Introduction: Laser Cut Parametric Flex Box Generators

Over at Just Add Sharks we had an idea to put a literal twist on the familiar laser cut parameteric flex boxes; by rotating the second curve 90 degrees we were able to create a box using just two panels (a bit like a tennis ball).

These boxes were designed as sample models to coincide with the launch of our new vanillabox lasercutter.

The scripts allow you to generate 3D models of the boxes in both flat and assembled configurations so that you can use them as part of a larger model. You can also use them to create a flat 2D version of the box that can be exported in a format suitable for a laser cutter.

Step 1: OpenSCAD Parametric Modelling

OpenSCAD is software for creating 3D models using a scripting language to draw the model. This allows you to effectively program that shape that you desire using software. The advantage is that you can define parameters such as the size of the box and the thickness of the material you're cutting.

OpenSCAD is a cross platform program that runs on your computer, but there are several web based versions that allow you to try out a design quickly and easily. http://openscad.net/

Each version of OpenSCAD is implemented differently, the web based version doesn't allow you to create a 2D profile for laser cutting and the desktop based version doesn't allow you to change the colours of the parts.

You can download the scripts we created to make these boxes from our github account, this will let you use the files but you can also improve upon the files and share them back again if you like.

One minor issue of this 3D modelling is that you are unable to draw a single line you can only draw rectangles and cubes, these will cut successfully but in the case of the living hinge you may wish to remove the excess lines before cutting because multiple passes on the laser within close proximity of each other could potentially start a fire on your material.

Step 2: Living Hinge Script

The most critical part to all of these flex boxes is the living hinge. This is a technique where you can cut a material with a concertina style pattern and turn it into something so flexible that it can be used to bend round corners.

The hinge has a fixed height but it's length is determined by the angle that you want the material to turn through and radius of the bend you want. There are 2 functions in this script module, one to draw a flat version of the living hinge with all the cuts in the correct places, the other to draw a 3D model of the hinge bent at the desired angle. The bent model does not generate the full cutting pattern because it will never be cut.

There are a number of other parameters at the top of the script that effect the pattern drawn on the hinge.

  • Slot Repeat Minimum: Is the smallest distance in mm between horizontally repeating slots. The script will make as many horizontal repeats as needed to fill the whole length.
  • Slot Length Minimum: Is the smallest length for a repeating vertical section of hinge. This is essentially half the pattern and the script will grow the slot length to fill the entire height of the hinge.
  • Slot Length Gap: Is the vertical distance in mm between one slot ending and the next slot beginning,
  • Slot Width: Has no effect on the design on the hinge, but a wider slot is easier to 'correct' in an editor afterwards (see the rectangle problem described in the previous step)

Step 3: FlexBox Style 1

This Script will generate the two part flex box, it has all the living hinge parameters described in the previous step. It also has new parameters to control the style of the box

  • Height, Width, Depth: These are fairly self explanatory, it calculates the box size based on the internall mm value.
  • Thickness: Is the thickness of the material you are using for the box
  • Corner Radius: Is the size of the corner you want on the box, the script currently uses the same size radius for both of the rounded edges.
  • Tab Length: Is the size in mm for the tabs that connect the two panels. It is the length of the tab passing through the side but also the gap before the next tab.

There is an initial check before any drawing begins to see if the model is to be drawn as a 2D or 3D shape. Once a 2D shape has been rendered it is possible to export this drawing to dxf or svg vector formats.

Step 4: Flexbox Style 2

This Script generates a more traditional 3 part flex box but it has oversized end caps which allow the tabs to be inserted into the ends and it allows the box to hold together even without glue.

  • Height, Width, Depth: These are fairly self explanatory, it calculates the box size based on the internal mm value.
  • Thickness: Is the thickness of the material you are using for the box
  • Corner Radius: Is the size of the corner you want on the box, the script currently uses the same size radius for both of the rounded edges.
  • Tab Length: Is the size in mm for the tabs that connect the two panels. It is the length of the tab passing through the side but also the gap before the next tab.

There is an initial check before any drawing begins to see if the model is to be drawn as a 2D or 3D shape. Once a 2D shape has been rendered it is possible to export this drawing to dxf or svg vector formats.

Step 5: Raspberry Pi 3 Case

For anybody who has made it this far through the Instructable we thought we'd include a special bonus raspberry Pi 3 case that we made using the 2 part flex box generator. It can be a little difficult to assemble owing to the tight bend radii on required for such a small box but once it is assembled it is pretty sturdy and functional.

If you use our scripts for anything we would love to hear about it (info@justaddsharks.co.uk)

If you are considering purchasing a laser cutter to cut boxes like this then please take a look at our vanillabox laser cutter (UK only sadly).

Comments

author
BrenoJ (author)2017-06-05

This is great! It's sparing me considerable time in my project. But I am actually trying to do something bigger. Do you think it would work well with 6mm laminated plywood? I'm afraid that the laminated surface will crack on the hinge.

author
marmak3261 (author)2017-04-07

Came back to the problem and figured out the routine for importing into Inkscape. Select the object > Document Properties > Scaling. It was not scaled at 1.

author
JustAddSharks (author)marmak32612017-04-08

That's great news thank you for the update.
I imported the svg into inkscape and realised it was out of scale so I imported the dxf and that was correct so I used that instead. Never investigated the svg problem.

author
marmak3261 (author)2017-04-07

Nice sketch and illustration. This is a very attractive design. I've been working with it but when I bring the exported SVG into Inkscape, the slots for the tabs are only .8 mm and not near the 2.7 that is the thickness of the acrylic I'd like to make this in. So I'll keep playing with it. And my non-3D brain can't quite determine the height, width, depth and how they correspond to the model or the object. So I adjusted one at a time to see how the work XYZ wise. Thanks for your work and best of luck on the new laser!

author
mrsmerwin (author)2017-04-05

these are really beautiful--as well as functional. How sturdy are they.

author
JustAddSharks (author)mrsmerwin2017-04-05

This is actually the point of the parametric script.
In 3mm laser ply as show here they're actually quite sturdy but you could change the thickness of the material in the script to be 12mm and make them really sturdy, or even out of lasercut steel or another material.

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Bio: At Just Add Sharks we don't only sell laser cutters, we love to make things on them too. Born out of a love of ... More »
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