Borders curl up

Hi. I have this issue: When printing some border of an object, close to be name overhang, the borders curl up, no matter if the material is ABS or PLA, so I can say is not a material issue? I have tried printing this parts useing more perimeter, less perimeters, it doesnt help. Any suggestions about how to avoid this? the probem is that one that section is curled, when the noozle pass over it, it crash against it, ruining the print
Here you have a couple of images of what Im talking about

This is the object and I have marked the problematic section, but this is an example, this problems arises in other objects where this overhangs exists:




And this is the sliced image: from hre till like something about 20 layers, the borders curl up nd if I dont wont a ruined print, I have to use a piece of metal to correct the curl , following the noozle path... wich is a pain in the....



Thanks in advance for your advices

You need a layer fan or layer minimum time (reduced speed) or print more at once to allow cooling time.

But a layer fan is good for ABS?

No, only for PLA. For ABS use an enclosure to keep it warm, if you cannot use an enclosure use a high power light bulb facing the printed part.

Yes, it is good if you have no other mean to allow layer cooling. You need to find means to allow plastic too cool and stabilize before the hotend comes and deposits the next layer on top of it.

A layer fan with ABS is not a 0/1 problem. If you cool too fast, it will shrink fast and delaminate. If you don't cool (active or passive) you will put hot plastic over hot plastic. It also depends on the filament, too. I have "bad" filament that delaminates even without a fan (I don't have an enclosure) and "good" filament that works beautifully even with the fan running (layer "cool down" settings in slicer).

It also depends on the part geometry, slicing options and so on. The absolute shrink length depends on the layer horizontal size. A small part and/or thin walls part has little chanches to pull to delaminate, but a big one will pull like crazy (that's why you can have some parts that print perfectly and others with first layer adhesion issues - the top layers with infill will attempt to shrink more than the bottom layers, near the bed, so they will pull from the edges of the part with big force).

I've read somewhere (I don't remember were) that you need to cool down ABS to a specific temperature after depositing to stabilize the layer. You can do that either passively, by allowing some time until next pass, or actively, with a fan. Of course you will never reach the ideal temperature, but you can experiment.

In your specific example, on the second part, I would blast my fan (you can find this in layer cooldown settings of your slicer). That area has little chance of delamination.

@ggherbaz: an enclosure will not not resolve curling, the most probable cause being a too warm previous layer when the next one comes.

Ok. All of you are talking about general curling and delamination but that is not my problem. I print big ABS pieces with no delamination and perfect first layers. I print very nice PLA pieces too. The problem is very specific to certain parts of certain models, like the one I posted in the pictures, the curling happens only in the section while being printed.
If I slow down the print there, it is worst, it is like more heat is radiaed and the curling is worst.

Did you try to start the fan on that area only? Event manually starting it will do it. I don't know about other reasons, but thin areas like this curl because of high temperatures.

This is an example: [ultimaker.com]

Edited 1 time(s). Last edit at 07/13/2016 02:29PM by sigxcpu.

For the last 2 years I have printed ABS without a fan in an enclosed printer with a 150 watts bulb inside that keeps the temperature at 90 degrees and have never had issues with curling or delamination. For my understanding curling in ABS is due to low extrusion temperature and too fast cooling of the part, as it cools the ABS will shrink and pull up or inwards.

One remedy you can use is to reduce the infill by 10 to 15% to minimize the pulling effect of the infill on the shell.

I've achieved the best results on small detailed overhangs, printed in ABS by:

* Using a chamber (mine stabilises at around 45 degrees)
* Using a layer fan at around 10% (obviously your numbers will be different)

Yes, using a layer fan on ABS does reduce curling. Yes it's weird to have both a chamber and a layer fan, but it works exceptionally well for me.



On the left, I have a layer fan at 10%. On the right, layer fan turned off.

Clearly the layer fan helps a lot.

With no layer fan, the layers curl up a lot, I think due to more of the part staying above the glass transition temperature for longer. Each successive layer pushes the existing print around a bit, like a smooshy lump of butter.
With 10% layer fan, each layer goes on and the nozzle leaves a sharply defined track.

Try it, you might be surprised.

When I print small parts or parts that have small layer perimeters in any material I usually include a sacrificial cylinder (15-20 mm dia) that is as tall as the print to give the extruder something to do while the part I care about cools a little before the next layer.

I have a vibrating air pump that I've been intending to test for print cooling for PLA, but haven't gotten around to it because I rarely print PLA. If it will do some good for ABS I'll have to move it higher on my list of things to try. I'll run a small, very flexible silicone tube from the pump to the extruder carriage. I guess I'll have to mount the pump inside the enclosure so it isn't blowing cool room air on the print.

---

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