IKEA Lack: enclosures, legs and joints

The Lack table costs about the same as a roll of filament, and that is exactly why it has become the go-to chassis for half the 3D-printing world: stack two or three, close the sides with acrylic or foam board, and you have an enclosure that traps heat for ABS and keeps the noise and smell in. But a table on its own is not an enclosure. The structure comes from the printed parts that tie one table to the one below and clamp down a moving machine. Design them like an ornament and they split along a layer line the day the printer starts accelerating. This article is about the Lack's dimensions and how to print the joints and legs so they hold.

What it is and why you stack it

The Lack is IKEA's cheap side table: a square top on four hollow, coated chipboard legs. The appeal for our use is the geometry. The top is a flat, rigid surface to stand the printer on, and the legs are straight prisms that run up to the next top. Stack two tables — one as a base, another inverted or raised on top — and the gap between the tops is your enclosed volume. With three you get a chamber plus a shelf for spools and electronics.

The catch is that IKEA never designed this to be stacked. The table stands on its own, but the moment you put a second one on top, the upper legs have to anchor to the top below, and that is where your design comes in. The printer sits on the top of the lower table, and its weight runs straight down that table's legs to the floor; your parts do not carry that. What the four printed joints hold is the upper assembly — the top table with its spools and electronics — and, above all, they act as a lateral tie: they take the vibration of every direction change of the print head and stop the stack from wobbling.

The dimensions are a guide: measure them

The square Lack has a top of roughly 55 x 55 cm, legs about 45 cm tall, and a square cross-section of around 45 mm a side. Those figures let you size a joint that wraps the leg, but do not print anything off this table without checking your own table.

Note too that the top is hollow: two chipboard skins with a honeycomb cardboard fill inside. The only solid material inside is at the corner blocks, where IKEA anchors the legs. This dictates where and how you drive the screws, a point we return to below.

The stacking joint: wrap the leg with clearance

The centrepiece of the enclosure is the joint that wraps the leg of the upper table and fixes it to the top below. Geometrically it is a box: a square cavity that envelops the 45 mm prism, with a flange or lip through which the screws pass down into the lower top.

You do not draw the cavity at 45 mm. A printed cavity comes out narrower than you model it — FDM's bias closes gaps and fattens features, always in the same direction — so at a nominal 45 mm the leg would not seat, or would only seat with a mallet, splitting the wall along a layer line. You do not want a tight fit here: you want the leg to slide in and the screws, not friction, to do the holding. Model the cavity with a sliding-fit clearance, on the order of 0.3–0.4 mm per side over the real measurement of your leg — that is, an inner square of about 45.6–45.8 mm if your leg measures 45.0. Always reason per side; only when you write the final dimension do you add both sides together: 0.3 mm per side is 0.6 mm more total width in the cavity. Why those figures, and how to measure your own number, is in Real printed clearances.

That generous margin is not just there to let the leg slide in: chipboard legs are neither exact squares nor identical to each other, and a snug cavity that fits the front-left leg may not fit the rear-right one. The clearance absorbs that variation, which is inherent to the furniture. If you want to remove what little play remains, don't do it by tightening the cavity: put a side screw that pushes the leg against one face, or drop in a wedge, and keep the base clearance generous.

Orienting load-bearing parts

A stacking joint is not a decorative shell. It ties down the upper assembly and takes the vibration of the running printer: every reversal of the X axis sends a jolt through the part, thousands of times per print. That completely changes how you make it.

FDM's failure mode under load is delamination: the part does not yield like metal, it opens along the plane between two layers, which is its weak direction. Adhesion within a layer is continuous material; between layers it is a weld, and always weaker. The rule is to orient the part so that the main load travels within the layer plane rather than crossing it in tension. On a flange screwed to the top, the load pulls the screw straight out of the board; print the flange so that tension runs along the beads and does not peel stacked layers apart. If you are unsure about orientation, print two and break them by hand: you will find the weak plane straight away.

From there, oversize the part itself. It is not competing on grams.

On screws: do not rely on the part's grip on the leg alone. Have the screws pass through the flange and bite into the top of the lower table — a wood/chipboard thread, on the order of 4–5 mm in diameter — and place them over the solid corner blocks, or run them right through the board, never over the hollow central area, where the thread won't grip. If you are going to assemble and disassemble the enclosure often, a heat-set insert in the printed part itself gives you a reusable metal thread that will not strip; that pattern, and how to size the boss that receives it, is in Metric fasteners: M3/M4/M5 patterns, bosses and inserts.

Legs, feet and mobility

Beyond the stacking joint, the Lack calls for other printed parts around its legs. Feet are the most useful: a cap that fits over the end of the 45 mm leg to add a non-slip base, or to raise the table so cables pass underneath, or to level an uneven floor. You design them just like the joint's cavity — they wrap the prism with the same sliding margin of 0.3–0.4 mm per side — but they carry pure compression against the floor — the direction FDM handles well: the layers stack in line with the load and work in compression, not peeled apart. Even so, a wide base spreads the load better and does not tip.

To move the whole thing, a castor adaptor that fits over the leg and takes a standard braked wheel turns the enclosure into a trolley. Here orientation matters again: the castor introduces lateral load and bending moments when you push, not just vertical weight, so the adaptor works in bending. Orient so that bending does not open layers, thicken the walls, and if the machine is heavy, favour castors with a bolted plate on a thick printed part rather than a thin stem that acts as a lever. An enclosure with a printer inside weighs a fair amount, and a castor that splits while the trolley is moving drops the machine on the floor.

Before printing any of these parts, come back to the basics: measure your actual leg. The 45 mm cross-section and the 55 cm top are starting points, not fixed facts; the part that holds your printer should be sized from a calliper, not a catalogue. Once you have your dimensions and your measured clearance, Real printed clearances gives you the per-side number for your material and your nozzle.