Looking for Tips on Production ABS Prints

[EL Cuajinais]

How well do your 45-degree overhangs print on ABS? I’m designing a 3D printed production part and am not satisfied with the quality I get on 45-deg unsupported ABS. (I’ve gone as low as .100 layers, 3 outlines, different print speeds). I don’t use PLA all that often but I do recall it performs better on overhangs. In your experience, is it safe to say the 45 deg rule applies only to PLA? That for ABS it is more like a 60 deg rule? Do all of you get higher quality overhangs on PLA vs. ABS?

Also, any general tips on custom-designed supports would be appreciated. I’m leaving a gap of .26 between the custom support and the part. How much gap do you leave on your custom supports?

Any general tips on creating production ABS parts? Especially on magically defying conventional orientation problems like printing a hex nut cavity vertically? Anyone here know 3d printing-magic? (Hey it can’t hurt to ask)

Thanks

[Polygonhell]

The issue with ABS and overhangs is largely about cooling, if you print cooler, you'll get better overhangs, however to get good layer adhesion, you need to print hotter. PLA is better for overhangs because generally you are using a layer fan and as a result it cools faster and distorts less.
For ABS I do what everyone here will tell you not to, print even hotter and use a fan, but you probably won't get away with it on the stock hotend and it's a balancing act, too much cooling, or too little temperature and the part will warp and split.

[Jimustanguitar]

Agreed. Crank up the heat and turn on the fans. It's not for every part, and it's not for every feature of a part, but it can definitely help if done properly.

[bot]

I wonder how the machines with heated chambers do it? I imagine if the chamber is a balmy 90C, the nozzle only has to be at like 220 to get good layer adhesion. Anyone know?

[Jimustanguitar]

I'm not sure if enclosures do much for layer adhesion. I mean I'm sure that they help, but the main idea is that the part as a whole doesn't contract and fully cool until the part is done printing. It all shrinks and warps together instead of individual layers and features doing it on their own.

[BenTheRighteous]

It might be a material issue. Try ABS from a different supplier. I'm using MakeShaper and I just got done printing a part with 55 degree overhangs and it came out perfectly. (Because no one can agree on a convention, that's 10 degrees more challenging than 45.)

One other thing you can try is try changing your "dimension ratio" (I'm not sure there's a better term for it). For example, a 0.4 nozzle and 0.2 layer height gives you a ratio of 2. If you change to a 0.6 nozzle and a 0.15 layer height you'll get a ratio of 4 and probably better overhangs. Changing the layer height alone (which you've tried) will influence the ratio to some extent, but for maximum effect, also consider the nozzle size.

[EL Cuajinais]

Thanks for the replies. Will definitely start playing with the layer fan then.

I wonder about the filament brand... I'm using MatterHackers ABS. I just put in an order for 220g spool of MakeShaper Black ABS. I think the fact that they have small quantities of their filament available in their store means they have confidence in their product. And it is also convenient to be able to test filament before committing to a 1kg spool. We'll see how it goes but in the meantime I will be doing a slight redesign and playing with the fan settings which I've never tried for ABS. I wish more people would chime in but I've always had the impression ABS is not very popular in these forums.

[BenTheRighteous]

I love ABS. It doesn't string, doesn't melt in the car, and you can retract the heck out of it without the extruder chewing through the filament. Also, you can put screws in it without worrying that each twist is going to snap a piece off the print.

Way back when I was first starting out in printing, I bought some MatterHackers filament, both PLA and ABS. It was all garbage, *especially* the ABS. Every single print was brittle and weak. I kept a box of failed prints thinking I might some day figure out how to recycle them, but failed MatterHackers prints went straight into the trash.

I've seen some favorable reviews of their filament here. Maybe they've switched suppliers or something, I don't know, but their stuff won't ever run through my machine again.

[Captain Starfish]

I regularly rock ABS at 30º overhangs, no problems at all, no fans required either. Try a different filament, I reckon, and try printing even hotter (so the filament bonds the previous layer rather than just rolling off it). Slowing down the print might also help layers already printed cool down some so they can better support the fresh stuff. Or a layer fan would help.

[0110-m-p]

Generally, I print with no supports using ABS (IC3D brand primarily) with overhang angles up to 60-deg (or 30-deg depending on your slicing software) with no fans. Generally I use a 0.44-0.50 extrusion width, 0.15-0.25 layer height, and use 2 perimeters.

Couple of other tips that might help...
- Print your perimeters from the inside-out. The outer perimeter will then have it's neighbor to rely on as well as the layer below.
- Slow down your print speed on outer-most perimeters. I generally print at 40 mm/s with 60% speed on outer perimeters.

As far as your question about supports. If I'm supporting an angled overhang or a flat overhang with corner fillets I like a X/Y gap of 0.2mm. If supporting a flat overhang with sharp corners I like an X/Y gap of 0.3-0.4mm. My Z-gap is usually 1 layer thickness.

[EL Cuajinais]

Wow some great tips here, thanks again everyone. All this time I was thinking printing hot with fans was a contradiction of sorts but now I finally get it: We want plastic being laid as hot as possible, but the layer used to support this fresh plastic to be as cold as possible.

Thanks for the info and concrete numbers. Having the z-gap between my custom supports and part measure exactly one layer height seems like an obvious choice. Why didn’t I think of that!? I’ll make that change immediately.

However, I’m not sure about the x-y support gap mentioned. I think I know what you mean but in my case, there is no x-y support gap. Isn’t one of the beauties of designing custom-made supports the fact that you only get support directly below the print? At least that’s how I’ve designed mine. Or am I missing something? Is there some advantage to having “lateral” support on a print?

[0110-m-p]

However, I’m not sure about the x-y support gap mentioned. I think I know what you mean but in my case, there is no x-y support gap. Isn’t one of the beauties of designing custom-made supports the fact that you only get support directly below the print? At least that’s how I’ve designed mine. Or am I missing something? Is there some advantage to having “lateral” support on a print?

My comment was more geared towards slicer generated supports rather than custom modeled supports. The X-Y gap is lowest allowable gap between the support material and the model. If you have custom supports and finely tuned bridging, this doesn't mean much.