“A design engineer instead aims for adapting the part geometry to best work with the current state of the manufacturing processes.”

— Rahix, Design for 3D-Printing, 2025

A printed part is made in the same moment as its material. The orientation on the bed, the number of walls, the layer height and the temperature decide how strong it is, how close it comes to its drawing and how much of its grip it keeps after a month. They change the result by factors. This part collects the rules for designing parts that will be printed by fused filament fabrication (FFF, also called FDM), the process our 54 printers use and the one most students meet before any other.

Every rule here carries its basis: a source we have checked, or a test we have run on our universal testing machine, most of them with a whole student cohort printing the same specimen on different printers. A rule that has neither is marked as practice to be tested. Rahix’s design rules [1] are the starting point for the process detail, and the chapters of Machine Elements link here for the rules instead of restating them; they keep what is particular to their element. Why the book returns to printing at all is set out in the introduction.