Lead screw vs. ball screw linear actuators
A lead screw actuator (LYNX LSA) converts motor torque to linear force through a sliding nut; a ball screw actuator (LYNX BSA) does it through recirculating balls. The ball screw is about twice as efficient, lasts longer under continuous duty, and costs roughly $175–$250 more per axis at the same travel. The lead screw is self-locking, quieter, and cheaper. For a vertical Z axis that must hold position with power off, choose the lead screw; for a horizontal axis cycling all shift, choose the ball screw.
The physical difference, and why it matters
Lead screw. A threaded nut slides on a threaded shaft. Friction is high — typical efficiency is 30 to 50% — so a good share of motor torque becomes heat, and the same friction means the screw will not back-drive: a vertical load stays put when power is removed. Wear is gradual and predictable; duty cycles above roughly 50% shorten life. Ball screw. Hardened balls roll between nut and shaft in a ground groove and recirculate through a return path. Efficiency is around 90%, so a smaller motor does the same work, heat is low, and life at continuous duty is several times that of a lead screw. The same low friction means a ball screw will back-drive under a vertical load — a brake or a holding motor is needed for Z. Ball screws cost more because the shaft is ground, not rolled, and the nut is a precision assembly.
| LSA lead screw | BSA ball screw | |
|---|---|---|
| Efficiency | 30–50% | ~90% |
| Back-drives under load | No — self-locking | Yes — brake needed on vertical axes |
| Continuous-duty life | Moderate; best under 50% duty | High; rated for continuous cycling |
| Backlash | Small, grows with wear | Near zero with a preloaded nut |
| Noise | Quiet | Audible ball recirculation |
| Leads offered (LSA45 / BSA45) | 1, 2.54, 6.35, 12.7, 25.4 mm | 5, 10 mm |
| Max speed | 20 mm/s (1 mm lead) to 500 mm/s (25.4 mm lead) | 100 mm/s (5 mm) to 200 mm/s (10 mm) |
| Rated load, NEMA 17 frame | 7 kg (to 12.7 mm lead), 1 kg at 25.4 mm | 7 kg (5 mm), 5 kg (10 mm) |
| Rated load, NEMA 23 frame | 15 kg (LSA60) | 15 kg (BSA60) |
| Repeatability | ±0.025 mm | ±0.025 mm |
| Price, 100 mm travel, inline stepper | $875 (LSA45) · $1,125 (LSA60) | $1,025 (BSA45) · $1,325 (BSA60) |
Choosing by application
Vertical Z axis, pick-and-place or dispensing. Lead screw. The self-locking nut holds the tool when power drops, the loads are intermittent, and the 6.35 mm lead gives 150 mm/s at 7 kg — enough for most lab and light-assembly Z moves. This is why every LYNXSYS gantry ships with an LSA on Z. Horizontal positioning axis cycling continuously. Ball screw. An axis indexing a conveyor or a test fixture several thousand times a shift wears a lead screw nut in months; the BSA runs years. Fine positioning under a heavy thrust load — pressing, clamping, micro-adjust. Lead screw at 1 or 2.54 mm lead. The low lead multiplies force and the friction holds the setting. Fast, long travel. Neither — that is a belt actuator (SBA), which reaches 850–2,500 mm/s and 1,275 mm of travel. See the belt-versus-screw guide.
Lead selection on a lead screw
Lead is the distance the nut travels per revolution, and it trades speed for force one-for-one. On the LSA45, a 1 mm lead moves 20 mm/s and carries 7 kg with large force margin; 6.35 mm gives 150 mm/s at the same 7 kg; 12.7 mm gives 300 mm/s but the rating drops to 5 kg; 25.4 mm gives 500 mm/s at only 1 kg. The price is the same for every lead, so the choice is purely engineering. The Engineering Decision Engine maps your target speed to the lead and then reports the payload margin that remains at that lead — which is how most lead-screw sizing mistakes (fast lead, heavy load) get caught before quoting.
Where the ball screw earns its price
Three places. Duty cycle above 50%, where the lead screw's friction heat limits it. Motor size, where 90% efficiency lets a NEMA 17 do what a lead screw needs a NEMA 23 for. And accuracy over time, where a preloaded ball nut holds near-zero backlash for the life of the axis instead of growing a few hundredths as the lead nut wears. If none of those applies, the lead screw is the better buy, and the engine will say so.
Size it yourself in about a minute
Type the task — payload, travel, speed — and the Engineering Decision Engine returns a validated, priced 3D system with the torque margins, inertia check, and cycle-time math shown. Free to design and quote.
Frequently asked
Is a ball screw more accurate than a lead screw?
Both LYNX families repeat to ±0.025 mm when new. The ball screw holds that over a longer life because a preloaded ball nut has near-zero backlash and wears far more slowly than a sliding lead nut.
Can a ball screw actuator be used vertically?
Yes, but it will back-drive when power is removed, so the motor must hold or a brake must be fitted. A lead screw is self-locking and is the usual choice for Z axes.
How much more does a ball screw actuator cost?
On the LYNX catalog, $150 to $250 more per axis at the same travel and motor: for example LSA45 100 mm inline stepper $875 versus BSA45 100 mm inline stepper $1,025.
Which lead should I pick on a lead screw actuator?
Pick the smallest lead that still reaches your required speed; a smaller lead gives more force and holding margin. The engine does this automatically from your speed and payload.
Can I get a lead screw or ball screw actuator with a servo?
Yes — LSA45, LSA60, BSA45 and BSA60 are all offered in parallel-mount servo versions at a $100 premium over the stepper.