PLA curling up from bed

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sprior
Posts: 379
Joined: Thu Apr 10, 2014 8:37 pm

PLA curling up from bed

Post by sprior » Sat Apr 19, 2014 5:32 pm

Last night I printed a Google Glass case for a friend (http://www.thingiverse.com/thing:297975). First I'll say that I paid about the same for my MakerGear M2 kit as he paid for his Google Glass and I think I got a way better deal. I used Simplify3D to slice this and used the default settings for my V3B 24V hotend - 215C extruder and 70C bed. This was printed with the black PLA filament that came with the printer. I've been quite happy with the bed adhesion on the bare heated glass, but wonder if the bed temperature might be too hot and causing my problem or is it something else.

As you can see from the first photo the part bent up at away from the bed at the point:
2014-04-19 12.10.08.jpg
2014-04-19 12.10.08.jpg (219.61 KiB) Viewed 2984 times

I notice how the bottom layers look a bit melted and bubbly where everything looks pretty good above that. This is the biggest piece I've printed and it takes up most of the bed.
2014-04-19 12.10.16.jpg
2014-04-19 12.10.16.jpg (231.72 KiB) Viewed 2984 times
This also looks like the problems I've read about with ABS where the solution is to enclose the printer, but I'm doing this in PLA and didn't think that would be necessary. I've been wondering about turning the bed temp from the default value of 70C, but don't want to lose bed adhesion.

Any suggestions?

jsc
Posts: 1863
Joined: Thu Apr 10, 2014 4:00 am

Re: PLA curling up from bed

Post by jsc » Sat Apr 19, 2014 6:00 pm

Bare glass adhesion is nice, but sometimes you need the strong stuff, especially for large objects, even with PLA. Try painter's tape, hair spray, and glue (in approximate order of strength).

sprior
Posts: 379
Joined: Thu Apr 10, 2014 8:37 pm

Re: PLA curling up from bed

Post by sprior » Sat Apr 19, 2014 6:48 pm

So you think the bubbling up to about a centimeter from the bottom is fundamentally caused by bed adhesion and not too much bed heat?

jsc
Posts: 1863
Joined: Thu Apr 10, 2014 4:00 am

Re: PLA curling up from bed

Post by jsc » Sat Apr 19, 2014 6:53 pm

Did you watch it going down? I doubt that 70C could cause ABS to bubble. What I would think is happening is that it is detaching early and those "bubbles" are a result of defects resulting from the warping layers interfering with the layers above until it adjusts. They are basically getting overextruded because the lower layers are intruding where they shouldn't be.

sprior
Posts: 379
Joined: Thu Apr 10, 2014 8:37 pm

Re: PLA curling up from bed

Post by sprior » Sat Apr 19, 2014 6:54 pm

This is not ABS, it's PLA.

sprior
Posts: 379
Joined: Thu Apr 10, 2014 8:37 pm

Re: PLA curling up from bed

Post by sprior » Sat Apr 19, 2014 6:55 pm

If it's not the heat from the bed and overextruding I'm trying to understand why it stops so suddenly.

jsc
Posts: 1863
Joined: Thu Apr 10, 2014 4:00 am

Re: PLA curling up from bed

Post by jsc » Sat Apr 19, 2014 6:58 pm

At some point, it works itself out and the layers above that point are as if they would have been. I bet the bubbles are just all the extra plastic that would have gone into the area that is now empty due to the warp.

Toby
Posts: 330
Joined: Wed Apr 09, 2014 9:44 pm

Re: PLA curling up from bed

Post by Toby » Sat Apr 19, 2014 7:01 pm

Yeah, that's the curling we all get. Think of it as a rite of passage. I don't know how long you've been printing, but it also seems to be the case that bare glass works at first, but later starts to fail. Maybe just because it gets dirty- some people have said that being meticulous about cleaning keeps it working.

I think the bubbling look may be caused by the nozzle running into the plastic that got raised up as a result of the curling. I don't think it's caused by the bed temp being too high, though I used to run mine at 70 for PLA and switched to 60 and I think I get better results. It stops because eventually the nozzle has flattened it all out and is back to normal printing each layer.

I'm not sure I agree with Jin's ranking of adhesion strength. Depending on how its applied, glue can be a lot stronger than hairspray. My current favorite is white glue diluted with about 3-4 times the amount in water and brushed/rolled on for a nice even coat. keeps working for about 3 or 4 prints before it needs to be changed. Let it cool all the way down to room temp though or else you may find it sticking more than you bargained for.

Toby
Posts: 330
Joined: Wed Apr 09, 2014 9:44 pm

Re: PLA curling up from bed

Post by Toby » Sat Apr 19, 2014 7:03 pm

Boy you have to be quick on this board. I took a few minutes to edit my post and pretty much everything I had to say was already covered in the meantime.

Toby
Posts: 330
Joined: Wed Apr 09, 2014 9:44 pm

Re: PLA curling up from bed

Post by Toby » Sat Apr 19, 2014 7:05 pm

oh wait jin's order was in increasing strength.

that's odd because the one and only time I tried painters tape I could not get the part off it.

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