Trying to replace PLA with ABS with no success...

Hey guys

Am using PLA for over a year, and now for some prints I would like to use ABS.

I read all over the internet how ABS is awesome, and in all those readings I see ABS is "much" stronger then PLA so I give it a shot ordered yellow and white ABS from different sellers and prints looks good very good indeed BUT brakes every time I tryed to print ring for aluminium wheel I'l post picture how ring looks and every time even small force "feathers" break... It looks like there is no wall infill...

I use Cura... Settings are in att

There is a thing that affects especially thin, round walls.
No clue how it is called but I call it wall seperation.
I encountered this the first time when I changed to my now standard 0.3mm nozzle.
Something I printed with a wider nozzle and great success had no staility once twisted.
As it was a bottle opener this was quite frustrating ROFL
Through observation I noticed a few things:
1. Most slicers have problems creating solid walls on round objects if the wall is relatively thin compared to the extrusion width.
In my case I noticed that with certain line widths I ended up with two single walls seperated by a tiny gap.
2. Thin walls have a strong relation to the layer height and extrusion width!
For example:
You want to print a 2mm thick wall with a 0.4mm nozzle.
In theory that would give us 5 lines for this wall.
In reality however the extrusion width is always wider than the actual nozzle width.
But with a good 0.43mm you can no longer fit 5 lines.
To make things worse 4 lines only make 1.72mm!
If on top you have a 0.3mm layer height you see how the trouble starts...

Observe how the wall is printed!
If there is gap your slicer has two ways of dealing this.
A) By making on or both inner perimeter lines wider - this only works if you extrusion width has enough room to play and make it work!
By adding a "gap fill". Most slicers have additional settings on how to handle these gaps, you might have to play with them to get it perfect.

Some slicers still mess up in rare cases.
Here the algorithm simply fails and you already see in the preview that there might be a gap that is too far for more extrusion.
In such a case try to lower the layer height by a fraction - often this is enough for the algorithm to decide between gap fill or more extrusion instead of doing nothing at all.

I print structural parts all the time with ABS and there are tricks to making them strong. First off you want to go to 100% infill. Next you need to print it hotter, if you have an all metal hot end you can try 245 or 250 if it's not all metal then 240 is the max you can go but that extra 5 degrees makes a lot of difference.

Next you want to make sure the perimeters and infill touch, it's hard to explain but in your preview go up and down your print and make sure there are no gaps inside, this happens when the wall is thin and there is not enough room for several perimeters and infill so the software leaves a cam this means it will be hollow inside and very weak. One method to overcome this is to use only 1 perimeter so there is more room for infill, if that does not fix the issue then the wall is just too thin for both and if possible make it thicker, even 1mm can make the difference.

I will put 2 examples below that show how the infill is good and how it's missing making a weak part.


Hollow walls = Weak Part



Full infill = Stronger part


Edited 1 time(s). Last edit at 03/17/2016 04:08AM by tmorris9.

Good one with images - that was what I meant with the gap filling.
An image explains it so much better...

As for higher temps:
This only works if the part allows for it.
Especially smaller parts can suffer here.
I usually print several copies at the same time if the part I need is quite small and I have nothing bigger to print along to increase the layer time.

See [richrap.blogspot.com]

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]