Lego Technic Frame Enclosures
Trigger Warning: Lego aficionados may consider this use of Lego Technic Frames blasphemous. My apologies. Fortunately, Chinese clones work just as well.
I saw this Lego Technic Frame on YouTube. My first thought was "This is perfect for making enclosures!" My second thought was "Why have my geeky Lego friends never told me about these???"
There are several ways to make electronics enclosures using laser-cut acrylic, but I find these lacking, often presenting too much of a DIY appearance.
A few examples of traditional laser-cut boxes/enclosures are shown here. "Slots and tabs" may be glued together to form an enclosure, but providing a secure removable panel is a challenge.
The next enclosure remedies the removable-panel problem but the corner pieces to retain the screws consume a lot of panel real estate.
The console box is a nice enclosure for some applications, but still has access issues.
T-Slots can be used to hold an enclosure together. Versions are shown in wood and clear acrylic.
I prefer to inset the sides and add slots and tabs for added strength. XYK has a nice design and tutorial on T-Slot joints.
Parametric generators for these types of enclosures are available on the Laser Cutter resource page.
When I saw these Lego Technic frames, I recognized they can bring an entirely new level to laser-cut enclosures – they form a fantastic support structure for laser-cut panels. A little experimenting revealed that 3mm heat-staked thread inserts fit perfectly into the frame holes. Two frames allow making an enclosure with 6 laser-cut panels.
Lego frames are available in three sizes. Large is 120mm x 88mm. Medium is 88mm x 56mm. Small is 56mm x 40mm. The frames are based on 8mm spacing. The alternating holes are 8mm apart, The frame is 8mm thick and frame members are 8mm wide. This common modulus makes it extremely easy to design enclosures around these frames. The grid in the pictures is at 8mm spacing.
An example of a simple enclosure using small frames is shown below. This is an ideal size for small power supplies or small devices.
Notice in this picture how the panels overlap. I try to mininize visible edges. The end panels are the same size as the frame. The top and bottom panels are the width of the panel, while the length is increased by 6mm to overlap the 3mm end panels.
The side panels are where creativity can come in. The panel overlaps the ends and top and bottom, and actually extend past those panels to serve as feet. The ends are curved to avoid sharp edges, and extended to provide protection to the cables.
For a front panel arrangements, a printed circuit board can be mounted to the back side of the frame, The 8mm spacing to the front panel is perfect for 12mm tactile switches with buttons and for 7-segment displays and bargraphs visible through a transparent panel. Keep the length of screws in mind to prevent interferences.
One neat feature of this type enclosure is that any panel can be removed without the enclosure falling apart. In fact, up to five panels can be removed without problems. To illustrate this, here is a work in progress, with only two printed circuit board panels holding the frames together. JLCPCB's black soldermask is flat black – a printed circuit board panel provides an actually machined and labeled panel at a cheap price.
The circuit board will be attached to the top of the bottom of the frames. I didn't install thread inserts on the bottom. Bolts through the bottom panel will secure the board. The center frame is added to stiffen the panels and top and bottom. You may recognize a problem. The pcb is wider than can be fit through the center frame, If you closely, you'll see the center frame has been notched out in the center of back side, allowing the frame to be put around the board.
Below is an example of a control board with a frame. This shows the distance between board and front panel should be perfect. The bottom of the rocker switch should be just below the surface of the panel.
Stay tuned for updated pictures.
