Category Archives: White Papers

Motion Control White Paper – Unlocking the Linear Motion Specification Query

Motion Control – White Paper – Linear Motor Specifications

Understanding the specifications needed to properly size my motion control application –  

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Santa Clarita, CA —– Motion Control Tutorial – Every motion control problem begins with a need to move a certain payload over a certain distance. However, there are many types of moves possible, and determining the right motion control solution may require some calculations to match the specifications found on a given motors data sheet. Most sales engineers will ask you for three basic questions when directing you to the proper motor or motion control solution. What is the stroke or displacement required What is the force or thrust required? At what duty cycle do you plan on operating the motor? Travel Distance The travel distance is the first piece of information needed to unlock any specification, because a solution to move a few microns would utilize different motion technology from an application requiring several meters of travel.

Motion Control White Paper – Unlocking the Linear Motion Specification Query

Motion Control White Paper

motion control- h2w
Understanding the specifications needed to properly size my motion control application –

Santa Clarita, CA —– Motion Control Tutorial – Every motion control problem begins with a need to move a certain payload over a certain distance. However, there are many types of moves possible, and determining the right motion control solution may require some calculations to match the specifications found on a given motors data sheet. Most sales engineers will ask you for three basic questions when directing you to the proper motor or motion control solution. What is the stroke or displacement required What is the force or thrust required? At what duty cycle do you plan on operating the motor? Travel Distance The travel distance is the first piece of information needed to unlock any specification, because a solution to move a few microns would utilize different motion technology from an application requiring several meters of travel. In addition to understanding the total travel required, it would be necessary to determine whether the travel is oscillatory, constant velocity, or the motion profile is defined by a pick-and-place application. Oscillatory systems typically will move back and forth at a specific frequency or range of frequencies. While constant velocity systems either need to operate for a known distance or time at a constant velocity, or they need to get a payload up to a velocity, in these cases the distance and time to accelerate up to the velocity needs to be understood and accounted for in the overall displacement. With this information you can determine the acceleration necessary to make the move. To learn more about calculating acceleration you can read our white paper about calculating acceleration for linear motion. Force

The next step is determining the amount of thrust or force required. Force is simply the amount of acceleration multiplied by the mass of the moving object. If the motion is horizontal, this equates to the mass of the payload added to the mass of the moving part of the linear motor or stage and multiplied by the amount of acceleration required by the motion. Vertical applications must add or subtract the acceleration due to gravity depending on the direction of motion.

motion control specification formula Duty Cycle

Finally, how long is power going to be applied to the motor? Many oscillatory systems will be operating continuously, and thus would have a duty cycle of 100%, while other applications will be short bursts of power, 1 second or less, while being off for several seconds, and will have a duty cycle of less than 10%. Duty cycle is defined as the time on divided by the total time per cycle (time on + time off). Depending on the linear motor selected, the amount of force available at a duty cycle of 10% can be as much as 3 times the continuous force rating. This last piece of the puzzle helps break down the necessary components required to properly size any motion control problem.

motion control specification formula - Duty Cycle

Once these three pieces are determined, any application can be sized and verified that it is sufficient based on the specifications found on any standard data sheet.   About H2W Technologies, Inc. H2W Technologies, Inc. is dedicated to the design and manufacture of linear and rotary motion products that are used in the motion control industry. The complete line of linear electric motors includes: Single and dual axis linear steppers, DC brush and brushless linear motors, voice coil actuators, and AC induction motors. Also offered is a complete line of ball screw, lead screw and belt driven positioning stages. Other motion control products include: Limited angle torque motors for compact, limited angular excursion rotary servo applications, 3 phase brushless rotary servo motors with matching digital servo amplifiers and permanent magnet linear brakes for fail-safe, zero power braking for baggage handling and people moving applications as well as amusement park rides. With over 75 years combined experience in the linear and rotary motion field, the H2W Technologies team of engineers offers the optimal solution to the most demanding motion control, requirements. For other Motion Control Components, Applications, and Technology from H2W Technologies visit: http://MotionShop.com For additional information contact Mark Wilson at H2W Technologies, 26380 Ferry Ct, Santa Clarita, CA 91350; Tel: 888-702-0540, Fax: 661-251-2067, E-Mail: info@h2wtech.com or visit the website at http://www.h2wtech.com


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Linear Motion – Voice Coil Actuators vs. Solenoids: What is the difference?

Linear Motion – White Paper

The question of whether to use voice coil actuators or solenoids for small displacement motion control applications comes up often.  This article explains the key differences between each product and why you might choose one over the other for your applicationA non-commutated DC linear actuator, typically referred to as a voice coil, is capable of a displacement in excess of 5 inches.  In addition, voice coil actuators, can move bi-directionally, and has a constant force over the stroke and can be used for closed loop position and force applications.

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A solenoid can generate high forces at very short strokes, however it requires a spring return because they are operated unidirectional and the force output declines rapidly through the total displacement, and therefore are normally used only for short strokes, not typically longer than 0.5 in.  The typical application for a solenoid is the simple opening or closing of a switch or valve, and are not typically used for force or position control applications.

A voice coil generates a force based on an interaction of a current carrying conductor in a permanent magnetic field.

H2W-Voice Coil Illustration

A solenoid generates force based on an electromagnetic field that is created by a current carrying conductor.

H2W-Solenoid-Illustration

What is a Voice Coil Actuator?

Voice coil actuators or non-commutated DC linear actuators consist of a permanent magnetic field assembly (permanent magnets and ferrous steel) and a coil assembly.  The current flowing through the coil assembly interacts with the permanent magnetic field and generates a force vector perpendicular to the direction of the current.  The force vector can be reversed by changing the polarity of current flowing through the coil.

The force generated by the voice coil is proportional to the cross product of the current flowing through the coil and the magnetic flux in the permanent magnetic field, as dictated by Lorentz’ force equation.  Either the coil assembly or permanent magnetic field assembly can be used as the moving member in a voice coil actuator.

The force generated is relatively constant throughout the stroke of the actuator, with minor dips at the beginning and end of the travel length.

Voice coil actuators are typically used in focusing applications, oscillatory systems, mirror tilting, and miniature position control.

What is a Solenoid?

Solenoids consist of a coil that is contained in a ferrous steel housing and a movable steel slug or washer.  An electromagnetic field is generated by current being applied to the coil.  The magnetic field intensity determines the amount of force that can be generated by the solenoid.  When the power is turned off, the force drops to zero and the spring returns it to its extended position.

The forces are initially high, but as the stroke increases the force decreases.

Solenoids are typically used to open latches or open or close valves, and are either used to apply a holding or latching force.

Comparison

  Voice Coil Actuator Solenoid
Force Low to medium High
Stroke 5 inches maximum ¼ inch maximum
Constant Force Yes No
Reversible Yes No
Position/Force Control Yes No
Cost Moderate Low

Should I select a Voice Coil Actuator or a Solenoid?

If your application simply requires opening or closing a valve a solenoid might be an option, however they have limitations when it comes to force linearity and stroke length.

Due to the fact that voice coil actuators typically cost more than an off-the-shelf solenoid, many customers try and use a solenoid when a voice coil actuator is the more appropriate solution.  Some applications require a constant force throughout the travel length, and in these situations a solenoid is insufficient due to the diminished force through the travel, while a voice coil actuator provides constant force.  This is particularly important in oscillatory systems.  Another advantage that the voice coil provides is force control, without a feedback device, because the force output (at any position in the stroke) is directly proportional to the current input.

This type of actuation lends itself to generally a higher force density, thus achieving higher strokes and forces in a smaller package size to the solenoid counterparts.

H2W Technologies, Inc. is dedicated to the design and manufacture of linear and rotary motion products that are used in the motion control industry. The complete line of linear electric motors includes: Single and dual axis linear steppers, DC brush and brushless linear motors, voice coil actuators, and AC induction motors. Also offered is a complete line of ball screw, lead screw and belt driven positioning stages.

Other motion control products include: Limited angle torque motors for compact, limited angular excursion rotary servo applications, 3 phase brushless rotary servo motors with matching digital servo amplifiers and permanent magnet linear brakes for fail-safe, zero power braking for baggage handling and people moving applications as well as amusement park rides.

With over 75 years combined experience in the linear and rotary motion field, the H2W Technologies team of engineers offers the optimal solution to the most demanding motion control, requirements.

For additional information contact Mark Wilson at H2W Technologies, 26380 Ferry Ct, Santa Clarita, CA 91350; Tel: 888-702-0540, Fax: 661-251-2067, E-Mail:info@h2wtech.com or visit the website at http://www.h2wtech.com

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Linear Bearing Engineers Design Camera Sliders for the Pro and Beginner!

Designed by Linear Bearing Engineers Camera Sliders for the Beginner and the PRO

PRODUCTS | CONTACT US | NEWS | VIDEOS | Designer Spotlight | Artist Spotlight | NEW SLIDER

The difference between rolling and sliding friction in camera sliders. Mike Quinn

Take a quarter and roll it on its edge across a table – goes forever and moves quickly. Now take that quarter and lay it on its side and push it…that’s the difference. Sleeve bushings inherently have much more surface area under load. Simply put, they have big feet. Conversely, a ball and roller have much smaller feet ensuring them a meaningfully lower co-efficient of friction. A ball offers point contact loading and loosely reside in 4 rows within a steel or plastic shell:

ball

These balls literally kick each other along as the balls roll down the shaft. Because they have so little contact area, the coefficient of friction is as low as .001 – they roll easily and smoothly. The drawbacks in a camera slider are readily recognizable:

1. Resonance – noise – ZING! ZING! ( Metal on metal contact and because they push each other from load to preloads, they create resonance, noise and vibration.
2. They are made from steel and can rust – they require lubrication.

Rollers have internal ball or needle bearings at their core, between the inner and outer race. They are separated in a retainer, unlike linear ball bushings which run loose in their track ways.

roller roller

These are sealed and lubricated for life. They have more contact area but the coefficient of friction remains low approximately .003 – not as low as the ball – but very close. These rollers come in dual angular contact ( gothic arch ) or V geometries. They are very smooth, take high loads/moment loads ( overhanging loads )and provide great stiffness. They are however steel and they run on steel shafting or V groove rails. They can produce noise and are vulnerable to the elements.

Plastic Sleeve Bearings are truly all weather and can run very smoothly and tolerate debris. However, the real world coefficient of friction is around .2 – factors higher than ball and rollers. They are also prone to a phenomena called edge loading. This effect can cause the carriage plate ( slider ) to ratchet or get sticky due the bearings digging into the shaft. This is particularly troublesome when you attempt to slide the carriage plate with top heavy rigs like a DSLR with a Red Rock system. You will need two hands.

There is an answer…Camera Motions new ” Silent Slider “

Why? Because we offer a solid, 1 piece precision machined aluminum carriage block that is black anodized. Not an extrusion that is cheap and has varying tolerances one lot to another. We have selected the best industry urethane cam followers with needle bearing rollers – tight and true. Moreover, the rollers damp any noise or vibration yet hold a 25 pound load. Smooth, quiet and solid. The Silent Slider is a product of linear motion engineering – pure and simple. It was was designed to run on a 16mm twin extruded rail which is ubiquitous in the the camera slider industry. Keep your rail and tripod shoe and move to the future – The” Silent Slider!”

Let engineering win – not salesmen. Only $ 230.00. Call Mike Quinn @ 1-800-698-5820.