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  1. #1

    Mod for Prusa that detects jams?

    Hey, me and a couple of friends were thinking about making an attachment for Prusa printers that would detect jams, and if one was detected then heat up the nozzle and retract the filament. Does anyone know if something like this exists?

  2. #2
    Technologist
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    The prusa mk3 from prusa research has a sensor for this, what it does when it detects a jam is up to what you do in firmware and I can't remember what they chose to do.

  3. #3
    Student
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    Nov 2017
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    The MK3 uses a laser sensor to track filament movement. If filament stops moving, its a problem. Unfortunately if the item unsticks from the bed, that won't help much.

    I own an MK2S printer, and its a good piece of machinery, but I notice they brag about some innovations, but they often aren't the full solution. For example, yes it does have mesh bed leveling, not that manual leveling is that hard, but what it DOESN'T have is auto Z-height adjustment, and that is tricky for many and a pain.

    If you search for mishaps of the Prusa, jammed filament isn't a real problem that happens much, an item breaking off the bed IS a big problem, and usually it happens hours after the print is started.

  4. #4
    Interesting, what have you tried/done to fix prints coming off of the board?

  5. #5
    Technologist
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    Prusa does boast a lot of innovations, and I agree that they aren't always the full solution or they're solving a problem that shouldn't be there. Prusa's solution to adhesion (? not entirely sure what the motivation was here, adhesion or print surface damage) is a powder coated PEI bed. I imagine the surface roughness helps things stick.

    As for z offset adjustment, I think the ultimakers do a great job of this and have the best system for "calibrating" a probe that isn't the nozzle itself. They run the nozzle straight into the bed and monitor for the point where the readings stop changing, i.e. it's hit the bed and the bed is no longer getting closer. The compliance of the leveling springs dampens the impact but the print surface might get damaged. For the ultimakers that use glass the print surface wont suffer, but PEI might. Getting the starting z level correct is very important to making sure prints stay stuck, and can be hard to do with an offset probe like on the mk2.

    I think one of the simplest and best ways to help a print stay stuck is to not shake the bed back and forth, my little jab at the mendel style printers.

    Back to the filament sensor thing. I think they should have tried using the trinamic drivers to detect the extruder motor stalling for jam detection. I imagine they could have incorporated some kind of dog clutch that causes the extruder gears to bind when there's no filament feeding through and detect run out filament that way. Adding the extra sensor only makes sense to me if it helps you calibrate/track exactly how much filament is being fed through like a servo. But as far as I understand it only detects presence and movement, not exactly how much movement.

  6. #6
    Student
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    Quote Originally Posted by Trakyan View Post
    As for z offset adjustment, I think the ultimakers do a great job of this and have the best system for "calibrating" a probe that isn't the nozzle itself. They run the nozzle straight into the bed and monitor for the point where the readings stop changing, i.e. it's hit the bed and the bed is no longer getting closer. The compliance of the leveling springs dampens the impact but the print surface might get damaged. For the ultimakers that use glass the print surface wont suffer, but PEI might. Getting the starting z level correct is very important to making sure prints stay stuck, and can be hard to do with an offset probe like on the mk2.
    That all is so true.

    One of the "problems" with 3D printing is it looks easy, but there are so many variables for each bed material, printing material, and this can even vary from manufacturer to manufacturer. When I send a job to my laser printer, I walk over and pick it up, which is how 3D printers need to be. If my $50 laser printer runs out of paper it stops, and many very expensive 3D printers still don't have filament detection. Its crazy.

    Detecting when an object breaks free is quite important because 3D printers are often unattended. They have cameras that can detect motion in a certain area, so it seems possible that a camera could also recognize an object breaking free.

  7. #7
    Technologist
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    Jul 2017
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    I don't think you can compare the cost of 3d printers to 2d printers. For one, the scale on which they are produced, for two they fundamentally have fewer components.

    That second point about 3d printers fundamentally having more components also means that on a level playing field, they won't ever be as reliable simply because there are more things that can go wrong because there are more things that are being done.

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