So, who’s’ got some tips on dealing with overhangs with ABS? - I can get nice non-warpy prints with an appropriately prepared bed surface and an enclosed build area to keep the ambient temperatures up but any overhang beyond 30-40 degrees gets pretty messy due to curling. With PLA, I just aggressively cool things but If I do that with ABS - the part as a whole can start to warp as I’m screwing with the airflow around it. Obviously support structures are an option but I see other folk posting successful ABS overhands without supports.
I swear by my ducted cooling fan, set to about 25-30%, inside the heated chamber. I’m pretty sure the extra draught helps to prevent the ABS curling. Still need to balance the speed and temperature carefully to prevent delamination though.
What layer height are you using? How hot are you running?
@Richard_Gain I’ve re-purposed your E3d duct for my reasonably unusual carriage design (vertical mount to a CNC linear guide) I think I may need to alter the vertical orientation to get the airflow directed onto the print area more effectively.
@Whosa_whatsis 0.14mm at 235.
I haven’t tried it but i thought ABS uses no fan.
On the replicator 2x we have at work, it doesn’t have a fan and overhangs are not as easy as on PLA. But lowering the layer height and increasing perimeters helps. Your layer height is already low though. We extrude at 230. Maker ware doesn’t show down layers for cooling, so I notice that if the abs doesn’t have time to col between layers, it’ll droop just like pla
@Eric_Moy My problem is curling not drooping in this case. I think I just need to approach it in a more scientific manner. I’m also going to pinch the Utlimaker2 fan design (2 fan ducts with the airflow directed almost horizontally and see if that helps.
I suggest you don’t use the fans. The curling is caused by long length runs. First try building parts with smaller cross sections, i.e., build up not out. The longer the runs, the worse the CTE effects, if you must build with large bases, keep the number of floors low, and perimeters low. Also use hex infill. I’ve tried raft, which helps sometimes, but if you have very long runs, nothing will keep it from curling. I read a blog post about someone castellating the lower portions of long walls to make them into a series of short wasps so that the castellations act as strain relief
@Eric_Moy Ah, sorry I’m talking about upwards curling on the edge of an overhang not at the base, I wouldn’t allow the fans to come on until the base layers are done.
Doh. I’m still not sure what that looks like. I just know that abs has a high shrinkage, so generally a fan is taboo. I don’t think I’ve ever heard of somebody using a fan for abs. Guess it can’t hurt to try
The reason you don’t want a fan for ABS is not because of the shrinkage, it’s because extruded ABS won’t bond properly to the previous layer if it’s already cold, leading to delaminations in the middle of the print.
For curling of overhanging perimeters you need a gcode controlled ducted fan. I’m not sure if Slic3r would trigger it for perimeters if the layer isn’t small enough to trigger cooling, or it isn’t a bridge. KISSlicer will let you have the fan turn on for all perimeters. The idea is to freeze the perimeter before it has a chance to curl.
Having the fan on for all perimeters wouldn’t be ideal if your print is mostly perimeters with little infill, but delamination shouldn’t be a problem if the fan isn’t running all of the time. Keeping the printer enclosed helps, and heating the enclosure with something like a space heater helps more, just make sure the airflow isn’t directed at the print.
Using the E3Ds cooling fan isn’t a good idea, because an always-on fan will create a weak print. This duct is pretty handy, because it clips on to the E3D’s fan shroud-http://www.thingiverse.com/thing:120249
@Ian_Johnson I’m using kiss and my intent was to use the perimeter cooling feature however as @Whosa_whatsis points out over cooling=bad layer bonds so I’m going to do some experiments to see if there’s a sweet spot. The fan duct I mention above is similar to the one you posted. http://www.thingiverse.com/thing:91931
A guess would be to boost the extrusion temp a little. Since it is getting cooled coming out of the nozzle, a hotter extrusion may give you an equivalent temp by the time it makes contact with the previous layer so you get a decent bond before the fan freezes it.
But if you overheat the plastic, it starts to break down, changes color, and releases nasty stuff
So, it definitely looks like a ‘sweet spot’ question. As an example of successful cooling on ABS. I’ve used an UP! and that produces lovely ABS prints with an active fan. I have an inkling the fan gets used when it’s printing supports (which is does by default) to deliberately produce a poor layer bonding at the interface.