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Levitating Raft

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Posted · Levitating Raft

OK, the tag may be a little misleading but I am a bit dumbfounded.  I've printed this part before and always with rafts but today, not sure what is happening.

I'm also not sure I've picked the correct 3mf file but think so.  


Long story short, as the raft prints, first two layers of the raft go down perfect but suddenly the third layer of the raft starts to break apart as can be seen here. Of course once it gets loose the print is pretty much done.  :-)


Any thoughts? I just tested the bed and the heat is actually best in the middle and the first two layers are happy as larks needing good pull to get it off the build plate. PP can be a PITA but I've generally had luck with it.  Today is a new one for me.   


Even if there is no known cure, thoughts are welcome!

Sinking Raft.jpg

Trump Hld Dn Spcl SF v2 Cura.3mf

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    Posted (edited) · Levitating Raft

    Is it possible the filament has picked up moisture?  Steam pockets can form and push a layer up.  That third layer is the first one that "seals" the gaps that are in the first two layers.  I've seen that happen when gaps in infill get sealed off (looks like a bunch of land mines went off) so it's possible that the same sort of thing is happening with your raft.

    This is just to show how much denser layer 3 is than 1 and 2.


    Edited by GregValiant
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    Posted · Levitating Raft

    Hey Greg, thanks for the thoughts.


    As a spit balling attempt to rectify what we both feel could be a moisture issue,  I'm going to heat the filament for a couple of hours prior to use, I'm going to preheat the chamber, I'm going to up the heat of the hottend after the first couple of layers as well as I'll increase the flow hoping to force the two layers together. Oh, and maybe slow it down at that point?   Heck, I might even stand over the printer and lower the hottend a few thou while it is in this third layer. :-)


    As an FYI, supposedly PP is not bothered by moisture but moist air can rest on the filament. Anyway, I still "dry it" when I get it, I store it in a constant 18% humidity bin, and just prior to using it I "toast" it again. All of which means squat other than I'm trying.


    IF I get this sorted, I'll come back and let you know. Shall we leave this open for a short while in case someone else has an idea?

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    Posted · Levitating Raft

    It's a pretty odd failure mode and I've only seen it a few times (one was with my own printer and a brand new roll of filament).

    Sometimes you can get ridges/bubbling on a 1st layer.  Usually that has to do with one or more areas on the build plate that have some sort of contamination.  Having it happen on an upper layer pretty much points at the filament.

    I think if you just put the filament in the printer with the build plate at around 50°C for three hours or so you should see a difference in the prints.


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    Posted · Levitating Raft

    I can't attack this until Monday but will give all the above a good shot. Huge thanks for your help as always.

    I will let you know how it all turns out as an FYI to file away.  Close this for now but lets agree, the mystery still remains.

    All the best, PC

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