Dual motor on single extruder without compromise

Hi,

I recently bought the Vulcono from e3d and now I need more powerful extrusion. To use the 1.2mm nozzle at 1mm layerheight an 2mm layerwidth im reduced to 10-20mms, so I thought I could double this by putting a 2nd motor on the 5th slot on my RAMPS.
I would like to avoid to wire the 2nd extruder motor in series or parallel to the first extruder motor to keep full torque and full speed and not strain the driver.

I checked marlin but so far as im interpreting this correct this function can not just be enabled. I can activate the pins of the 5th slot but it is by default connected to the 2nd independent extruder.
Any idea on how I could get the 5th driver to perform the same task as Extruder0?

Cheers

How are you planning on having two motors pushing on the same piece of filament? The only way I could envision this is if you had two hobbed bolts or gears facing one another rather than one with a bearing. Kind of unusual.

In any event, why couldn't you just take your cue from the way most Z axes are configured. In my printer, I run 2 motors off of the same stepper driver for the Z axis. Perhaps you could also do that for the E axis?

Edited 2 time(s). Last edit at 03/19/2015 12:41PM by jbernardis.

Yes I already designed a frame with two mirroring motor holders, that both use a directly driven (and later geared) MK8 hobbed bolt. I imagine that would not only increase speed but also grip.

I looked into splitting parallel or series but I loose either half of the speed or half on the torque and I would need to use medium or low power motor to not push the driver to far. If I do that I get more grip from two hobbed bolts from two side but I wont double speed.

It should take much less force to extrude through a bigger nozzle, I am surprised you need more motor power.

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[www.hydraraptor.blogspot.com]

Its true there is less oozing but the sheer mass of material that has to be driving through takes quite some effort. When I switched nozzle the 2nd time I forgot to adjust the speed and I started driving with 50mms and it started slipping/underextruding and Ive never seen my the gearing on the extruder spin so fast.

I also talked with another guy on G+ and before I had ordered the Vulcano and he also had trouble getting over 20mms. With a non bowden setup you can probably push it a bit but imagine the kinds of speed you could get with two motors. There also was an failed indigogo called the kraker which had two worm gears motor on one nozzle and from the demo vids that looks awesomely fast.

I also just heard of ditto mode in repetier, that could be what im looking for...

Doesn't make sense to me because I am sure I can shift that much volume through a 0.5mm J-head. With a much bigger nozzle and much bigger heater I can't see why it is harder to extrude.

I once made an extruder with a long heater and a 0.6mm nozzle and that could go fast even with a tiny motor. [hydraraptor.blogspot.co.uk].

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[www.hydraraptor.blogspot.com]

Ok interesting, I cant really object to your reasoning, just from how I experience my extruder I get the feeling the double motor would make everything faster.

Here's a dual drive extruder I played with about a year ago: [mark.rehorst.com]

here's an earlier version: [mark.rehorst.com]

Both worked OK, but the second motor adds to the moving mass. I don't think it was any more reliable than a single motor extruder so I abandoned both designs.

A simpler solution is probably just a bigger motor. Makerbot used to use an extra long NEMA17.

If your motor drivers are Stepstick like a quick hack would be to solder one on top of the other and link all the pins except the four motor outputs, which you could take from the top one via pins sticking up and use the bottom one through the PCB.

Edited 1 time(s). Last edit at 03/19/2015 01:40PM by nophead.

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[www.hydraraptor.blogspot.com]

I am curious. My old not so good extruder with 1.7:1 ratio was able to feed my 1.5mm bored j-head to over 30mm/s. The amount of material pushed was huge, I had more problems with the j-head cooling too fast than the speed of extrussion. I was running my j-head at over 240c and saw temperature dip into 210c when it was moving quick. I suggest you increase the temp on your hot end to at least 240, if you have a good thermistor evern 260-270c would work. This thread makes me want to go home and bore one of my nozzles out to .8mm and see what my modicum extruder can push.

For referance, I only use ABS. So the temperatures above are for ABS. If using pla your on your own.

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Modicum V1 sold on e-bay user jaguarking11

@dentist: interesting, my idea was to put them facing each other. but thats a details I guess. Would you say the dual configuration in a bowden setup would be beneficial?

@nophead: true but there is a limit to how big the motor can be before even the DVR8825 are out of their range.

It might be OK in Bowden setup. I think the key to getting a lot of down force from the extruder is very heavy tension on the pinch wheel springs and having a gear reduced motor for increased torque helps, too. I am currently using a BullDog XL extruder and it seems very strong. I haven't had any extruder jams in the couple months I've used it.

If you put the motors so they face each other you will have to take it apart to clear any jams and to periodically clean the plastic dust off the filament drive gears. It might be easier if they both face the same direction.

Edited 1 time(s). Last edit at 03/19/2015 02:38PM by the_digital_dentist.

I agree, the tension is one of the key factors. My first idea even was to put the 2nd drive gear on it instead of a bearring, to get grip from the otther side as well, but it was to complicated to get the 2nd axis driven. I guess that even to half powered motors in one extruder would still be able to put out more material just because of better gripping.

Here's another one I worked on and may yet revisit. It produced a LOT of down force but was geared so far down that it would probably limit printing speed: [mark.rehorst.com]

and here: [www.thingiverse.com]

It did not retract well. I have some ideas to fix that, so may go back to it soon...

My theory is that if you extrude faster, the hotend will lose it's heat too fast, making it unstable. You can print 'hotter' to keep up, but the fluctuations will be big(-ger).

Maybe design a hotend with an even bigger heater block to store energy? And then wrap the block with fiberglass wool so the heaterblock really maintains the core temp and doesn't lose any heat to the air.

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The the phase change that occurs when the filament melts takes heat out of the block, so what is needed is a higher powered heater that can put heat back into the block faster. The reason the temperature drops is that even though the PID controller is trying its best to regulate the temperature, it has already turned the under powered heater on full blast and still can't keep up. A higher powered heater would allow the PID controller to do it's job. You don't need (or want) a bigger block, just a bigger heater, or maybe use two of the lower powered heaters.

True but I dont see this behaviour from the Vulcano, the heater block is already longer and even in my 50mms experiment I didnt see any temp jumps. So I guess there is room for more. But you are right indeed a 2nd heater or maybe 60 watt (if that exists) could go nicely with that.