How a custom measured insert is generated

A custom box insert is not drawn by hand for each order. It is generated: a program takes your measurements and builds the 3D model from rules. That is how we can offer any size between 80 and 300 mm in half millimeter steps at a fixed formula price. It also means the rules matter, so here they are.

Step 1: your numbers, in millimeters

You enter the inside length, inside width, the insert height, how many compartments across (1 to 5) and down (1 to 4), and whether you want finger cuts. If you typed inches, the numbers are converted to millimeters first. Everything after this is millimeters.

Step 2: take off the clearance

The outside of the insert is your length and width minus 1.5 mm, in total. That is about three quarters of a millimeter each side. It covers the print's own tolerance, which is about 0.3 percent, under a millimeter on a 250 mm part, plus a box that is a little out of square. The height is used as entered, because you have already allowed for the board on top.

A 250 by 200 mm box becomes a 248.5 by 198.5 mm insert.

Step 3: walls and floor

Walls are 1.68 mm. That odd number is four passes of the print nozzle, which lays down lines 0.42 mm wide; a wall that is a whole number of lines prints solid with no gaps. The floor is 1.6 mm, eight layers of 0.2 mm. The outer corners are rounded at 4 mm and the top edge gets a small chamfer so it does not snag the box.

Step 4: divide the compartments

The compartment width is the insert length minus one wall for every compartment plus one, divided by the number of compartments. Same for depth. For a 248.5 by 198.5 mm insert with three across and two down:

• Across: (248.5 minus 4 walls of 1.68) divided by 3 is about 80.6 mm.
• Down: (198.5 minus 3 walls of 1.68) divided by 2 is about 96.7 mm.

Every compartment has a rounded floor, a 2 mm fillet where floor meets wall, so pieces slide out instead of wedging in a corner.

If a compartment would come out narrower than 20 mm in either direction, the generator refuses. Nothing useful fits in a slot that narrow, and the walls would be closer together than they are tall. You would get an email asking for fewer compartments rather than a piece that does not work.

Step 5: finger cuts

With finger cuts on, every compartment gets a rounded notch in one wall: 24 mm wide or half the compartment width, whichever is smaller, and 14 mm deep or half the wall height, whichever is smaller. It is enough for a fingertip to reach under a stack of tokens or tip a deck forward.

Step 6: split if it is too big

Our printer reaches about 300 mm with both of its nozzles. The configurator caps inside measurements at 300 mm, so a standard order prints in one piece. For a larger box by email, the generator splits the insert into sections along a line through the middle of a compartment row, so the seam sits in open floor, and cuts dovetails into the floor so the sections drop together from above and stay square. The box walls keep them closed. There is no glue.

Step 7: checks before printing

The model is checked before it goes to the printer: that it is a closed, printable solid, that no wall is thinner than the nozzle can print, and that the outside size matches your numbers minus the clearance. A printed slip goes in the box with the measurements you entered and the size we made, so you can check it too.

Step 8: print

The insert prints open side up, with no supports, in the color you chose. A 250 by 200 by 60 mm insert with six compartments is about 280 grams of PLA and about 13 hours on the printer, which is the main reason it ships within 7 business days rather than tomorrow. The post on how long a print takes goes into that.

Why generate instead of draw

Generating means every order is consistent. The same numbers produce the same part, every time, and a fix to a rule improves every future insert. It also means we can be precise about the fit. The insert you get is your box minus 1.5 mm, not the nearest stock size. If it does not fit the numbers you entered, the fit guarantee remakes it free.

Before you order, the box measuring guide shows where to measure and how to work out the height.