Printing larger parts with PC Blend Issues  

warpy

That is good results.  I have had the same warping on a lot of prints.  

Strength or Toughness

However, it needs to have some strength and will be outside, so I have been trying in PC Blend.

PC Blend isn't any stronger than some brands of PL... it's a LOT tougher, but no stronger.
(Note however that some brands of PL are significantly weaker - not all PL is created equal!)

High temperatures and sunlight are the enemies of PLA.  It can survive surprisingly well outdoors in a temperate climate if well painted.

Some plastics, like PC, are very prone to warping.  One preventative strategy is to incorporate transverse voids to break the long dimension into a series of shorter ones but that can compromise strength.  In others measuring the distortion and calibrating the negative shape into the part can help.

Cheerio,

switch to PETG?

@cwbullet, the top photo is PLA, this photo is PC Blend.

Thinking of giving up on this material for this part. One of my main reasons for picking PC Blend was the outdoor requirement. After some reading, it looks like I might try PETG instead. I didn't think it had a high enough temperature before getting soft, but a lot of people seem to be recommending it. 

infill angle part of the problem?

Hi there,

I was about to start a new thread about PC, warping and large and flat parts, but it seems that this could be as good a place to add the questions.

Regarding warping it is my limited understanding that material shrinkage during cooling "pulls" the part together. (please correct me if I'm wrong) Is therefore the direction of the infill a potential problem/part of the problem? In the case of the OPs part, what infill was used and what would be the main direction of the shrinking force exerted during cooling?

In my case, I'm trying to print a sheet like part (4mm high, but about 20x10 cm). A lot of the gyroid infill is printed along the long axis. The warping happens perpendicular to this axis, lifting the outer parts upwards. ( Sorry currently no good pictures available, as I've thrown away the misprints).

Rotating the infill angle by 45 degrees unfortunately rotates everything, so that now the top and bottom infill is parallel and 90 degrees to the long axis of the part and thus probably exacerbating the problem rather than solving it. Does anybody know if it possible to influence the infill angle with a modifier? I couldn't find one, but that basically means nothing 😉

Any clever thoughts on this? Am I completely overthinking this and should I just continue with try and error until I get lucky and my parts look ok?

Cheers

Hansjoerg

PETG

PETG softening is not an issue for me in GA.  PLA is another story,  

Posted by: @chris-4

@cwbullet, the top photo is PLA, this photo is PC Blend.

Thinking of giving up on this material for this part. One of my main reasons for picking PC Blend was the outdoor requirement. After some reading, it looks like I might try PETG instead. I didn't think it had a high enough temperature before getting soft, but a lot of people seem to be recommending it. 

Regarding warping it is my limited understanding that material shrinkage during cooling "pulls" the part together. (please correct me if I'm wrong) Is therefore the direction of the infill a potential problem/part of the problem?

Warping is due to the thermal contraction of the cooling filament.  The unconstrained top layer (the current top layer, the one being printed) shrinks, and, as you say, it pulls the upper layers of the part together causing it to bend around the infill, the type, angle and density of the fill has little effect.

You might try constrained annealing.  Clamp the part in the desired position then heat it, in an oven or other enclosure, to just below the glass transition temperature for a few hours then cool it slowly.  You are allowing the polymer molecules to slip slightly against each other and release stress.  There may be some shrinkage but you should be able to measure and calibrate for it.

Cheerio,

Engineer??? 😉

Thanks @diem, you must be an engineer.

While your reply is entirely correct, as precise as it can get and even potentially potentially helpful by presenting a solution that was never asked for it nevertheless ignores the original question 😉

SCNR

But on a less cheeky note, has anybody any experience or knowledge about the influence infill patterns have on warping/tensions within a given object?

I could so far only find two discussions in old forums (one from here: https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-print-tips-archive/effect-of-infill-pattern-on-warping/). But everything was in the there is only PLA aera and nothing more contemporary. My setup here is way too random and uncontrolled to run a proper test series and I wouldn't be able to devise a meaningful way of measuring the warp.

My hypothesis would be that an interrupted infill pattern would be beneficial over a continuous pattern because it should be less prone to transmit the shrinkage tension over the whole distance of its axis.

I'm probably overthinking this but would be curious how easily somebody with a proper background in engineering or physics can shoot down my idea.

Cheers

Hansjoerg

it nevertheless ignores the original question

The one where you said

Any suggestions welcome.

?

You are going to get warping: if you manage to adhere strongly enough to the bed, it will bend the bed.  If you clamp the bed hard enough, it will rip up the PEI...  Constraining and annealing is a way around this.

Fill has negligable effect at our scales, the voids within the fill and the thin walls mean the infill distorts to comply with the part.  Most of the strength is in the perimeters, most of the warping is in the perimeters.

Cheerio,

Thanks

Posted by: @diem

You are going to get warping: if you manage to adhere strongly enough to the bed, it will bend the bed.  If you clamp the bed hard enough, it will rip up the PEI...  Constraining and annealing is a way around this.

Fill has negligable effect at our scales, the voids within the fill and the thin walls mean the infill distorts to comply with the part.  Most of the strength is in the perimeters, most of the warping is in the perimeters.

Cheerio,

Thanks a lot, I think I have understood now. As I was suspecting, totally overthinking this.

P.S. I hope you're not taking my cheeky comment too serious, I really appreciated the first answer and will give the annealing a go.

Warping

Warping is the reason I print mostly small footprint parts.  They do not need to warp.  

Petg

Ok. Seems like it is just not the right material for this part. I ordered some PETG.