Prints pulling up at corners

[naturalstate720]

Yes plate is clamped. I've been trying to print this building for three weeks now. Been asking questions on here for two weeks. Read as much as I could. But so far, these are the best results I've seen. My boss is less than forgiving, and we had a last minute meeting come up with the money man.

[Jules]

Yes plate is clamped. I've been trying to print this building for three weeks now. Been asking questions on here for two weeks. Read as much as I could. But so far, these are the best results I've seen. My boss is less than forgiving, and we had a last minute meeting come up with the money man.

Okay, we'll just keep fingers (and toes) crossed.

[Jules]

You need a backup plan, just in case. (I'm a huge fan of plan B.)

Had you thought about designing a decorative band that could be placed around the seam to cover the gap? Maybe with a matching band at the base so the customer thinks it was designed that way? (You could print that a lot quicker.) Or have you started sanding down the warped one?

Seems to me if the guy is showing up early for the meeting, your boss ought to be a little understanding about the situation, but i know that only happens in books.

[naturalstate720]

It's actually looking good so far. It's printed around story 4 now, and 13 more stories to go. And then the second print which I'm going to glue on top.

Speaking of that, can you recommend a good glue? And if they don't match up perfectly maybe some kind of putty (bondo maybe) or something to fill in cracks and then possible spray paint it?

In arch school we always used basswood, so this is new territory for me.

Really appreciate the help

[Jules]

Anything with cyanoacrylate in it (Superglue) for PLA. I think Bondo works for fill, but I've never tried it. ( sorry, on cellphone now)

[jsc]

Superglue will work if you don't apply shearing forces. For your model, it will be fine. You can also try IPS Weld On #4 or other similar plastic solvent, which will get you a very strong bond. The downside is that it is water thin, tends to run along the filament lines, and can mar the finish. But CA fumes can also haze plastic, so it's a wash. If you have it, CA accelerant such as Bob Smith Insta-Set accelerator makes things very easy.

I've seen people using bondo for filling, never tried it. I have used Smooth On XTC-3D epoxy with good success to get very nice finishes, and spray paint will cover up a host of sins (SEM high fill primer is good). Practice any new technique on some non-essential parts beforehand, though.

[naturalstate720]

Woke up and print looks ok, No major warping at least. Before I took it off zebra plate it looks completely flush with plate The brim doesn't appear to have warped at all. No gaps.

But then I carefully take it off, peel and cut away brim. And set the model on the table and it rocks. It is not perfectly square. WTF? What the f*ck is going on? is it not possible to print something that is square. So now my second piece will not align properly.

[jimc]

Yes the part adhered to the olate and it just warped the plate which is why inpersonally quit using thise type of flexible plates. I know jules and many people like yhem. To each their own and if it huves them good results then thats great but not me. I need something rick solid and flat. You have to realize that your fighting mother nature here. Every layer is put down hot then as it cools ut shrink a little. It might ni be alot of stress but do that for as many layers are in your model and you end up with a ton of force curling your print. It like having to small boards with 1000 rubber bands stretched between. The larger and more square your print the worse it is. Your better iff printing things in small parts and assembling like a model. Your printing pla too which is considered very low warp. Abs is 2-3 times as bad lol.

[naturalstate720]

Well, I guess I haven't tried this new brim technique with glue and hairspray. Maybe that will work.

I'm flipping the second model piece upside down and redoing supports so the top will be the bottom and be more square.

[ednisley]

is it not possible to print something that is square

You can take a rectangular bar of cold-rolled steel, machine off the top surface, release the clamps, and watch it curl up. The rolling operation introduces stresses into the bar that are perfectly balanced until one side goes away, at which point steel can't withstand the stress.

You can cast the concrete floor of an aircraft hanger in one piece, but then you'll watch it crack as the concrete shrinks while curing.

Your model is asking too much of the 3D printing process: it's a large flat plate with ribs & other features on the top surface. The plastic shrinks as it cools, by perhaps 0.5% (depending on the material), so each raised feature "wants" to be smaller than when it was printed. As long as the plate stays stuck to the platform, those forces are balanced and all is well, but when you remove it, the unbalanced stresses will deform the plastic.

If that wall (it looks like a wall) is about as long as the platform, its length wants to shrink by 0.005 x 250 mm = 1.25 mm. It won't be quite that bad, because the plate adhered to the platform holds the upper features in place and they stretch as they cool, but it gives you an idea of how much distortion you're up against.

Just as the machinist would use hot-rolled steel and the contractor will put joints into the concrete floor, you must adapt your models to the "construction" technique you're using. Cut it up along whatever natural lines you have, add registration pin holes to the edges, print those smaller sections, and glue them together. They'll fit just fine and you won't have to worry about what happens to a lengthy print in the dark of the night...