Slic3r - raft settings, ABS
Hello,
I need to print some quite large ABS parts. I tried using raft on some prints with... limited success, at best. My current raft settings are default (3 interface layers, 0.1mm separation). Raft prints just fine, but first layer of object starts in air (more than nozzle distance above interface layer), and it seems to cause problems. These tended to be much worse before extruder calibration (managed to do it down to ~0.2mm), but still bottom solid layers look terrible and sometimes one of perimeter extrusions get dragged around with nozzle.
I don't really get this whole "extrusion in mid air", how is this supposed to produce decent quality? Is there some critical setting I'm missing?
TIA.
Re: Slic3r - raft settings, ABS
it doesn't produce good quality it is a compromise when you cannot alter the stl.
basically you are bridging when printing in mid air, the fan is super cooling the filament as it comes out of the nozzle. bridging can only go so far.
option one is add sacrificial elements to the shape, so that after a few layers of mid air bridging it finally clings to the first good layer then you have to go back and really clean it up.
Add a support piece with a gap of .2 between it and the part it will act as a bridge support and you can easily snap it off when the part is complete.
otherwise you need to have the slicer generate support material.
the more support material the better the final product but the harder it will be to get off the part you want. this is like the first idea above about adding sacrificial parts to your shape.
bridging and ABS isn't good because it cools the ABS too much and you don't get good layer bonding. ABS will crack on any weak spots.
you have to go as hot as possible with ABS and adjust layer speeds to give the ABS enough time to cool naturally and crystallize correctly for strength.
when designing parts and seeing how they print for the first time you usually have to go back into your 3d software and add supports designed to be broken off when printing is completed this reduces bridging giving you a stronger part that looks nicer because the layers will be better bonded together.
this is why people love meshmixer it comes with a automatic support generator that can then alter the STL And be brought into your slicer. it is primitive but can be done quickly to get something out ASAP without having to go back into say fusion 360 and create supports manually. again meshmixer is very primitive.
it looks like you are making a fan cover. in this case i would design an outer ring designed to snap off(IE an air gap between it and the real part) such that you get a loose first layer bond then the next layer has a solid foundation to come up from. like a raft or a support but 100% uniform all the way around where a raft or a support is not.
you can find examples in the open R/C project, look at the STL files for the Truggy Rims they have supports designed to snap off after printing is completed so it means additional work after completing your final model after a couple of test outputs to figure out the best way to have the printer make the part on the bed.
“One does not simply use a picture as signature on Prusa forumsâ€
Re: Slic3r - raft settings, ABS
This is just a part of larger project, I printed it to test this whole raft concept.
What I ultimately need is to print a large ABS part without warping, curling and cracking. I thought that raft was a way to go, but bottom surface quality makes it completely unusable. I will need to find alternatives.
Adding support in STL does not look to be a good idea - I would be limited by print resolution, while slicer has a way more control here. It is however curious that I don't have a complete control over airgap in Slic3r - it seems that any non-zero value automatically adds nozzle diameter (0.4) to layer.