Do bevelled corners hold any practical advantages or disadvantages over square ones for blocky functional prints?

Question

I'm producing a series of brackets to allow a laser cutter to be reliably positioned on a waste board\spoil board in that has a measurement grid on it, and to allow a honeycomb bed to be reliably positioned within it in relation to the laser cutter.

Essentially, I'm making 4 large right angle piece with mounting screws and stepped sides. Which will be screwed down to a piece of timber so that things can be fixed to them in the same position each time they're used.

It has a lot of corners, and 90° angles, and it looks like it was designed by a Brutalist architect.

Will bevelling¹⁾ the corners for purely aesthetic reasons have any practical effect on the print or the printing process. For example will rounder corners make the print stronger or weaker, or will it make warping more or less likely. Will it improve or harm bed adhesion, will it have any substantial effect on print time or quality?

Version 1.0

I'm using an Ender 5 with PLA and a 0.2 layer height. Because that's what I have on my shelf right now, and I don't want to spend any extra money on this.

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¹⁾ I'm using the word "bevel" because I'm using Blender to make the model (Because it's what I'm most familiar with), and you create rounded edges using the Bevel tool in Blender.

Answer 1

Bevel chamfer fillet, whatever. For correct semantics see the other excellent answer.

What are advantages of rounded (or at least, less sharp) edges and corners?

• In FDM, curved xy paths are stronger than sharp corners and if your printer supports acceleration, may print marginally faster.
• Curved surfaces feel nice in general and make the part more professional looking. Sharp corners are...well...pointy and sharp.
• Sharp corners and flat side faces can expose calibration issues with your printer that curved faces can hide, so the results look better.
• Vertically slanted surfaces with bridged inside horizontal curves are difficult to print without good support. The inside perimeter can separate from the infill, severely degrading print quality. Sometimes replacing circles of slanted holes with pentagons or octagons helps this and improves bridging, but good support works better. This could be construed as a slicer bug, but I've yet to see a slicer that does this well.
• For bottom layers, round corners (or just circles in general) can increase bed adhesion and reduce peel up where sharp corners make that worse. This is more of an issue with plastics with a shrink factor (like ABS) and nearly not an issue with PLA.
• In general (and fillets in particular), rounded corners anywhere are stronger. Inside fillets reduce stress concentrations, spreading it over the whole curve instead of concentrating it at the intersection. For outside corners, a sharp corner is a target for chipping and direct impacts on the corner can transmit concentrated forces into the part where a curved surface would spread them.
• As already stated, curved surfaces in the xy plane are stronger and higher quality with FDM, but even vertical curves can be stronger, as most slicers add extra material around them. However, if you have a buggy slicer that doesn't do this, an upper curved surface with too steep of an angle, like a sphere, may have holes and could collapse. On the other hand, a buggy slicer might not add solid layers under the corner and only have infill support under sharp vertical corners, creating a delamination risk, where a gradual curve or slant would at least have overlapping perimeters. Lower curved surfaces can have support issues.
• Curved or beveled edges can increase passive compliance for parts that have to slide to join with other parts, making them easier to fit. However, inappropriate use of this can add unwanted gaps at the edges of joined parts, in which case a gradual taper (or just a square corner) might be better than a bevel or round.
• Curved surfaces are harder to draw, and depending on your cad package, may require extra design planning.

Answer 2

Will bevelling the corners for purely aesthetic reasons have any practical effect on the print or the printing process.

No, not necessarily in this model. If one positive reason for using a chamfer¹⁾ or a fillet²⁾ would have in this design is that it may make it easier to insert the honeycomb plate in the recess of the corner model cutout.

But, fillets and chamfers can have more useful effects. E.g. a bottom fillet is usually harder to print well, on the other hand, a chamfer prints fine. See e.g. this answer or this answer.

A fillet can also be very useful in preventing stress concentrations in corners (of structurally loaded parts), preventing prints to fail prematurely (like a weld does between 2 perpendicular plates).

The effect on printing time and filament saving is negligible, there is usually not much volume involved.

One of the biggest advantages is that parts look more professional!

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¹⁾ from Wikipedia: In machining the word bevel is not used to refer to a chamfer. Machinists use chamfers to "ease" otherwise sharp edges, both for safety and to prevent damage to the edges.

A chamfer may sometimes be regarded as a type of bevel, and the terms are often used interchangeably.

²⁾ from Wikipedia: In mechanical engineering, a fillet is a rounding of an interior or exterior corner of a part design.