This was a fun one. I was asked to make a new style prop medical kit for our friends at Frontier Airsoft. It had to be rugged because it was going to be worn by people hurling themselves around while getting shot at, and it needed some way to connect a strap to it so it could be worn like a messenger bag. I was also sent a picture of the style they wanted. We discussed the possibility of the kits opening to hold some sort of prop medial supplies or maybe something for the game storylines.
My favourite projects are ones that have some sort of engineering. This one has a few since the overall size needed to be around 300cm square. The absolute busting-at-the-seams maximum for the 3D printer is about 250cm, and to be honest I never take it that close to the edge anyway because it gets… unstable.
Additionally I wanted it to open because that would mean more possibilities for use in games in the future, that meant hinges and a clip or closing mechanism that could with stand some beating.
Designing the 3D model.
I don’t really know the technical name for this (I’m still very new to 3D modelling), but I think of it as blocking-out the shapes. If I were working with wood this would be the bit where I’m roughly creating the basic shapes for later refinement. Once this is done I quartered the shape, then mirrored that quarter to create the full side again.3D modelling is brilliant because of this kind of thing, you can mirror and duplicate things, rescale and tweak to get the exact size and shape you want. Sculpting something like this by hand would have taken considerably longer, and if it turned out to be too large, or too small, it would have been very difficult to alter. With this model I can literally just scale it up or down to get the exact size we needed.
Then I added in the details and the curves. Next I added the holes along the join faces where I would glue in pins to strengthen the joins. Another mirror of the whole side made the bottom, then I had to pair up the quarters and make them unique shapes for some detailed modelling of those. To the front-bottom quarters I added the strap holder loops. Both the top and bottom back-quarters I added the slot where I’d glue in the hinge bracket. I modelled in the hinges at this point too, fairly standard loops on either side with a connecting bar through them. I did the hinges as one long bar running the length of the back because this would give the finished thing more strength.
‘Round the front I carved in a gap and added a bar that the front fastener would clip to, and on the lower half I added a slot with a ridge that would allow the clip to grip a little better.
Then I modelled the clip over the top of that, again as a single piece for strength.
I added little discs along the four seam lines to add a tiny bit more structural strength, though originally they carried the Frontier Airsoft “F” logo, but that turned out to be too small to print correctly on the finished item.
Finally the middle of the top side was filled with a square featuring raised details that could be quickly painted. this feature has an added bonus, since it’s the only part with the cross on it, I can easily and quickly model other icons on this for use as a different prop – we’ve already discussed one with a biohazard symbol.
Making it printable.
This actually took almost as long as modelling the whole thing. I had to work out how to print it to best effect, and make subtle alterations to the model to match. Mostly this meant creating angles that I know can be printed in place of hanging edges, allowing for the weakness of the layers along the joins – the joining pins for the hinge and the quarters were printed in two halves length ways which is much stronger (but slightly more annoying during bilding!).
Printing was pretty straight-forward, but because it was designed to be very tough it’s much thicker than it needs to be for pure structural strength. That meant that even on a fast print it takes about 2.5 days to print one of these things.