Industrial Automation - Motion Control Tips

How to specify motion components for cleanroom environments: Part 2

September 5, 2018 By Danielle Collins Leave a Comment

In this two-part article, we cover the products, materials, and features that designers and engineers should specify when choosing motion components for cleanroom environments.

In part 1, we looked at how to reduce particle generation due to friction between moving components. In this second part, we’ll look at another source of contamination — outgassing — and how to minimize it.

Objective #2: Minimize outgassing

Silicon wafer processing is extremely sensitive to contamination, including both particulates and outgassing.
Image credit: WaferPro

In cleanroom applications that involve the manufacture of LEDs, optics, or glass, or the processing of silicon wafers, a second type of contamination can damage the process or the product: outgassing.

Outgassing is the desorption of vapors or gasses, either from within a material or from the surface of a material. ISO standard 14644-8 addresses outgassing in cleanroom environments and specifically refers to airborne molecular contamination (AMC) as:

The presence in the atmosphere of a cleanroom or controlled environment of molecular (chemical, non-particulate) substances in the gaseous or vapor state that may have a deleterious effect on the product, process, or equipment in the cleanroom or controlled environment.

These types of airborne molecular contaminants take the form of molecular vapor. They’re smaller than particles and easily pass through HEPA and ULPA filters, making them particularly difficult to control once released.

Minimize outgassing through material selection

The first criteria when choosing motion components for cleanroom environments where outgassing is a concern is to ensure the material has a smooth surface, which makes it more difficult for airborne molecular contaminants to adhere to the surface. Stainless steel and anodized aluminum are the preferred materials, although some epoxy paints are suitable for environments where low-outgassing is required.

Fortunately, numerous motion control components, such as linear guides, motors, and gearboxes, can be made of stainless steel. When possible, plastic end caps on linear guides and screws should also be replaced with stainless steel versions to further minimize the use of plastics. And standard steel fastening hardware, such as screws or pins, should be replaced with stainless steel versions.

Although epoxy paint is sometimes suitable for motor and gearbox housings, stainless steel versions are better options.
Image credit: Wittenstein

When the required material has a high outgassing tendency, other solutions exist. For example, epoxy paint is suitable in some cleanroom environments and can be applied to the housings of linear actuators, motors, and gearboxes. And when steel is required — to maintain hardness, durability or load-carrying capacity — nickel plating can reduce the tendency of steel to outgas. (Note: Some nickel-plating formulas include a PTFE, or Teflon^®, top coat. The use of Teflon is generally advised against, so be sure to choose a nickel plating formula that does not include Teflon.)

Good: Nickel-plated steel, epoxy coated aluminum
Better: Stainless steel or anodized aluminum; minimal use of plastics
Look for: Smooth surfaces (no textured paints)

Reduce outgassing from lubricants

A wide variety of cleanroom-rated lubricants are suitable for bearings, motors, gearboxes, and other motion components.
Image credit: NSK

When it comes to outgassing, lubricants are one of the major offenders, readily spewing molecules of water and oil vapor into the atmosphere. Unfortunately, in the majority of motion systems, the use of components that require lubrication simply can’t be avoided. When lubrication is required, ensure the lubricant is suitable for cleanroom environments. Cleanroom compatible formulas that minimize outgassing while protecting bearing surfaces from rust and friction are widely available.

Good: Cleanroom-rated lubricants
Look for: Opportunities to minimize the need for lubrication through component selection

Feature image credit: Lin Engineering, Inc.

How to specify motion components for cleanroom environments: Part 1

August 29, 2018 By Danielle Collins Leave a Comment

In this two-part article, we cover the products, materials, and features that designers and engineers should specify when choosing motion components for cleanroom environments. In part 1, we look at how to reduce particle generation due to friction between moving components.

Designers of automation systems are tasked with many competing demands, such as balancing cost and performance, fitting motion components and systems into existing machine or process layouts, and designing for ease of manufacturing and assembly — to name a few. But when the system is to be used in a cleanroom, an additional layer of complexity is added, requiring designers to choose products that won’t degrade or compromise the cleanroom environment.

The level of “cleanliness” of a cleanroom is determined by the number of particles, broken down into six size ranges, that are present in a specified volume of air. In the United States, Federal Standard 209E is often used for cleanroom ratings, although it was officially canceled in 2001. This standard specifies cleanroom levels from 1 (best) to 100,000 (worst) in multiples of 10.

The current, and more universally-accepted, standard is ISO 14644-1, which defines cleanrooms on a scale from 1 (best) to 9 (worst). Each of the ISO classifications has a corresponding FS 209E level, with the exceptions of ISO classes 1 and 2, which are higher (better) than the highest FS 209E classification, and ISO class 9, which is lower (worse) than the lowest FS 209E classification.

ISO standard 14664-1 rates cleanrooms on a scale from 1 (best) to 9 (worst). Federal Standard 209E uses a scale from 1 (best) to 100,000 (worst) based on the number of allowable particles greater than or equal to 0.5 micron.
Image credit: Mecart Inc.

Objective #1: Reduce friction

One of the two primary sources of contamination, or particles, that can degrade a cleanroom environment is friction from moving components. (The other source is people.)

Virtually every motion system involves some amount of friction between sliding or rolling surfaces — whether from linear bearings, rotary bearings, or meshing gears. And when there is friction, particles are generated. Therefore, when specifying motion components for cleanroom environments, reducing friction should be the foremost objective.

Linear guides and drives

To minimize friction from linear guides, choose rolling contact rather than sliding contact and, when possible, avoid systems with high preload. For example, a non-preloaded miniature rail guide that uses two rows of recirculating balls emits significantly fewer particles than a preloaded standard guide with four rows of recirculating balls. And because there’s little chance of the bearing experiencing contamination in a cleanroom environment, use linear guides with low-friction or non-contact type seals.

Air bearings are another, although less common, method for guiding and supporting loads. In cleanroom applications, however, air bearings are often the best choice for low particle generation, since they are completely non-contact devices.

When it comes to linear drives, belts and chains should be avoided in cleanroom applications, due to the significant contact and wear they experience. Similarly, the meshing of gears in rack and pinion systems cause high friction and wear, so these should also be avoided. This means that ball screws are typically the default choice for linear drives in cleanroom applications.

However, ball screws require lubrication, and the rotation of the screw can cause lubrication to “sling” or “splatter,” contaminating the cleanroom environment. Using low-friction or non-contact seals (see above) will help keep the lubrication inside the ball nut and protect the cleanroom.

Like air bearings for linear guidance, linear motors provide a completely non-contact option for driving the load. But in their traditional setup, linear motors operate with the forcer (primary part) moving. This means the cables must move as well, and as we’ll discuss below, cables are another source of particle generation. A better configuration for cleanroom applications is to keep the forcer (primary part) and its cables stationary and allow the magnet track (secondary part) to move.

The combination of air bearing guides and a linear motor drive in this ABL 2000 stage from Aerotech provides completely non-contact movement, ideal for cleanroom applications.

Good: Rolling contact (rather than sliding contact) guides and drives
Better: Air bearing guides and linear motors
Look for: Low-friction or non-contact seals; cleanroom lubrication

Cables and cable management

Another source of friction and, therefore, particle generation, is the cable management system, including the cables themselves. Traditional round cables can generate particles when they rub against each other or against parts of the cable track. The best way to reduce particulates from cables and cable management systems is to use components and system design practices that reduce the amount of cabling required — for example, using an integrated motor-drive system instead of separate motor and drive components.

Cable carriers used in cleanrooms should have low vibration, low-abrasion fastening, and smooth interior surfaces to prevent abrasion of cables.
Image credit: igus Inc.

For the power, feedback, and data cables that are necessary in a motion control system, manufacturers offer cable designs with special low-friction coatings to minimize particulates and reduce outgassing. Similarly, several cable track manufacturers offer systems that reduce wear between chain sections through the use of abrasion-resistant joints. And for shorter lengths, so-called “trackless cables” are self-supporting flat cables that don’t require a cable track or carrier.

Trackless cables are self-supporting and don’t require cable carriers.
Image credit: W.L. Gore & Associates, Inc.

Good: Round cables with anti-friction coatings; cable carriers with abrasion-resistant joints
Better: Self-supporting flat cables
Look for: Opportunities to reduce cabling

Rotating equipment: motors and gearboxes

When it comes to rotating equipment in motion applications, the bad news is, motors and gearboxes use rotary bearings, and gearboxes require meshing teeth — all of which are sources of friction and particle generation. The good news is that these components are enclosed, so particles are less likely to “escape” and contaminate the cleanroom environment. And there is a wide range of cleanroom-compatible lubricants that can be used in the high-speed, high-load conditions found in motors and gearboxes.

To improve cleanroom compatibility, it is also possible to add a slight vacuum to the motor or gearbox housing. The vacuum serves to extract and remove particulates so they don’t have an opportunity to contaminate the cleanroom. Note that vacuum purge is also a good option for enclosed actuators that have a static (non-moving) seal. Although the enclosed design tends to keep particles inside the actuator, adding vacuum purge helps to achieve higher levels (class 100, 10, or 1) of cleanroom compatibility.

Vacuum purge is an effective way to ensure particulates from closed systems, such as this linear actuator, don’t have a chance to escape and degrade the cleanroom environment.
Image credit: THK Co., Ltd.

Good: Fully enclosed housings
Better: Vacuum purge
Look for: Cleanroom grease options

In part 2 of this article, we’ll look at another source of contamination — outgassing — and how to minimize it.

WITTENSTEIN alpha CAD POINT smart catalog for gearbox configuration and selection

July 23, 2018 By Lisa Eitel Leave a Comment

CAD POINT by WITTENSTEIN alpha helps engineers and motion control specialists access product information, data sheets, and CAD data in just a few clicks. This online smart catalog features the entire product portfolio for WITTENSTEIN gearboxes and actuators in conjunction with a database of more than 16,000 motors.

CAD POINT makes it easy for users to compare products, then download data sheets, generate CADs and request pricing — all with a few clicks.

Users can search by product type or specific ordering code. Once they’ve found the product they are seeking, they can finish the selection process by requesting a non-binding quote.

CAD POINT supersedes the old Info & CAD Finder, getting the same results in half the time. Linking databases for gearboxes, motors, and actuators (with an enhanced user interface) makes it even easier to find CAD data, product information, data sheets, and quotes.

Users can begin with a known gearbox type or a preferred size and then compare it with different gearbox and drive configurations. Once selected, the characteristics are subsequently remembered throughout the configuration process … even after switching to a different size. This makes comparing several possible alternatives simple and fast.

To further expedite results, users can enter a specific product ordering code. CAD POINT automatically validates entered code to eliminate data entry errors and then generates the specific results.

CAD POINT is the latest enhancement in the robust portfolio of sizing tools from WITTENSTEIN. There are three distinct tools:

CAD POINT is for design engineers who already use drive solutions from WITTENSTEIN alpha, are familiar with the applications and benefits, and would like to compare configurations or retrieve CAD data just a few clicks.

SIZING ASSISTANT is designed for engineers searching for the quickest way to select the most suitable gearbox for their servo drives or kinematics based on a specific motor or a predefined application.

cymex 5 sizing software is used for more detailed sizing tasks such as:

• Main axes involving shaft and bearing calculations

• Simultaneous definition of any number of axes in one project

• Examination of electrically preloaded drives

• Optimization of design spaces.

Available as a free download with license registration, cymex 5 is the optimal multifunctional sizing tool. For more information, visit the CAD POINT website or www.wittenstein-us.com.

Located in Bartlett, Illinois, WITTENSTEIN Inc. produces servo gearboxes, actuators, linear systems and motion control systems that optimize machine performance and lower cost of ownership. WITTENSTEIN is worldwide for the quality of its products and its global network of engineering expertise, which combine to deliver competitive advantage for its OEMs, system integrators, distributors and end user customers.

With around 2600 employees worldwide and sales of €385 million in 2017/18, WITTENSTEIN SE is internationally known for for innovation, precision, and excellence in the field of mechatronic drive technology. The group comprises six pacesetting Business Units with separate subsidiaries for servo gearboxes, servo actuator systems, medical technology, miniature servo units, innovative gearing technology, rotary and linear actuator systems, nano technology and electronic and software components for drive technologies.

Elmo Motion Control at IMTS: Making smart machines smarter

July 10, 2018 By Lisa Eitel Leave a Comment

At IMTS 2018, Elmo Motion Control will showcase its new Double Gold Twitter ultra-small servo drive and its Platinum Maestro motion controller, which controls up to 256 axes. These motion products suit the most demanding applications in the era of Industry 4.0.

The new Double Gold Twitter is among the smallest STO-certified (IEC 61800-5-2, SIL-3) servo drives on the market. It delivers to 10,000 W and weighs only 1.2 oz — with continuous currents of 160 A (80 V) and 140 A (100 V).

Platinum Maestro motion controller

This miniature drive can mounts on moving loads, on motors, or inside motors to help engineers save space, improve machine performance, reduce cabling, and eliminate electrical cabinets, all while delivering unprecedented power.

Visit Elmo Motion Control at IMTS 2018 (IAMD) in Chicago at Booth #134142 to see these and other innovative motion solutions and capabilities for efficient and cost-effective smart machines.

Also — learn how smart drives and controls can help improve machine performance while enabling manufactures to achieve more for less at an Elmo Motion Control presentation.

The Paradox of Smart Manufacturing — which won the 2018 first prize SPS Roberto Maietti Award (recognizing thought-leading abstracts) will be presented in a session — Challenges of automation: Efficiency and flexibility. Join Elmo product & sales enablement manager Tomer Goldenberg for this live presentation on Tuesday, September 11, 2018 at 3:15 pm (W196-A).

Also be sure to visit www.elmomc.com.

Conveyors with backlighting (and robotic backup) automate production of electrical outlets

June 26, 2018 By Lisa Eitel Leave a Comment

Michigan-based Byrne Electrical Specialists designs and manufactures power and data technologies for office, teaching, and hospitality environments. Recently, the company began using industrial conveyors from QC Conveyors to increase their throughput of electrical outlets.
A trio of robotic assembly cells — each with its own threesome of busbar conveyors and solo output conveyor — build electrical outlets for modular office furniture. Then one packaging cell at the end of the line collects the output from these assembly-cell feeds for final testing and shipping.

Byrne’s automated installation processes busbars in four different line, four different neutral, and three different ground variations … and it handles six different outlet body variations. That means the whole installation can output several dozen electrical-outlet models — each requiring dedicated vision-system programming for successful robot picking. In fact, sometimes operators must empty the hoppers (via an easy-purge dump and quick conveying back to a parts bin) for switching the output product several times a day.

1. Operators set the parameters for the current job via a human machine interface (HMI) based on the specifics of the current order being processed — including parameters such as color, size, needed outlet count per case, and so on.

2. Operators then load the outlets’ front shells and back plates by hand on one side of a machine … and put metal bus bars into hoppers on the other. “Each electric outlet has five parts — including three busbars for line, neutral, and ground. Each busbar has its own hopper and conveyor-based sorting line to let us take these raw components and basically dump them into hoppers. Then each hopper drops busbars onto a cascading three-layer conveyor system,” explained Byrne engineer Dan Wierenga.

A robot picks parts and places them into a holding station. Any parts that can’t be picked because they’re stacked or misshapen get dropped onto a third conveyor back to the hopper to go through again.

3. The first of the three conveyors moves very slowly and drops busbars onto a faster middle conveyor (in a way that spaces them evenly). In the middle of this conveyor is an underlit section — provided by Spectrum Illumination. The underlit conveyor region is monitored by a Datalogic vision system. As busbars travel over the underlighting, the vision system confirms they’re right-side up and clear of other parts — and then commands the conveyor to stop to allow pickup by a robot. Any busbars that are bad, misoriented, or clumped together continue onward until they fall onto a third (fastest-moving) conveyor that (via an elevator) returns them to the original hopper. Next a Nachi six-axis robot gets the X, Y, and angle of the busbar, grips and reorients it, and puts it in a holding station.

Conveyor backlights on 9 of 28 conveyors from QC Conveyors illuminate items above through a cutout in the conveyor frame and the translucent belt. The lights provide contrast to let a vision system inspect the parts and find good ones; find parts that aren’t stacked; and orient a robot arm servicing the conveyor to pick the parts.

4. Another robot takes the first of two plastic halves — the outlet’s front shell— and puts it into a nest. Then it picks three busbars (readied by the previous robot) and inserts them into the front shell. Then the robot puts the outlet’s back shell half on the front and presses them together. For there, the robot places the completed assembly on another conveyor (from QC Conveyors) to inspection and packout.

Assembly cell #1 might be making white outlets while assembly cell #2 is making black ones. These must be matched to the proper order at the packaging cell. So once the electrical outlets are assembled, a robot places them on a single takeaway conveyor with a dedicated lane for each assembly cell. The conveyor delivers the outlets to a packaging cell with controls that know the order to which each outlet belongs based on the lane it exited.

5. Finished electrical outlets are lifted off the conveyor and inspected visually on both sides. They then pass an inkjet printer that prints a symbol specific to the current order on the front of the outlet. The printer applies logos in three different colors depending on the outlet’s body color. After printing, all the electrical outlets get a label on the back and then go into the proper case for that order.

The system was designed for Byrne Electrical Specialists by Criterion Manufacturing Solutions, where Wierenga worked during the installation design before joining Byrne to keep the line optimized. A local QC Conveyors distributor, Industrial Control based in Zeeland, Mich., worked very closely with engineers at Byrne on the design specifications for the automated installation.

“We used QC Conveyors because Byrne has partnered with Industrial Controls on an array of projects before. Plus the conveyors have a convenient form factor and come in custom sizes and lengths — and with an array of belt types,” explained Wierenga. “The latter let us use low-friction belts, transparent belts, and high-durability belts to maximize functionality and lifespan. On QC Conveyors, the belts are also easy to install and replace.”

A major challenge was integrating the moving belt and stopping the belts and then coordinating the vision system’s vision space to real-world robot coordinates. Complicating matters is that the lines must do that for several dozen part variations. “That means we had to design a system that lets us program and calibrate the different parts very easily — which took a fair amount of development,” added Wierenga.

Before this automated machinery, parts were assembled by hand. Each assembler had a manual station where he or she would put the outlet parts together and then weld the part closed. Then the outlets went to another station to get printed and UL testing. All secondary audits, labeling, and packaging after that was manual. In contrast, now Byrne takes raw components and does 100% of its testing, 100% of its parts inspection, and 100% of its boxing for shipment with automation.

“We went from four or five different part handoffs to zero handling of the completed part … and much higher end-product quality,” said Wierenga.
For more information, visit byrne.com and qcconveyors.com.

Nine busbar hoppers and six outlet-body inputs feed three assembly cells.

Updated Motion Analyzer software from Rockwell cuts system design time

June 7, 2018 By Miles Budimir Leave a Comment

An updated version of the Allen-Bradley Motion Analyzer software tool from Rockwell Automation offers simplified workflows and improves design efficiency. The enhanced software offers an optimized user experience with intuitive navigation and in-workflow product selection. This can help engineers more easily and efficiently develop complete motion control systems for their machines.

Using the Motion Analyzer software, engineers can determine a system’s specifications, evaluate multiple products to find the best fit, finalize the design and create a bill of materials. The tool can also help reduce motion-system design time from a multi-day process to a few hours.

“Sizing a motion system can be time consuming,” said Brett McNalley, product manager, motion solutions, Rockwell Automation. “In the latest release of the Motion Analyzer software, we have simplified workflows to improve user experience. And we have added additional features that make the process of designing a motion system as efficient as possible.”

Key improvements include faster axis definition and sizing, redesigned solution search and configure components features, additional application template profile support, and the ability to import from a legacy motion profile with support of more advanced motion segments.

For more information, visit www.rockwellautomation.com.

Brushless dc motors for industrial power tools: Comparison of options including slotless motor variations

June 5, 2018 By Lisa Eitel Leave a Comment

Industrial power tools have operating profiles that differ from those of most other motor-driven applications. That’s why motors that go into these tools need specialized designs.

By Thomas Baile, Business Development Manager | Portescap

Most electric-motor-driven designs demand torque for the entirety of their motion. In contrast, power tools for fastening, gripping, and cutting applications have a motion profile consisting of two stages.

Motors for industrial power tools nutrunner Portescap

Power tools benefit from Portescap EC slotless motors with efficiency of copper turns to minimize joule losses; compact design; and strong coil integrity. The motors can also deliver a wide range of torque constants.

Power-tool speed stage: At first (as the tool drives a fastener to thread into place or the jaws of a cutting or gripping tool approach a workpiece) there’s little resistance.

Power-tool torque stage: Then when the tool performs the more forceful work of tightening, cutting or gripping, there’s a sudden torque demand.

These alternating speed and torque cycles constantly repeat in industrial power-tool applications even while necessitating different speeds and torques for various durations. That’s why such tools — especially those that are battery-operated so running off low voltage and limited available power — benefit from special motor designs that minimize losses.

As we’ll explore, motors that also operate at faster free-run speeds for the speed stage can trim cycle times to boost productivity … and motors that deliver high peak torque during the torque stage can perform a wider range of tough jobs without excessive heating.

Unlike typical motion designs that demand torque output from the motor throughout the motion, industrial power tools (IPTs) for fastening, gripping, and cutting often have a motion profile split into two stages. This cycle continuously repeats.

Selecting and optimizing brushless motors for power tools

Consider the primary options for handheld industrial power tools — brushed dc motors and brushless dc motors. Battery-powered industrial power tools run on low voltages of 12 to 60 V … so here, brushed dc motors are typically economical but have limited life. The brushes exhibit modes of wear due to electrical influences (from current related to torque) and mechanical influences (due to the friction associated with speed).

Brushless dc motors are more reliable in power tools, as they’re less susceptible to mechanical wear (no brush friction) and can sustain high peak current (no brushes) during the tightening stage, providing far greater life in the hand tool. Brushless dc motors are better suited than brushed dc motors for industrial power tool applications because they require high speed and high peak current.

Brushless dc motors for power tools are typically one of two configurations:

Conventional inrunner motor configurations include permanent magnets on the rotor with three stator windings around the rotor.

Conventional inrunner motors include permanent magnets on the rotor; outrunner (external-rotor) configurations have it reversed. Inrunner motors excel in certain handheld industrial power tools because they have reduced inertia, lower weight, and lower losses — plus their longer length and smaller diameter complement handheld designs for ergonomics.

Outrunner (external-rotor) configurations have it reversed — so coils are innermost on the stator and the magnets are on the O.D. In other words, the stator coils form the motor center while the permanent magnets on the rotor’s inner surface spin within an overhanging rotor surrounding that core.

Inrunner motor configurations excel in handheld industrial power tools because they have reduced inertia, lower weight, and lower losses. Their longer length and smaller diameter also complement handheld designs for ergonomics. Plus a lower rotor inertia brings better tightening and gripping control.

For slotted motors, magnetic induction in the lamination is high because the airgap between the laminations (stator) and magnet is small. However, the motors are inherently rugged. Slotless motors have independently formed coils. The diameter is usually optimized for magnetic induction with a given copper volume.

Brushless dc windings can be constructed in different physical configurations:

Motors with slotted stators: Here, the coils wind through the slots around the stator. Magnetic induction in the lamination is high because the airgap between the laminations (stator) and magnet is small. So, the motors allow a small magnet diameter. The volume of the copper is limited by the slot space and the difficulty of winding within the slot. Having the coil inside the stator slots is advantageous in that it reduces coil-stator assembly thermal resistance.

Without current, the rotor has preferred magnet positions in front of the lamination. That means the motor is prone to generating a cogging or detent torque. One way to decrease the detent torque is to skew the lamination.

But again, slotted motors are inherently robust because the coil is in the lamination.

Motor with slotless stators: Slotless motors have coils wound in a dedicated operation. This coil goes into the motor airgap during motor assembly. Magnetic induction in the coil is lower than in slotted motors because the airgap is larger. So the motor diameter is usually optimized for magnetic induction with a given copper volume.

In fact, induction in slotless motors is usually less than that of a slotted brushless motor. So bigger magnets are typically used to compensate for the loss of induction. One caveat to this solution is that it can increase rotor inertia.

But slotless motor power density is a strength. R/K² — the ability to maintain speed under load, with lower values being better — is low in slotless motors because induction for a given copper volume is optimized … as evidenced by a sloped curve. Without circulating current, the rotor sees a continuous permeance. That means slotless motors don’t exhibit cogging or detent torque. Iron losses at high speed in slotless motors are also far smaller than those of comparable designs.

There is another caveat: Slotted motors can handle higher temperatures than slotless motor designs — even to 200° C compared to 150° C, to give a typical comparison. That in turn allows more torque generation. Even so, in power tools usually the limiting factor is maximum temperature over time — to an average maximum of 47° C — or so — to accommodate what’s comfortable for the typical hand-tool user. Beyond that value, heating can become uncomfortable for the operator holding the tool. Safety regulations also require maximum temperature to be held lower.

Slotted brushless dc motors

Slotless brushless dc motors
(Ultra EC)

Pros

Small thermal resistance (coil/casing)

Maximum speed in excess of 100krpm

Fully customized motors

Hipot capability (to 2,500 V)

Torque

Smooth operation and no cogging

Little iron losses at high speed … low operating temperature and easier control

Low noise and vibration

Winding flexibility

Cons

Cogging

No standard products

Autoclavable option not available

High thermal resistance

Of course, the electrical performance of a motor is defined by the magnetic circuit. The magnet has a fixed value but the second component (the copper winding) can be easily modified. By changing with the wire diameter and number of turns, the motor’s torque constant k_t and resistance R can be fine-tuned for torque and speed. Consider the modes of industrial power-tool operation:

During the speed stage, the motor must operate at high rpm with little resistance:

ω = (U – R · I ) / k_t

Where ω = Speed in rad^.sec^-1 and U = Voltage; R = Resistance in ohms and I = Current in Amps; and k_t = Torque constant in Nm/A. Because the torque constant is in the denominator of the calculation, smaller k_t values make for higher RPMs. This allows more operations in the same time period which boosts productivity.

Now consider the power tool’s torque stage — when the motor must deliver peak torque at low speeds. Torque is the product of the torque constant and current:

C = k_t · I

Where C = Torque in Nm and I = Current in Amps. Higher k_t values here make for a higher output torque at a given current. So by adjusting a motor winding’s k_t design engineers can optimize either the speed or the output torque to balance optimization of torque with that of speed operation to reduce overall working cycle time. There is no unique solution: kt has to be chosen as the best compromise for a range of working profiles. Motor design experts can support one in this coil design process based on simulations and experience.

Reviewing thermal losses of motors during operation

Consider the losses of a typical industrial power-tool operating cycle. There is a relationship between copper losses and torque. So the design engineer may opt for a motor with a low k_t value to increase speed … and then compensate for a low k_t with more current (I) to get target output torque. But higher current increases copper losses:

Copper losses = R · I²

So with higher current comes faster heating of the motor and power-tool — thus limiting maximum possible torque. That’s why power-tool motors should be designed to draw as low a current as possible … to limit heat dissipation (and keep tool temperature cool enough to handle) and conserve battery life.

Copper losses and iron losses affect overall torque and speed output.

Now consider iron losses and how they relate to speed. Eddy-current losses increase with the square of speed to heat the brushless motor even if it’s just rotating under a no-load condition. That’s why high-speed motors need special design features to limit eddy-current heating.

Increased power-tool speed promptly makes iron losses exceed copper losses. So motor windings should be tuned for each duty cycle to minimize losses. Ultra EC winding technology greatly reduces iron and copper losses — which in turn gives design engineers more flexibility.

More specifically, some new electronically commutated (EC) brushless motors on the market build on a slotless motor design with specialty coil technology. These reduce copper losses because unlike slotless motors with skewed windings, they have windings parallel to the motor axis to maximize magnetic force and power. Plus they reduce iron losses at high speed. Among other benefits, these motors optimize speed and torque for the most challenging applications — including power tools that take the form of fasteners, grippers, and cutting tools.

High-speed motors in power tools must be of a special design to limit eddy-current heating. To this end, Portescap Ultra EC brushless slotless motors have a patented U-coil technology to reduce copper losses. Unlike slotless motors with skewed windings, Portescap Ultra EC motors have windings parallel with the motor axis to maximize magnetic force and power. Plus Ultra EC motors reduce iron losses at high speed. Straight windings also give the motors shorter rotor lengths compared to those of skewed windings which lowers rotor inertia and reduces iron losses.

Two example applications for EC motors in power tools

Assume for one design we have an average duty cycle including two seconds of moderate free speed — as in a pruning shear, nutrunner, gripper, or stapler. Speed is 20,000 rpm and at 2 seconds torque demand goes to 0.84 Nm.

Assume for the other design we have a heavy-duty cycle including three seconds very fast free speed — as in an automotive nutrunner optimized for productivity. Here, speed is to 40,000 rpm and at 3 seconds torque demand goes to 0.69 Nm.

For the first design:

Brushless motor type	Ultra 64	Skewed winding	Slotted motor	Ultra 90
Ø · L (mm)	30 · 64	30 · 64	28.5 · 88.5	30 · 90
Poles	4	4	4	4

Here straight-coil EC Ultra motors are more efficient (exhibiting less losses) than skewed-winding or slotted motors.

For the second design:

Brushless motor type	Ultra 64 HS	Slotted 90	Slotted 100	Ultra 90 HS	Ultra 64	Ultra Speed 60	Ultra Speed 80
Ø · L (mm)	30 · 64	28.5 · 88.5	34 ·99	30 · 90	30 · 64	35 · 60	35 · 80
Poles	4	4	4	4	4	2	2

There are higher iron losses than in the standard-duty design because the speed is doubled. Even so, straight-coil EC Ultra motors are still more efficient than skewed-winding or slotted motors.

Portescap | www.portescap.com

Motors with slotless construction excel in most industrial power tools because they have less induction in their laminations than other motors — which equates to no iron losses. Further Portescap improvements on slotless motor construction include straight turns, inner and outer heads, special outputs to prevent loose wires, and axial and radial forming.

For more than 25 years, leading manufacturers have relied on Portescap’s products, expertise, and support to develop corded and battery-powered tools while improving quality control and flexibility. Portescap innovation has helped transitions from pneumatic to electric tools while raising industrial power-tool performance standards. In 2013, Portescap patented the first slotless motor design with its Ultra EC coil.

AMK Automation Corp. launches new website

May 22, 2018 By Miles Budimir Leave a Comment

AMK Automation Corp. recently launched a new comprehensive website to provide a full range of product information and motion control insight to the automation community in the U.S. The new site, located at amk.systems, has been designed to help AMK Automation fulfill its mission: make motion control simple and help customers across multiple manufacturing and automation industry segments build better machines, faster.

The website includes separate sections on each of AMK Automation’s main product offerings: servo motors, servo drives and modules, and motion control systems. These products cover both cabinet-based servo drives and controls as well as a full array of decentralized, or “cabinet-free” drives, power supplies and controller systems designed to be mounted on machine frames.

“At AMK Automation, we think that the best ideas are often the simplest ones,” said Tom Jensen, general manager and technology evangelist. “We’ve applied that thinking to our website. It’s simple to navigate, with useful product information and insights on how to pick the right motion control technology for each customer’s unique requirements.”

Unique features of the new site include:

Frameworks: This portion of the site provides in-depth exploration and discussion about the three key motion control approaches or “frameworks” AMK supports: centralized, cabinet-based systems; decentralized, cabinet-free products that can be mounted on machine frames; and hybrid frameworks, which combine the centralized and decentralized technologies.

What’s New: This content hub links to multiple technical papers, web-based videos, trade publication articles and webinars, showcasing the latest product details, technology insights and industry recommendations from AMK’s motion control experts.

“What’s Right for You” Quiz: This simple online quiz asks three key questions about the operating environments and performance requirements of an automation system. With the answers, AMK is able to provide a smart recommendation for the most effective motion control framework to use, along with suggestions on product selection.

AMK Automation will be updating the site with new product information and technical material on a regular basis.

For more information on AMK Automation, visit amk.systems.

Heidenhain introduces new improved DRO for machinists

May 9, 2018 By Paul Heney Leave a Comment

Heidenhain has introduced the new ND 5023 digital readout (DRO) for use with manually operated machine tools. This new DRO replaces Heidenhain’s entry-level ND 522/523 models and consolidates it to one three-axis product. The new DRO comes equipped with a new TFT color display that significantly improves the readability of the information displayed over older models, plus features other design changes and enhanced functions.

To make installing the readout easier for users or an inexperienced machinist, a new installation guide has been implemented to assist in performing the basic configuration. When switching on the unit for the first time, the user can select this support feature and will then be guided through the required settings step-by-step.

A straightforward user management has been introduced in order to make it easier for multiple users to operate the product. Up to nine operators can save their personal settings with a user number and call them again.

Many new features are being introduced on the ND 5023 including the new dynamic zoom feature which offers a noticeable improvement in position value readability. Once activated, the display value for the axis currently being moved is magnified. For small numbers (i.e., numbers close to zero), the character height can be increased from 17 mm (standard height) to 25 mm. The operator immediately sees which axis is currently moving and can also easily read the numerical value from a greater distance. When the axis stops moving, the display returns to its standard size. The display is also easily configured for right-handed or left-handed operation.

The new ND 5023 DRO also has a powder-coated, die-cast aluminum housing and, just like its predecessor, uses a membrane keyboard. As before, encoders with a TTL interface (differential and single-ended) can be connected via a 9-pin D-sub connector.

The data interface on the ND 5023 was changed to USB Type C which has the advantage of allowing the digital readout to assume the tasks of both master and slave.

In addition, a universal mounting option has been implemented on this new DRO. It features a VESA-MIS 100 interface on the rear that allows the use of standardized holders for mounting. Heidenhain solutions are available.

Heidenhain
www.heidenhain.us

Beckhoff Automation expands Ultra-Compact Industrial PC Series

May 3, 2018 By Miles Budimir Leave a Comment

In order to improve coverage for all tasks in the fields of automation, visualization and communication, the C60xx series of ultra-compact Beckhoff Industrial PCs has been expanded with the addition of the new C6017. This latest addition to the Beckhoff Industrial PC (IPC) portfolio combines compact design and installation flexibility with an increased variety of interfaces and an integrated UPS.

With miniaturized dimensions, the C6017 is almost identical in design to the popular C6015, currently the smallest ultra-compact IPC from Beckhoff. The success of the C6015 quickly created additional demand, especially from applications that have increased requirements for connectivity and data security in the event of potential power supply failures. The C6017 was developed precisely for these requirements: the existing C6015 configuration with DisplayPort connection, onboard dual Ethernet adapter with two 100/1000Base-T connections and USB 3.0 and USB 2.0 ports, is being extended on the C6017 by adding two RJ45 and two USB 2.0 interfaces. Moreover, an optional capacitive 1-second UPS is integrated, ensuring reliable storage of persistent data in the event of a power supply failure.

With dimensions of 82 x 82 x 66 mm, the size of the C6017 is similar to the C6015. Only the overall width is extended by a mere 24 mm. Equipped with an Intel Atom CPU with up to four processor cores, the passively cooled IPC also features a robust aluminum and die-cast zinc housing. This means the C6017 is ideal for automation, visualization and communication tasks up to the mid-performance range.

The new ultra-compact IPC series from Beckhoff meets today’s demanding requirements in machine building, such as increased modularization, reduced space requirements in control cabinets, higher processing power and competitive pricing. Designed precisely with these requirements in mind, the new device generation is well-suited for a broad range of applications, for instance in distributed topologies and advanced IoT or Industrie 4.0 applications.

For more information, visit www.beckhoffautomation.com.