ABS prints are slightly bent.

Rhragnarok · Post by **Rhragnarok** » Fri Jan 08, 2016 1:16 am

Hello all, so I got my new Makergear M2 and ran a few prints with the black PLA that came with it and all went great. Prints are looking great. I tried to do a high detail print with the PLA and it didnt work as well as the large prints. Just came out too rough. Might need to adjust the settings but I prefer to print in ABS.

So I switched over to ABS and I am getting overall pretty good results, but one problem I am having is that the first 2 prints I have done with it that had any size to them came out warped slightly in the middle. Not warped because they came loose from the bed, they were totally flat when the print finished. But when I pulled them off, they bend upward from the middle. Imagine this is a profile of the part ____.....-------.....____ kinda like that only more tapered and even. I may put up a pic but I haven't got one to post yet. These parts are very flat and skinny. One in particular is only about 5mm tall but 170mm on one side. I had previously been printing these same parts on a Flashforge Creator Pro using Hatchbox and was not getting this warping issue. But the Makergear guys told me not to use Hatchbox because they said it would clog the nozzle because of the quality of the filament. Thought I never experienced that.

Anyway, I am using Inland ABS 1.75mm because that's the best alternative that the guys at Makergear recommended to theirs which is WAY overpriced!

Anyone else experienced this? I am not sure if I can do something in the settings to fix this issue? Or if its just that this filament does that.

Thanks!

jimc · Post by **jimc** » Fri Jan 08, 2016 6:02 am

the inland stuff is esun. i personally like their abs. good stuff. i hear a ton of people using hatchbox with no issues but heard some reports here and there of clogging and typical filament issues. never used it myself.

as for the warp, thats abs and what it does. when you print abs alot of internal stress is created. each layer goes down, bonds then shrinks as it cools. if you want something alot less prone to warping but stronger than pla then use petg.

Rhragnarok · Post by **Rhragnarok** » Fri Jan 08, 2016 1:43 pm

So I just did a big print and it was perfect. Stayed totally flat to the bed. The second I took a big piece off I set it on a flat table and watched and and when I laid it down it was totally flat. I then watched as it warped raising the middle from the table over about 10 seconds!! This is frustrating as hell!! There has got to be a way to prevent this. Do I need to let it cool on the bed more before taking the print off? Or less top and bottom layers? Might that help?

ednisley · Post by **ednisley** » Fri Jan 08, 2016 3:15 pm

Rhragnarok wrote:it warped raising the middle from the table over about 10 seconds!!

You can do that with a strip of cold-rolled steel: clamp it down, machine off the top surface, remove the clamps, and it'll curl up like a potato chip. When you remove the top layer, the remaining stresses in the middle and bottom layers aren't balanced.

On a 3D printer, the bottom layer of plastic stays glued to the hot platform at full size. The upper layers also go down at that size, but they cool more during printing and therefore won't contract as much at room temperature.

When you take the part off the platform and let it cool, the bottom layers contract more than the top layers and produce that graceful bend at room temperature.

Letting the part cool on the platform will help, but won't solve the problem; it's inherent in the "manufacturing process". Assuming ABS shrinks by 0.5% (a SWAG) your as-printed 170 mm bar "wants" to be 169 mm long at room temperature, which means the bottom pulls the top by that much as it cools. The numbers won't be precisely accurate, but you get the general idea.

You might be able to anneal the part by clamping it in the proper shape, heating it just above the glass transition temperature, and letting it cool, but that pretty much wipes out the charm of 3D printing.

The real solution is to design the object with the process limitations in mind, perhaps by assembling larger parts from smaller sections that don't accumulate such high stresses.

Thinking about that stuff will definitely keep your mind occupied... [grin]

innkeeper · Post by **innkeeper** » Fri Jan 08, 2016 5:27 pm

I'm not sure i have an answer, just passing along some information.. hope it is helpful

since the upper layers cool and contract last plus the HBP keeps the bottom layers also hot and playable, you get uneven contraction when cooling... you can try and mitigate the effect by keeping the whole build warm to allow more even cooling and contraction. To that end, some people will build enclosures to keep the whole build warm and even pre heat the enclosure before starting printing. and then, during cooling allowing it to cool evenly before removing it from the plate.

Additionally not all brands strink as much or the same when cooling.. so you can start by using a brand that effects you least.
the bigger the print the more of a factor this is.
somone did some experiments on shrinkage of different brands of abs, but cant find this right this moment. if i find it i will post

Jules · Post by **Jules** » Fri Jan 08, 2016 5:38 pm

Or you might want to try PETG. Doesn't shrink or warp. (Well, hardly any.)

jsc · Post by **jsc** » Fri Jan 08, 2016 11:25 pm

Thinking about Ed's explanation, I had a thought. What if you introduced small grooves, three or four layers in depth, latitudinally across the bottom of the part. They might act as stress breaks, allowing the contraction to occur within each segment instead of extending through the entire length. Kind of a flat extension of the corrugated wall idea for relieving ABS shrink tension.

Rhragnarok · Post by **Rhragnarok** » Sat Jan 09, 2016 2:05 am

What you guys are saying makes a lot of sense. So if I understand what you're saying, to fix the problem I would need to enclose my printer somehow so that the heat stays more even over the course of the print. That way the top layers are not contracting as much.

So what I am confused about then, is how does anyone print anything of any size using ABS on this printer? Since it is not enclosed? And if this is the case, why would Makergear bother making the open chassis printer?

Wouldn't it make more sense to design it with an enclosure from the get go to avoid this problem?

I would love to hear from someone using ABS on this printer who has gotten large prints to turn out successful without warping like this.

Matt_Sharkey · Post by **Matt_Sharkey** » Sat Jan 09, 2016 2:15 am

an enclosure is a box, no need to spend $300 more for what IKEA or even Cardboard can accomplish.

I don't think that MakerGear intended this printer to be used to print large ABS prints with the stock setup; At least nothing that depends on accuracy. It will do well enough to draw up the bust of Stephen Colbert {http://www.thingiverse.com/thing:9104}, but maybe not accurate enough for engineering mock-ups.

Pekish79 · Post by **Pekish79** » Sat Jan 09, 2016 2:16 am

probably not in winter anyway i honestly us PLA 80% and PETG the remaining 20% i don't really like ABS and not sure why people use it instead of PETG i guess price and color availability. (it even smell bad!)

i would only use PLA as is "natural stuff" but sometimes u really need something with different proprieties in that case PETG work perfectly

ABS prints are slightly bent.

ABS prints are slightly bent.

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Re: ABS prints are slightly bent.

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Re: ABS prints are slightly bent.