The right fastener depends on access, not just load
Four common ways to fasten into a printed part, a through-bolt, a heat-set insert, a self-tapping screw, and a captured nut, each need a different amount of physical access and offer different tradeoffs in strength, cost, and how many times the joint can be taken apart. Choosing based on load alone misses the practical constraint that often matters more: whether you can actually reach both sides of the joint during assembly, and whether the part needs to come apart again later.
How the plan works
Access to both sides of the joint favors a through-bolt with a captured nut, generally the strongest and most serviceable option when it is physically possible. One-side access with a real serviceability need favors a heat-set insert, which gives a durable, reusable machine-thread socket. One-side access without serviceability and a thin wall favors a self-tapping screw, the simplest option for light or infrequent use; a thicker wall without serviceability needs opens up a captured nut pocket instead.
Worked example
One-side access, a 6 mm boss, repeated assembly and disassembly expected: the tool recommends a heat-set insert as the best fit, since the wall is thick enough to support one and the stated serviceability need favors a reusable machine-thread socket over a self-tapping screw that would strip with repeated use.
A common mistake
A frequent error is sizing the boss around the fastener alone without checking wall thickness against the part's outer surface. A boss that is thick enough for the insert but leaves only a sliver of material to the part's exterior wall is a common, avoidable crack point; check both the inner clearance for the hardware and the outer wall thickness around it before finalizing the geometry.
Limitations
This compares fastening routes qualitatively based on access, wall thickness, and serviceability; it does not calculate actual pullout or shear strength for your specific hardware and material. Pull- or torque-test a sample boss before committing a load-bearing joint.