Parametric Magic Magnet Polarity Tool – optional Two-in-One mode!

Note: This is a parametrized model using OpenSCAD. The STLs are only provided as example/reference. See below on how to use the OpenSCAD file.

Remix (full rewrite) of the super cool Magic Magnet Polarity Tool by tjdesign, including a parametric OpenSCAD model, as well as the option to connect two pens so you only have one tool lying around on your workbench.

I really like the magnet polarity tool, but I was looking for something slightly smaller, and ideally a single pen with the magnets at either ends, so I'd have less stuff rolling around on my workbench. I took tjdesign's cool polarity tool and remodelled it in OpenSCAD, adding an option to connect two pen halves to a whole.

I kept everything else mostly the same, especially the screw-on lids so you can swap them out after you get a bit too much glue on them. You can select the decoration on the pen side (same patterns as the original, though with some small differences because I didn't care enough about replicating the patterns faithfully), and more importantly, the magnet size and tolerances for the best magnet fit.

The files I uploaded here as examples should be a match for the original model, with the same 8x3 magnets and the same diameter, and the threads in the covers are compatible with the original too. The bigger strength is in setting your own parameters though:

OpenSCAD

You need OpenSCAD installed. Open the .scad file with it, and then play with the values in the Customizer panel on the right hand side. If it isn't visible, enable it via Window -> Hide Customizer.

The model will look a bit rough at first because the render quality is set lower on purpose to make changes fast even on slow PCs. You can change this in the "Output" section in the Customizer. The default quality, "auto", makes the preview fast and rough, but the export to STL fully detailed. Set to "Final" to see a more detailed preview (slow to render on account of the threads, sorry).

All parameters have descriptions, and invalid parameter combinations should raise an error message (at least in the cases I thought of).

In the "Pen" section, select "Plain end" if you want two separate pens. Because this model prints the pens in one go, the end will be not as rounded as the original, just slightly chamfered.

Once you are happy with the values, render (F6) and export to STL (F7).

You can select which parts to render in the output options, too. If you render all parts (pen, cap, connecting stud) and open them in a slicer, they will appear as a single item. Break them apart with the context menu, selecting "Split" and then "To objects".

Printing

I found that layer heights larger than 0.2mm led to pretty bad threads, but 0.2 and below worked great. Otherwise, it's a very undemanding print. You might need a brim, depending on your material and printer, and the size you choose for the pen.

You'll have to print two pens, two lids, and if you go for the two-in-one-mode, the stud.

Assembly

You can glue the magnets in, but for me, just sticking them in was good enough (with the lid screwed on, it's not like they are going anywhere).

Insert a magnet in the first pen element, then screw on the lid. Put the second magnet on the outside of that lid, then scoop it up with the second pen (so it will be in the right orientation automatically). Screw on the second lid. Finally, if you are using the two-in-one mode, screw in the stud and the second pen.

Use

When you have to assemble something where magnets need to attract each other, first put one magnet on either end of the pen, and only then insert them in whereever they need to go. They'll be guaranteed to be oriented correctly now.

If you use superglue for this a lot, print some replacement lids in advance, as they will inevitably look terrible over time. (You can scrape off the glue, sure, but that will only go so far.)