What's the correct height of a bin + lip?

[GCheung55]

Assume that the bin is 1x1x2. So it.s 41.5mm x 41x5mm x 14mm.

gridfinity-rebuilt-openscad says the lip should be 3.8, making the bin height 17.8mm.

Specs shows the lip should be 4.4, making the bin height 18.4mm.

What's the correct bin height?

[EmperorArthur]

Will edit this when I am at my PC, and can look at the code.

The spec assumes the lip ends at a sharp point. However, we radius the top of the lip, lowering the height slightly.

I am the one who wrote the current profile code describing the lip based on that spec, and believe there is a picture included in the images folder which maps the lip to measurements in standard.scad

[EmperorArthur]

Congratulations

Congratulations, you found a bug. Just not the one you think. Also not one I want to look at fixing until I can get some of my current work in progress merged.

h_lip

Take a close look at the top of the lip when setting h_lip=4.4; You will see the top is no longer rounded, and is instead flat.

Wall Profile

I ran the following to generate the profile used for the wall:

$fa = 8;
$fs = 0.25;
profile_wall(9);

I previously gave the number of 11.858mm, and I'd say 0.1mm off is pretty close. Especially given how OpenSCAD does circles.

PrusaSlicer Measurements

Commenting out the base, I see 12.55mm. Which is within tolerance of the 12.458mm I calculated earlier.

I then loaded just the base and got these numbers.

FreeCAD Measurements

I have loaded the model into FreeCAD, converted it to a wireframe, and took some measurements.

4.788+12.174+0.6 == 17.562

The Bug

Take another look at the FreeCAD Wireframe. Does something look odd to you?

Here's a close up, with the error measured.

That's the source of the problem, but it isn't jumping out at me in the code, and the part which creates the base takes a significantly different approach than the wall and my PR for the baseplate.

[GCheung55]

Congratulations, you found a bug. Just not the one you think. Also not one I want to look at fixing until I can get some of my current work in progress merged.

Yay, glad I could help.

If I'm understanding you correctly, the bug is that there's 0.367mm that is causing the height to be wrong? Any suggestions how I could mitigate the issue until you have time?

[GCheung55]

Take a close look at the top of the lip when setting h_lip=4.4; You will see the top is no longer rounded, and is instead flat.

Is there something wrong with having a flat top instead of a radius? Just trying to understand if/why that's an issue.

I may have misunderstood, and the bug isn't actually impacting the height of the bin. If a 1x1x2 bin with the lip is supposed to be 17.5515mm tall, then perhaps the code comment needs to be updated, since it's saying that the height of the bin is supposed to be 17.8mm tall. If that's the case, I can submit a PR to make the correction.

[EmperorArthur]

If I'm understanding you correctly, the bug is that there's a 0.367mm reduction that is causing the height to be wrong?

Looking into the issue some more, it does appear to be an issue with something in how the radius is applied to the profile_wall code. Verified by first fixing the issue with the base.

Any suggestions how I could mitigate the issue until you have time?

Ignore it. I've done some basic testing by removing the chamfer completely and the lip was the expected 4.4mm height. The only consequence is the chamfer being slightly lower than it should be. However, as the first inner transition is not affected, bins will stack exactly as if the lip came to a sharp point.

Remember, the spec notes a 0.5mm tolerance. So, while this should be fixed, it' not that big of a deal.