Just started with ABS, need advice.

I just started printing with Ultimachine silver ABS and I have issues with the printed objects that I think can be solved by disabling the fan. The only problem is that my x-carriage is PLA and I don't want to melt it! I'm trying to print this object to direct airflow across the thermal break (and my x carriage) and keep it away from the print. Hopefully that'll buy me enough time to print a new x carriage in ABS. The problem is that bridged areas don't connect and parts of the print delaminate especially at the top where it's thin (this object prints vertically BTW). I started the print at 230 degrees on my hot end and immediately realized that was too hot since it came out liquidy and wasn't even solid when the next layer was deposited on top of it. So I reduced the temp in 5 degree increments and eventually settled at 210 degrees. In slic3r I have the max fan speed set to 50% (hopefully a good compromise to keep the bed temp constant) and bridges fan speed set to 100%. Mind you, my bridges were fine when printing PLA (even the 50mm torture test came out great) and I've printed this object before with PLA and had no problems. I can't use the PLA object since it gets too close to the hot zone and I'm betting just the bed temp alone would be enough to melt it. I have Slic3r set to disable the fan for the first 5 layers to hopefully maximize bonding but you can see a definate delamination on the 5th layer right when the fan kicks on. The rest of the part prints fine (except bridges) until it gets to the top where the filaments just flake off. For people printing ABS, do you use a fan at all (assuming your x-carriage and extruder are ABS)? What about just to cool the PEEK? I would think that would reduce thermal stress on it and make the parts last longer.

I use a fan to blow at the extruder! That keeps it nice and cool and it tends to draw heat away from the PTFE. I don't use a fan for prints with ABS. I'm puzzled why you're ABS is "liquidy" at 230C. Are you sure that's not PLA?

I'm pretty sure it's ABS. The filament "feels" different than my PLA filament in that it's much more flexable, less brittle and softer. It also has that characteristic odor when it's being extruded (although it's very faint, it does make my eyes water if I get too close while it's printing and it's certainly not that "sweet" PLA smell). It definately does not like to be extruded above about 215 degrees. At 220 degrees the prints look "sloppy" and delaminate regularly. At 230 degrees the free air extrusion is not smooth and appears to have tiny bubbles in it. Printing at that temperature results in a mess. My latest issue is that it keeps jamming up. I tried to print a new x-carriage twice and it fails at the same point (where it starts to print the bearing clamps) resulting in shredded filament/clogged nozzle and a dirty hobbed bolt. I tried at 210 degrees first, then switched to 220 degrees. At 210 degrees most of what did print looked good, but parts of the perimeter in the first layer delaminated from the print (although it stuck well to the print bed during printing). I'm thinking it might be because my first layer bed temp is 115 degrees vs other layers which are 110 degrees. I'm going to try using a constant 110 degree bed temp and see if that helps with the first layer delamination. At 220 degrees the print actually looked lopsided (looked almost like a motor skipped a step or something, but I've never had that happen before and I haven't changed anything other than the temperature of the hot end) and delaminated on several layers. Looking at my g-code, Slic3r is constantly varying my fan speed between 20% and 50%, so I'll try printing at a constant 50% and see if that helps with the extruder jamming. Everything I've read so far says you DO need a fan when printing PLA to avoid jams, but you DON'T need one for ABS. Maybe I have PLABS?

PLABS haha, yeah that would be cool
I'm in the no fan camp as far as ABS is concerned because it stiffens up quite quickly but you certainly need to aim some air at your x carriage or cold end to prevent the x carriage from bowing upwards. Also, I do wonder if your hot end thermistor is reporting the correct temp, either because it may be faulty or there is some other issue.

I found a setting that seems to work okay, 215 degrees on the hotend, 110 degrees (constant) on the bed, and fan at 70% (constant, with a duct aimed at the PEEK). I managed to print an x carriage in ABS but there was some delamination that I hope I can fix with acetone. I'm betting my delamination problem is because I'm using a fan, but I needed it to prevent my PLA x carriage from melting. Hopefully after installing my ABS x carriage (and disabling the fan) I won't have a problem with delamination any more. We'll see.

I will say that printing ABS seems to yield a "cleaner" product than PLA. When I print with PLA there is usually a little bit of stringing and blobbing during travel moves that has to be cleaned up after the print, but when I print with ABS there isn't any of that since (in my experience) ABS doesn't tend to ooze as much. Maybe I need to change my retraction settings as well?

Maybe post a pic of the delamination

I attached pictures of the delamination. Notice how most of the delamination is on the solid top layer that's printed on top of the infill. I'm using 40% "honeycomb" infill and the bond between that and the solid layer above it is very weak. Those prongs (especially the middle ones) break off easily right at that point. The same part printed with PLA (only difference being the filament settings in Slic3r, no difference to infill or layer height/width) is much stronger. I wouldn't suspect the prongs to be very difficult to break, but it feels better and more tightly bonded.

From what I know,(not much) delamination is caused by temps being too low, if other settings like nozzle size and so forth are good.

I've sometimes noticed delamination on my parts where there is a change in printing time per layer. I suspect that when my extruder temps are barely hot enough, and a new layer takes longer the the previous, things cool down more and I get delamination.

In Slicer, is Horizontal Shell set to just 1 solid layer? Can you set that to 2 or 3 solid layers?

I don't actually like honeycomb too much - I seem to get better solid layer adhesion with "rectilinier"

After breaking this x-carriage trying to install it (arrgghh), I just decided to put my older ABS x-carriage back on (no fan mount for PLA, but made of ABS). Then I changed the mirrored x carriage design by increasing the bearing clearance by 0.5mm and moving the extruder mount holes over just a bit (so I can get my socket wrench in there to tighten the mounting bolts). Without the fan and at 210 degrees, the print quiality looks much better and the prongs are more solid, and I can attach a bearing without breaking it. So I'm thinking that the fan might be at least partly responsible for the lower print quality. Also, 210 degrees seems to be the sweet spot for my machine with this filament. Anything higher and the print looks sloppy and produces more fumes, and anything lower and my hobbed bolt chews up the filament.

Well that is good, now you have at least printed a new ABS part that holds together...

I find that -very- light air movement can drop the temp on the work piece quite a bit(and kill adhesion). Maybe when things are marginal it takes very little air flow to drop temps enought to ruin things.

I'm actually having the opposite problem. I'm using a hot end of my own design, and the heating resistor is too close to the work. It's cooking everything! I've just barely brought it under control today.

I should add that checking the size of the filament is important. If it is physically smaller than what is set on the software side, that can lead to adhesion problems. You pretty much need to use a micrometer to do this right.

Edited 1 time(s). Last edit at 04/29/2013 01:13AM by Yvan.

This filament I'm using now is slightly oval which makes it difficult to enter an exact diameter. I'm using a value I calculated would give me the same cross-sectional area and that seems to be working. I watch the first layer as it prints and if I see it's using too much or too little plastic I can adjust my E steps/mm with M92 while it's printing. I could be wrong here, but I think a micrometer would be overkill in this case since the diameter varies slightly along the length of the filament and you're just using an average anyway.

Sorry, I misspoke! I meant a caliper(dial, vernier, digital). As long as you can read thousandths of an inch, that is good enough. Less accuracy than that and it can be hard to trouble shoot a problem. In any case taking multiple measurements throughout the spool, half of them offset at 90˚ then doing an average is the right way to do it.

Sounds like that might somehow be one of the factors contributing to delamination. From what I know, there are only three variables. One is temps too low. Two is not enough extrudate. Three would be "defective" ABS, like it would have some adjuvant(is that the right word?) that inhibits sticking once it has been melted.

A couple of days ago I was getting delamination, burning, and excessive extrudate. All in the same part!