I’m trying to diagnose an issue I’m having with a Robo3D printer. Printing 60mm/s to Black Hatchbox ABS. Bed temperature = 80C,. Hotend temp I’ve tried between 224 and 228C. Retraction is .6mm at 60mm/s. I created a test at .5mm thick, 15mm tall and wide. For one its not printing smooth, and for two and most importantly the overhangs always sag, badly. Even when printing top layers (5-6) it ends up potted.
Im no expert but my first thought is too hot and too fast. How long has it been doing this?
Do you have a fan to cool your print? Printing bridges without a fan is very difficult.
Bridges work best with low temperature and fast speeds.
Its a boy!
Right?
If it’s the only part on the bed you need to slow it down and have way more active cooling.
228C actually sounds cool to me for ABS. (I regularly print PLA at 230, and ABS up around 240C (Ultimaker 2)) It’s tricky with ABS as too much cooling can cause shrinkage, but definitely you’ll need more cooling on the top layers. You have ok bed adhesion?
With ABS its been doing it pretty much the entire time I’ve had it. I thought too hot as well, but I’m at the lower end of the temp. settings for ABS. Also as I went lower it got worse. I did a comparison I did at 230C vs 224C and the 230C was a better result but still not perfect. Also the 230C one has less retraction.
What @Griffin_Paquette said. Sometimes microbenchmarks produce results that don’t match reality. What does it look like printing a Benchy?
By the look of the plastic, it was overheated. Your particular machine’s temperature sensing may give slightly incorrect values, and different ABS formulations will need different temperatures. Set your temp only 5 or 10°C above what is needed to extrude and make it stick. The actual numbers aren’t that critical until you know how your machine behaves with that filament. For example, I print ABS at 205-215°. That’s a big difference from some of the numbers being reported here.
Also, like the other said, that part is too small for adequate layer cooling.
.5mm layers are pretty large, layer height less than 80% nozzle size should give better results.
Thanks for the suggestions. The layer size is .1, the extrusion with is .4 (nozzle size) and the wall is .5 just so it wouldn’t get confused. I wanted something I can print quickly. Not so worries about the buggers, those are from the size. My concern is the sag where there is an overhang. That’s the problem I’m trying to diagnose. It does that irrelevant of the size of the print. Obviously as the overhang gets bigger so does the sag. But as I mentioned even with a solid object the top layer gets pitted relative go the percentage infill. I get good adhesion because I use glue stick (best thing since sliced bread) and it grips good.
Have you check the nozzle to bed height?
Yes that was an earlier problem I had but was long since corrected. I just found an article about bridges and it said slow down and reduce extrusion amount so I’ll try that next also. Thanks all.
FYI, I don’t think it’s advisable to use a fan on abs. I don’t believe it will fuse to the layer below properly. A fan is used on pla, because it’s so liquid like coming out of the extruder, whereas abs has a much thicker viscosity, to the point of solid. Also, for bridging, I’ve never personally gotten PLA type performance from abs. But as a disclaimer, I used abs only on a replicator 2x, and PLA only on a homemade reprap style printer, with extruder fan. Good luck
The best thing you can do to fix this part is print something next to it to give it time to cool. ABS may not like a fan but it is still a thermoplastic just like PLA so giving it time for the last layer to cool can really only do good in my opinion. I haven’t printed a lot of ABS, but this is what I have found in my tests.
I’ve printed a fair amount of ABS (well, a couple of kilos) and yes, although it needs less cooling than PLA to reach adequate stiffness, it definitely does need time to cool. Back when I was printing 40mmx5x5mm towers for calibration, the top centimeter or so was still soft when the printer finished.
Also, the blobbing on this print really makes me think you’re running hotter than you need to for good extrusion.
ABS printing ,extruder at 240 and bed at 110 , retraction 3,5 mm at 40mm speed , cooling for ABS always off . This is working always for me.