Explanation of Grid Cell Width/Length Bin Calculations

[GTIRacer]

I’m new to the world of 3D printing and appreciate all of the time, effort and attention to detail that went into developing the Fusion 360 Gridfinity AddOn. I am struggling to understand the Grid Cell Width/Length values that is calculated by the AddOn in the Bin Compartments section and was hoping someone can help me.

For the sake of my question assume a simple 1x1 hollow bin with the default settings (42 mm L/W, 7mm Height, 0.25 mm offset, 1.2 mm wall thickness, 1x1 units, 5 unit bin height and grid widths and lengths of 1). Here are 2 scenarios:

1. Scenario Automatic Pinning to Toolbar #1: No lip for stackability. The calculated Grid Cell Lengths and widths are both 39.6 mm. I assume this is calculated as 42 mm- 2x1.2mm. If my assumption is correct Im not sure what this parameter represents or what it’s used for. At first I though its supposed to represent the inner (ie usable) dimensions of the bin but for this to be true the calculation should include the 0.25 mm offset (for each side), in other words 39.1 = 42 - 2x(1.2) - 2x0.25.

2. Scenario Enhancement Request - Ability to print magnets into the magnet holes of the bins. #2: Same as Automatic Pinning to Toolbar #1 but with Lip for Stackability engaged. The calculated Grid Cell Width and Length in the Bin Compartment section are now 19.6 mm. Which is a 20 mm reduction.

These calculated values get even stranger when you add additional bins in the Bin Compartment section.

I guess my ultimate questions regarding these calculated values are

1. How are they calculated?
2. What is their significance?
3. And is it something I need to pay attention to?

Any clarifications would be greatly appreciated