Tag Archives: applications of linear motors

The future for linear motors and electric actuators

January 10, 2017Blog, Newsapplications of linear motors

Leading figures from the motion engineering and automation industries were asked to look forward to the next 30 years in Drives & Controls magazine’s 30th anniversary supplement. This informative 50 page supplement discussed advances in components, materials and initiatives such as Industry 4.0 and II0T and along with 3D printing, cobots and much, much more.
Ernst Blumer the marketing director of NTI (LinMot) contributed by reviewing the relevant technical advances, which when added to decreasing prices and the increasing variety of products is leading to a rapid increase of applications for linear motor technology. The full article (along with the other contributions) is available on the link above but I have picked out some of the key themes of Ernst’s article below.

What’s driving the rapid increase in applications for linear motors?

Ethernet
Faster control
Easier integration
Lower price for drives

Increased efficiency, the increased variety of products optimised for different applications and lower prices have opened up a profusion of new applications for linear motors. In many applications induction motors are substituted by servomotors due better performance and energy efficiency. More and more traditional motor-gearbox combinations are replaced by direct drives for high dynamic, higher precision and longer life. Due to the higher efficiency, higher flexibility, lower energy costs, reduced contamination and lower maintenance costs more and more pneumatic cylinders are being replaced by electric actuators.

The biggest improvements in the last 5-10 years have been made in the control systems and the integration of electric actuators. Faster bus systems such as industrial Ethernet and real time communication makes the use of electric actuators simpler. Servo systems require a lot of fast communication and exchange of real time data between the drive and the overlaid machine control. The bus was always the bottleneck in these systems but now with the much higher data rates and real time capacity of industrial Ethernet, the integration and the use of electric actuators has become much easier.

New applications driving linear motor design and development

The need for new machines is driven by changing consumer trends while more stringent requirements and the need to consider total cost of ownership (TCO) are driving changes to machine design and the incorporation of linear motor technology.

Consumer trends spurring development

Consumer trends are driving the design of innovative machines for new markets. One example already discussed in this blog is the growing need for automation in the fish industry as worldwide fish consumption continues to increase. Today we already have a high degree of automation in plants and production/packaging lines for meat and sausage production but the requirements for automation in fish farms, the preparation of the fish and the packaging is completely different. One example of the innovative machines developed for this market is the automated vaccination machines for fish.

Another market trend in the food and beverage sector is the fact that consumers want to reduce their sugar consumption. The concentration of sugar in food and drinks is decreasing. Sugar is not only added to make the products sweeter, but also helps to conserve the products. Therefore, new machines to fill or pack reduced sugar products have higher demands regarding the hygienic standards and design and must be cleaned more often. In many applications with highly concentrated cleaning detergents or with high temperature cleaning cycles (overheated steam). During the last few years, manufacturers of electric actuators have started to offer stainless steel actuators with hygienic design and high protection rates up to IP69K.

Regulations (hygienic design, safety, traceability, quality control)

Linear rotary motor in capping machine — By using the linear-rotary motor from LinMot, Tölke was able to decouple the closing process from the motion of the turntable. This allows a closing station to be swapped out much faster in case of damage, thus minimizing downtime. (Photo: Rossmann)

Production processes and producers are increasingly subject to regulations and/or higher demands regarding quality control and traceability from their customers. As a result, machine builders have to implement more and more quality control and production tracing capability into their existing machines. This includes more and more detailed production data from each single product produced on the machine. While years ago it was sufficient to verify product quality taking regular sample probes, nowadays customer increasingly require detailed production information about all the production steps for each single product. One example is capping machines. In the first generation machines, the capping process was completely mechanical (linear cam and magnetic coupling). In order to control and monitor the tightening torque for each single bottle, the second-generation machines used servomotors for the rotary movement (linear cam plus servomotor). The third generation machines today use linear and rotary servo motors to control and monitor linear force and rotary torque applied during the capping process for each single product. On top of this, force and position feedback is used to verify presence of the cap and the final vertical cap position. To monitor all this data for a simple product like toothpaste may sound excessive, but as soon as it comes to medical or pharmaceutical products, it becomes indispensable for a producer to prove the quality and document each single production step for each single product. To find out more, read our case study on the use of linear-rotary motors in closure lines to enable frequent changeover.

Total cost of ownership & flexibility

International companies and multinational groups are increasingly considering total cost of ownership when buying new production lines. Service and energy costs can become dominant in high productivity machines running two or three shifts a day. In almost all cases the cost for production loss during servicing of a production line is much higher than the service cost itself (not talking about the investment cost for the spare parts, which is normally a small part of the servicing costs). Rising energy prices during the last 10 years changed the priorities for the machine builders choosing the actuators. Compressed air always has been an expensive energy. But with rising energy costs, machine builders, end users and international groups are increasingly replacing the pneumatics with electric actuators (with much lower service and maintenance costs). We have previously published a case study showing the total cost calculation for the replacement of pneumatics.

The final much reported trend is product customisation with some industry analysts predicting that to stay competitive companies will have to embrace customisation at every step in their processes. Machines will be increasingly designed with flexibility in mind allowing extremely short production change times, and the ability to store and document changes to guarantee that a product will be produced with the same quality as in the last production lot. With just in time production, production lot quantities became smaller and product changes on machines and production lines become more frequent. Flexible machine designs with very short product change times are possible with the use of linear motors. Using flexible and programmable electric actuators, different movements for different products may be stored in the machine control. Reducing the manual changes in the machine reduces setup time and will reduce material waste during setup, as all movements and production data for the new product are defined and stored in the machine control. Also further changes and improvements for each single product are automatically stored and documented in the machine control and will guarantee that a product will be produced with the same quality as in the last production lot.

Machine developments are being driven by not just by technology but by regulation and customer needs. In future posts we will continue to cover new applications and case studies for this rapidly growing field and if you would like to be interviewed please contact us, we’d love to hear from you.

Linear motors enable greater flexibility for robot grippers

July 1, 2016Blog, Newsapplications of linear motors, Energy efficiency, Linear Motor, robotadmin

With a robot that can handle tennis balls, tissue packs and champagne glasses, what more do we need for Wimbledon (apart from weather)?

Robot gripper developed with linear motors, is universally deployable and can safely and gently pick up even sensitive products and group them prior to setting them down. — The new robot gripper arm from Keller HCW eliminates pneumatics with the use of linear motors, so reducing operating costs and protecting the environment. (Image source: Keller HCW)

By changing from pneumatic cylinders to linear motors, German machine builder Keller HCW has developed a universally deployable robot gripper with a high payload rating that can safely pick up hollow bricks, glasses, cat food packages, tiles, tissue packs and tennis balls with just the right amount of force. Benefits included improvements in precision, repeatability, maintenance and energy efficiency in addition to negating the need for multiple grippers and lost changeover time.

Keller HCW, who is one of the world’s leading manufacturers of machinery and plant for the heavy clay industry, also develops customised robotic solutions with over 500 robot installations. Robot grippers from Keller HCW (mainly pneumatic drives) have proven themselves for years in brickyards and other heavy ceramics operations. However, there were significant disadvantages of using pneumatic cylinders when different shapes and formats of bricks are run on the same line so alternative designs were investigated.

For example, they are used to grip unfired bricks (blanks) and to place them with a certain spacing that guarantees an optimal drying and firing process. The bricks are fed to the gripper on a continuously running transport belt in the form of a consolidated stack consisting of about 20 to 30 blanks. The gripper picks up the entire stack, spaces the individual bricks optimally while the robot is moving, and then places them as a group on special carriers or transport belts.

“The challenge here is that the strength of the blanks can vary, and therefore we can only apply a limited gripping force at a limited approach speed. There is also a limited time window available during which the bricks have to be picked up from the feeder belt as it continues to move,” explains Reinhold Ungruhe, the manager of Automation and Electrical Engineering at Keller HCW GmbH.

Up to now, the robot grippers that have been used for singulating bricks, as well as other handling process in the heavy ceramics industry, have mainly used pneumatic drives.

Stroke adjustments were previously limited to 10 mm by the pneumatics

Due to the limited stroke and the relatively slow speed of the pneumatic cylinders, the stroke adjustments had to be no greater than 10 mm. This is disadvantageous if different shapes and formats of bricks are run on the same line, which is increasingly the case.
In developed industrial countries today, it is typical that the few thousand bricks required for the roof of a house, including the special bricks (such as gable and ridge tiles), are produced for a specific customer in one batch on the same line.
In practice, this has meant that the brickyards have had to procure several grippers for each robot—typically 6-axis robots—and use them alternately in order to cover all of the formats and styles. With procurement costs of about 50,000 Euro per gripper, this can tie up a great deal of the company’s capital. An alternative possibility for the user is to procure just one gripper per robot and then to reconfigure it whenever a format or style change requires it. In order to minimize this time-consuming setup process for the user, Keller has come up with a hybrid gripper design. The pneumatically powered grippers can be adjusted by means of a rotary servo drive in order to be able to group more brick formats and styles using the same gripper.

Pneumatic adjustments require manual finesse

“In practice, however, it is very difficult to adjust the pneumatics,” says Reinhold Ungruhe. “Just the fact that the pneumatic actuators behave differently depending on the ambient temperature, and therefore the precise adjustment of the gripping point and the grip force is only partially possible.”

The condensate water and other contaminants in the compressed air are another factor. Pneumatic cylinders are also not maintenance-free. They need to be oiled, for example. Seals harden or leak, especially when the drive works at a high frequency, so that the entire cylinder needs to be replaced.
Keller therefore took a step further and developed a completely electrically powered demonstration gripper that does not have these disadvantages. Twelve linear motors, model PS01-37Sx120-HP-N from LinMot*, move the gripper jaws that are mounted directly on them. They have a maximum stroke of 120 mm, a maximum force of 122 N, and an especially compact form factor.

High dynamics and repeatability with linear motors

“Linear motors can be controlled more precisely and are more dynamically than pneumatic drives. They can also cover a much longer stroke in a short time,” says the Keller specialist for automation and electrical engineering, summarizing the advantages.

The pattern in which the bricks are placed can be entered at the system’s user interface and changed at the push of a button. No time-consuming gripper change or setup is required. Unlike with pneumatic drives, the grip force can also be controlled directly. This ability and the long stroke, combined with high dynamics, are what make this gripper so universally deployable and why it can handle sensitive products, such as glasses or cardboard packages, as safely as robust products.
The linear motors in the new gripper are actuated by 12 ProfiNet servo controllers from LinMot’s C1100 series. These have been specially designed for applications where pneumatic cylinders are replaced by linear motors. The controllers are very compact and lightweight, with a height of 146 mm, width of 26.6 mm, and depth of 106 mm.

“This is important for the payload capacity of the gripper, because we wanted to mount the controller directly on the gripper, in order to keep to a minimum the number of cables running along the robot,” explains Reinhold Ungruhe.

The disadvantage of the additional weight, however, is typically more than made up for by eliminating valve banks, mechanical components, and sensors that used to be required, as well as by the greater flexibility and repeatability of the electric drives.

“For this series, it would also make sense to use LinMot multi-axis modules or distributed motors with integrated drive electronics to further reduce the weight and space required,” adds the automation expert.

Environmentally friendly and economical

In developed countries, users also focus on another consideration of the direct electric drives: their frugal use of energy.

“More and more manufacturers of heavy ceramics products are discovering energy efficiency in their production facilities as a differentiator and image factor that drives sales,” reports Reinhold Ungruhe.

Compressed air does not fit this image, because after all it is one of the least efficient and therefore most expensive energy media. Only about 5% of the energy applied is available as useful power at the actuator. For fast cylinders, in particular, the high noise level is an indication that a lot of energy quite literally disappears into thin air. The higher procurement costs for an electric drive are quickly paid back. Even using conservative figures, its efficiency of about 97% means that it amortizes within a maximum of three years.
No wonder, then, that more and more companies are attempting to eliminate compressed air entirely in their production facilities. Keller recently built a system for packing hollow concrete blocks with rock wool with no pneumatics at all.

“The great interest that this gripper drew at the Automatica in Munich confirms our assessment that many other industries beyond the field of heavy ceramics will also follow this trend, and are looking for flexible, reliable gripping and singulating solutions based on linear motors,” says Reinhold Ungruhe, optimistically looking to the near future.

This post is taken from an article written by Franz Joachim Rossmann, technical journalist, Gauting.

The Closing Twist

June 8, 2016News, Pressapplications of linear motors, capping machines, linear rotary motoradmin

The use of linear – rotary motors in closure lines to enable frequent product changeovers

Capping processes can be designed much more flexibly with linear-rotary motors than with conventional cam disc technology. Tölke, a packaging machinery specialist, has outfitted a new high-performance filling and closing line for a well-known pharmaceutical company with linear-rotary motors from LinMot. The resulting benefits included shorter setup times, lower downtime, and a wider range of applications for the machine.

Tölke specialises in machinery for bottle closing and capping machines and provides complete lines for sorting, aligning, filling and capping for well-known manufacturers in the beverage and cosmetics industries. These cappers have an output up to 500 bottles per minute with a packaging cycle for each bottle of only 0.12 seconds however when Tölke was commissioned for a high performance filling and capping line for an application that required frequent product changeovers a more flexible solution was required.

A limitation of conventional cam-stroke technology, as utilised in traditional capping machines, is that, if the closing process itself needs to be modified for a product changeover, it is usually necessary to change out the mechanical cams involved in the linear motion of the screwing process. This is a time-consuming and costly process and modern production lines require quick product changeovers. As a consequence a carousel machine was developed with 16 closing stations. The entire screwing process is handled by one linear-rotary motor (model PR01-84) at each station.

This electric motor, part of the PR01 series from LinMot, was specially developed for the closing and screwing process. It combines both a linear motor and a rotary direct drive in a compact housing, each of which is controlled separately. This means that any combination of linear and rotary motions can be implemented.

“For the rotary part of the screwing process, we have been using a rotary servomotor instead of a pneumatic motor for a long time wherever the screwing application requires a defined turn angle and a defined torque, and when we want to perform a product changeover at the push of a button,” explains Franz-Josef Patzelt, one of the managing directors of Franz Tölke GmbH.

What is new, however, is the use of an electronic linear axis in the closer.

“The cap needs to be picked up, placed on the bottle, and then guided so as to provide optimal support for the rotary motion,” says Markus Kröger, the Tölke project manager responsible for this job. “If this linear motion were controlled by a cam disc, then the heights at which the cap is picked up and placed down would be fixed, and the entire motion sequence would be defined.”

Filling and capping machine — Flexible filling and closing machine from Tölke for output capacity of up to 300 bottles/min and a filling volumes of up to 250 ml. (Photo: Tölke)

If modifications to the motion sequence were required for a product changeover, then the mechanical solution would require different closure heads or even different cam discs to be installed, or the machine builder would have to integrate adjustable cam discs. In some cases, a spring would also need to be installed to compensate for the weight of the head.

“With a direct drive and an electronic stroke curve, none of this is needed anymore,” explains Markus Kröger. With the right parameter sets for the programmed motion sequence, or by invoking a predefined recipe, the motion of the linear motor can be designed as needed and optimally adapted to the individual requirements of the application.”

This means that different types of closures, including screw-on and press-on caps, can be processed on the same machine. Even different press forces or thread pitches, such as are found on containers with and without safety caps, can be handled by a linear drive without any mechanical reconfiguration.
In addition, a linear-rotary motor like the PR01, with its two independently controlled axes, can start the rotary motion during the linear stroke, decoupled from the position of the turntable. The machine builder therefore has more freedom when designing the machine, allowing the cycle time to be shortened.

Other advantages include modularisation of the machine, simple changeover of the screwing station and the ability to analyse the data produced by the drive (torque, speed, angle, vertical position, speed and force) to improve performance.

“We can use the data provided by the drive to determine the number of revolutions actually performed, so that a separate check of the height of the closed container in order to monitor the screwing process can also be eliminated,” adds Franz-Josef Patzelt, citing a practical example.

Tölke have considerable expertise in this area and had developed a solution prior to the use of the PR01 linear-rotary motor, wherein the linear motion was generated by a servomotor in conjunction with a ballscrew spindle. The ballscrew, however, had to be protected against dust, which requires additional design effort that is not necessary for the fully assembled linear-rotary motor.

“The linear-rotary motor from LinMot is much simpler to use, as an integrated unit, and takes up less space,” says Markus Kröger. “The PR01 is thus the ideal solution for lines like our high-performance closing machines, where the rotary screwing process must be as flexible and efficient as possible.”

To find out more about linear-rotary motors take a look at our web site or alternatively we would love to hear from you.

Technology with a heart

May 11, 2016Blog, Newsapplications of linear motors, Linear Motor, LinMotMike Webb

Linear motors mimic the heart in testing of artificial cardiovascular devices

Linear motors are used in increasingly diverse applications and much of the pioneering work is being done in our universities. This is the first in a series of posts that looks at some of the more interesting and promising applications and starts by looking at the work of Queen Mary University of London who are using linear motors to simulate the human cardiovascular system. Heart disease is the most common cause of death globally and this important research will help in the development of treatments by allowing reliable in vitro (outside the body) testing of artificial heart devices.

Dr Paula Ruiz-Hincapie (Queen Mary University of London), Professor Theodosios Korakianitis (Saint Louis University) and their collaborators have designed a device which simulates the human cardiovascular system and significantly improves on previous implementations so allowing reliable in vitro testing of artificial devices such as heart valves, ventricular assist devices (VADs) and mechanical circulatory support (MCS) devices. Artificial devices need to be tested in vitro prior to in vivo testing and this work improves the reliability of testing so allowing development and introduction of new medical devices.

“This work by, funded by the NHS, has now moved from testing and proof of concept to the development of new medical devices for implantation,” adds Paula.

Unsurprisingly, simulation of the cardiovascular system is a complicated and challenging task requiring simulation of in vitro flow rates, pressures and other parameters representing normal and diseased conditions of the human cardiovascular system. Such devices are sometimes called bioreactors or ‘mock’ simulators of cardiovascular loops (SCVLs). Most SCVLs only simulate the systemic circulation (the circulation of the blood to all parts of the body except the lungs) and have other limitations such as capturing accurately the pressure waveform. Paula Ruiz, Theodosios Korakianitis and their collaborators from Shiraz University of Technology, Barts and the London NHS Trust have designed and implemented a mechanical cardiovascular system using linear motors which models all four chambers of the heart and the systemic and pulmonary circulation loops. Systemic circulation is the part of the cardiovascular system which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart. Pulmonary circulation is the portion of the cardiovascular system which carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart.

Diagrammatic representation of the SCVL in which linear motors represent the ventricles and atria. — Diagrammatic representation of the SCVL. Ao: aorta artery; C: compliance; Ca: carotid artery; CT: celiac trunk; IVC: inferior vena cava; LA: left atrium; LM: linear motor; LV: left ventricle; PA: pulmonary artery; PT: pressure transducer; RA: right atrium; Re: renal artery; RV: right ventricle; SVC: superior vena cava.

Four rubber gaiters of the correct size are used to model the four chambers of the heart which are accurately activated by a separate linear motor (P01-37×120 from LinMot) to simulate the suction and ejection stages. The linear motors consist of a stator and a slider accurately controlled by an E300 LinMot controller with four channels to accurately the position of each slider according to a predefined time-varying elastance function. This allows precise emulation of the contraction and filling phases as found in the native cardiac muscle. A high speed, high performance data acquisition card from National Instrument is used to send the desired displacement trajectories from the PC to the linear motor controller and to read the measurement signals from the pressure transducers and the flow-meter to the PC. NI LabView software is used for the desired trajectory generation and monitoring tasks.

This research demonstrated that the use of linear motors for displacing individual chambers provides an accurate technique for emulating different physiological (rest and exercise) and pathological conditions of the human cardiovascular system with and without mechanical circulatory support. The experimental results demonstrated the capability of this device to replicate normal and diseased conditions. The details of the experimental simulation of the various conditions and the measurements recorded to assess the success of the simulation are published in Artificial Organs, 2013 Vol 37 No 6 p 549-560.

Paula Ruiz-Hincapie is now affiliated to the University of Hertfordshire where her work has expanded into an exciting new area. Applying her experience of simulating the cardio vascular system with linear motors, she intends to use these motors to stimulate cardiovascular cells to reproduce themselves. The intention is to populate a bespoke geometry or scaffolding that can then be transferred to a patient for replacement of a malfunctioning organ or tissue.

“The cells will be grown in the laboratory and supplied with oxygen and nutrients. Linear motors will used to apply a force profile simulating that of the cardiovascular system. We hope, one day, to use cells grown in this way to implant into diseased hearts replacing damaged tissue. To do this type of transplant today tissues would be taken from a washed and sterilised cadaver, but there is always a risk of infection or rejection by the recipient’s immune system. Our work hopes to overcome these issues by growing replacement cells from cells taken from the recipient and thereby overcoming these problems,” Paula continues.

We look forward to hearing more about this innovative work in the future and wish Paula the very best with her research.

To learn more about LinMot’s range of linear motors please take a look at our website or contact us to discuss your application.

Source: Artificial Organs 2013 Vol 37, No 6, p549-560

In Vitro Cardiovascular System Emulator (Bioreactor) for the Simulation of Normal and Diseased Conditions With and Without Mechanical Circulatory Support
*Paula Ruiz, *Mohammad Amin Rezaienia, ‡Akbar Rahideh, †Thomas R. Keeble,
†Martin T. Rothman, and §Theodosios Korakianitis
*School of Engineering and Materials Science, Queen Mary University of London; ‡Shiraz University of Technology, School of Electrical and Electronic Engineering, Shiraz, Iran; †Department of Cardiology, Barts and the London NHS Trust, London Chest Hospital, London, UK; and §Parks College of Engineering,Aviation and Technology, Saint Louis University, St. Louis, MO, USA

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