Category Archives: Tutorials
Motion Control – Steinmeyer Tutorial Series – Ball Screws – Explaining Load Capacity!
Motion Control – Ball Screw Tutorial
Tutorial presented by Steinmeyer – Many engineers are confused about this topic, especially if they don’t work frequently with ball screws. So let’s take a moment to explain the terminology.
BURLINGTON, MA — There are generally two load capacities given for a particular ball screw: Dynamic and Static.
Dynamic Load Capacity
The dynamic load capacity (DLC) is simply a load rating. It’s the load for a (theoretical) life of 1 million revolutions (ISO/JIS standard) or for 1 million inches of travel (ANSI standard). The DLC is critical for making lifetime calculations, since the expected life goes as the cube of the ratio of DLC to actual load. So, if the load is only 10% of DLC, then the expected life is 1 billion revolutions.
But that still doesn’t mean you could run the screw with this kind of load and expect a to achieve that life! Why? The normal maximum operating load of a general use ball screw is about 30% of the DLC. (Above that, the elastic deformation of the balls and races is too large, which may cause excessive wear.) So, if you run a ball screw with a load equal to its DLC, you may not get as much life as you expect.
Static Load Capacity
The static load capacity (SLC) indicates the load above which the screw may be damaged. Staying below SLC ensures that balls and races don’t suffer brinelling (or plastic deformation). This is critical! But bear in mind that a ball screw may be damaged in other ways with loading below the SLC: you could easily tear off the flange of the nut, snap the bearing or drive journal of the screw, or even collapse it from exceeding the buckling load.
About Steinmeyer
Steinmeyer is the world’s longest continuously-operating manufacturer of commercial ball screws. In the realm of linear motion control, our company has become synonymous with precision, innovation, and exacting standards of quality.
Steinmeyer’s extensive product line is used widely in drive systems for industrial machines as well as precision positioning in optical instruments, medical devices, and mechatronic applications.
Contact Steinmeyer for further information on their extensive product portfolio:
781-273-6220
Visit Steinmeyer.com
Steinmeyer Ball Screw Resource Center
See this and other Motion Control Ball Screws, Stages, Technology Notes, Custom Components from Steinmeyer featured on:
http://MotionControlBlogger.com
http://motioncontrolBuyersGuide.com
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Steinmeyer -BallScrew-Tech Blog
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Motion Control White Paper – Unlocking the Linear Motion Specification Query
Motion Control White Paper
Understanding the specifications needed to properly size my motion control application –
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Santa Clarita, CA —– 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.
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.
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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FDA/USDA and 3A-Dairy Compliance Brochure features Linear Motion Components from LM76!
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E. Longmeadow, MA — Motion Control Components – Linear Motion – Food processing and beverage plants’ wash down areas are unique environments that undergo harsh treatment from high pressure washers, steam, and a multitude of caustic chemicals used in the cleaning and sanitizing production equipment. OEMs and maintenance departments need to select components that will not trap contaminating debris and can be thoroughly evacuated following Sanitation Standard Operating Procedures (SSOPs). SSOPs are detailed schedules and procedures specifying what to clean, how to clean, how often to clean, and the record keeping used for monitoring.
A helpful component selection guide from LM76, “Linear Bearings, 6 Simple Steps – FDA Compliance, Wash Down Compliance,” details the linear motion components available from LM76 that are FDA/UDSA/3A-Dairy compliant. Included are: Foodstream electrodeless nickel plated pillow blocks, PTFE lined stainless steel bearings, ceramic coated linear bearings, self-aligning corrosion resistant linear ball bearings, and Thomson® Super SmartTM corrosion resistant, self-aligning, high load linear ball bearings. Shafting to compliment the type of bearing selected includes: Class L Stainless 303/304/316, 440C case hardened stainless, Rc 60 case hardened steel with an Armoloy coating and also Rc78 Class L for enhanced hardness and wear resistance. End blocks and shaft supports that have a ceramic or electrodeless nickel coating are also available, as well as new ETX Scraper Seals that prevents intrusion of contaminates adding another line of defense.
LM76 also designs and custom builds linear slides from Stainless Steel and other FDA wash down compliant materials
Shafting options include: Solid and hollow Class L RC60, 300 series stainless steel in lengths to 12 feet. FDA/USDA/3A-Dairy compliant, shafting features: Excellent corrosion and chemical resistance, custom machining to print, pre-drilling and assembly.
About LM76
Founded in 1976, LM76 has been a leading designer/manufacturer of linear bearings, slides and linear motion systems. LM76 is renowned for its industry leading Minuteman PTFE Composite linear bearings. LM76 is a leading supplier of precision linear shafting: RC60, 300 Series Stainless Steel, and ceramic-coated aluminum shafting. LM76 also offers several FDA/USDA compliant linear bearings and slides for the food processing, pharmaceutical, medical, and packaging industries.
For additional information contact Mike Quinn at: LM76, 140 Industrial Dr., E. Longmeadow, MA 01028; Telephone: 413-525-4166, Fax: 413-525-3735 or E-Mail: mquinn@lm76.com or visit the website at http://www.lm76.com
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Motion Control Tutorial – Slotted vs. Slotless Motor Technology
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Motion Control Tutorial –
When first introduced, brushless DC motors, despite their many advantages, were cast as a costly alternative to brush-commutated motors and were typically only specified for low-power applications where long life was the primary desired requirement. Without the mechanical brush-commutator mechanism that would wear and eventually result in motor failure, brushless motors could be relied upon to deliver performance over time. As for other advantages, conventional wisdom held that brushless motors provide high speed and fast acceleration, generate less audible noise and electromagnetic interference, and require low maintenance. Brush-commutated motors, on the other hand, would afford smooth operation and greater economy. In the past decade, though, brushless motors have gained broader appeal and greater acceptance in industry for a wider range of applications previously dominated by brush-commutated products, due in part to dramatic reductions in the cost and size of electronic components and advances in motor design and manufacturing.
At the same time, manufacturers have further sought to challenge conventional wisdom by improving brushless motor design in an effort to combine the traditional advantages of brush-commutated and brushless types. A noteworthy example of how far these innovations have progressed involves the slotless (instead of slotted) construction of the brushless motor’s stationary member, or stator.
The slotless stator design originated with the goal to deliver smooth running performance and eliminate cogging, which is an unwanted characteristic especially in slower-running applications (less than 500 rpm). The absence of cogging is, in fact, the most-often cited reason for selecting a slotless brushless motor.
Slotted Motor Construction
Most brushless motors (slotted or slotless) use electronic commutation, usually Hall-effect sensors and magnets, in place of brushes. The motor’s rotor consists of a steel shaft with permanent magnets or a magnetic ring fixed around the circumference of the shaft. The magnets are responsible for producing torque. As the flux density of the magnet material increases, the amount of torque available from the rotor assembly increases.
In traditional slotted brushless motors, the stator features a group of slotted steel laminations (0.004 in. to 0.025 in. thick), which are fused to form a solid uniform stack and create a series of teeth. Wound copper coils, which produce electromagnetic fields, are then inserted into each of the slots. Together, the laminated stack and wound copper coil form the stator assembly. The return path completing the magnetic circuit consists of the laminated material outboard of the copper windings in the stator and the motor housing.
These brushless slotted motors are especially powerful, because the teeth around which the copper wire is wound place the iron closer to the magnets, so the magnetic circuit is completed more efficiently. As the air gap between iron and magnets is reduced, the torque available for the motor is increased.
However, slotted stators are known to cause cogging, which is attributed to the teeth in their construction. Cogging occurs when the permanent magnets on the rotor seek a preferred alignment with the slots of the stator. Winding copper wires through the slots tends to increase this effect. As magnets pass by the teeth, they have a greater attraction to the iron at the ends of the teeth than to the air gaps between them. This uneven magnetic pull causes the cogging, which ultimately contributes to torque ripple, efficiency loss, motor vibration, and noise, as well as preventing smooth motor operation at slow speeds. A slotless stator offered a solution to the problems experienced with cogging in slotted brushless DC motors.
Advantage of the BLDC Slotted Motor Technology
The main advantages of the slotted technology are:
- ease of winding customization
- increased heat dissipation
- ability to withstand high peak torque
- high power density
Slotted Motor Applications
The Slotted Motor is ideal for applications such as:
- Medical Hand Tools
- Hand held shaver system for arthroscopic surgeries
- High speed surgical drills for ENT surgeries
Slotless Motor Construction
Instead of winding copper wires through slots in a laminated steel stack as in conventional slotted brushless motors, slotless motor wires are wound into a cylindrical shape and are encapsulated in a hightemperature epoxy resin to maintain their orientation with respect to the stator laminations and housing assembly. This configuration, which replaces the stator teeth, eliminates cogging altogether and results in desired quiet operation and smooth performance.
The slotless design also reduces damping losses related to eddy currents. These currents are weaker in a slotless motor, because the distance between the laminated iron and magnets is greater than in a slotted motor.
Slotless motors are typically designed with sinusoidal torque output that produces negligible distortion, rather then a trapezoidal voltage output. The sinusoidal output reduces torque ripple, especially when used with a sinusoidal driver. Because the slotless design has no stator teeth to interact with the permanent magnets, the motor does not generate detent torque. In addition, low magnetic saturation allows the motor to operate at several times its rated power for short intervals without perceptible torque roll-off at higher power levels.
Compared with slotted motors, slotless construction also can significantly reduce inductance to improve current bandwidth. The teeth in a slotted motor naturally cause more inductance: the coils of copper wire around the teeth interact with the iron in a slotted motor, and this interaction tends to send the current back on itself, resulting in more damping (or dragging) and impacting negatively on slotted motor response and acceleration.
In terms of delivering power, conventional slotted motors used to enjoy the advantage over slotless types, due (as noted) to the proximity of iron and magnets and the reduced air gap.
However, this advantage has virtually evaporated, in large part due to the utilization of high-energy, rare-earch magnets (such as samarium cobalt and neodymium iron boron). By incorporating these magnets, manufacturers of slotless brushless motors have been able to routinely compensate for the greater air-gap distance. These more powerful magnets effectively enable the same (or better) torque performance for slotless products compared with slotted. Eliminating the teeth and using stronger magnets both serve to maximize the strength of the electromagnetic field for optimum power output. Rare-earth magnets, along with the fact that fewer coils, or “turns,” of the wire are required in slotless motors, also help contribute to low electrical resistance, low winding inductance, low static friction, and high thermal efficiency in slotless motor types.
One more important difference between slotless and slotted designs is the rotor diameter. Slotless motors have a larger rotor diameter than slotted construction for the same outside motor diameter and will generate a higher inertia, as well as accommodating more magnet material for greater torque. For applications with high-inertia loads, the slotless product is more likely to be specified.
Slotless Motor Applications
In general, brushless motors are usually selected over brushcommutated motors for their extended motor life. (While motor life is application-specific, 10,000 hours are usually specified.) Other reasons for specifying brushless motors include a wide speed range, higher continuous torque capability, faster acceleration, and low maintenance.
In particular, slotless versions of brushless DC motors will suit those applications that require precise positioning and smooth operation. Typical niches for these motors include computer peripherals, mass storage systems, test and measurement equipment, and medical and clean-room equipment.
As examples, designers of medical equipment can utilize slotless motors for precise control in machines that meter and pump fluids into delicate areas, such as eyes. In medical imaging equipment, slotless brushless DC motors decrease banding by providing the smoother operation at low speeds. Airplane controls supply smoother feedback to pilots. And, by eliminating cogging and resulting vibration, these motors can reduce ergonomic problems associated with hand-held production tools. Other appropriate applications include scanners, robots for library data storage, laser beam reflector rotation and radar antenna rotation equipment, among many others./span)
Customization Options
Slotless brushless DC motors, as with most motors today, feature a modular design so they can be customized to meet specific performance requirements. As examples, planetary or spur gearheads can be integrated on motors for an application’s specific torque and cost requirements. Planetary gearheads offer a higher-torque alternative. Slotless motors can further be customized with optical encoders, which provide accurate position, velocity, and direction feedback that greatly enhances motor control and allows the motors to be utilized in a wider range of applications. As a low-cost alternative to optical encoders, rotor position indicators (ie. Hall Sensors) can be specified.
When using optical encoders, differential line drivers can be utilized to eliminate the effects of electrically noisy environments. Differential line drivers are designed to ensure uncorrupted position feedback from the encoder to the control circuit.
Motor Selection Guided by Application
Despite the overall design and performance comparisons reviewed here for slotless and slotted brushless DC motor types, one should remain cautious in drawing any conclusion that one type is the ultimate choice over the other. There are simply too many variables that must be evaluated, ranging from rotor size and windings to housing and special components. A given application and its requirements should (and will) be the guiding factors in selecting a particular motor type and the customized components to be incorporated.
Some encouraging news in those applications that would clearly benefit from a slotless brushless motor is that costs are coming down to be more in line with those for slotted motors. This is because of new streamlined manufacturing techniques and an increasingly available supply of powerful magnets, which are both beginning to have a positive impact on end-product costs.
Regardless of any cost differential, however, for many applications, slotless brushless DC motors will be the preferred choice to resolve specific requirement issues. While advances in electronics are beginning to be applied that promise to reduce normal cogging in slotted products as a step toward making these motors more smooth running and quiet, the industry is not there yet: slotless motors remain the best alternative where cogging and life are defining performance issues
This Tutorial and other Motion Control Tutorials are available through www.Servo2Go.com
For further information on this new product or others in our extensive product portfolio, call 1- 877-378-0240 or e-mail Warren Osak at warren@servo2go.comor visit Servo2Go.com at: www.Servo2Go.com
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Linear Motion Tutorial – What is a Voice Coil Actuator?
Understanding the Basics of a Voice Coil Actuator
A voice coil actuator, also known as a non-commutated DC linear actuator, is a type of direct drive linear motor. The name “voice coil” comes from one of its historically first applications: vibrating the paper cone of a loudspeaker. They are currently used for a wide range of applications, including moving much larger masses. It consists 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.
A non-commutated DC linear actuator, typically referred to as a voice coil, is capable of a displacement of up to 5 inches, whereas most actuators have displacements up to 2 inches. Voice coils come in a range of sizes, from devices that generate a few ounces of force, to others that generate several hundred pounds of force. In addition, voice coil actuators can move bi-directionally, have a constant force over the stroke, and can be used for either open loop applications or closed loop position or force applications.
A voice coil actuator generates a force based on an interaction of current carrying conductors in a permanent magnetic field. 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:
F = B x I
F= Force (lbs or N)
B = Flux density (Tesla)
I = Current (Amps)
The force generated is relatively constant throughout the stroke of the actuator, with minor decreases in force at the beginning and end of the stroke.
Either the coil assembly or permanent magnetic field assembly can be used as the moving member in a voice coil actuator.
Moving Coil
Voice coil actuators come in a variety of packages. The standard type, which most people are familiar with are moving coil type actuators. These typically involve a coil wound around a bobbin, which can be made from many non-magnetic materials, which moves in and out of a permanent magnetic field assembly consisting of a steel housing with a concentric permanent magnet assembly in the middle. A typical example can be found below:
Moving Magnet
Another common type of actuator would be the moving magnet design, where the coil is fixed and magnet assembly moves. This construction change would prevent moving leads during operation. The package operates similarly, but instead of an exposed coil that moves in and out of the magnet assembly, the moving magnet style utilizes a permanent magnetic field assembly “piston” moving inside a cylindrical coil tube. This style often comes with the permanent field assembly attached to a shaft, and end caps containing bearings so that this style is most commonly supplied with an integrated bearing system. A typical example can be found below:
There are variations on both common designs of either actuator design that allow for unique geometry, and the integration of voice coil actuators into several applications.
A few examples of customizations available are:
- Large radial clearances so that the voice coil can be used in limited rotation applications
- Designs that intentionally operate the voice coil motor in an arc (commonly referred to as a rotary voice coil actuator)
- Using low outgassing materials to enable use in vacuum environments
- Integration of feedback devices for closed loop control
Voice coil actuators are typically used in focusing applications, oscillatory systems, mirror tilting, and miniature position control.
Advantages of Voice Coil Actuators
- Simplicity of construction
- Very low hysteresis
- Small size
- High accelerations
- No cogging or commutation
Typical Specifications for Voice Coil Actuators
| Type | Stroke | Peak Force | Diameter | Power Consumption | Frequency Range |
| Moving Coil | 0.1 to 5.2 inches
0.1 to 134 mm |
0.1 to 1755 lbs
0.1 to 7020 N |
0.4 to 10 inches
10 to 254 mm |
1 to 2700 watts | 1 to 500 Hz |
| Moving Magnet | 0.1 to 4 inches
0.1 to 101 mm |
0.1 to 419 lbs
0.1 to 1865 N |
0.4 to 6.5 inches
10 to 164 mm |
1 to 3400 watts | 1 to 500 Hz |
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 FREE, Fax: 661-251-2067, E-Mail: info@h2wtech.comor visit the website at http://www.h2wtech.com
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Motion Control – Steinmeyer Tutorial – Ball Screws – Maximum Load!
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Tutorial presented by Steinmeyer – Their Ball Screws are specially manufactured for dynamic performance
BURLINGTON, MA –Motion Control Tutorial – Ball Screws – Maximum Load
There are five ways a ball screw may fail due to overload:
- Excessive dynamic loading, which means the screw makes too many revolutions under a certain load resulting in material fatigue. This can be avoided by selecting a ball screw with sufficient dynamic load capacity (or by reducing the number of revolutions and/or reducing the load). This is the subject of the load capacity discussion.
- Exceeding the static load capacity, which causes instant and permanent damage to the ball screw due to brinelling of balls and races, and prevents any further normal operation of the ball screw. Static load capacities are listed as technical data.
- Buckling of the shaft under compressive load. Buckling load value depends on bearing method and free length of the loaded ball screw shaft.
- Failure of the nut body or of the bolts that connect it to the slide. This may happen even before the static capacity is reached. Safe loads are discussed on the following pages.
- Radial loads. It means the load capacities given in this catalogue apply only to pure axial loading. As there are always tolerances in the alignment of bearings and linear guideways, there may be a small amount of radial force, which should be minimized. Under normal conditions, a radial load less than 5% of the minimum axial load will not cause any problems. When considering a ball screw for use under radial load, please consult Steinmeyer engineers.
BUCKLING
There are several analytical ways to demonstrate safety from buckling. In machine design, the most frequently used is a simple calculation using formulas based on Euler equations.
Other, more accurate methods include non-linear FEM analysis and more involved mathematics. These methods are normally used in aerospace applications, where excess safety margins are not possible due to weight limitations. Please contact us if you require such an analysis.
Please CLICK HERE for a simple form of buckling analysis. Buckling
FRACTURE LOAD
Some ball screws cannot be loaded all the way to their static capacity. Screws with high dynamic load capacity (which might be selected to obtain a long enough service life at a much lighter load) will necessarily have a high static capacity. But the term “static capacity” is misleading, since the ball screw may actually fail due to fracture of the nut flange, nut body, or connecting bolts before reaching this load!
Please CLICK HERE for the maximum safe loads. Fracture Load
TECHNICAL TIP
A reasonable load for a ballscrew, which may be sustained for significant travel, is about 10% of its dynamic capacity.
A mean load of 10% of its dynamic capacity results in a theoretical life of 1 billion revolutions, which is the upper limit of the range where the life equation is valid. Mean loads of a reasonably sized ball screw will therefore be somewhat higher than this, but normally not exceed 20% of its dynamic capacity.
For short peak loads, the loading may be higher, but normally the loading of a ball nut with 2-point contact should not exceed 2.8 times the preload. And preload is around 5% – 10% of dynamic capacity.
As a rule of thumb, this all means the load range for a ball screw, to be used in a machine tool application, is really about 10% to 30% of its dynamic capacity. However Steinmeyer ball screws are used in many applications as force actuators where the loading is up to 100% of dynamic capacity but with low speed and acceleration. For example, they may be used to power injection molding machines, where high forces occur at reduced speed. Please consult our engineers for details.
Please CLICK HERE for information on Accounting for preload.
About Steinmeyer
Steinmeyer is the world’s longest continuously-operating manufacturer of commercial ball screws. In the realm of linear motion control, our company has become synonymous with precision, innovation, and exacting standards of quality.
Steinmeyer’s extensive product line is used widely in drive systems for industrial machines as well as precision positioning in optical instruments, medical devices, and other mechatronic applications. www.steinmeyer.com
For further information on Steinmeyer our extensive product portfolio, call 1-781-273-6220 or visit the Steinmeyer FMD group at: www.steinmeyer.com/en/steinmeyer
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Motion Control White Paper – Life Expectancy for Single Vs. Double Nut Ball Screws
Motion Control Components – White Paper – Life Expectancy for Single vs. Double Nuts by Steinmeyer!
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Life expectancy equations provided by some manufacturers only cover nuts having two-point contact. But what about four-point nuts? And what about the effects of preload?
BURLINGTON, MA –Motion Control Components – The fundamental determining factor of life expectancy is duty cycle, which includes load, thrust, speed, and duration of the travel. Calculating these forces is commonly understood. But preload is a very important factor in ball screw life calculations and must always be considered. In cases where the applied external load is low, preload can determine as much as 90% of the life.
Steinmeyer engineers have developed a preload graph that consists of two curves: each representing the force-deflection curve of one ball nut in a double nut configuration. It shows how deflections increase with greater force (and vice versa). It also displays how the forces in the opposite nut decrease as soon as deflection results in an axial displacement. For example, with double nuts, the higher the thrust carried by one nut, the more likely it will be the first to fail if not properly preloaded.
Since single nuts have four-point contact there are twice as many load/unload cycles for each given spot on the ball surface. The preload penalty of the four-point contact configuration is anywhere between a 50% life reduction (if the only force the nut sees is due to preload), and no reduction at all if there is zero preload. Real-world applications fall somewhere in between.
Lastly, if thrust is high enough to cause sufficient deflection, one set of balls in a double nut may run unloaded, which is generally unacceptable and potentially catastrophic. The preload must be high enough to ensure unloading will never occur. This isn’t the case for single nuts since there is no ball set to be unloaded, and exceeding the limits in the preload graph above is not a problem. Therefore, the life penalty depends on preload – life increases as preload is reduced
Does a Single Nut Have the Same Life Expectancy as a Double Nut?
Learn more about the nut designs from Steinmeyer Go to:
Nut Designs – https://drive.steinmeyer.com/technology/preload-and-rigidity/nut-designs/
Single Nut – https://drive.steinmeyer.com/technology/preload-and-rigidity/nut-designs/single-nut/
Double Nut – https://drive.steinmeyer.com/technology/preload-and-rigidity/nut-designs/double-nut/
Steinmeyer Technology Catalog – https://drive.steinmeyer.com/fileadmin/media/downloads/en/steinmeyer-catalog_technology_engl_2017.pdf (see pages 21 through 23)
Key Takeaways:
- Differences between single and double nuts
- Determining the life of a ball screw
- Calculating impact of usage/application
- Understanding the effects of preload
Contact Steinmeyer engineers to the see if which nut design is right for your application.
About Steinmeyer
Steinmeyer is the world’s longest continuously-operating manufacturer of commercial ball screws. In the realm of linear motion control, our company has become synonymous with precision, innovation, and exacting standards of quality.
Steinmeyer’s extensive product line is used widely in drive systems for industrial machines as well as precision positioning in optical instruments, medical devices, and other mechatronic applications. www.steinmeyer.com
For further information on Steinmeyer our extensive product portfolio, call 1-781-273-6220 or e-mail Rosmary Belt at rosmary.belt@steinmeyer.com or visit the Steinmeyer FMD group at: www.steinmeyer.com
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Motion Control Tutorial – Linear Induction Motor: How it Works.
What is all the hype about the Hyperloop? How does it move? What is the technology that makes it possible?
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Santa Clarita, CA —– Motion Control Tutorial – How Does a Linear Induction Motor Work? – Linear induction motor (LIM) theory is most easily understood as a rotary motor that has been cut and unrolled to generate linear motion, instead of rotary motion. It is comprised of two parts, the primary and secondary, which interact with one another only when power is applied. Either the primary or the secondary can be fixed while the other moves.
When three-phase AC power is applied to the primary, a travelling electromagnetic flux wave is induced and moves relative to the primary. The wave induces an electric current in the conductive reaction plate. The induced electric current interacts with the magnetic flux to produce a linear force. The speed of the motor can be varied by changing the input frequency using an adjustable frequency drive.
The primary consists of a three-phase coil assembly, equivalent to the stator of a rotary motor. The three-phase coils are wound and inserted into a steel lamination stack along with thermal protection components. The coil windings and stack are then encapsulated in a thermally conductive epoxy.
The secondary, known as a rotor in a traditional rotary induction motor, is a reaction plate. This plate can be comprised of aluminum or copper, and a steel backing. The reaction plate length is equal to the length of the coil plus the stroke. A bearing system is required to maintain the air gap between the primary and secondary.
See the YouTube Video
https://www.youtube.com/watch?v=bJD5d2-b5ZI
Linear induction motors can be manufactured in a wide range of force outputs, speeds, and footprints. For single-sided assemblies, the reaction plate consists of 1/8″ thick aluminum backed by a 1/4″ thick steel plate, and for double-sided assemblies the reaction plate is 1/8” thick aluminum or copper only. If the reaction plate is round and it has a center shaft with rotary bearings, the system will produce rotary motion.
Why Use a Linear Induction Motor?
Linear induction motors are ideal for applications that require rapid movement of large payloads. Linear induction motors can achieve speeds in excess of 1800 inches per second (45 m/s) and accelerations in the range of 3 to 4 g’s. Standard LIMs can produce forces in the range of 720 lbs (3200 N) at a 3% duty cycle. Multiple motors can be used in conjunction with each other to generate larger forces.
Linear Induction Motor Applications
LIMs can be found in theme park rides, water rides, people moving systems, high speed transportation and maglev propulsion applications. Here are some well-known examples:
Hyperloop
Hyperloop is a high-speed transport system for passengers and goods, incorporating reduced pressure tubes, pressurized pods, linear induction motors, and air compressors. Linear induction motors are used to propel and decelerate the pods over the tracks and through the tubes. The LIMs are reversible so the same motor that propels the pod in one direction down the track can be used to propel the pod back to where it started. The pods could potentially “float” on an air bearing to eliminate friction.
Big Thunder Mountain Railroad at Disneyland Resort
Big Thunder Mountain Railroad is one of the first roller coasters to use linear induction motors to accelerate cars out of the station. This allows the cars to start moving at high speeds from a stationary state, without the typical hill-and-chain start. The LIMs are also used to park cars in storage.
California Screamin at Disneyland Resort
California Screamin utilizes LIMs to launch the cars of the roller coaster. They are used again further into the ride to accelerate the cars as they travel over the hills.
Tomorrowland Transit Authority at Walt Disney World, Magic Kingdom Park
Linear induction motors power Tomorrowland Transit Authority (formerly known as the People Mover), moving large cars at smooth, slow speeds through Tomorrowland.
Dawwama at Yas Waterworld Abu Dhabi, Yas Island
The first section of Yas Island’s Dawwama water coaster is powered by LIMS. At each of the hills, the linear induction motors launch the tubes through the uphill sections. This method of propulsion in water coasters is called hydromagnetic technology.
Thunder Rapids in White Water Bay, Six Flags Fiesta Texas
Thunder Rapids, to open in 2017, will be the first water coaster is the USA to utilize hydromagnetic technology. Linear induction motors are combined with turbine technology to keep the tube speeding along the slide and over the hills.
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.
See Article: https://www.h2wtech.com/article/linear-induction-motor-how-it-works
See Video at Youtube: https://www.youtube.com/watch?v=bJD5d2-b5ZI
See Product: https://www.h2wtech.com/category/linear-induction#productInfo1″
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 Control – 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.
A solenoid generates force based on an electromagnetic field that is created by a current carrying conductor.
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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Motion Control – Linear Motors: How Do They Work?
What is a Linear Motor?
Motion Control White Paper – A linear motor should be thought of as a rotary electric motor that has been cut along a radial plane and unrolled. The resultant motor is a direct drive linear electric motor that can produce linear motion without the need of pneumatic, hydraulic cylinders, or translation of rotary to linear motion with the use of belts or screws. Rotary motors produce torque whereas linear motors produce linear force.
Bridging Terminology
| Rotary | Linear |
| Torque (lb-in) or [N-m] | Force (lbs) or [N] |
| Velocity (rpm) | Velocity (in/sec) or [m/sec] |
| Acceleration (rad/s2) | Acceleration (in/sec2) or [m/sec2] |
| Duty Cycle (%) | Duty Cycle (%) |
Basic Types of Linear Motors
As there are various types of AC and DC rotary type motors, there are also different types of linear motors, which include AC, DC, and Stepper:
For a PDF of this article with additional information on Linear Motors including: Types of motors, Performance factors (force, peak force,maximum stroke,maximum velocity and acceleration), what amplifier or drive types to use, bearing type, and for other options – CLICK HERE
Brushless
Ironless
Iron core
DC brushless linear motors provide non-contact operation for maintenance-free operation. Available in both ironless (cog-free) and iron core versions. They are capable of high speed and high acceleration motion profiles. They can be driven using standard 3 phase brushless servo amplifiers. Brushless linear motors can achieve an acceleration of up to 12 g’s, and speeds in excess of 200+ inches per second [5+ m/s].
Brush
DC brush linear motors are ideal for long stroke, open or closed loop servo, linear motion applications. They can be used at speeds up to 100 in/sec [2.5 m/sec] and as low as 1 in/sec [25 mm/sec]. They are capable of very precise position, velocity, and acceleration control when coupled with a linear encoder.
Voice Coil
Voice Coil
Moving Magnet
DC voice coil actuators are ideal for short stroke (typically less than 2 inches) closed loop servo applications. Their compact size allows them to fit into small spaces. They have very low electrical and mechanical time constants. The low moving mass allows for high accelerations of light payloads. They are available in both moving coil and moving magnet versions.
Linear Stepper
Single Axis
Dual Axis
Linear stepper motors are used in both open loop and closed loop positioning applications. Since the positioning is built into the forcer and platen, no additional feedback devices are required which reduces the overall cost of a system. For open loop operation, no servo tuning is necessary. Multiple forcers can operate on a single platen. With linear steppers, acceleration of 1 g and speeds up to 100 in/sec [2.5 m/s] are typical. They are available in both single-axis and dual-axis versions.
Linear Induction
The flat AC linear induction motor (LIM) is typically run directly off of 3 phase line voltage, with an adjustable frequency, or vector drive if speed control is required. Accelerations of up to 1 g with speeds in excess of 1800 inches per second [45 m/s] are possible with LIMs. They are ideal for high speed, long travel applications moving heavy payloads.
Polynoid
The tubular AC linear induction motor (polynoid) is typically run directly off of single or 3 phase line voltage. Accelerations greater than 1 g are possible with polynoids. They are ideal for short stroke, low duty cycle applications. They can be used to replace air cylinders when compressed air is not available.
Force Multipliers Based on Duty Cycle
| Basic Types of Linear Motors | Continuous Force/ Motor Area
lbs/in2 [N/m2] |
Peak Force/ Motor Area
lbs/in2 [N/m2] |
| AC Linear Motors | 0.2 | 1 |
| DC Linear Motors | 2.5 | 7.5 |
| Linear Stepper Motors | 2.5 | 7.5 |
Linear Motor Force
As explained, linear motors produce force (measured in pounds or newtons) along a straight line axis to move its payload. Each motor type provides different force levels.
Force depends upon duty cycle. Duty cycle is specified as a percentage:
Linear Motor Advantages
Faster Acceleration: From 1 to 10 g’s; this leads to shortened cycle times and improved productivity for the customer.
High Speeds: Speeds to 1800 inches per second [45 m/sec].
Highly Accurate: Accuracy to 0.00004 in/ft [1 µm/305 mm].
Very Repeatable: Repeatability to 0.00004 inch [1 µm.
No Backlash: A direct drive approach has no backlash such as obtained in leadscrews, gears, belt drives, and pinions.
High Stiffness: Direct drive linear motors provide higher stiffness than ball screw / lead screw systems.
Very Smooth Operation: Linear packages provide smooth operation due to the elimination of mechanical linkages.
Non-Contact Parts: This reduces component friction and wear, thus reducing the customer’s maintenance.
Long Life: Indefinite life expectancy under normal operating conditions can be expected due to the simplicity and part reduction
Low Maintenance: This helps to reduce the customer’s overall costs.
Unlimited Stroke: Stroke lengths are not limited as with ball screws. It is easy to extend the stroke by simply adding another section.
About H2W Technologies:
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
Linear Bearing Engineers Design Camera Sliders for the Pro and Beginner!
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Designed by Linear Bearing Engineers Camera Sliders for the Beginner and the PRO
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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:
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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. |
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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.
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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.
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There is an answer…Camera Motions new ” Silent Slider “
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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.
Motion Control “White Papers” – Welcome to the Kollmorgen “Engineer’s Library”
Motion control technical white papers Here you’ll find best practices and other resources to help you envision, design and realize a truly differentiated machine. We’ll be updating the Engineer’s Library several times per year, so check in often.
Achieve Superior Motion Control Servo Performance, Quickly, with Auto-Tuning!
The highest quality flexographic printing machines use direct drive rotary motors to control and synchronize the motion of the anilox roller and plate cylinder.performance digital servo drives can increase machine throughput, support more sophisticated functionality and reduce commissioning time.
RADFORD, VA — Compliance in motion control transmission components tends to decouple the load’s inertia from the servo system at higher frequencies. First-generation auto-tuners didn’t take this “rubber band effect” into account, and even the best tuning specialists need lots of time and a little luck to get optimum performance. Kollmorgen’s chief engineer of servo technology, George Ellis, explains how full-frequency auto-tuning can achieve perfect performance in a matter of minutes.
To down load this informative motion control White Paper Click Here
You may also want to look at these White Papers:
How Today’s Flexible Digital Servo Drives Help OEMs Build a Better Machine, Faster!
High-performance digital servo drives can increase machine throughput, support more sophisticated functionality and reduce commissioning time.
Direct Drive Technology Improves Flexo Printing Quality and Throughput!
The highest quality flexographic printing machines use direct drive rotary motors to control and synchronize the motion of the anilox roller and plate cylinder.performance digital servo drives can increase machine throughput, support more sophisticated functionality and reduce commissioning time.
How to Effectively Minimize EMI issues When Best Practices Are Not Available!
Grounding and shielding is an often misunderstood process. It is common to hear quotes ranging from , “It’s just black art!” to “the rules changes all the time.”
Servomotor Configuration: Expanded Offering Provides the Best Servomotor Solution for Your Application!
Brush-type motors, stepper motors, and brushless AC servo motors are widely used in semiconductor manufacturing, aerospace controls, electronics assembly machines, packaging equipment, medical devices, robotics, and in many other industries. time.”
To download as many of the Kollmorgen white papers as you like Click Here
