"round corners"?

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Tinkerer
Posts: 176
Joined: Mon Oct 09, 2017 8:30 pm
Location: Germany

"round corners"?

Postby Tinkerer » Thu Dec 14, 2017 6:29 pm

Hello again.

Here's another effect I'd like to understand the root cause for to get around it.

The edges of this part should be perfectly sharp and in a 90° angle.
As one can easily see by the picture, this is not the case.
Instead, the edges are somewhat "rounded" and "overprinted",
making the printed part useless for the intended use.
DSC_4079.JPG

Any tips here?
...there's nothing like the smell of fresh ABS in the morning...

zemlin
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Joined: Sat Oct 21, 2017 2:02 pm

Re: "round corners"?

Postby zemlin » Thu Dec 14, 2017 6:37 pm

The machine is extruding a round bead of material. It's not possible for it to create a perfectly sharp corner. A smaller nozzle will have a smaller radius, but FDM will never make a perfectly sharp edge.

The hump is overshoot. You can reduce that by reducing your print speed and accelerations. It will take some messing around to find a compromise between print quality and print speed.

Slowing the outer perimeter will help some, but humps like that are cumulative so slowing only the outer perimeter won't clear them up.

Squenz
Posts: 140
Joined: Fri Dec 01, 2017 11:18 pm
Location: Stuttgart/Germany

Re: "round corners"?

Postby Squenz » Thu Dec 14, 2017 6:59 pm

what zemlin wrote, plus, to me, it looks like a bit of over-extrusion. Turn down the extrusion value by one or two percent and be a happy camper.

If you want to have the sharpest corners possible on these machines, you'd print it it that the sharp corners are produced at the z-axis. In other words, if you put it vertical on the bed, these corners will be much more sharp, but the now upper and lower corners will have to take some "rounding".

Tinkerer
Posts: 176
Joined: Mon Oct 09, 2017 8:30 pm
Location: Germany

Re: "round corners"?

Postby Tinkerer » Thu Dec 14, 2017 9:13 pm

Thanks for the suggestions.
Running a print at lower speed right no.

Reg. the extrusion I am already at 90%, let's see.
...there's nothing like the smell of fresh ABS in the morning...

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Michael.P@Raise3D
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Re: "round corners"?

Postby Michael.P@Raise3D » Thu Dec 14, 2017 9:37 pm

PLA Defaults at 94% extrusion, after that you will need to adjust for your individual filament used.
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Squenz
Posts: 140
Joined: Fri Dec 01, 2017 11:18 pm
Location: Stuttgart/Germany

Re: "round corners"?

Postby Squenz » Thu Dec 14, 2017 9:48 pm

Just in case, did you measure and enter the correct filament diameter in the filament settings ?

That's a major factor, because of it's square function. Every tenth you're off accounts for a serious miscalculation in the software and is a root cause for over- as well as underextrusion.

Tinkerer
Posts: 176
Joined: Mon Oct 09, 2017 8:30 pm
Location: Germany

Re: "round corners"?

Postby Tinkerer » Wed Dec 20, 2017 9:56 pm

Found out that I need to go down to max. 35mm/s to get nearly rid of the overshoot effect.

Is that normal?

Squenz:

Actually I did measure the filament diameter, yes.
It is pretty exactly at 1.75mm.
But even if it would be off that, this would not cause the overshoot edges, I assume.
As you say, it would cause over or underextrusion across the whole part?
...there's nothing like the smell of fresh ABS in the morning...

Squenz
Posts: 140
Joined: Fri Dec 01, 2017 11:18 pm
Location: Stuttgart/Germany

Re: "round corners"?

Postby Squenz » Thu Dec 21, 2017 8:18 am

If you're overextruding, the "round corners" will be overexposed.

I.e. in the middle of a three shell body, the overextrusion of the inner shell will go both ways, towards inside and the outside of the part, the inner shell will overextrude inwards and make a designed hole smaller than it should be, in theory in a perfect world, the hole will be smaller with half of the amount of overextrusion of the middle shell and the overextrusion of the inner shell.

The overextrusion on the outer shell in this case will expand outwards by the same extra amount and this will "round the corners" even more than acceleration alone does it. I can't explain it, but in my opinion, outer shells seem a bit more affected than the inner.

Of course, the IdeaMaker doesn't operate the middle first, inside then outside sequence, but if you not choose to print external shells first in Advanced/Other, most of the overextrusing will go towards outer shells, simply because it has to add up somewhere and this will be where the last shell is layed up.

So, if you need to have super-precise finish on the outer shell, you need to print these first and slow the speed of the outer shell down to what you find good enough for your purpose.

Tinkerer
Posts: 176
Joined: Mon Oct 09, 2017 8:30 pm
Location: Germany

Re: "round corners"?

Postby Tinkerer » Thu Dec 21, 2017 11:05 am

Squenz,

thanks for detailing that!
...there's nothing like the smell of fresh ABS in the morning...


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