When I attached our children’s swing to the ground there was still a significant piece of sharp-ish threaded metal sticking out above the bolt head and I was worried about them falling on it. Grinding the end off might still leave some sharp parts, so I thought it safer to print plastic covers for them.
Sharp bolt end protruding from the ground
Screenshot of bolt cap design in OpenSCAD
Screenshot of gcode printing plan
Photo of 3D printed bolt cap
I designed the caps using OpenSCAD, using the ScrewsMetric library for the bolt-shaped inset.
The biggest challenge was to find an acceptable compromise in shape and size:
– tall enough to cover the top of the bolt
– narrow enough base to fit next to the swing’s leg
– should be printable without overhangs and no need for supports
The final design I went with is a bit different from in the photo above because that one didn’t fit. I kept the size the same and chopped off one side of the dome to leave space for the swing’s leg.
There’s this fantastic device we have at home that I’m fairly sure is for giving back rubs, or maybe massages in general, like on your legs or something. I’ve tried it a few times but mostly the kids play with it. However it bothers me that there’s holes in it where the little knobs are supposed to be, so it doesn’t roll properly. I think the kids pulled them out, but maybe they were just never glued in properly.
holes from missing knobs in massager
Anyway, I doubt I could go in a shop and say “please give me tiny wooden knobs to this size” so I decided to attempt to print some. I’ve done some basic 3D modelling work before so with a bit of work and the right measurements, this should be doable, and it’s an interesting shape.
sketch with measurements for wooden knobs
Here’s a hand-drawn sketch I did quickly after measuring the wooden knob with a pair of callipers. It immediately became apparent that this was not going to be as simple as I thought because shaft part isn’t straight, but more like a chopped-off cone, and the head part isn’t round on every axis, it’s an ellipsoid. I Googled that word 😅 just to write it in this blog post, it’s the 3D version of an oval. Continue reading →
The Hungarian coat of arms features an iconic cross with two horizontal beams. In Hungarian it’s called “Kettős Kereszt” which translates to “Double Cross”, usually called the Patriarchal cross in English. This cross is present on other emblems around the area of Central and Eastern Europe too and has been featured on the Hungarian coat of arms at least since the reign of King Saint Stephen of Hungary.
3D model of the patriarchal cross as shown on the Hungarian coat of arms
Seeing as it’s a Hungarian national holiday today, in memory of the heroes and martyrs of the Hungarian revolution of 1956, everyone has their Hungarian flags out. I decided to do something Hungarian too, while trying out some tools for preparing models for 3D printing. So far I’ve been using Blender, because I have some experience with it, but it’s for creating 3D scenes and although you can use it to design 3D models for printing, it’s not CAD software. This time I tried Autodesk’s web-based program Tinkercad, which although lacking many of the features you’d get in a full-blown CAD program, is plenty enough for me to design simple things like this. Not being a mechanical engineer, I probably wouldn’t even know what features I’m missing!
3D printed “Kettős Kereszt” painted in the colours of the Hungarian flag
The program is very intuitive to use. I put a few cubes on the workplane, stretched them out into intersecting rectangular boxes and exported an STL file for printing within minutes. You can see a screenshot of the result above. I also made a version with a hole cut out of the top so you could hang it on a key chain. That turned out to be as easy as putting a cylinder in one of the boxes, stretching it out of the top and bottom box faces and marking it as a “hole” in the model.
After scaling the model down to 30% so it fits on my print bed, the final print came out as shown in this photo. It took less than 10 minutes to print at 30% in-fill and seems pretty rigid. I’ve painted on the red, white and green of the Hungarian flag and will hang this up somewhere, who knows, maybe it’ll even be good for a Christmas decoration. If you’d like to print your own Hungarian cross you can download both of my STL files here: