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Spitting out filament at start of print


doktrmike
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Posted · Spitting out filament at start of print

Hi all,

I just started using Cura with my MendelMax and the first print turned out great. The second print, however, yielded a strange problem. I loaded and sliced this object to gcode:

http://www.thingiverse.com/thing:24238

It's a 5mm calibration blocks test that I'm sure many of you know and love/are completely sick of.

Anyway, I sliced this and loaded the gcode to Pronterface, just as I did with the first attempt at using Cura. However, on printing, the extruder ran in reverse and very quickly pushing the filament all the way back out of the extruder immediately upon starting the print. The printer homed the axes, then reversed out the filament.

I turned off the retraction feature in Cura and tried again. This time it reversed only a few mm such that the material started coming out again not long after the skirt had been drawn out.

Anyone seen anything like this, and what else can I share to help?

Thanks,

Mike

 

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    Posted · Spitting out filament at start of print

    Something about the start gcode isn't working, so that it isn't resetting the extruder position. At the start of the print, it zeros the extruder position, then extrudes a few mm of filamant to prime the head, then resets the extruder position to zero, then starts printing.

    The initial 'zero the extruder' isn't working, so that when it tries to move the extruder to its 3mm position (from zero, hence extruding 3mm of filament), it instead thinks you want to go to the 3mm position from whatever position you are at, and so runs the extruder backward to where it was 3mm into the previous print.

    Are you running Marlin firmware on your printer?

    Can you post the first few lines of a sample gcode, up to the point where it starts the skirt lines?

     

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    Posted · Spitting out filament at start of print

    I recommend maybe power cycling your printer Arduino before printing. Like Illuminarti says, it's probably remembering the position where you last printed and backing back up to the beginning with the extruder and doesn't know that that filament is gone now.

     

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    Posted · Spitting out filament at start of print

    Thanks. I am using Marlin, though I've never needed to power cycle the printer. I've been using Slic3r for some time and never had this issue. Here's the start of the gcode:

    ;Generated with Cura_SteamEngine 13.11.2

    M140 S65.000000

    M109 T0 S180.000000

    T0

    M190 S65.000000

    ;Sliced at: Sun 01-12-2013 08:19:13

    ;Basic settings: Layer height: 0.2 Walls: 1 Fill: 30

    ;Print time: #P_TIME#

    ;Filament used: #F_AMNT#m #F_WGHT#g

    ;Filament cost: #F_COST#

    ;M190 S65 ;Uncomment to add your own bed temperature line

    ;M109 S180 ;Uncomment to add your own temperature line

    G28 ; home all axes

     

    ;Layer count: 125

    ;LAYER:0

    M107

    G0 F5940 X100.95 Y108.75 Z0.30

    ;TYPE:SKIRT

    G1 F2400 E0.00000

    G1 F1140 X109.05 Y108.75 E0.19062

    G1 X111.25 Y110.95 E0.26366

    G1 X111.25 Y113.75 E0.32959

    ...

     

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    Posted · Spitting out filament at start of print

    Add "G92 E0 ;zero the extruded length" to your start.gcode. Cura doesn't automagically insert that like other slicers tend to do. If you don't reset the extruder postion, first extrude command in the gcode will end up reversing the filament on your second print.

    Ask me how I know that. ;-) Scratched my head for a while before realizing this one.

     

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    Posted · Spitting out filament at start of print

    It looks like you're not using any start gcode at all - just a single G28, so you aren't resetting the filament length as amramsey says.

    Here's the standard start gcode that you can enter in the Start/End-Gcode tab:

    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 E3 ;extrude 3mm of feed stock

    G92 E0 ;zero the extruded length again

    G1 F{travel_speed}

    ;Put printing message on LCD screen

    M117 Printing...

     

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    Posted · Spitting out filament at start of print

    Thanks, all. This was super helpful and solved my problem. I guess I got a little carried away deleting the standard start script :oops:

     

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