NEMA17 Belt-Drive Camera Slider

This is a motorized linear camera slider for time-lapse and product shots. Two 8 mm smooth rods sit 60 mm apart between a motor end block and an idler end block. A carriage rides the rods on four LM8UU linear bearings, two per rod, which answers the common complaint that single-608 sleds sag under a camera. A NEMA17 sits on top of the motor end block with its shaft pointing down. It turns a GT2 20T pulley, and a 6 mm GT2 belt runs flat just below the rods, around a printed flanged idler drum on two 625 bearings. One run of the belt is clamped to a tab under the carriage. The other run passes freely underneath it. The carriage deck has a 1/4 in camera-screw slot and four M3 heat-set inserts on a 40 mm square for a ball head or accessory plate. Rod length is up to you. A 500 mm pair gives about 360 mm of travel.

Every hardware interface uses verified standard sizes: the NEMA17 31 mm bolt square and 22 mm pilot, 8 mm rod, LM8UU, 625 bearings, M3 and M5 fasteners and GT2 belt. The two end blocks and the carriage are the structure. The idler drum and the belt clamp plate are the small moving and clamping parts. Both end blocks print lying on their outboard face, so the rod sockets print as vertical blind holes. The carriage prints deck-down.

Assembly order:

1. Press M3 heat-set inserts into the rod pinch holes of both end blocks (4), the carriage belt tab (4) and, if you want them, the carriage deck (4).
2. Press the four LM8UU bearings into the carriage bores, flush with each end.
3. Press two 625 bearings into the idler drum, one from each end.
4. Bolt the NEMA17 to the top of the motor end block with 4x M3x10. Slide the GT2 20T pulley onto the shaft through the pilot hole so the teeth centre about 22 mm above the bench, then tighten the grub screws.
5. Push an M5 nut into the hex pocket under the idler block fork. Fit the drum in the fork with one M5 washer on top, then drop in the M5x35 bolt from above.
6. Slide both rods through the carriage. Seat the rods 25 mm deep in each end block and lock them with M3x8 pinch screws.
7. Loop the belt around the pulley and the drum. Lay both belt ends teeth-in against the carriage tab, pull the belt snug and clamp it with the belt clamp plate and 4x M3x12.

Tuning notes: Set belt tension at the clamp. Tighten one side's screws, then pull the free end until the belt pings, and tighten the other side. Pulley height depends on your motor's shaft length. The clamp holds the belt within ±1.5 mm of Z=22, and you can move the drum up or down with M5 washers. Run the NEMA17 from any stepper driver (A4988/TMC2208) and controller. At 1/16 microstepping, 80 steps are 1 mm of travel (200 × 16 / (20 × 2)). Stick rubber feet under the end blocks.