Problems with ABS-printing

[KLucky_13]

This week I upgraded my printer with a MOSFET controller so now I can reach 90-100 degrees which is required for ABS printing. Well this new material means a new learning curve. The first problem that occurred to me is this one:

Layers that have been printed (not the bottom layers) curl up a bit. (Higher then the current nozzle height). Is this due a wrong extrusion temperature? I'm printing at 245 °C

I made some pictures of the problem i'm seeing:








If you look closely, you can see that the problem only occurs at the right side of the print. So it seems to me the fan cooling the hot-end might be the problem. Can draft from this fan be causing this warping? Once the print came to a certain height the time between each layer increased since the vase gets bigger to the sides, the print became good all the way around.


If the fan may be causing this, what can be done to prevent this? Did anyone had this same issue when printing ABS? If the fan is the cause I don't understand why the problem vanished when the layer to layer time increased..


here is the completed print:





It's clear that it only happened at 1 side of the part and only at the first 70 layers or so

[KDog]

Nice to see you trying out ABS. If you suspect that the fan is cooling your nozzle tip then you might try rotating it 90 degrees so that the air is blowing straight away without hitting the other shroud.

I've had pretty good luck printing on glass (I actually use 3mm glass mirror tiles cut to fit) with a piece of thick mil kapton on top. It looks like you may be printing on the same. I keep several of these around and spray them with aquanet hair spray. I do this in the bathroom sink rather than on the printer. Let it dry and you are good to go. I seem to be able to get several prints between hair spray applications.

In my experience, 245 seems to be a bit high but I generally print slow so this could be ok for your machine. With ABS, curling is a constant battle. Lots of folks use "ABS Juice" instead of hairspray. I prefer not to do this but it may work for you. There are a couple new surfaces being tried out right now that I'm watching closely as well. I ordered a sheet of Polyetherimide (PEI) from Amazon this week and will let everyone know how it goes.

Cheers,

KDog

[KLucky_13]

What do you mean turning it 90 degrees? No matter how the fan is orientated it will cause a draft no?

I don't have warping at the bottem layers. The problem is about curling on upper layers when printing fine things like the corners on this little vase. When printing straight lines I don't see this kind of behavior

[KDog]

I can't tell for sure but it looks like the hot end "fan wash" points directly at the nozzle shroud so it might blow back down at the nozzle and the print. Maybe a far fetched observation but worth checking out.

[jaguarking11]

Your cooling the nozzle. Plain and simple, with ABS from what I gather from others is that you want to precisely control the temperature of the build area, not just the bed. I would suggest you cut the design to those 70 troublesome layers and try some cardboard shielding on the nozzle, to me it looks like the duct is engulfing the hot end of the nozzle. You could try insulating the block as well. I would look for some fiberglass mat to insulate it. The temperature of the hot end also depends on the print speed. The higher the speed the higher the temp. Just make sure the hot end is not jaming before you do any work.

If that fails, you should try to put the printer in a cardboard box and see if that makes a difference.

See the diagram attached.
HOT_END.jpg