Pausing prints

Discussion in 'Calibration, Help, and Troubleshooting' started by R Design, Mar 11, 2016.

  1. R Design

    R Design Well-Known Member

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    I remembered the instructions from the build manual on Pausing prints (on this page http://wiki.e3d-online.com/wiki/Your_First_Print )

    They're not entirely clear because the photo shows the menu set to "stop print" which I'd already determined was definitely a "stop" with no chance of "resume".

    Just now something weird was happening with the infill (is it the case that a small part with high percentage infill can get messy, with a build up of plastic even with a well adjusted Z? Could it be that putting the printer on polystyrene is not a good idea when there are lots of zippy movements because it seems to rock a little?). Decided now was time to tryout "Pause".

    Noticed that, unlike in the build manual, after a "Pause" there's no chance of pushing the printhead out the way. So used the steppers and moved it aside to study the print.

    When satisfied, decided to "resume" (after removing a lump of plastic) and, as the manual says, hit "auto home". Since it was a small part, and given the position of the printhead, this was possible. But then when I selected "resume" - in blind faith - the printhead went directly for the part with predicable consequences. Too bad the kill switch is not yet installed.

    Note to self: supergluing the IR sensor is not really enough... Print one when you've got the XT spool in.

    Anyone else try the "Pause" feature?
     
  2. Spoon Unit

    Spoon Unit Well-Known Member

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    I tried it. Yes it just sits there. I figured no point in pushing it out of the way as the printer would lose position. Never considered auto home as a way to re-educate it. I'm guessing the nozzle hit the part and pinged it out the way?
     
  3. R Design

    R Design Well-Known Member

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    Build manual says:

    - "If you need to stop the print for any reason, to change the offset for example, use the function via the LCD."

    - "You will be able to push the Printhead out of the way by hand once the print has been stopped. I recommend moving it into the docked position."

    - "Before restarting the print you need to run the Auto home sequence." ( IN RED!!!)

    So that's what I did.

    Based on what I saw IT DOESN"T MAKE SENSE.

    Basically for it to be able to work, the Rumba would have to be a lot cleverer than it is.

    Printhead smashed into the part and mashed up the IR sensor. Superglued it and half an hour fiddling to get it all back together and in place.

    Come to think of it, is the IR sensor one of the parts that's supposed to be in Material X? Tell you the truth everything on the printhead looks like Edge.

    ps Have been wondering why, occasionally, my Z offset sometimes changes. Present theory is that, from time to time the Rumba does something a bit weird and the IR sensor and / or fan scrape on a bed clip or the ooze wiper, changing their alignment. IMHO the Rumba - or rather 1.1 RC3 - is the weak link in this rock-solid machine.
     
  4. Spoon Unit

    Spoon Unit Well-Known Member

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    Ahhh. I see. AutoHome reset the height ! Come to think of it, from OctoPi you can do an X,Y home only rather than a full home. Perhaps that's accessible somehow from the front end. Quite agree on the weak link. I don't know how many times I've reset the box now, but it's probably over 100 already.
     
  5. R Design

    R Design Well-Known Member

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    How big is the Marlin community?
     
  6. UlrichKliegis

    UlrichKliegis Well-Known Member

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    If I am not completely mistaken, there is an option to tell Marlin that any operation of the z-limit switch outside the zeroing / abl-ing shall be disregarded. On my famous OrdBot, it happened from time to time before I corrected the flow rates that the nozzler rumbled over aggregated plastic somewhere. My special FSR-based Z-switch triggered, but printing just went on. Too busy to browse the .h code now, but something rings there in my backup memory.
     
  7. mike01hu

    mike01hu Well-Known Member

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    I've been using Marlin for some time and have used the "pause" function. It really does stop the head on the spot and you need to be quick to move the head with the controls, not by hand, then there is no need to do anything but hit resume. It would be good if the "pause" function triggered a head lift and move to the bucket. Moving the head by the control panel means that Marlin is still counting move steps so knows where to return to. I have never successfully recovered from pause by using auto-home then resume, it usually crashes into the model before the Z-axis recovers its position. A mod to the code should be made to force the Z-axis to restore first. Another issue is that the blob that accrues under the head when it pauses is a potential head-crash if not dealt with.

    Mike
     
  8. UlrichKliegis

    UlrichKliegis Well-Known Member

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    Somewhere in the Marlin sources, not necessarily in config.h there is some space where you can tell it what to do when pause is hit, if I remember it right, and how to return (puts the current position on some sort of stack or so). Maybe I have a memorry error there, so don't hit me if it is not the case.

    Besides that, it's a good idea to have some baking paper (the isolation layer you put between dough and baking plate) ready to put between nozzle and object immediately after initiating the pause. That paper is my tool of choice whenever I have to isolate something sticky (like epoxy resin sipping out from a seam between parts) from its neighbourhood. Recommendable, cheap, reusable (but not in the kitchen then!) easily dimensioned. Don't forget to pull it off again before printing resumes.
     
    #8 UlrichKliegis, Mar 12, 2016
    Last edited: Mar 12, 2016
  9. R Design

    R Design Well-Known Member

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    Great insights guys, so there is something wrong in the build manual about how to pause prints.

    Baking paper: will get some!

    ps no Z limit switch on BB, and as far as I can tell the X, Y microswitches are only used for calibration during autohome and do not serve as limit switches
     
  10. Spoon Unit

    Spoon Unit Well-Known Member

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    R Design, There are three end stops that serve as movement limiters on the big box. They all limit movement past zero. Looking at the rumba board, there is space for 6 end stops. All of ours plug in the minus (-) stop, so we're limiting the number from getting to small. The X and Y are pure on off switches activated by a microswitch, thus only requiring two cables to be connected to the board to complete a circuit. The Z endstop is in the form of an IR sensor. This has three cables plugged into the board, which tells us that it's powered and also returns information to the board, i.e. how far the bed is from the print head. All three end stops are used as part of the auto-home process to kick things off. I've never yet had the print head hit the X or Y switches during a print, so I don't know what would happen in that case. Z only ever increases during the build, so it should never be hit after a print starts. If you accidentally, as I have done, run a Z-only home with the print head over the dump bucket, you'll experience the terror of the bed being continually drive upward into the frame at the top of the screws; yet another moment where a kill switch could return minutes to your life span. In this case I was actually upstairs learning the ropes with Octoprint and had to run for it down the stairs to kill power ASAP :)
     
  11. Kanedias

    Kanedias Well-Known Member

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    ON my Makerbot clone running sailfish when you pause it drops the bed, autohomes and then when you resume goes back to continue on. I assumed the BB would do the same. :(
     
  12. Spoon Unit

    Spoon Unit Well-Known Member

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    I think this implies that your Makerbot has some specific control commands that are built into to it's firmware to do this. This is achievable with BB, but in order to allow you to decide how this works, and tweak it to your perfection, you have to do it yourself. I haven't got around to this yet myself as I have a dual printer, somewhat obviating the need for changes (though not entirely, so I'll come back to it).
     
  13. Alex9779

    Alex9779 Moderator
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    There is an option for filament change in the firmware. Currently deactivated.
    This enables an option on the LCD and also an M600 command.
    There you can define values in the firmware where to move the head, lift Z and retract.
    This could be used for pausing also, just don't change the filament... I did not test it myself how it works but it is worth a try.

    Just uncomment
    Code:
    //#define FILAMENTCHANGEENABLE
    in line #450...
     
  14. Spoon Unit

    Spoon Unit Well-Known Member

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    @Alex9779 , that's really good to know because so far, exchanging filament is really laborious. I had thought of writing a little GCODE for this, but maybe it's already covered. Do you know if that firmware option also increases the extruder speed during ejection, because it's really tedious using the dial and actually seems to reveal a bug in the firmware when it throws you out of the axis control screen.
     
  15. Alex9779

    Alex9779 Moderator
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    As I said I have no experience with that option.
    The BB is my second box and the first one with the real Marlin. So far I only have experience with my UM2 and the clone clone (yes two clones) Marlin...
     

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