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Printed parts
NEMA17 Leadscrew Push-Pull Actuator
A compact linear actuator for props and animatronics. A NEMA17 turns a T8 leadscrew, and a carriage on twin 8 mm rods pushes and pulls through a clevis with about 120 mm of travel.
This is a short-travel linear actuator you bolt down and drive. A NEMA17 stepper turns a 200 mm T8 leadscrew through a printed 5-to-8 mm coupler. A carriage rides on two 8 mm rods on LM8UU bearings, carries the brass T8 nut and moves about 120 mm end to end. On top of the carriage is a clevis tower with an M3 pin, so you can attach a pushrod, a cable or a linkage. It's built for animatronics and prop makers, and for anyone who needs a slow, strong, self-locking push/pull motion that holds position with the power off. It uses only standard parts: a NEMA17, T8 leadscrew, 8 mm rod, LM8UU and a 608 bearing.
The frame is two end blocks joined by the two rods. The motor block holds the NEMA17 face and clamps one end of each rod. The idler block clamps the other rod ends and holds a 608 bearing that supports the far end of the leadscrew. Each block has a foot flange with M5 slots, so you can mount it on 2020 extrusion with M5 T-nuts or on a board with #8 wood screws. The carriage is a 30 mm-long block with LM8UU press-fit pockets. It holds the T8 nut in four radial slots, so any flange hole pattern from 15 to 23 mm PCD fits. The carriage's top face has a 20 x 20 mm M3 heat-set pattern (the same as an MGN12H carriage), so the clevis tower or any of your own tooling bolts on.
Assembly order:
- Press the heat-set inserts into both end blocks (4 rod clamps) and the carriage top (4).
- Press the 2 LM8UU bearings into the carriage and the 608 bearing into the idler block.
- Bolt the NEMA17 to the motor block with 4x M3x10. Slide the coupler onto the 5 mm shaft and tighten its set screw.
- Thread the T8 nut onto the leadscrew. Screw the nut flange to the carriage's slotted face, with the nut body inside the carriage.
- Push both rods through the carriage and seat them 16 mm deep in the motor block sockets. Lock them with M3 grub screws.
- Feed the leadscrew into the coupler's 8 mm bore and tighten its set screw. Slide the idler block over the rod ends and the leadscrew until the 608 seats. Lock the rods.
- Bolt the clevis tower to the carriage top with 4x M3x10. Screw the feet down to your base.
Tuning notes: Tighten the rod grub screws only after the carriage slides freely along the whole stroke. If the carriage binds near one end, loosen the idler block, let the leadscrew centre itself in the 608, then re-lock. With a standard T8 (8 mm lead) screw, one full motor turn moves the carriage 8 mm, which is 25 steps/mm at full step on a 200-step motor. Set end stops in firmware, or home against the motor block.
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