ABS print lifting

I am new to 3d printing and have successfully printed several small items.
Today I printed a large item and all was going fine for about an hour. Suddenly at around 10mm thick, the piece started to shrink on all four corners. The current layer stayed flat at all times and printed perfectly but as the piece got thicker the edges shrank more and more.
As the item was printed up side down, I now have a perfectly flat bottom face and a very curved top face.
The item varies from 22mm to 15mm in thickness but should be 22mm all over!!

Prusa i3
Heated bed (100 deg)
Kapton tape with Abs juice

With that bed temperature you must have been printing ABS. Did you remember to turn the print cooling fan off ? ABS does not like being cooled quickly.

Were you printing with 100% infill ? If so could you reduce this? The higher the infill the more the contraction forces.

Here's something the marketing department doesn't tell you about your i3 or any other open frame printer: you can't actually print anything but very small parts using ABS. As soon as your ABS print gets any height/bulk, it will warp and delaminate unless you enclose the printer and keep the enclosed area warm (45-50C). If you don't do that, forget about printing ABS.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Yes it was Abs
The fan is not on and the thickness was set to 15%
The maximum wall thickness is 3mm

What I don't understand is the fact that all was fine for about an hour then it all went wrong. The bed temp was still the same

How tall was the print though.
I find anything above 2" on my open i3 warps and cracks. Im hoping to switch to a coreXY setup that is enclosed to print ABS better.

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What I don't understand is the fact that all was fine for about an hour then it all went wrong. The bed temp was still the same

The layers close to the bed stay warm. As the print gets higher the layers cool to lower and lower temperatures and shrink more. The forces build up until something gives - either the bottom layer pulls away from the bed or the model splits. By using an enclosure and keeping the temperature around the print higher you can reduce the amount of shrinking.

An enclosure helps a lot, but can be tricky to set up.

A couple of things that will help with ABS warping is to:
1) Use a really fat first layer. I use 0.8mm with a 0.5mm nozzle, or 0.65 with a 0.4mm nozzle.
2) Print the first layer slowly, like around 15 mm/s. This gives the plastic time to bond to the surface.
3) Use a wide brim. This works like a suction cup, and helps to keep the corners stuck down.


That said, an enclosure really helps, even if it's not heated. You need to try to make it as airtight as possible, especially at the top. Then the bed heater works to heat the air in the enclosure. One caveat is that you don't really want your electronics heated, so it's best if your electronics is outside the enclosure.

Why would the first 10mm shrink but not the next 12mm?
There is a definite line around the item as if it were printed in two parts.
Below the line has shrunk to 4mm thick in places
Above the line is perfect

By the way, the print is a custom size project box with 2mm thick sides and face with a few added extras for perfboard support etc

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TonyPagett
Why would the first 10mm shrink but not the next 12mm?
There is a definite line around the item as if it were printed in two parts.
Below the line has shrunk to 4mm thick in places
Above the line is perfect

By the way, the print is a custom size project box with 2mm thick sides and face with a few added extras for perfboard support etc

Sounds interesting, any chance of photos?

Not a brilliant picture due to this cheap tablet

That's a good bit of warp for sure. I can't answer the question as to why the top half came out the way it did. There's a whole load of physics going on as a 3d print is formed and you do get some pretty weird stuff happening from time to time.

Nebbian's suggestions are good for improving that first layer adhesion. My feeling is that you should be able to get a workable print of that object. I print my first layer at 15mm/s onto gluestick on glass and rarely have the first layer lift, although it does depend on the shape of the part. Rounding the corners helps reduce the stress that builds up there. Eventually you reach the point where the first layer stays attached but the print rips itself apart at regular intervals (I tried printing a 7" single walled cube recently, that didn't work out so well). The best way forward is an enclosure, even if it's just a cardboard box put over the printer temporarily, but printing with wider extrusion at higher temperatures and slower speeds can help with layer to layer bonding.

Try printing on Kapton tape or a sheet of PEI, I think that would solve your issue with warping while it prints. However, I've still heard of people experiencing warping while waiting for the heatbed to cool down with ABS.

Thats a TON of warp. Make sure you have no fans on in the room anywhere near the printer.
I print on glass with purple glue stick and rarely have a print pop off unless it has a small contour. And if it does I change from skirt to brim ~3-4mm off the part

Looks as expected to me, you are lucky the middle part still stuck to the printplate. The upper part coming out well is pretty common from my experience (if the part sticks), but it would break again if you were to go higher.
Any kind of cold air moving will kill large ABS prints, you really need an enclosure and the only side you might leave open is the bottom. Especially the top has to be sealed since warm air rises and any cracks will voide the effect of the enclosure.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Thank you all for your comments

Today I have constructed an enclosure and will report back if all goes well

I now have another problem. I had to remove the filament and reel as part of the enclosure construction and now the filament will not feed back into the hot end. I just keep on getting a clicking sound at the hobbed gear

I assume the hot end is blocked but I have no idea of how to dismantle/clean it. I was supplied with a small spanner which does not seem to fit anywhere, a hex key and some fine wire brushes

Any ideas please???

"Hexagon All metal hot end" is all the details I have

Try to determine how deep the blockage is. In some cases the filament might be stopped before it even gets into the hotend. If it is the hotend this can help you to see if it is deep in the nozzle (maybe a problem with dirt/foreign objects) or in the heatbreak (gap).

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

I have dismantled the hot end and removed a large piece of filament that was blocking the hollow beneath the hob bolt

I have re-assembled everything but I now have some play/wobble where the hot end bracket attaches to the stepper housing. The bolts are tight and the hot end is seated in the bracket correctly