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Post Print ABS Warping



Having joined teamfdm less than 24 hrs ago it feels a bit impertinent to just jump in with a Q. rather than contributing someting first .

I havent been able to find a useful reference to counteract warping in ABS After objects have come off the plate. This is an object from Printables that I have printed many times successfully in PLA . I've attached 2 images one showing the full object and the other the symmetrical warping that I see at each corner. Its a tray 100mm square so almost to the edges of my V0 and 20mm high.

The details : stock LDO Voron 0.1 , enclosed , thermistor estimates temp of chamber at 45 C after 15mins of warm up time , heat from plate and hot end ,Superslicer tuning configuration files done ,  nozzle 0.4 mm temp 210 , Bed temp 100 C for all layers . Filament Polymaker ABS , Nano adhesive on print bed , print settings as per Voron parts recommendations.

It is apart from the corner warping not a good quality print . But its the defect I'd like to address first ,if possible .

At the end of the  print in the photo I let the printer cool down for 1 hour . By  the time the enclosure was opened and the object was released from the plate it was all at room temp with absolutely no sign of warping at that stage . Then imagine my surprise when 20 minutes later it assumed its current shape . 

I'm assuming I've taken the most common measures taken to minimise ABS warping , have I missed something.?

What do you think might be a way of countering this post print behaviour ? Thanks for taking the time to consider this problem 



Edited by Xplaner
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I've had issues with asa prints warping while cooling down and I've had some limited success annealing the parts and "massaging" them back in shape. The reality is some plastics are just not conducive to holding certain shapes and your part looks way past this solution.

To make boxes like the one shown, I draw them with the base tapering inwards before curving back out. This has helped alot though I understand it's hardly any help here...




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Thanks for taking the time to have a look at this.  

I was puzzled when I saw my print because I  have printed several iterations of V0.1 toolheads in ABS and no problems with warping . But the dimensions and so the potential for shrinkage with these would also be smaller. 

Thanks for confirming that the phenomenon might be because of the design . I imagine what you're doing is what civil engineers do when designing  structures ; they take into account how the materials will behave when the construction is complete. 


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Roughly 15 minutes later after release from the plate and by that stage the print had been allowed to cool back to room temperature for an hour or so .in the enclosure .  I suspect there were built up tensions in the side walls , but because of the strong adhesion of the part to the build plate these tensions weren't relesed until the part was taken off the plate . Just theories though , really I'm not sure. One passing thought is that the infill is rectilinear and perhaps if I make it something else it will contribute less to the wall tension . I'm also thinking of increasing the enclosure temp so there is less of a gradient in the wall temp as it gets laid down .

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That first picture shows that it lifted while printing, not after. If it lifted post-printing it would not have that excessive buildup of filament where it was higher and had to squish the filament on top of the last layer (that happened to not be anchored to the plate). It would have even layer lines if it was post.

I would suggest a brim, or at the least, tabs for those corners. But that is a non-adherence to the bed issue, not a cooling after the fact issue.

I'm speaking of the left AND right corner in the first picture. The right side is less pronounced, but the same issue.

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With ABS, some designs are really tough to produce without warping.  

In your specific case, it's the long, uninterrupted extrude lines.  When a material cools it contracts at a rate the is usually expressed in unit of length, per unit of length per degree temp.  So, the longer the object is, the more it contracts per degree of temp change.  Shorter sections will result in reduced forces.

With a design like yours, in order to reduce the magnitude of warping, i might change the model to look something like this.  I added some vertical flutes to break up the long, strait lines.   For ABS specifically, the coefficient of linear expansion is .00005 inches,  per inch, per degree.  So, a 5" long plastic wire/extrusion that cools from 230c to 30c will try to be .095" shorter after cooling.   Since it's glued to the previous layer and can't contract, it will just create a force.  Each layer will cool and attempt to contract the same amount, after being layed down on a previous layer that is already producing stress.  Each layer will add its own warping stress to that all of the previous layers.


So, for this part:



You could reduce the warping issues with some changes like this.  It may not eliminate the issue altogether, it would reduce the magnitude of the problem.  Perhaps that, in combination with higher chamber temps, and some brims, you might get the results you need:



If aesthetics are of little concern, or if the intended use allows for it, even more severe changes could eliminate the warping problem.  An example:



The higher the long, strait extrude lines are above the build plate, the more leverage (arm) they have, to further magnify the warping forces.  So, breaking up those long lines on the higher portions is more important than those lower on the part.



It's one of the reasons that parts like yours are so difficult to keep from warping with ABS, and parts like the one below are so easy.  With a circular part,  contraction forces from cooling only create a hoop stress that tends to reduce the parts diameter,  and has little leverage with which to pull up the edges of the base with.



Edited by ken226
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