Folding desk lamp for a USB LED puck
An architect-style desk lamp built around a cheap USB LED puck. A twin-bar lower arm and a slim upper blade fold flat or reach out, the head tilts, and the whole arm swings on a turret that turns on the base. Each joint is a plain M4 bolt with a spring washer and a nylock nut, so it holds wherever you leave it. The USB lead snaps into channels along the arm, loops round each joint and leaves under the base at the back. The checks prove the lead never bends tighter than five times its thickness in any pose, each hinge holds at least twice the arm's weight at full reach while still moving with a light push, and with coins or washers in the base the lamp stays standing and the arm gives way before it tips.
Ask for the sizes you want to tweak, e.g. “make the width adjustable”.
Specs at the default size
Measured from the actual build on a Bambu Lab A1 in pla. Every number updates live when you drag a slider above.
- Overall size
- 280 × 160 × 220 mm
- Parts
- 7
- Filament
- 221 g
- Print time
- 5 h 31 min
- Build plates
- 2
- Supports
- Some parts
Engineering checks
- Lead lies free in its channels in every poseworst overlap 0.00 mm3 over 6 poses
- Lead bends gently in every posetightest bend 17.5 mm = 5.0x the 3.5 mm lead (folded 17.5, rest 17.5, reaching 17.5, rest, head up 75 deg 17.5, reaching, head up 17.5, folded, head up 17.5)
- Fixed run bends gently14.0 mm (4.0x) down the ear, across the turret axis and under the base, where the lead never flexes
- Lead slides to follow the armthe arm run changes 52 mm between poses (373-424 mm); every seat is 1.5 mm wider than the lead and the mouths only stop it falling out, so it slides; leave 80 mm of slack behind the base
- Lead leaves low at the backexits under the base rim at the back, 2.6 mm above the desk
- Puck fits its pocketpocket 60.6 mm for a 60 mm puck; it rests on the 45 degree cone, no contact with the walls
- Puck held by the bezelbezel lip covers 3.0 mm of the puck rim all round; 0.45 mm float between cone and bezel; three M2 screws into heat-set inserts in a 5.6 mm rim
- USB plug threads through the head and the postplug 16.5 x 8.5 mm (18.6 mm across) through a 21 mm apex opening and a 28 mm post bore
- Lead snaps into the arm and stayslower arm: lips leave a 3.0 mm mouth over a 8.4 mm seat; upper arm and ear: a 3.0 mm mouth over a 5.0 mm groove
- Friction hinges hold the arm in every poseshoulder 0.72 N m vs 0.365 N m (x2.0); elbow 0.90 N m vs 0.187 N m (x4.8); head 0.25 N m vs 0.035 N m (x7.2); mu 0.3 PLA on PLA, 6.0 mm mean friction radius, clamp 200/250/70 N
- Moves with a light push3.6 N at the head swings the whole arm at full reach; 4.3 N on the shade rim tilts the head
- Hinge bolts and bores take a knock20 N knock on the head: 0.63 MPa on the 8 mm blade bore, 0.8 MPa shear in the steel M4
- Clamp does not crush the knuckles0.95 MPa on each knuckle face at 200 N; PLA allows 5.0 even across the layers
- Links outlast the hingesat the slipping torque: lower bars 3.4, upper blade 6.1 MPa (along the layers, allow 16.7); ear root 1.5, head cheeks 1.7 MPa (across the layers, allow 5.0); Kt 1.49
- Stays standing at full reachcentre of mass 29 mm from the axis, rim at 79 mm, with 652 g of coins or washers in the pocket (1015 g lamp); takes 2.6 N pressed down on the head to tip; needs at least 45 g of ballast
- Pushing the head down moves the arm before the lamp tipsat full reach the shoulder gives at 1.13 N on the head; tipping needs 2.62 N (x2.3)
- Collar holds the turret downcollar overlaps the turret's ledge by 5.8 mm all round; two M3 into heat-set inserts in the post
- Head tilts its full rangeshade clears the upper arm tilted 75 deg forward (overlap 0.00 mm3)
- USB LED puck goes in20 poses along its path clear of every part.
- ballast: coins or steel washers goes in20 poses along its path clear of every part.
- USB plug through the head goes in30 poses along its path clear of every part.
- USB plug through the post goes in30 poses along its path clear of every part.
- driver: hinge bolts goes in20 poses along its path clear of every part.
- driver: collar screws goes in20 poses along its path clear of every part.
- driver: bezel screws (bench) goes in20 poses along its path clear of every part.
Adjustable sizes
| Setting | Default | Range |
|---|---|---|
| Arm link length | 160 mm | 130–180 mm |
| Base diameter | 160 mm | 160–200 mm |
| Head tilt range | 75 deg | 40–110 deg |
| LED puck diameter | 60 mm | 50–70 mm |
Parts list
| Part | Qty | Size (mm) | Filament | Time |
|---|---|---|---|---|
| base | 1 | 160 × 160 × 26 | 102 g | 2 h 19 min |
| turret | 1 | 136 × 136 × 50 | 59 g | 1 h 25 min |
| collar | 1 | 56 × 56 × 4 | 5 g | 11 min |
| lower arm | 1 | 177 × 18 × 17 | 18 g | 30 min |
| upper arm | 1 | 161 × 8 × 17 | 9 g | 18 min |
| head | 1 | 72 × 72 × 54 | 22 g | 38 min |
| bezel | 1 | 72 × 72 × 2 | 4 g | 10 min |
How to make it
- Set the arm length, base size, head tilt and your puck's diameter with the sliders; the checks rerun for every size.
- Print the seven parts in PLA, press in the heat-set inserts (two M3 in the base post, three M2 in the shade rim) and fill the base pocket with coins or steel washers.
- Thread the puck's USB plug up through the hole in the shade, screw the bezel on, then bolt the head, upper arm, lower arm and turret together with M4 x 25 bolts, spring washers and nylock nuts.
- Press the lead into the arm channels, drop the plug down through the hollow post, lay the lead in the groove under the base, and tighten each nut until the joint holds its pose.
Print tips
- Print both arms lying on their straight back edge so the layers run along the arm; the bolt holes are shaped to print without support.
- Print the shade mouth-down: the inside is a 45 degree cone, so it needs no support either.
- Use about 15% infill for the base and turret; the weight comes from the coins or washers, not the plastic.
FAQ
Which LED puck does it fit?
Any round USB puck light about 50 to 70 mm across and 10 mm thick with the lead coming out of the back. Set the puck diameter slider to match yours.
How tight should the hinge nuts be?
Snug, then about a quarter turn more so the spring washer is partly squashed. If the arm droops at full reach, give the shoulder nut a little more.
Does it need weight in the base?
Yes. About 650 g of coins or steel washers fill the pocket under the turret; with that the lamp stays put even with the arm fully stretched out.
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