 1 Wade's Geared extruder. And the nozzles themselves are located closer to each other and each nozzle can reach more of the build area, reducing loss of build size when using multiple nozzles. It allows you to print up to 26x20cm with 1 nozzle, 23x20cm with 2 nozzles and up to 15x20cm with 4 nozzles on a standard build Prusa Mendel.
The Kraken's Unique Mechanism
The core of the Kraken is a radically new gearing arrangement with a 20:1 gear ratio. This gearing ratio means that filament extrusion rates can be controlled better than ever before. According to BrainyDeep's founder, Zbigniew Mioduszewski (aka Ziggy), a mechanical engineer, currently they have developed complete mounts for reprap Prusa Mendels, and all printers that use the same mounting (2x 8mm rods 50mm apart). The Kraken also has plenty of mounting holes to adapt it to other printers on the market.
The Kraken starts at $350 and the project is currently live on IndieGoGo, where additional project details and updates are available.
Posted in 3D Printer Accessories
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Ziggy wrote at 8/25/2013 3:34:42 AM:
Hi guys, Ziggy here. You guys have raised some excellent points. @syous: Looking at my material, I guess I didn't make this too clear - the drive shafts are spring loaded initially (tension is adjusted via the set screws on either side of the motor), with a "top up" from the worm gear train (which is why the graph in the video doesn't start at 0 force at 0 speed). You are right about the tangential force being reversed in retraction. So yes, filament force is reduced during retraction. This actually helps by not crushing and grinding the filament excessively during retractions (essential when doing very fine layer heights with lots of retraction over the same bit of filament). It doesn't cause any problems as the drive force required for retraction is considerably smaller than that for extrusion, so we can get away with lower filament force. @JD90 - There are two configurations. In one of them, a single motor is use per filament for 2 colours. In the other 2 motors are used on a single filament. The dual colour print didn't really have enough dialling in for the print calibration. This print was just done without any special tool change G code (no temperature change when disabling a nozzle) and with normal retractions, and probably a touch too hot. There was a bit of ooze out of one of the nozzles while the second was printing. Apologies about the video - for anyone else finding this, please mute the audio and turn on the subtitles. @sas - Summer in Australia is hot, and ambient temperatures of over 40C are common. I put heatsinks on almost all of my motors just as a matter of course, and the motors themselves are rated for a +80C temperature rise over ambient. Now that it's winter here I don't have heatsinks. The motors get warm to the touch, but nothing too far out of the ordinary. The motors we use are a lot smaller than what you would be used to - in fact the Kraken in dual nozzle mode is not significantly heavier than a single Wade's extruder. You might ask how this is possible, but a NEMA 17 motor weighs almost 300g, whereas our motors are only 170g each. As far as price, we feel that it is appropriate given the performance, accuracy and reliability is far beyond what is available even in commercial machines. Thanks all for the time taken to check out the campaign!
syous wrote at 8/24/2013 7:56:46 AM:
@sas Yes, but the BFB extruder still used spring tension. This design doesn't appear to, relying only on the force of the gear being 'pushed' down the length of the worm. While it might be a clever way to make the grip scale with extrusion rate, retraction would be severely handicapped.
Pottertown wrote at 8/23/2013 5:52:08 AM:
That's exactly what I was wondering syous.
sas wrote at 8/22/2013 10:45:24 PM:
@syous, worm drive was originally used by bits from bytes on their BFB 3000 ( redesigned as CubeX now ) I don't think it's would be an problem..... what might be the problem is the price for getting this experimental extrusion system. 350,- usd is quite allot for this... I would have supported it just to test it for 100,- usd .... and in one of the pictures you see several heatsinks applied to the motors..... so the motors still get an beating.... for the extra weight those 2 motors carry... it might be better to switch to an geared stepper motor for less than 100usd and get the extra torque that way... or get the new QU-BD geared nema 17 extruder for 130,- usd with extruder and all ...
JD90 wrote at 8/22/2013 10:31:47 PM:
Wait, is this using two motors to drive one filament? The dual extrusion example is not very good quality, for the price, I'd want much better results. The music in the "background" is loud enough to be considered foreground music, and it's very distracting. I had to fight the urge to kill the video while watching the explanation.
SeeMeCNC wrote at 8/22/2013 7:31:30 PM:
Our "steve's extruder" was a dual pinch wheel extruder, and we started making ans selling them 2 yrs ago
syous wrote at 8/22/2013 5:46:24 PM:
If it uses the rotation of the worm gear to create the lateral pinching force then how does it handle retraction when that force switches direction during counter rotation?