Square Desk Lamp – E27 Base with Slide-On Diffuser Cover

A simple square desk lamp in two printed parts. The base holds a standard E27 socket. The cover is a thin-walled diffuser that slides down into a groove around the top of the base and sits on the rim. There are no screws or clips, and you lift the cover off to change the bulb.

Highlights

• Two parts: a base and a cover, with no screws or clips. There's also an optional light plate if your base lets light through.

• Slide-on cover: an 0.8 mm lip on the cover drops into a 1.2 mm groove in the base, so there's 0.2 mm of clearance on each side. It slides on and off by hand.

• Soft, even light: the cover has 0.8 mm walls and a 0.6 mm top, so the light comes through the whole cube.

• Standard parts: a regular E27 socket and lamp cord, with an inline switch or with a smart bulb and no switch.

• Hidden cord: the cord comes in through a slot at the bottom of the back wall and runs up through the centre of the base.

• STEP files included so you can adapt the socket seat to your own socket.

• Size: 110 × 110 × 220 mm assembled.

What you need

• The 2 printed parts:

  • 1 Base

  • 2 Cover

• Optional: 3 Light plate (see "Light leaking through the base?" below).

• An E27 socket that fits the seat (see "Socket and bulb size" below).

• A lamp cord with a plug: with an inline switch, or without one if you use a smart bulb.

• An E27 LED bulb that fits inside the cover (see "Socket and bulb size" below).

  

Printing

The files are already the right way up. Load them as they are. Neither part needs supports.

• 1 Base: upright, floor on the bed. Use at least 3 perimeters (wall loops) so light doesn't shine through the walls of the base. 15–20 % infill.

• 2 Cover: closed top on the bed, lip up. Infill doesn't matter, because the walls are only 2 perimeters thick.

• 3 Light plate (optional): flat, notches down, 100 % infill, in an opaque filament.

General settings: 0.4 mm nozzle, 0.2 mm layers. I printed the base in wood-filled PLA and the cover in regular PLA.

Tips:

• Print the cover in white or natural filament so it glows evenly. Darker or opaque filaments block most of the light.

• The cover walls are 0.8 mm, which is exactly 2 perimeters with a 0.4 mm nozzle. Check the slicer preview to make sure the walls are solid with no gaps.

• If light shows through the walls of the base, print the optional light plate (see below).

• If the cover feels tight in the groove, lightly sand the outside of the lip. The fit is set up so it shouldn't need it.

How it goes together

Please read: this lamp runs on mains voltage. I'm not an electrician, so this section only describes how the parts fit together. It is not a wiring guide. Connecting the socket to the cord should be done by a qualified person, with certified parts and according to your local regulations. You build and use the lamp at your own risk.

1. Cord: it enters through the slot at the bottom of the back wall, runs across the floor of the base, and goes up through the Ø13 mm hole in the centre to the socket seat.

2. Socket and bulb: the E27 socket sits in its seat at the top of the base (Ø39.8 mm, 40 mm deep), and the LED bulb screws into it. The socket just sits in the seat, with no glue and no press fit. It sticks up a little above the base on purpose, so the bulb sits more centred in the cover.

3. Cover: it slides down over the bulb, the lip drops into the groove, and the cover rests on the rim of the base. To reach the bulb, lift the cover straight off.

Light leaking through the base?

Start without the light plate. Depending on the filament, some light can get down into the base and shine through its walls. With my wood-filled PLA base, some of it did.

If you see that with your filament, print 3 Light plate at 100 % infill in an opaque filament (a darker one blocks the most light).

• It sits on top of the four ribs inside the base, with the notches facing down, so it can't slide around. The centre hole goes over the socket.

• To fit it, unscrew the bulb, drop the plate in over the socket, and screw the bulb back in.

• To take it out, lift it by the two knobs.

• The cover goes on the same way as without it.

Socket and bulb size

The only way to check the fit is to measure your parts before you print. These are the limits:

• Socket body: up to Ø39.8 mm. That's the seat's exact size, so a socket a little smaller fits more easily; it only needs to sit in the seat. The seat is 40 mm deep, and a socket that sticks up a little above the base is fine. Mine does, so the bulb sits higher in the cover.

• Cord or cable entry under the socket: up to Ø13 mm, which is the hole it passes through.

• Room above the base: about 99 mm from the top of the base to the inside of the cover's top. The part of the socket that sticks up above the base plus the bulb (measured from where it screws in) has to stay under that.

• Bulb width: the inside of the cover is about 106 mm wide. Leave a gap so the bulb doesn't touch the walls.

Use LED bulbs only. Incandescent and halogen bulbs get hot enough to soften printed plastic.

Make it your own

The STEP files for all three parts are included. If your socket is a different size, change the seat (Ø39.8 mm, 40 mm deep) and the cord hole (Ø13 mm) in the base. Keep the groove and the cover's lip as they are, so the cover still fits.

Design notes

• Groove and lip: the cover's lip is 0.8 mm thick and 10 mm long. The groove is 1.2 mm wide and 15 mm deep, so there's 0.2 mm of clearance on each side. The lip stops 5 mm above the bottom of the groove, so the cover's height is set by the rim, not by the groove floor.

• Inside the base: four diagonal ribs with hexagon windows hold the socket seat in the middle. The cord runs under them from the back slot to the centre hole.

• Cord slot: 20 × 10 mm at the bottom of the back wall, so the lamp sits flat on the desk with the cord out of sight.

• Light plate: 1.4 mm thick (7 layers at 0.2 mm). The 0.6 mm notches on its underside key onto the 3 mm ribs. There's about 0.7 mm of clearance to the walls, and its top sits 0.8 mm above the rim, inside the cover's lip.

• Testing: I checked the fit between the cover and the base in CAD, adjusted the lip position to centre it in the groove, and then printed it. It went together and works well.