How bad is inter-layer failure with ABS?

Hi.

I am thinking of moving to ABS, but I want to get something cleared up first.

I have read that the weak part of ABS parts is between layers. So ABS is stronger, but are the layer bonds weaker than PLA, so is it actually weaker in certain ways?

A PLA part that I just had fail was a 3/16 (5mm) diameter post protruding from a base, onto which a snug rotating arm is fixed. I'm not sure if it was from a torsion or straight shearing force, but it seems to have been a layer failure. Does ABS decrease this?

I realize that ABS has better material properties, but that doesn't help me if the layer bonds are weaker, and I am looking for a straight answer to this. Thank you!!

(By the way, in case anyone is wondering, I made the rotating part snug by making a bushing out of semiflex. It's going to be a toy with stiff movable parts. Also, there was a chamfer at the bottom of the post. It broke just above it.)

Two things:

1. Layer separation is a risk with any FDM machine.

2. Layer separation is not an issue with the correct temperature, print speed, and cooling for your layer height and machine.

Well, three:

3. Small considerations when designing the part will make it print more easily and more reliably.

ABS is difficult to print well.

I talked with P Boichut of Spiderbot and in order to print ABS to a high quality standard with good repeatability, he intensely improved his machines : part heater, enclosure, fan to homogeneize temp, heated bed, ... the list is long and the development took time but you can find some info there : http://www.spiderbot.eu/en/products/upgrades.html

And the -impressive- result is there :
http://www.spiderbot.eu/en/media-inf...-pictures.html

Unless you have the means and dedication to strive to such pro results with ABS, why don't you try other high temp materials like PET ? PET is still heat resistant without that goddamned cooling shrinkage that makes it so hard with ABS.

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Originally Posted by LambdaFF

ABS is difficult to print well.

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I disagree. I print in ABS nearly every day.

ABS is easy to print with if you are properly set up to print ABS.

ABS is difficult to print with if you are not properly set up to print ABS.

Heating the chamber definitely helps when printing ABS.

Quote:

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Originally Posted by Davo

Heating the chamber definitely helps when printing ABS.

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I agree with this. On the flip side I have read that steppers shouldn't be run over 80 degrees C as too high a temp can damage them. Not sure how true this is.

I have found post-production with Acetone or Acetone/ABS slurry applied with a brush greatly strengthens the layer bonds.

ABS Warps more than PLA ,
very obvious difference when doing large base area objects.

I've got a Craftbot with a heated build plate, insulated bed, glass plate with glue stick, and heating chamber in the works. My original question stands:


Does ABS have weak layer bonds compared to PLA?


If I stress test an ABS part in shear, will it fail before my PLA part fails?

Scientifically I can't say but from a practical standpoint I see no difference.
If my printer and software are tweaked correctly they both print the same. It takes a little more work to get ABS to be just right but is worth the effort in my opinion.

If you need a strong plastic with extreme layer bonding then petg is for you. Generally there are no layers when its done. The stuff fuses better than any other plastic we can run through our printers. Stronger than abs and temp falls between pla and abs.

Hmm.. Well, I just found this page from a google search. It's one guy's word, but he is authoritatively stating my suspicion.

http://robosavvy.com/forum/viewtopic.php?t=9655

"Myth 3: ABS is much stronger than PLA
This is the most recurring one and it's also the most inaccurate: if you compare injection molded parts, ABS parts are indeed stronger than it's PLA counterparts; however we're doing 3D Printing layer by layer, not injection molding and this changes things considerably:

A 3D printed part in PLA is MUCH stronger than a part printed in ABS. This is because PLA has significantly stronger layer bonding than ABS."

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I'm going to start looking at other filaments. But would any of them be an improvement? Maybe inserting metal pins is the way to go. Edit: Cool, jimc, I will look into that!

Comparing ABS and PLA, is like comparing copper versus cast iron. Really, that's the best extreme comparison that gives the best idea, ABS being copper and cast iron being PLA.

Because we're on the internet, info are spread easily and too much people believe in that.

ok you have to realize the word "stronger" is a very general term. stronger in what way? every material has its strengths and weaknesses. its a matter of finding the best material for the job. pla at room temp is a very hard and strong plastic however its has such a low thermal resistance that parts will get soft just holding them in your hand from your body heat. for me that makes pla completely useless and the weakest of all filaments. i only use it for a quick prototype that will end up being tested and tossed in the trash or something that will just sit on a shelf in my house. abs is softer which in some ways may make it seem weaker but its more impact resistant because of that. the glass point is also a good 40-50c higher so its a much better plastic for something that is a functional part. abs does layer bond really well IF you get a good quality abs and you print it at the right temps. all in all though there is no perfect, strongest filament that will fit the bill for everything. definately look into petg though. esun makes some good stuff.

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Originally Posted by jimc

abs does layer bond really well IF you get a good quality abs and you print it at the right temps.

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This is my point. Some people use crap filament and/or the wrong temp and/or the wrong print speed, and claim it doesn't work.

never had layer issues with abs. never had them with ANY filament.

To avoid layer issues print at the Highest temp that still gives you sharp and clean prints.

Most books tell you to print at the lowest temp you can get away with - experience has taught me that with modern plastics this is no longer necessary, and higher temps will give you consistently better results.
Oh yeah and ALWAYS use active cooling - air blowig directly onto the print area. Putting layers down hot and cooling them quickly seems to give all round best results.

I - personally - find pla (reprapper tech ltd is what I mostly use) not only stronger than abs, but tougher and less brittle as well. It's also easier to print, doesn't smell and doesn't warp anywhere near as much as abs.
That said how you print a part: shells/layers infill % and type - has a very significant effect on each print.
Probably has more effect than the type of plastic you use.

It's one reason desktop 3d printing is as much an art as a science.

So the actual answer is: no abs doesn't have layer adhesion problems.
A particular machine and user might have problems - that isn't the fault of the abs.