Wiper Designs

Discussion in 'Getting Started' started by Andy Cohen, Sep 26, 2019.

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  1. dc42

    dc42 Well-Known Member

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    I am probably missing something; but is there any reason why you can't have an empty tpre file, and put M116 at the start of the tpost file to wait for temperature, followed by the purge, tool pickup and wipe?
     
  2. Greg Holloway

    Greg Holloway Administrator
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    You can do anything you want David!
     
  3. garethky

    garethky Well-Known Member

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    Today I learned: High temperature 500C Nomex felt exists and rather than it being unobtanium, they sell it cheap on Amazon as "BBQ Gasket"!

    My next design task will be a descent wiper/flicker and I'm going to try felt. All the brushes I can find are far less dense than the ones on the professional machines. Seen here:



    The brushes they use look custom made and cost an eye watering $80 each. They also use a metal or silicone blade to wipe then nozzle, they call this a "flicker".

    So my plan is:
    • Ooze buckets under the heads in the parked location.
    • Priming happens in the dock when the tool is grabbed and dumps unto the ooze bucket.
    • Silicone "flicker" at the edge of the ooze bucket cuts the ooze off.
    • Head goes from the flicker directly to print.
    • When its time to return the active tool wiping will happen on Nomex felt on the side of the tool changer
    • Then the tool goes back into the dock, across the flicker and back over its ooze bucket.
    No idea if its going to work.
     
  4. Nibbels

    Nibbels Well-Known Member

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    I let pictures speak:
    Screenshot_7.jpg Screenshot_9.jpg Screenshot_10.jpg
    Screenshot_8.jpg

    I dont use a prime tower and I dont use a ooze shield for this.

    So there is some tiny amount of ooze which randomly gets placed on the perimeter but it is not much.
    Most of the white pieces can be removed by the fingernail.
    The rest I cut with a sharp knive. A ooze shield might be an Idea to remove the rest of the tiny artifacts.

    When I finally was able to set the flow to real <= 100% material flow the nozzles stayed quite clean when I printed full material.

    But the Idea of using a brush from time to time is still nice.
     
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  5. garethky

    garethky Well-Known Member

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    Nibbels, that is looking great! Cant wait to get to that point.

    This sounds familiar, what did you find out? So I tried setting my extrusion multiplier with PETG to 95% and I really didn't see a difference. Is that because there is some issues that stops the setting from taking effect?
     
  6. Nibbels

    Nibbels Well-Known Member

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    I add this link for more pictures showing the razor blade nozzle closer.
    3mm / wiring forces and toolchanger docking challenge

    My setting is:
    - 2x TitanAero 3mm
    - 2x PETG (not in the pictures here, in the other pictures)
    - Real PETG diameters are ~2.98mm and 2.8mm
    - The slicer always knows 2.85mm is 100% flow.

    What I first did was googling steps/mm for a TitanAero. What I researched was 837 or 834 @16MS/0.9° ... And I set this within the config.g.
    But I had way too much filament pushed out.

    Normally a 3mm instead of 2.85mm has around +10% material flow, So I normally decrease my flow from 100% down to values like 90% if the filament is more 3mm than 2.85mm.
    So I printed alot 100% infill on and stopped decreasing the amount when the nozzle stayed clean but the top layer was still closed.
    One PETG landed at 91%, the other at 89%. This is much less than I expected. (I suppose that my other printer had a higher steps/mm ratio at stock value. My guess was ~95% and ~92% flow would be right.)

    (The more soft a material is the more "flow" I need because the steps/mm are not quite the same when the soft material can avoid some traction from the extruder. Hard material 100% vs. Ninjaflex=107% on my old printers bad extruder. But the better a extruder is the less this effect should show.)

    I suppose that this might be similar on 1.75?
     
    #26 Nibbels, Feb 20, 2020
    Last edited: Feb 20, 2020
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  7. garethky

    garethky Well-Known Member

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    The nozzle closing/blocking thing is something I'm considering doing with a silicone sheet. I'm a little worried that the filament in the nozzle would get cooked but I can always purge it.

    The Nomex felt I got is too soft to really be useful. I also got some 'strip brush' from McMaster Carr and I'll be going forward with that. Its much denser than any brush I've seen and the end of the brush is flat which is prefect.

    A "Before" picture. This is with Prusa Slicer, purge block turned on and the purge volume set to 10mm^3. This was try #2, the first print didn't fail but it warped horribly because the cooling fans got shut off and I had to add an `M106 R2` command to tpostN.gcode to get the fans to restart. I'd say this is a surprisingly OK result for no ooze control and no purge/wipe: IMG_5045.jpg
     
  8. Paul Arden

    Paul Arden Well-Known Member

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    I’m still trying to find a source in Australia for the BCN3D silicon cloth wipers they use in their printers to try out. The wipers themselves are very cheap but EUR95 to ship to Australia. Once we have uptime in RRF3 macros I’m hoping to try and emulate the smart purge those printers use where the prime time is dependent on the idle time. I think the ooze buckets under the park location will definitely be better for wiping.

    Was interesting to watch how Stratasys do it, thanks for sharing that!
     
  9. Andy Cohen

    Andy Cohen Well-Known Member

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    The Fortus and the Mojo use a wire brush.
    The problem with a brush or wipe with the surface facing upward is as the drips and wipes pile up on the surface it becomes ineffective. Works fine for single tools but with 4 tools and lots of changes it does not work all that well. Hence I went with bungee cords. It still can pile up a bit but most of the stuff simply drops off and down.
     
    #29 Andy Cohen, Feb 23, 2020
    Last edited: Feb 23, 2020
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  10. Nibbels

    Nibbels Well-Known Member

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    I have seen within my set of abrasives that rotary brushes like this one can have very fine wires. Finer than I know from other brushes.
    And there are very cheap models that you could simply press in a row one after the other in a hole pattern.

    https://www.amazon.de/Merryland-Drehwerkzeug-Miniaturbürste-Messingbürste-Elektrowerkzeuge/dp/B07QP5K7M6/

    Soon I will try to start such a brush in a circle. Thereby I try that the nozzle tip (because it is dipped) is not scratched, but the heating block and the rest of the nozzle is rubbed off.

    I probably will not need more aggressive "brushing" because I lock the nozzles when the tool is parked.
    But I found out that at least some removal of leftovers is a good thing for longer prints using petg and other stringy materials.

    Or maybe I just install some of the cheep brushes infront of the parking position. And I can then easily switch them out if needed.
     
  11. garethky

    garethky Well-Known Member

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    I believe you are right, 4x the tools means we need 4x the wipers to get the same runtime between maintenance.

    Just brainstorming:

    One idea is having a brush on either side and forking the wiper script so 2 tools go left and 2 tools go right. The panels came with mounting holes for this.

    Another is putting the wipers under the tools themselves, like you have done. This has a certain appeal as the height for each wiper is adjustable individually allowing a mix of tools. But there are no mounting holes for this and, if you keep the stock bowden setups, the extruders are in the way.

    Perhaps a third idea is having 2 dual wiper setups on either side with individually adjustable height (think stacked turrets on a battleship).

    And a fourth idea is Greg's (I think its Greg's?) stepper driven adjustable height wiper. But that only gets you 1 wiper.

    I'm sure by the end of the day I'll have 3 more ideas!
     
  12. garethky

    garethky Well-Known Member

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    This is the strip brush I received from McMaster Carr. It compares very favorably to a brass brush. The fibers are much denser and finer. 2 strips about matches the width of the regular brush. The end is cut pretty much dead flat. Still haven't tested it out though.
    IMG_5058.jpg
     
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  13. Andy Cohen

    Andy Cohen Well-Known Member

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    I'd sure like to see if you get wear or damage on the brass nozzles. FWIW the soft silicon brushes (look at the earlier threads) work fine. They catch anything that stays on past the bungee wipe.
     
  14. Spoon Unit

    Spoon Unit Well-Known Member

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    I think it's been confirmed previously by Greg that such brushes will definitely damage a brass nozzle and will also damage the coating on Nozzle X. I would imagine the hardened nozzles would be fine for some time with this, but the damage will still not be absolute zero. My silicon brushes also do the job just fine.
     
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