Using ABS

[Toby]

I may not have the right picture of your geometry, but I think you need to account for two different measurements: the layer height and the extrusion width. If the bottom of the box is flat on the bed and is 1.75 mm thick, then with a layer height of .25 mm you want 7 bottom layers.

If your walls are perpendicular to the bed and also 1.75 mm thick, then if your extrusion width is (say .43), you will want to have 2 perimeters, since 1 perimeter actually takes up twice the space as it goes around each outline. If the infill is 0, that would give you a 1.75 - 4x.43 = 0.03mm gap in the middle, which is completely negligible.

On another note, 1.75 mm is pretty thin. Is there a need for it to be that thin? I usually think of 3 mm as about the minimum thickness on any wall that's meant to have some strength and stability. But that's PLA so maybe ABS is different.

If this isn't working, you could upload your stl file and I'm sure more than one of us will have a look at it.

[imsmooth]

This is my first CAD file. I have the box and another file that has the top. The box is not complete since I still need to put some access ports on the side. Still, I'd love to send one to you to see if I'm doing things correctly. I will attach the STL.

As far as thickness, I've copied the thickness of one of my electronic project boxes. It only holds electronic parts and only needs to protect them.

I've included the zipped box.stl file.

[jsc]

Your box looks fine, and would print fine.

[Toby]

I think you would be fine setting the layer height to .25 and top and bottom layers to 2, with infill at 50 %. That will give you a nice solid bottom to the box.

The walls being 1.75 mm makes it trickier than it really needs to be I think. To get them solid the best way I can see is to use 2 perimeters with extrusion width set to .43. That doesn't fill in the corners though since they are a bit wider, so just use 3 perimeters and it gets those.

But then I'm not getting a nice clean slice of the cylinders in the corner since they appear to be thicker than the walls. To get those looking good I had to turn down the extrusion width to .38, but then the walls don't get filled in as solidly. They have about a .23 mm gap in the middle, which probably is fine, but if you wanted it to print really cleanly I'd recommend making the walls have the same thickness as the cylinders.

But if you're just getting started printing with the M2 I think this is all overkill. You should just print it! Best thing is to just go with the basic settings that S3D loads with whatever material you're using. PLA is really good to start with. All these details about the settings you'll learn over time. There's nothing about your box that requires special handling (except needing to be flipped over so the bottom is on the bed.) It should print fine.

Attached is a factory file I used to slice it in case that's helpful. (Factory files load in S3D with File->Open or Ctrl-o. They contain both models and slicing parameters.) This is just meant to show the slicing though, not to be used for printing. I didn't check carefully the rest of the parameters like temperature or start and stop scripts.

If it's not clear or something else comes up, just ask.

[Toby]

Except there used to be one bug in the S3D default start script. I don't know if it's still there. If you see a line like:

M108 S155 ; turn on M2 fans

at the beginning, then either change it to

M108 S255 ; turn on M2 fans

or else just comment it out with a semicolon:

; M108 S155 ; turn on M2 fans

or else just delete it altogether.

[Capt. John]

Newest version of S3D comes with the correct code and no need to change it.

[imsmooth]

I do appreciate the help.

I'm unclear about defining the resolution. I understand that if I set it to 0.2mm or 0.25 I am setting the Z axis layer height. What defines the X and Y resolution? Is this fixed? When talking about perimeters, if I say do 3 then the machine will do 3 solid ones and then infill everything else based on the "percent infill" setting?

[ednisley]

What defines the X and Y resolution? Is this fixed?

That's what I call "the big lie" when somebody asks about "50 micron resolution!" during one of my presentations.

The extruded thread width defines the XY resolution, not the motor & belt positioning resolution and definitely not the Z axis resolution. The slicer can position the thread anywhere on the XY plane, to the limit of the positioning resolution, but it's still a plastic thread with a more-or-less fixed width.

The smallest feature you can build is a peninsula sticking out from the object, which requires two threads, one on each side. A typical thread runs around 0.4 mm wide, so the feature can't be less than 0.8 mm wide. Even with a tiny nozzle, the thread doesn't get much narrower than 0.25 mm and, while you can play tricks with under-filling the threads, the peninsula will still be about 0.5 mm wide.

Touting "50 micron resolution!" omits the inconvenient fact that the XY resolution remains just under 1 mm. The side walls may look better, with less of that characteristic striation, but the objects still have that Jabba the Hutt look due to the unchanged XY resolution.

Which is OK for the stuff I design: I loves me my M2...

[Toby]

When talking about perimeters, if I say do 3 then the machine will do 3 solid ones and then infill everything else based on the "percent infill" setting?

Yes. You can see what it's doing if you model a flat plate and look at the middle of the gcode preview in S3D. You'll see how ever many perimeters around the outside and a crosshatch pattern for the infill.

Like Ed, said, the xy resolution is going to be limited by the width of the extrusion itself. If your nozzle is .35 mm then this is typically going to be around .4 mm. There's a setting in S3D ("Manual extrusion width" in the Extruder Tab) where you can tweak that number a bit to fine tune your print, but it's not something you can just set at whatever you want. You can't really go below the width of the nozzle, though again, like Ed said you can trick the machine into laying down less plastic in the hopes that it will come out centered on the tip and act like a thinner line. Sort of works, sometimes, and sort of doesn't most times.

The smallest feature you can build is a peninsula sticking out from the object, which requires two threads, one on each side. A typical thread runs around 0.4 mm wide, so the feature can't be less than 0.8 mm wide. Even with a tiny nozzle, the thread doesn't get much narrower than 0.25 mm and, while you can play tricks with under-filling the threads, the peninsula will still be about 0.5 mm wide.

Well you can print pretty good corners. Even at a sharp angle the rounding at the corner appears to be right around .4 mm with a .35 mm nozzle. And that's a fillet. It's a feature!

I was wondering, why can't you print a .4mm peninsula by just going out and not back? Or go out, raise z and come back on the same line?

[imsmooth]

I was wondering, why can't you print a .4mm peninsula by just going out and not back? Or go out, raise z and come back on the same line?

I was thinking about asking the same thing. Why not just print a line in one direction, or wipe it coming back?