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gasgano

PLA bends

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hi everybody

i started to print different things and it works quite good. but the pla seems to bend when it cools down. i unplugged de fan so it woun't cool down so fast and it got better, but it still bends a lot. from time to time the parts even come of the table and the nozzle moves them around.

i read about a heatable table, but this sounds like a lot of work. does anybody know how to fix this and knows making the pla cool down without bending?

greetings

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Hi Gasgano

I'm getting the same problem and it varies from print to print so I'll be watching this thread too.

As far as parts coming off the table you might want to start your print with the nozzle closer to platform but not by much you don't want to stop extrusion on the first layer, just be pressing the pla down firm onto the platform.

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I've seen a 2mm warp up on a 100mm print, which is not that much. And when I print at a lower temperature this gets even better. I do have a very low start Z, it takes a lot of effort to take the parts off the bed then, I need to fix the tape after every print.

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the height of the nozzle seems ok to me. the first layer sticks on the platform, but after some layers it starts to come of. i remove the parts from the platform with a cutter or something similar, this works quite well to me.

my plan is to place some kind of heater next to the printer which keeps the platform warm. maybe this will make the pla bend less. but i accientally broke the nozzle so i have to fix that first -.-

at what temperature do you print? i print with 250° as it says in the ultimaker wiki.

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at what temperature do you print? i print with 250° as it says in the ultimaker wiki.

Don't. 250C is "safe" as in that it always prints. But at 250C PLA starts to get really smelly and really soft. When I need fast prints I print at 230C, when I need high detailed small slow prints I print at 200C.

Warping should also be less at lower temperatures.

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I print at 240, the only reason is I find the strength of the finished plastic is greater. The transparency of the plastic and the strength both seem to drop along with the temperature.

I have noticed the warping you are talking about, I find having fewer solid layers helps a lot, also not printing objects completely solid, but having about 20% infill (also helps for bridging at higher temperatures). It is an ongoing challenge, you might want to drop your temperature for a more difficult piece. Even a very good first layer will not help when the plastic decides to warp, it will pull the tape up from the platform, or even break loose from the acrylic if there is no tape.

In another thread this

http://www.orbi-tech.de/shop/Kunststoff ... 30_46.html

supplier was mentioned to have "low warp" PLA, could be worth looking in to.

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I posted this video a while ago, but it still is relevant:

 

nice parts :D but it's a bit wasting of time and material if you have to print such big parts several time until it works. in some cases the pla even warps when it's only 1cm long. so this makes it a bit difficult to make the contactsurface smaller as you show it in the video.

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Hi Gasgano

I'm printing quite a lot of big parts to build remote controlled aircrafts.

See post:

http://forum.ultimaker.com/viewtopic.php?f=19&t=297#p1588

High Temperature increases the wrapping (bending) mainly if there are big differences in the structure width of the things you print.

It's just the usual engineering problem of plastic casting. Every unevenness in wall thickness causes differences in cooling rate which results in internal stress which causes the wrapping.

For example:

- A cylinder with no infill will have no wrap, because the wall thickness is constant.

- A cube with no infill, the edges will tend to wrap in z-direction because there is more mass in the corners

- A rhombic footprint (As my SR71 fuselage segments) has a huge mass in the sharp corners. They wrap quite a lot

- Infill causes the whole structure to wrap because the ribs cool down faster then the thick walls.

A heated build platform may solve the problem for not too high parts but when using the whole 200mm there is a risk the stress in the layers gets high enough that the print just breaks apart.

After quite some experimenting with different temperatures and settings I found the premium PLA 45 type from Orbi-tech in Germany.

This PLa has the least wrap of all materials I tested. I print it with 240°C at 100mm/sec with no problems (120 hours the last two weeks)

It's a bit more expensive but if you use double the material because you have to throw the prints away, it's always worth the money.

Michael

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Thank you very much, for sharing your experience.

I looked at their page

http://www.orbi-tech.de/shop/Kunststoff ... 30_46.html

, did you try the pla90 as well?

The graph indicates, that pla45 seems to be more flexible, than the others, maybe somewhere inbetween "standard" and the soft type.

And, regarding to the graph, it looks like this type of PLA45 starts to soft below 50°C.

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Thank you Michael for your detailed post. It seems there is a lot of experience required to print a really good part. I tried to print this one:

http://www.thingiverse.com/thing:17395

but even the small foot starts to warp after some layers. but as you said, there is a lot of mass concentrated in some corners.

Micha, the PLA45 seems to warp very little. I'm currently using the PLA that comes with the kid. I'm not sure which one it is, but I guess it's the standard one. Maybe I'll buy one roll of the PLA45 if i can't handle the problem.

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0.2mm to small for your nozzle? Bollocks! 0.2mm with a 0.4mm nozzle (Ultimaker default) should be the highest layer I found to be "good" to print at. At 0.3mm layers my layers where not sticking to eachother. And at 0.1mm the prints become pretty. I've printed at 0.05mm layers, but that causes problems with top infills (might need some more configuration settings to fix this)

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