The open-source new frontier of Z-delamination resistance
A hobbyist's field guide to Z-strength in FDM printing without tripping over patents, and a defensive publication of PinLoK (pinned infill).
By Matthew Armstrong (The-Dorkknight), United Kingdom. First published 13 October 2026.
📄 Read it: PAPER.md · PDF · web page
Every strength number for my own ideas here, including Shift-LoK, FlatLock and PinLoK, is theoretical: it comes from a 2-D computer simulation with known blind spots (paper, section 3), not from printed and tested parts. They are not product claims and say nothing about anyone else's products or patents. Real-world numbers quoted from others are linked to their sources. Not legal advice.
In one minute
Printed parts snap along their layers. The famous fix, staggering walls by half a layer ("brick layers"), is patented in the US. I went looking for every way to get stronger layers without beads of different heights, ran twelve ideas through a strength model, and wrote down what happened, failures included.
| Idea | Simulated result across the layers (theoretical) | Verdict |
|---|---|---|
| "Loopholes" (variable first layer, smaller or multi-phase staggers) | about the same as normal; still needs different bead heights | geometry doesn't care about wording |
| Different layer height per wall | −1 to −11 % | weaker |
| FlatLock (fat/thin walls) | −4 to −17 % | weaker |
| Squish-LoK (over-extruded squish bead) | −8 to +1 % | nothing to fill |
| Squish-KeyLoK (keyed gaps) | −19 to +3 % | keys snap off |
| Wide inner walls (about 1.5 × nozzle) | +2 to +9 % | partial success, just a slicer setting |
| PinLoK pinned infill | +16 to +27 % against solid infill of the same weight | best result; costs print time |
PinLoK builds on Oak Ridge National Laboratory's published Z-pinning. Every few layers the nozzle stops over half of the open gaps in Grid infill and pushes a blob of plastic down into each one; the other half get theirs next time, so the joints never line up. A potato mode keeps each push to about a second for stock printers like the Ender 3. A late discovery: pins that end half-way through a layer, not on a layer line, did far better in the simulation.
Why it's published
- To keep it free. Once a method is published, nobody can validly patent it afterwards. Section 9 of the paper discloses PinLoK and its variations in buildable detail, and the methods are dedicated to the public.
- To bring makers together. Open notebooks let tinkerers build on each other's work instead of repeating it. Print the test plan, post your results as an issue or discussion, fork it, improve it: everyone who contributes gets credited in the next version (paper, section 11).
- To save you the dead ends. Most of the ideas here didn't work. Now you know without trying.
- Selfishly: more cool 3D-printing techniques come back from the community, and I am now 22.713333…% more employable. High-efficiency synergy.
What's in here
| Folder | What |
|---|---|
PAPER.md, the PDF, docs/
|
The paper as Markdown, PDF and a web page |
figures/ |
Every figure |
pinlok/ |
The PinLoK G-code post-processor (Python 3.8+, no dependencies): python3 pinlok/engine.py file.gcode --mode potato
|
tests/ |
Its tests: python3 -m unittest discover -s tests
|
model/ |
The strength model and every result file (needs numpy, scipy, matplotlib) |
PUBLISHING.md |
How this was published, and what makes it count as published |
The full app (LoK Walls: FlatLock, PinLoK and a locked brick-layer pattern, with installers for Cura, PrusaSlicer and OrcaSlicer) is in a separate repository, to be published after ADDMAN, the brick-layer patent holder, has been asked. I haven't contacted them yet; I intend to.
Cite
See CITATION.cff (GitHub shows a "Cite this repository" button). Once archived, the DOI goes here: DOI to be added.
Source code: The-Dorkknight/a-bonding-experience on GitHub
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