Design into 3D: Boxes: Coopered boxes

Weird doubling/halving errors — not sure if I’ve got things correct, but this ought to be the part needed for the lid:

Next is placing it at the top of the lid and rotating multiples through the arc of the lid — arguably it should always be odd — will have to add logic for that.

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Unfortunately, BlockSCAD/OpenSCAD makes doing contextual changes of variables (which aren’t really variables for some architectural reason) difficult, so we won’t be able to force things to odd at this juncture (so that there’s always a keystone — might add a parameter for that).

We do however have a coopered lid (finally):

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and the lidarcproportion parameter works:

(currently subtracting 1 from that — will hopefully revisit that)

Next up is ends and fixing the lid skirt.

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Except that I can’t get the logic for the in-between dimensions to work — if I adjust for one in-between dimension, it works for that specific on, but breaks for others. The general solution works for the flattest option:

and the fully round one:

so I guess I’m going to just run with those two specific options. Not sure that designs such as:

make any sense.

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And the end pieces now work for the lower lids:

The fully rounded ones will be left for a later revision (they work, but are single piece which is not how I wish to handle them).

Next up is the metal banding around the chest — we need some more variables:

  • angle width
  • angle thickness
  • hardware diameter
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With those variables added, it’s just a matter of adding the angle and strapping around the chest:

(repurposing boardgap divided by 4 as the spacing for the metalwork)

In addition to the angle there will be metal strips of the same thickness and slightly lesser width to fill in where needed where the angle doubles up.

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With the base laid down:

the next challenge is modeling the angle for the end pieces — it will need to be the correct length for folding into a U shape and to have suitable holes for securing.

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The sheet metal work may need an additional variable, for now we set up a V to cut halfway through the angle thickness, and assume that dimension when bending:

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Working on a module to “bend” the parts:

next is putting in a slight radius at the corner, then offset geometry which will show if there’s any interference.

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Okay, bottom is pretty much done:

Next up, a strip with V down the middle to bend for the front and back edges of the lid (which will get installed into rabbets which I’ll need to work out adding) — this will be an optional feature, then the edge pieces for the ends of the lid.

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Of course, it’s always better to have a more general and more modular codebase:

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Much easier:

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A hard-coded bodge, but we have the penultimate piece:

and the final one:

Next I have to resolve the curves at the bend points, and remove some extra flat strips I added and shorten the front/back strips at the bottom and adjust spacing for all that, and lastly work up some sort of hardware for the bottom corners.

Last will be working out a way to export all the parts and a cut list/B.O.M.

Then, cut a prototype to test the metal bending and how the boardgap value works out — probably for the first one I’ll cut the metal and assemble it, then tweak the board dimension values to fit inside.

Last consideration is more hardware — probably one would want to buy hinges, but it should be possible to make some sort of hasp. Probably the easiest way to do the assembly would be to drill holes and then use blind rivets — nails with round heads would probably be a better choice though.

After that we’ll have to look into the rounded variant which I hope can go together with just joinery, no straps:

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Reworking this in its entirety, from beginning to end here:

https://willadams.gitbook.io/design-into-3d/a-final-project

The wooden version with rounded lid will get worked up as the preceding chapter most likely.

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Will, have you actually gotten time to put this into a machine? It looks really interesting.

I need to finish the design files — it’s supposed to be rainy here all weekend, so hoping to finish the design work today, then make a hardware store run this evening and actually cut and assemble tomorrow.

Challenges:

  • if doing aluminum strapping you either need a fixture which will secure the angle to cut out the bulk of the V relief cut, then rotate to make the V or U shaped groove at the bottom, or a toolpath which will make a flat cut all along that V edge while it’s mounted flat
  • for cutting out the lid parts — V endmills are not available in arbitrary angles, so this would need to be done as a 3D cut using a ball-nosed endmill, or you would need to have a fixture which would secure the stock at the correct angle and make it a two-sided operation — or, I’ve been wanting a shooting plane and shooting board for a long while — this might be the justification for finally getting one, though I’d need to get a board w/ a donkey’s ear or make one.

The problem of course, is working all day at a day job, and with a house full of other people whose schedules (esp. sleeping) I have to accommodate, my machine time is limited.

First though, we need to get a full set of design files. I’ll probably simplify them to use only flat metal strapping and leather around all the edges where angles are needed — that should be more manageable, but I found the metalwork fascinating as noted at:

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Traditionally, one would use “trunk corners” to stay away from the bending.

TRUNK CORNERS

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Just about done on this, but I’ve been wondering — would anyone be interested in the idea of making the strapping out of a single sheet of material?

The cut away parts would be nice rectangles for the most part, so not too bad from a materials usage standpoint (so long as one could find suitable projects for them) — it really simplifies things, and I’d like to think it would make for a markedly strong box (and it would eliminate the voids underneath which annoy me in the modeling, but which I can’t bring myself to make half-lap joints to avoid).

How thick would the material be? Fixturing would be a problem or require a unique solution and/or probably just an additional thin wasteboard.

1/8" is what I’m using in the design at the moment — I may try modeling a box which would be exactly the maximum size an XXL could cut and see if it’s something reasonable (then I’ll price out a sheet of alu. that size which will probably put the kibosh on this.