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jerry-blade

Ultimaker 1 "Oozing"?

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I am getting a weird "oozing" issue when the extruder head heats up, it just starts oozing PLA nonstop... its a problem because it drags this all over the first layer and then gets on the head and is a mess unless i try and scrape it off before it ruins the print. The first robot print actually turned out decent. Once the unit gets going, it seems to be fine - just this weird issue with it oozing filament nonstop once heated and the extruder motor/wheel isnt turning... anyone have an idea why this is happening?

Thanks!

-Jerry

gallery_35649_1178_468740.jpg

 

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I believe the oozing is caused by the thermal expansion of the PLA(it also oozes when upside down). It should happen just at the start for a little while, and then stop.

Before I print I always grab the ooze that is sticking to the print head as a part of my startup routine. I am looking for a better way though, With the oozing I wouldn't be able to operate the printer remotely. Perhaps cutting a hole in the buildplate at 0.0 or an other spot to let it ooze out, and scrape it of or something like that is a solution.

I'm eager to hear others about their startup routines.

 

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I was alway using a piece of paper for this at startup. .. but since cura 14.7 its massively improved. Oozing takes place in the left front corner with a raised bed... no more chunks of plastic in my first layer.

@daid. Thanks for this. Like it a lot.

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The oozing occurs because the feeder applies pressure to the filament forcing it into the nozzle during printing. At the end, the nozzle cools faster than the pressure is released from oozing trapping some of the pressure.

You can change the end code to retract the filament a bit removing the pressure (or most of it) at the end of the print. But then you must add some gcode in the start code to overfeed the filament at the start of the next print so that the slack has been removed and the pressure builds to the correct amount for the start of the print.

Alternately, as long as your build surface can tolerate the heat, you can use the surface to prevent oozing by homing the printer. NOTE however that I think the standard bed of UM1 will melt if in remains in contact with a hot nozzle.

 

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so I always start the print by preheating the pla - then rotate the wheel and grab the thread with tweezers then hit print for the object (from the sd card) and gently pull the thread while slightly turning the wheel - once it homes still clear the thread until it has started the outline and then pull the thread away.

I do it this way as a) it is fresh pla (the nozzle is purged) and b) no threads/blobs on the print.

James

 

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That oozing is normal. After the printer homes and warms up it squirts out even more. At that moment I grab it with my fingers and pull it towards the front of the machine as the bed raises. When the nozzle touches the glass/bed/tape I drop the blob down in front of the bed (over the edge) and the ooze stream creates a line to the start of the print and then I can walk away.

Other printers do a wipe before starting the print across the front edge. I don't know why Cura doesn't do this. For UM Original it's easy to add a wipe or other start sequence to the start.gcode in Cura. For UM2 you can't do that unless you print in reprap mode which isn't worth it for me.

 

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Thanks - I tried that last night, and the results were much better. When it homes, sometimes that glob gets stuck on the head which is a problem waiting to happen later in the print so I am frantically trying to pull it off before it starts printing hehe. I have been using needle nose pliers for most of this - does anyone have a better tool or way of getting a potentially disruptive glob of PLA off the head without disrupting the print?

Here are the results of my first "official" print:

gallery_35649_1178_11846.jpggallery_35649_1178_8504.jpg

 

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For better quality print slower and cooler. 190C and 20mm/sec will give the best quality. Make sure shell thickness is a multiple of nozzle, so .8mm is good. No infill needed. 210C at 35mm/sec is still very slow but quite good quality.

 

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Yeah these are I think 220C @50mm/sec which was the "default". I'll try 190C @20mm/sec tonight and make sure shell is 0.8mm. Any other settings I should look at that can have a big impact? I haven't "calibrated" the X-Y-Z steppers yet or checked my filament thickness to fine tune extrusion (micrometer coming today!). Leveling the bed was a pain until I saw that Cura has a wizard. When I replace the tape, I run it twice and that seems to work really well. Once I get dialed in, I want to print some replacement parts (new fan hood, z-axis endstop adjuster, extruder gear).

Thanks!

 

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(new fan hood

 

Not recommended. The fan isn't designed for high restriction fan hoods and the one that comes with the machine works very well. Most printed fan hoods work worse than the one that comes with the machine. Or if you melted it make one out of kapton tape.

Also if you print a fan hood with PLA and it is anywhere close to the nozzle it may melt so ABS is recommended for fan hoods.

Adding a second fan might be good though (on the other side).

 

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Not much idea. Some people blew out their darlington transistor when they added a second fan so I guess you want one that uses not much current. The voltage is 19V and many 12V fans blow up at 19V. Some 12V fans are fine at 19V but only run at 2 speeds: full and off. So the whole 50% duty cycle thing doesn't work with those fans. Somewhere around 70% they suddenly start spinning. Hard.

 

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