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Thread: Extruders

  1. #11
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    Grip does not equate to precision in 3d printing. reliability maybe. for precision we hunt more steps/mm of travel. Double drive gears do nothing for this effort so they can have no impact on precision. And I think what you read about backlash was directed more towards wade extruders with printed gears that must be set up loose so they don't bind rather than the precise mesh of the geared titan extruder that has no backlash that can be felt by a human hand. What you are obviously missing here is that stepper motors spin at a very slow speed in extruders. So low of a speed do these extruder stepper motors have to live at that companies make gear reduction extruders to the tune of 3:1 and 5:1 because even when we are printing at a fast pace these stepper motors spin at a fraction of their max potential while pushing filament.

  2. #12
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    I wont be using a metal gearbox or injection molded parts like the titan, since they are too heavy, expensive, or both for my application, so I'll have to consider the backlash of printed gears. That being said, the quality and backlash of gearboxes varies a lot based on manufacturer, and a couple of degrees of backlash, which is negligible to a human hand, is several steps of the motor.
    Also, that reliability is important, if you're running at 100+ mm/s and your filament is slipping even let's say 5-10%, that, to me, is lost precision. if your motor changes e steps based on the speeds due to slippage, you no longer have a precise (or accurate, if you prefer) extruder, no matter how geared down it is.

    My main question left, though, is still which extruder (geared vs not) can push plastic through an extruder faster. I suspect it is the geared extruders because as you say, an extruder doesn't push the limits on the motors speed, so the added torque is likely more beneficial than the loss of top speed which you wont end up reaching. I know the power rating of the heater cartridge in the hot end also limits your extrusion rate, but lets assume that's a non issue.

  3. #13
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    If you are worried about pushing a lot of filament fast then you will want a volcano hotend. And Just so you know the titan is one of the lightest extruder setups you can get because the gear reduction allows for a lighter stepper motor because not so much torque is needed. Here is the newest version of the titan the aero:
    http://www.ebay.com/itm/3DMakerWorld...MAAOSwFJBZRCHe

    But if you are looking to push a lot of filament fast then you will want this titan:
    http://www.ebay.com/itm/Titan-Extrud...UAAOSw4shX5fVG
    This e3d v6 with volcano hotend:
    http://www.ebay.com/itm/3D-printer-A..._JbuP21GM3FbkQ
    And maybe this stepper motor:
    http://www.ebay.com/itm/Nema-17-42mm...8AAOSwHoFXqtAx

    And you know if you are chasing speed it is a real good idea to run all this hardware at 24volts.

  4. #14
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    I'm not sure most NEMA 17 motors are rated for 24V. Also, this thread is about designing an extruder, not buying a ready made solution. I'm not really planning to design and build an affordable printer just to buy an extruder to double the price.
    Also, I get that a larger nozzle lets you pump more filament through (since less force is needed for the same volumetric flow), but to be clear, I'm asking for any given nozzle, with a heating cartridge that can supply sufficient heat, where the only thing changed is if the extruder is geared or not, would the geared or non geared extruder be able to push filament faster?

  5. #15
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    Quote Originally Posted by Trakyan View Post
    I'm not sure most NEMA 17 motors are rated for 24V. Also, this thread is about designing an extruder, not buying a ready made solution. I'm not really planning to design and build an affordable printer just to buy an extruder to double the price.
    Also, I get that a larger nozzle lets you pump more filament through (since less force is needed for the same volumetric flow), but to be clear, I'm asking for any given nozzle, with a heating cartridge that can supply sufficient heat, where the only thing changed is if the extruder is geared or not, would the geared or non geared extruder be able to push filament faster?
    Ok first off the forward current I measure to the stepper motors is usually under 1v. BUT ANYWAYS, If it help you understand MOST control boards support 12 or 24v input. And most printers run nema17 stepper motors. In truth even the heater cartridges and heat beds that are optimized for 12 or 24v can be run in either scenario as they are controlled by a pwm circuit that lets you tune it in the form of ki, kp, and kd settings in marlin firmware. The reason you want the volcano hotend is because it stands the heater cartridge up on its side and gives more heated surface area to the incoming filament. See at high speeds the incoming filament wants to cool the nozzle faster than the heater cartridge can heat it and if you look at the volcano hotend it is easy to see this is what it is trying to correct for. And if you are buying many components to make up an extruder than technically you are still building it, right?

  6. #16
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    I think you're really missing the point of why I started this thread, and my previous replies.

    I think the volcano also has a more powerful heater cartridge, and I understand that the heating of the hot end is a limiting factor, that's why I said before to assume it's a non issue since I'm only interested in the geared vs non geared part of the extruder. This thread was supposed to be about extruders, not hot ends.

    I started this thread to get ideas and opinions on DESIGNING an extruder, and which features to include or choose (direct or geared, single or double sided drive etc. anything you can think of) for this particular design. I did not start it asking which extruder to buy and which hot end to screw into it, which to be honest is not my idea of building it. Two components hardly counts as 'many'. And again you're missing another point, the E3D Volcano and titan combination cost 70 pounds at minimum, that's the old titan and the cheapest volcano kit I could find on E3D's website. I'm not looking to design a low cost printer just to slap on a hot end and extruder that doubles the price. That last bit isn't an exaggeration, if anything it's an understatement. Even with those E-Bay suppliers the hot end and extruder combo will cost about as much as the remaining mechanical parts.

    To re iterate. I am not looking for specific hot end and extruder combinations, I'm not even interested in the hot ends for this topic. I'm looking for features which people like in a hot end. Accessibility/visibility to the filament path, fully supported filament path, quick release/filament change, spring loaded or positive pressure (like the flexion), since or double sided drive (like the bondtech). I'm looking for features and ideas I should include to my own extruder design, not who else's design I should buy.

  7. #17
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    If you're building an extruder from scratch, why not build it with an auger screw, so it can handle pellets rather than just filament? Most thermoplastics come in pellet form, and are a lot cheaper that way than when extruded into filament. It would also give you more flexibility in terms of nozzle size - you can design a set of interchangeable nozzles, so you could switch between fast and thick deposition and slow and fine. If it works, let me know, because I want one...

  8. #18
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    If it was run by a stepper motor, you would be able to throw it into reverse for retraction.

  9. #19
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    Quote Originally Posted by Trakyan View Post
    I think the volcano also has a more powerful heater cartridge
    I believe most if not all hotends use the standard 40watt heater cartridge. Someone correct me here if I am wrong. But so far as I know that is the standard. It is not a temperature issue with pushing a lot of filament. It is a surface area issue because the filament is at room temperature so as it enters the hotend it wants to cool the nozzle and maybe at higher speeds you can actually see a temperature difference between the nozzle that is being cooled by the incoming filament and the heater cartridge. Because we want a specific temperature and cant just go hotter to compensate for the temp drop from the incoming filament at the nozzle we need more surface area of the heating source to overcome the cooling capacity of the incoming filament without just raising temperatures. I hope I have explained this well and cleared up the confusion you were having about volcano hotends. And I will backout of your thread now. Sorry if I was irrelevant.

  10. #20
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    Quote Originally Posted by awerby View Post
    If you're building an extruder from scratch, why not build it with an auger screw, so it can handle pellets rather than just filament? Most thermoplastics come in pellet form, and are a lot cheaper that way than when extruded into filament. It would also give you more flexibility in terms of nozzle size - you can design a set of interchangeable nozzles, so you could switch between fast and thick deposition and slow and fine. If it works, let me know, because I want one...
    Augers are not super precise with their deposition, filament makers use an auger screw, but they use the tension on the filament to control diameter. Augers are not positive displacement pumps so they don't really such and push like you're thinking. Augers more 'suggest' which way things should go rather than demand, like how a filament extruder pushes or pulls filament.

    Anyways, onto the real issue. You'll need to use direct drive, since the plastic wont stay hot and molten through a bowden tube, and even if it did an auger would not be able to force the molten plastic through since it isn't a positive displacement pump. Next let's ramp up the heater block and cartridge, because you will need a much bigger melt zone to cover where your auger is. You'll also need a fairly big auger because of the size the pellets come in. Now add a big (and noisy) vacuum to feed this extruder with pellets from an outside source (or mount a barrel of them onto the extruder, but good luck moving it then). Basically, you end up with this.
    http://imgur.com/AITgxiz
    See that slightly larger than normal hotend? It's actually massive.
    http://the3dprintingnerd.com/wp/wp-c...umbnail-18.jpg
    Don't forget the shop vac to feed the pellets.

    You wont be using that on any desktop machine, no matter how rigid you want to boast your set up is. Filament extrusion is probably one of the few ways a bowden set up would work, and it allows direct drive to work without carrying too much material on the extruder at once. I think it's as good as it's gonna get for thermoplastic FDM, a couple of decades of R&D haven't found a better method for thermoplastic FDM.

    And you're right about the volcano having a standard heater cartridge, I just remember reading somewhere a while ago that they used a more powerful one. But I understand how the volcano works and why the heater cartridge is positioned the way it is and that incoming filament cools the hotend, this is why I said earlier which extruder would be able to push more filament, if we assume the hot end heating the filament is a non issue.

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