FAQs

Are the wiring diagrams available for your motors?

Nippon Pulse stepper motors are available with either bipolar or unipolar windings. Bipolar motors have four leads, while unipolar motors have five or six leads. Additionally, some motors are designed with eight leads, so they may be connected in a variety of ways.

Connection Instructions

Fig 1. PF/PFC/PFCL series (Tin-can type) Bipolar

Fig 2. PF/PFC/PFCL series (Tin-can type) Unipolar

Fig 3. Eight-Lead Inner Connections and Rotation Direction

Fig 4. Eight-Lead Unipolar Drive

Fig 5. Eight-Lead Bipolar Parallel

Fig 6. Eight-Lead Bipolar Series

Are versions of the Linear Shaft Motor available for use in waterproof, vacuum or clean rooms?

Yes, the Linear Shaft Motor can be built for a variety of operating environments. To determine which Linear Shaft Motor is suitable for your application, contact an applications engineer to review your specifications.

Can a Linear Shaft Motor be mounted vertically?

Yes, a linear motor provides the same performance when mounted vertically or horizontally.  However, it is recommended that a vertically mounted Linear Shaft Motor be counterbalanced to reduce RMS and counteract the impact of gravity on the motion system.

Can I drive a unipolar stepper motor with a bipolar driver?

A six-lead stepper motor, which is a unipolar stepper motor, can be used when a bipolar drive is being used to run the motor. Since bipolar motors only need four wires to run, there are options in connecting a six-lead wire to a bipolar drive. Typically, we refer to the six wires as A, /A, A Common, B, /B, B Common. Half-coil connection would be to use A, A Common, and B, B Common (or /A, A Common, and /B, B Common). To use full-coil, also known as series connection, you would use A, /A and B, /B. For full-coil the two common wires are ignored. The full-coil connection (or series) is ideal for lower speeds requiring more torque. The half-coil connection will give an overall amount of torque across a wider range of speeds.

Can more than one forcer be used with a single shaft?

Yes, more than one forcer can be used in conjunction with a single shaft as long as the forcers do not physically interfere with each other. Two forcers may also be tied together and driven with one drive to double the output force.

Do magnets ever lose their magnetism over time?

The Linear Shaft Motors use rare-earth magnets, which are the strongest magnets available and produce magnetic fields that are significantly stronger than any other type of magnets. However, when operating at high ambient temperatures (>80°C), these magnets can lose strength. Lower temperatures have no effect on the magnets.

Do standard rotary motor electronics work with linear motors?

Yes they do. In most cases, the only differences between the two is the terms used in the software and manuals. For example, torque will become force; RPM will become velocity. A Nippon Pulse applications engineer would be happy to assist you in understanding the corresponding terms in your case.

How accurate are Linear Shaft Motors?

The Linear Shaft Motor is a high-performance, accurate motor. There is no need to convert rotary motion to linear motion, which is a major source of positioning error among rotary-to-linear systems. While the Linear Shaft Motor does not have inherent resolution, position accuracy is ultimately determined by the linear encoder feedback accuracy and the core stiffness of the motor. Testing has shown that, with encoder resolutions less then 10nm, the Linear Shaft Motor will, at worst, enable a position accuracy of ±1.2 pulses of encoder resolution. This position accuracy is not affected by the expansion and contraction of the shaft.

How can 4 wire, 6 wire and 8 wire motors be connected?

A 4-lead motor can only be connected to a bipolar driver. The 6-lead and 8-lead motors can be connected to either a unipolar or bipolar driver. See the wiring diagrams under "Are the wiring diagrams available for your motors?" to view the possible connections.

How can an encoder be used to determine position and speed?

There are many different types of encoders. The basic function of an incremental encoder is to output signals that help the control electronics determine the speed and direction of travel of the motor. The control electronics then use calculations to determine the relative position of the motor. The basic function of an absolute encoder is to output signals that help the control electronics determine the exact position of the motor. The control electronics then use calculations to determine the relative speed and direction of travel of the motor.

How do I calculate the number of teeth and the available step angle?

Nt = 360º / (S x Np )
or
S  = 360º / (Nt x Np )
Nt = Number of rotor teeth (must be an integer)
S  = Full step angle
Np = Number of mechanical phases (must be an integer)
      = Number of full steps to repeat the same mechanical line up
         between the stator tooth and the rotor tooth
Np = 4 for 2-phase bipolar motor
      = 10 for 5-phase bipolar motor
      = 3 for 3-phase unipolar motor

How do I check if my stepper motor has shorted or burned?

Use a multimeter to check the resistance of each phase. Check between Phase A and /A and then between B and /B. Check the data sheet provided to ensure there is no more than a 10 percent difference. Also, sniff the motor to ensure there is not a burnt smell. This operation is necessary when too much current or voltage is applied to the motor.

How do step accuracy and microstepping relate to each other?

Step accuracy is inherent in a motor's mechanical design and is controlled by the torque stiffness. Microstepping increases the number of steps required to move between each motor pole, but does not increase the step accuracy. Microstepping a motor without good step accuracy will not provide the smoothest motion.

How fast can the Linear Shaft Motor go?

The maximum speed is a two-step calculation. First, max acceleration is calculated by (acceleration = accl force / mass). Second, the maximum speed is calculated by (velocity = acceleration * time). Outside of this, the Linear Shaft Motor itself does not have inherent speed limitations.

There are several factors that can limit the maximum speed of a Linear Shaft Motor system. The control must provide sufficient bus voltage to support the speed requirements. The encoder must be able to respond to that speed, and its output frequency must be within the controller's capability. Finally, the speed rating of the stage's bearing system must not be exceeded.

How many steps per revolution does a 0.9, 1.8, 3.75, 7.5 and 15 degree motor have?

Steps per revolution equals 360° divided by step angle (0.9°, 1.8°, 3.75°, 7.5° and 15°).

  • 0.9° = 400 steps/rev
  • 7.5° = 48 steps/rev
  • 1.8° = 200 steps/rev
  • 15° = 24 steps/rev

These numbers are when the motors are driven in full-step excitation mode.

In a tandem or parallel drive-application, do both motors need Halls?

In the case where both forcers are connected to the same drive, no; only one motor needs Hall effects. In an application where two forcers are connected to the same drive, the same phase of each forcer must be above a like magnetic pole in order to run. As such, only one set of Halls is needed by the servo drive.

In the case of each forcer being connected to separate servo drives that require Halls, yes; you will need Halls on both motors.

In certain tandem forcer applications, why does one motor need to be physically flipped?

The physical flipping of one of the two forcers in a tandem configuration is sometimes used to reduce the overall footprint while maintaining the magnetic alignment of the two forcers.

Is the Linear Shaft Motor difficult to integrate into a machine?

One of the key design aspirations of the Linear Shaft Motor is simplicity. That simplicity extends to the integration process. As all systems are different, it is generally difficult to make specific statements about machine integration that hold true. A Nippon Pulse applications engineer would be happy to assist you with integration questions relevant to your individual project.

Should I worry about heat dissipation?

If your motor will operate in a confined space, or if you plan to run your motor beyond its rated capabilities, you should be concerned about heat dissipation in your application. If your motor is in a confined space, you should consider how the heat given off from the motor might affect nearby components and raise the ambient temperature. If you plan to run the motor above its rated specs, you should consider ways to cool the motor proportionally to keep it operating near its specified maximum temperature.

What advantages does the Linear Shaft Motor offer over traditional linear motion systems?

The Linear Shaft Motor is the first linear servomotor designed for a the ultra high-precision market and, as a result, has several advantages over traditional linear systems. The Linear Shaft Motor is compact and lightweight, has no cogging issues, is up to 50 percent more energy-efficient than traditional linear motors, and features a non-critical air gap, which reduces maching costs.

What are the advantages of the Linear Shaft Motor over a lead screw?

The advantages of the Linear Shaft Motor include higher velocities [>240 in/sec (>6 m/s)], non-wear moving part, free movement when power is off, no backlash because there are no mechanical linkages, easier alignments, and easier manufacturing.

What are the advantages of using stepper motors?

There are several advantages of using stepper motors. Speed can easily be determined and controlled by remembering speed equals steps per revolution divided by pulse rate. Stepper motors can also make fine incremental moves and do not require a feedback encoder (open loop). Stepper motors also have fast acceleration capability and have non-cumulative positioning error. Along with excellent low speed/high torque characteristics without gear reduction, stepper motors can also be used to hold loads in a stationary position without creating overheating. All stepper motors have the ability to operate on a wide speed range.

What does “Maximizing Torque at Desired Speed” mean?

Every stepper motor can be wound with more or fewer coils in order to change the characteristics of performance. Thus, if you need a certain amount of torque at high or low speeds, we would build the right kind of motor with the right number of coils in order to maximize the motor's ability to perform at its best in those ranges.

What happens if the system loses power or velocity feedback?

If a power loss occurs, the system loses all stiffness. So, if the payload is moving, it will continue to move until it hits a stop or until friction brings it to a stop. If the feedback loop is lost, it may lead to a runaway situation. This condition can be avoided with the use of soft and hard stops as well as braking systems.

What is a Linear Shaft Motor?

Linear Shaft Motors are direct drive linear servomotors that consist of a shaft with permanent magnets and a forcer of cylindrically wound coils.

What is a Stepper Motor?

It is a motor that uses input pulses to take proportional steps. These motors can be used for positioning and/or speed control in various applications. To change phases, steppers require power and sequence circuits.

What is cogging?

Cogging is a resistive torque or force caused by the interaction of a magnetic field with a ferrous (magnetic, iron-containing) material, even when there is no current present. Cogging causes jerky, uneven motion in servo systems.

Because our Linear Shaft Motor contains no ferrous material, it does not experience cogging effects.

What is continuous current? What is peak current?

Continuous current is the current that can be supplied from the driver indefinitely. The peak current refers to the maximum amount of current the driver outputs.

Non-microstepping drivers
Peak Current = Rated Current

When using a driver that only does full stepping, the rated current is the same as the peak current. (Rated current = Peak Current).

Microstepping Drivers
Peak Current = 1.4 x Rated Current

When using a driver that is capable of taking microsteps (at a rate of a half-step, fourth-step or any other fraction of a step), the definition of peak current becomes 1.4 times the rated current. Microstepping drivers are made differently in order to maximize their ability to drive the stepper motor. Therefore, step motors can handle up to their rated current multiplied by 1.4. (Peak Current = 1.4 x Rated Current). This will not damage the motor because the power output is more or less the same.

What is microstepping?

Microstepping increases the number of steps required to move between each motor pole by controlling the phase-current ratio. Microstepping allows a motor to run more smoothly and with less noise, though it does not improve step accuracy. When microstepping, you should always stop on either a multiple of the microstep or the full step position every time. This will allow the motor to stop at a magnetic pole, which is the rotor's natural position, giving you the best possible accuracy.

What is motor motion duty cycle for a motor?

Motion duty cycle is defined as (time moving/total time). It is possible for motor power duty to be 100 percent while the motor is not moving, or the motor's motion duty to be nearly 100 percent with very low motor power duty.

What is motor power duty cycle for a motor?

Duty cycle for a linear motor is different than for other types of systems. While it is defined as (time on) / (time on + time off) per cycle, in servo systems the motor can be on even when not in motion. Thus, for a servo motor, the duty cycle is based upon the time the motor is actually working (when current is applied) and NOT the percentage of time the motor is moving. It is possible for motor power duty to be 100 percent while the motor is not moving, or for the motor's motion duty to be nearly 100 percent with very low motor power duty.

What is RMS Current?

RMS stands for "Root Mean Square." It is the effective average current. It is most commonly used when referring to AC current.

What is system resonance?

To determine system resonance, take the square root of (torque stiffness divided by total inertia). Although resonance frequency cannot be completed eliminated, it can be changed by altering the rotor or system inertia or by altering the torque stiffness.

 

What is the difference between Holding Torque and Pull Out Torque?

Holding torque is the maximum torque generated to prevent the motor from moving. Pull out torque is the maximum dynamic torque that can be generated at a given speed to start the motor moving. Pull out torque varies at different speeds with different drivers and power input.

What is the difference between the PF, the PFC, and the PFCU motors?

The PF series is a flying lead version of our tin-can stepper motors. This series of motors can be built in any of our factories around the world.

The PFC series has a non-removable connector between the lead wires and motor. This allows for automated machine production of the windings. This series is typically only produced in our factories in Japan and China.

The PFCU series has a molded housing and a removable wiring harness. This allows for fully automated machine production of the full motor. This series is typically only produced in our factories in China.

We are able to produce small volumes of the PF series stepper in our U.S. model shop, but the PFC and PFCU series must be built in one of our overseas factories.

PF
  • PF = Flying lead joint type
  • Manual lead lead-wires assembly
  • Can be built in any of the NPM
    factories around the world
PFC
  • PFC = Connector joint type
  • Automatic motor lead lead-wires assembly
  • Only built in Japan and China

PFCU
  • PFCU = Molded joint type
  • Fully automated motor production
  • Only built in China
 

 

What is the difference between Unipolar and Bipolar?

Unipolar motors have two windings per coil, though they only employ one winding at a time. Each coil only ever has one polarity, always acting as either a north or south electromagnet, and must be switched on and off to create movement. This makes the drive electronics very simple. Unipolar motors are preferred for high-speed applications because they do not need the current to decay in one winding before the opposite polarity coil can be energized.

Bipolar motors, on the other hand, only have one winding per coil, and switch polarity to create movement. This means the current must fully decay in order to switch polarity and create movement. The drive electronics for bipolar motors are slightly more complicated than those for unipolar motors. Bipolar motors are preferred for lower-speed, high-torque applications.

What is the minimum number of steps to get the best accuracy?

Due to resonance, it can be very difficult for a stepping motor to make only a single step. As such, the best results are seen when the motor moves at least one electrical cycle. For Nippon Pulse's stepping motors, this will be four full steps.

When using half-stepping or microstepping drives, multiply the level of microstepping by 4. Example: 1/16 microstepping would mean 16*4=64 steps.

In addition, when microstepping you should always stop on either a multiple of the microstep or on the full step position every time. This will allow the motor to stop at a magnetic pole, which is the rotor's natural position, giving you the best possible accuracy.

What is the MTBF (Mean Time Between Failure) for the Linear Shaft Motor?

The Linear Shaft Motor components operate in a passive manner when properly designed into your system. As such, there is no MTBF on the motor.

Any installation that causes any component of the motor to be active (example: flexing of supplied lead wires, using shaft or forcer as load-bearing member, etc.) is beyond the intended design of the Linear Shaft Motor. This will void the warranty and is done at your own risk.

With the proper settings, the Linear Shaft Motor will not wear out.

What is the reliability of the Linear Shaft Motor?

The Linear Shaft Motor is a non-contact device. As such, it does not have any parts that can wear out. If the system is designed properly and the operating parameter limits are not exceeded, the Linear Shaft Motor should last indefinitely.

What routine maintenance is required for Linear Shaft Motors?

The Linear Shaft Motor itself is entirely maintenance-free. Because of its simple structure, the Linear Shaft Motor does not have any parts that can wear out. However, Nippon Pulse recommends you perform periodic inspections on all systems, including the bearings and supports. See the Maintenance and Service section of the Installation and User's Guide for details about the recommended inspections.

Why can I run step motor drivers at higher voltages than what my step motor is rated?

Most stepping motors are driven using current-controlled drives (such as PMW or chopping drives), as opposed to voltage-based drives. The rated voltage can be exceeded by the bus voltage on a current-controlled drive as long as the current setting for the drive keeps the current low enough to prevent the coils from burning up. Stepper motors typically have a current label because they are usually current-driven.

Will the step motor heat up if it stalls?

No. A stepper motor does not draw any increased current when in a stalled position.