Frequently Asked Questions

A linear shaft motor is a cylindrical, ironless direct-drive linear motor made by Nippon Pulse America. It produces linear motion through electromagnetic induction — the forcer (coil assembly) surrounds the magnetic shaft without ever touching it. Applying three-phase current to the forcer coils creates a traveling magnetic field that pushes or pulls the shaft, producing smooth, contactless linear force.

The key difference is geometry. A flat linear motor has a flat magnet track and a flat coil assembly that faces it from one side. A linear shaft motor has a cylindrical magnetic shaft running through the center of a tubular coil forcer — creating a 360-degree electromagnetic field all the way around. This cylindrical coupling is why linear shaft motors are approximately 50% more energy efficient than flat linear motors and why they produce zero cogging force.

Ironless means the forcer coil assembly contains no iron core. Most electric motors use iron to concentrate and guide magnetic flux, but iron also creates cogging forces — magnetic attraction between the iron teeth and the permanent magnets. An ironless design eliminates this entirely, producing perfectly smooth motion at any speed. The tradeoff is slightly lower peak force density, but the gain in motion quality is significant for precision applications.

Cogging (also called force ripple or detent force) is the uneven, jerky thrust that iron-core motors produce as the coil teeth move past the permanent magnets. It shows up as velocity ripple at low speeds and positioning errors in high-precision applications. Linear shaft motors have zero cogging — the ironless forcer design means there are no iron teeth to interact with the magnets, so the force is perfectly smooth across the entire stroke.

No. The forcer and shaft never make mechanical contact. The forcer surrounds the shaft with a small air gap, and all force is transmitted electromagnetically. This is why linear shaft motors have infinite mechanical life in the drive mechanism — there is nothing to wear out between the motor's moving and stationary parts.

Nippon Pulse linear shaft motors can reach speeds over 10 m/s depending on the model and control system. The speed is limited by the encoder bandwidth and servo drive capability, not by the motor itself. This is significantly faster than ball screws, which are typically limited to 0.5–2 m/s before resonance and critical speed become problems.

Sub-micron repeatability is achievable with the right linear encoder and servo drive. Because there is no mechanical linkage between the motor and the load — no screw, no coupling, no backlash — the encoder directly measures load position. Typical applications achieve ±1 micron or better repeatability.

Nippon Pulse linear shaft motors range from a few Newtons for small precision models up to approximately 950 N continuous thrust for larger forcers. Peak force is typically 2–3x the continuous rating. Force scales with forcer length — longer forcers contain more coil turns and produce more thrust. Custom configurations are available for higher force requirements.

Stroke length is determined by shaft length and is effectively unlimited. Unlike ball screws, which sag and resonate at lengths beyond 3–4 meters, linear shaft motors can use long shafts without resonance issues. Multi-shaft configurations can extend stroke further. The practical limit is the linear guide system, not the motor.

Because the 360-degree cylindrical magnetic coupling uses all of the magnetic flux from the shaft's permanent magnets — not just the flux facing one flat side. A flat linear motor only couples with the magnets on the surface facing the coil, wasting the flux on the other sides. The cylindrical design captures all available flux, reducing the current needed to produce a given force and cutting heat generation significantly.

The motor itself requires zero maintenance. There are no wear parts, no lubrication points, and no scheduled service intervals for the motor drive mechanism. The only maintenance in the system is for the linear guide bearing (which is a separate component), and whatever the application demands for the encoder and cables.

The motor drive mechanism has infinite mechanical life — because the forcer and shaft never contact each other, there is nothing to wear out. The practical system lifetime is determined by the linear guide bearing, electrical insulation, and connectors. Systems installed decades ago continue operating without motor replacement.

No. The motor itself needs no lubrication. The linear guide bearing that supports the load does require standard lubrication per the bearing manufacturer's specifications, but that is a separate component from the motor.

Yes. Because the forcer and shaft never touch, the motor generates no particulates from friction or wear. There is no lubrication that could outgas or drip. Linear shaft motors are widely used in semiconductor wafer handling, pharmaceutical manufacturing, and other cleanroom applications where contamination control is critical.

Yes, with appropriate motor variants. Nippon Pulse offers vacuum-compatible linear shaft motor configurations for use in electron beam, ion beam, and other vacuum environments. The non-contact design is inherently well-suited to vacuum — there is no outgassing from lubricants and no particulate generation from friction.

The key parameters are: required continuous thrust force (N), required peak force (N), maximum speed (m/s), stroke length (mm), duty cycle (%), move profile (acceleration, constant velocity, deceleration times), and load mass (kg). With these values, a Nippon Pulse engineer can recommend the right forcer model and shaft size for your application.

A high-resolution linear encoder is required — the motor does not have a built-in position sensor. Most applications use optical or magnetic linear encoders with resolutions from 1 micron down to 1 nanometer for nanopositioning applications. The encoder is mounted to the linear guide carriage and reads a scale fixed to the base. Nippon Pulse can recommend compatible encoder options.

Linear shaft motors work with any standard three-phase linear servo drive that supports sinusoidal commutation. Common compatible drives include those from Aerotech, Galil, Delta Tau, Copley Controls, and others. The motor requires a drive capable of field-oriented control (FOC) with encoder feedback. Contact Nippon Pulse America for specific drive compatibility.

Yes. Linear shaft motors can be oriented vertically. In vertical orientations, the drive must be sized to overcome gravity on the load in addition to the motion requirements. A counterbalance or brake is often added to hold position when power is off, since the motor produces no holding force without current.

Ball screws are the better choice when: (1) you need very high force at low speed and initial cost is the primary concern, (2) the application is cost-sensitive and precision requirements are modest, or (3) you need high force in a compact package where a ball screw's mechanical advantage is valuable. For everything else — speed, precision, cleanliness, maintenance-free operation, and long-term TCO — linear shaft motors lead.

Both are ironless, non-contact linear motors — but they serve different use cases. Voice coil actuators are single-phase devices optimized for short strokes (typically under 25mm), high frequency oscillation, and force control. Linear shaft motors are three-phase devices optimized for longer strokes, higher speeds, higher continuous force, and precision positioning. For strokes over 25–50mm or applications requiring both force and position control, linear shaft motors are typically the right choice.

In most cases, yes. A linear shaft motor replaces the rotary servo motor, coupling, ball screw, and ball nut as a single integrated direct-drive unit. The result is a simpler mechanical design, zero backlash, no maintenance on the drive mechanism, and typically higher speed and better positioning accuracy. A Nippon Pulse application engineer can help you evaluate your specific retrofit.