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looking for a better way to pre-extrude PLA


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Posted · looking for a better way to pre-extrude PLA

Hey, that subject rhymes - badly...

At the moment my method for beginning a print having warmed the UM up from cold is as follows (I'm using an ulticontroller):

1. use Prepare/Preheat PLA

2. do something else till pre-heat is done

3. load print gcode from card selection menu

4. begin print and observe as PLA begins to flow normally.

5. stop print and select auto-home

6. wipe aware the small amount of badly printed PLA from the print bed.

7. select the print gcode again and restart print.

From here on I can usually walk away while the printer completes its job.

On the whole this method is good but I know I could bypass steps 4 to 7 if only I could increase the amount of pre-print - that bit where the printer runs a printed line or two around the print job.

Is this just a matter of adding some more gcode to increase the amount of pre-printing before the job proper begins? I mean, I'm sure it is but can this 'pre-print' phase be extended when I generate gcode via Cura?

Mmmm - maybe this is a Cura forum question, but I wondered if there were other alternatives to achieve this so thought posting a general question a better approach, at least initially. Many thanks for your replies and comments in advance.

- Graeme

 

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    Posted · looking for a better way to pre-extrude PLA

    or,

    1. use Prepare/Preheat PLA

    2. do something else till pre-heat is done

    turn the wooden gear manually, until you feel the pla coming out smoothly,

    remove the extruded pla under the nozzle.

    (by doing that, you are sure that there is no blockage in your hot end)

    3. load print gcode from card selection menu

    4. begin print and observe as PLA begins to flow normally.

    brim or skirt are always good, depending on your model

     

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    Posted · looking for a better way to pre-extrude PLA

    or,

    1. use Prepare/Preheat PLA

    2. do something else till pre-heat is done

    turn the wooden gear manually, until you feel the pla coming out smoothly,

    remove the extruded pla under the nozzle.

    (by doing that, you are sure that there is no blockage in your hot end)

    3. load print gcode from card selection menu

    4. begin print and observe as PLA begins to flow normally.

    brim or skirt are always good, depending on your model

     

    Thanks - good to keep in mind if I forget to compile gcode with a brim.

    I'm very pleased to report my first print with Brim has nailed this problem and I'll be printing a brim on future prints to ensure there's a good even flow before the real job begins - problem solved.

     

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    Posted · looking for a better way to pre-extrude PLA

    If, after printing the brim, it still looks lousy you probably need to "re-level" the bed so it's the perfect height everywhere.

     

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    Posted · looking for a better way to pre-extrude PLA

    Brim may be overkill - it's normally set to a lot of loops, and its attached to the print. I usually find that a skirt of 3 or 4 passes is sufficient, and you don't have to worry about separating that from the print afterwards.

    The other thing that will probably help is to increase the amount of priming extrusion in your starting gcode. In cura, there's a line in the starting gcode that looks something like:

    G1 F200 E3 ;extrude 3mm of feed stock

    I prefer to change this to:

    G1 F90 E6 ;extrude 6mm of feed stock

    This extrudes twice as much plastic, and at a slower pace that won't over-tax the nozzle. You could also add a delay command after that, to give yourself a chance to clean up the nozzle for easily...

    G4 P2000 ; pause 2000ms

     

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    Posted · looking for a better way to pre-extrude PLA

    Brim may be overkill - it's normally set to a lot of loops, and its attached to the print. I usually find that a skirt of 3 or 4 passes is sufficient, and you don't have to worry about separating that from the print afterwards.

    <snip>

    Wow, really appreciating all these insights that are incrementally levelling me up as a 3d print maker. Seriously though, just adding Brim means I can, for the first time, just start a job and walk away. Such a big improvement..

     

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    Posted · looking for a better way to pre-extrude PLA

    Ha, thank-you.

    I was about to post the same question as Graeme. Same process here so far except I was feeding by hand at the beginning instead of starting a print. I will go for extra skirt or brim tonight...

     

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    Posted · looking for a better way to pre-extrude PLA

    Brim may be overkill - it's normally set to a lot of loops, and its attached to the print. I usually find that a skirt of 3 or 4 passes is sufficient, and you don't have to worry about separating that from the print afterwards.

    The other thing that will probably help is to increase the amount of priming extrusion in your starting gcode. In cura, there's a line in the starting gcode that looks something like:

    G1 F200 E3 ;extrude 3mm of feed stock

    I prefer to change this to:

    G1 F90 E6 ;extrude 6mm of feed stock

    This extrudes twice as much plastic, and at a slower pace that won't over-tax the nozzle. You could also add a delay command after that, to give yourself a chance to clean up the nozzle for easily...

    G4 P2000 ; pause 2000ms

     

    That works very well for me, I was always failing adhere on first print then success on starting again, those lines cure that for my set up. Thanks.

     

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    Posted · looking for a better way to pre-extrude PLA

    These manual steps work well for me (no Ulticontroller) with just an outline.

    1) Load the print file

    2) press 210 C pre-heat button under the "temp" tab

    3) when temp gets close, switch to "jog" tab

    4) press extrude button until good PLA is flowing and the correct color if changing colors

    5) clean the nozzle and remove dross, quickly to keep pressure in hotend

    6) press print button

    7) grab the Z axis and crank it while making the outline to crush the extruded bead to desired thickness ex to get .2 mm thick layer with .4 mm nozzle, crush down half the bead height, 0.1 mm with 0.4 mm crush down 75%.

    Scott

     

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    Posted · looking for a better way to pre-extrude PLA

    My workflow is :

    1/ Preheat PLA

    2/ Wait the preheat is done

    3/ Move axis/ 1mm / extruder then turn the controler of 2 or 3 steps until the pla is coming

    4/ Load the Gcode and clean the head until the print begin.

    It works at 100%

     

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    Posted · looking for a better way to pre-extrude PLA

    I know, topic is a bit older but - would an M0 instead of G4 P... be an alternative?

    @ Illuminarti, what do you think?

     

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    Posted · looking for a better way to pre-extrude PLA

    Yes, if you have an ulticontroller, you can use M0 at the end of the start gcode instead to wait until the you're ready to start the print - if that's what you're referring to.

     

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    Posted · looking for a better way to pre-extrude PLA

    Yes, that's my intention - I will give it a try :-)

    Thank you !!

     

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    Posted · looking for a better way to pre-extrude PLA

    As well as priming and wiping the nozzle manually, and using the skirt of 2-3 lines, I have my start gcode slightly modified (on my UM1). It now looks like this - added part in red:

    G21 ;metric values

    G90 ;absolute positioning

    M107 ;start with the fan off

    G28 X0 Y0 ;move X/Y to min endstops

    G28 Z0 ;move Z to min endstops

    G1 Z15.0 F{travel_speed} ;move the platform down 15mm

    G92 E0 ;zero the extruded length

    G1 F200 E2 ;extrude 2mm of feed stock

    G92 E0 ;zero the extruded length again

    G1 X10 Y10 Z-15 F{travel_speed} :move head to 10,10 and bed back up to 0

    G1 F{travel_speed}

    M117 Printing...

    It makes the primed nozzle drag across the bed in transit to the skirt while not extruding. The boogers from priming are mostly wiped off. The skirt starts to print nearly perfectly and I have enough time to adjust Z manually if needed.

     

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    Posted · looking for a better way to pre-extrude PLA

    hmmm... just for wiping - might some kind of brush be a solution - mounted near the x/y-0/0 and passed during the way to the skirt ?

     

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    Posted · looking for a better way to pre-extrude PLA

    Yes but then you wouldn't be able to print in that spot so you couldn't print full size prints unless they didn't reach that spot of the build plate. You would probably also have to cut a slot in the Z stage so that when the stage is all the way up it doesn't hit the wiper.

     

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    Posted · looking for a better way to pre-extrude PLA

    To follow up belatedly on a n earlier comment, I don't recommend using the ulticontroller to advance the extruder on a UM1. For a start it's a pain to do, having to click several layers deep. And secondly, it advances the filament much too fast, compared to normal printing speeds. It's so much easier to just grab the gear wheel and turn it - and you can get a much better feedback as to the resistance that the extruded is encountering, and slow down before doing any damage.

     

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