Finn,

I've been doing 3D printing for awhile now, never tried ABS though.

I've used 3D printed parts primarily for model rockets, things around the house, etc.?? The stuff holds up well, moreso than one would think normally.

One suggestion I'd have is higher infill - when I'm printing something that needs to hold up, I usually??run about 75% infill.?? I'm not sure if that's possible with ABS or not, so I don't know if that's actually good advice.?? One thing you can do, and only with ABS, if you take a shop rag and wet it with Acetone (I think, google it) if you wipe the part with the acetone, it dissolves the first layer or so (until the acetone evaporates).?? This allows you to smooth the ABS with the rag and get a gloss finish on it.?? You can also do vapor polishing:??https://www.matterhackers.com/articles/how-to-vapor-polishing?? I don't like the hot method, if you look down the comments section someone explains how to do the "cold" method.?? I'd try that.

Good luck!

Dustin

On Thu, Sep 19, 2019 at 8:36 AM Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:

My first experience with 3D printing.

I had bought a new Ender-3 and a 1Kg spool of ABS for less than $200.

Article and pictures here:

https://drive.google.com/open?id=1LbQcJIGnjsfNWfL5qiwz5ev7ze9IWAzm

I copied the "best" picture from the RET_Bellmouth_Sept.pdf article,
pasted it into Paint and saved as Bellmouth.bmp.

Imported that into Fusion360 as canvas. Calibrated it so throat was
19.972mm (1.18")

Made a spline matching the left curve up to the top.

Added a tangent arc (radius).

Added a 2mm rectangle that extended the throat about 1" with an 1.25"
ID. (The bell mouth will slide 1" down on the 1.25" OD pipe.)

Added a "looks good" spline from part of the arc down to the throat. (I
believe that in our case, where most of the air comes from behind the
bell mouth, air should have a smooth path along the outside of the pipe
and radius of bellmouth.)

Revolved the whole thing to get the solid bell mouth.

[The result is actually a bit smaller overall diameter than the
recommended 2.13 * 30 + 2 * (0.08 * 2.13 * 30) = 74mm]

Exported to a .stl file.

Downloaded and installed Ultimaker Cura 4.2.1.

Opened the .stl file with Cura and "sliced" it. 20% infill. This changes
the solid inside to a criss-cross pattern. Looking at it being printed
it appeared?? to produce about 3/32" thick walls by default.

Saved result to .gcode file.

Printed with the Ender-3. Took 3 hours and 15 mins.

Nozzle temp default for ABS is 240*C. Spool says 230-260*C. Seeing how
some of the strands didn't stick and pulled across the mouth, I think
I'll use a higher nozzle temp on the next print.

I printed it with mouth down. Unfortunately that resulted in a radius
quite different from the design model. I'll try to smooth the lip on my
first attempt with epoxy or JB Weld and sandpaper. If I print it throat
down, it'll probably need support along the outside that'll have to be
cut after printing.

Will ABS be strong enough? I think so. The airflow should keep temps
well below 85*C.

Finn


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