Device Makers Spark Innovations in Motion Control
Product Announcement from BEI Kimco Magnetics
Four recent BEI Kimco motion control developments for the medical market are the subject of an article appearing in the March 2011 issue of Medical Design magazine.
The article, "Device makers spark innovations in motion control technology," shows how BEI Kimco teamed with medical device makers to meet specific challenges and advance existing technologies.
Device makers spark innovations in motion control technology.
Mar 18, 2011 12:19 PM, Written by: Jim McNamara Application Engineer BEI Kimco Magnetics Vista, CA beikimco.com
Four examples show how.
Customer Requirements Spark New Innovations in Motion Control Technology
New products that are smaller, faster or in some respect better than existing technology are always in demand. If a product equals existing technology, but is somehow produced more economically, it's also a hot button for medical designers looking for quality and economy. In many other cases, however, a new product is developed solely to meet the engineering requirements for a specific new product design or re-design. In these cases, it's a win-win. The engineer creates the need for innovation and receives a solution to his specific requirement, while new technology advancement is made for the industry at large.
BEI Kimco engineers were faced with the challenge of meeting a valve control actuator requirement for a medical ventilator system used for critical care patients. In this case, the customer was using a stepper motor and lead screw mechanical arrangement to produce the linear motion required for the application. However, speed wasn't as high as desired and the overall package was cumbersome. Additionally, the customer wanted higher reliability and reduced power consumption.
The first challenge for BEI Kimco engineers was to design a self aligned, housed actuator capable of producing 15 N of peak force within a 40.6mm diameter size. The second challenge was to meet the aggressive speed requirement. In order to get there, it was necessary to use different bobbin materials.
To accomplish these goals, engineers developed the Voice Coil Actuator (VCA) LA16 series with a patented Magnetic Spring. The magnetic spring eliminated the need for a mechanical return spring or alternative option which may fatigue or fail. Over time, these mechanical type springs exhibit wear and tear, resulting in a reduced spring constant that causes undesirable performance deviations, especially critical for medical equipment operation. The magnetic spring design was an important design element to support maximum battery life and the fail-safe valve mechanism.
The resulting performance characteristics included a 6 mm stroke, a peak force of 60 N, and a continuous force of 17 N. Small size featured an outside diameter of just 40.6 mm and a length of 46 mm.
The new ventilator uses two LA16 Actuators to support different functions within the ventilator. One actuator controls the diaphragm valves that regulate the air pressure within the patient's lungs during the inhalation and exhalation cycles. The second actuator operates a safety valve that diverts the air flow around the ventilator in the event of a system malfunction or power failure. Both actuators incorporate the magnetic spring that establishes the preferred or home position.
By using the newly developed actuators, the customer was able to increase the valve actuation speed and simplify the assembly because of the direct drive advantage. Other benefits were better resolution and control.
Another technological advancement resulted from a voice coil actuator requirement needed for an Optical positioning control application.
The customer was using a mechanism based on a gear motor and fixtures to mount the lens. Outgassing was an issue for them and the speed to move the lens was limited.
Key to the optical focusing mechanism design was a voice coil actuator that would produce near zero outgassing levels. The actuator would move the lens attached to the coil assembly, which in turn would provide precise focus to the system. The operation must be accomplished without contaminating the lens.
The challenges were to design and develop an actuator 38 mm in diameter with a 12 mm middle hole, with low outgassing materials while maintaining the peak force of 66 N, which was necessary to move the lens at the desired speed.
To achieve near zero emissions, BEI Kimco developed a Linear Voice Coil Actuator without adhesives or inks and manufactured and assembled all parts by mechanical means utilizing clean manufacturing processes, thereby eliminating any substance that could cause outgassing. High energy Neodymium Iron Boron (NeFeB) magnets were incorporated to provide superior operating efficiencies, and a thermocouple was integrated to monitor and control the coil temperature. With the additional customer specification for an optical clear aperture, the design also included 6.4 mm of stroke and a 12 mm middle hole. The resulting high performance VCA measured 38.1 mm in diameter and 39.6 mm in length (at mid-stroke).
In this application, following several different product interactions, BEI Kimco engineers were able to exceed customer expectations. The low outgassing actuator is part of high quality, expensive equipment and it must perform at those levels. The specially designed VCA eliminated the outgassing problem and allowed the customer to simplify the system by mounting the lens directly in the moving coil of the actuator, thus eliminating the fixtures. Speed was also increased. High quality optical devices demand low outgassing levels to minimize contamination. The devices also require high precision actuation for exact motion control positioning.
Another application involved a VCA for a cutting tool utilized in an Ophthalmic Lens Grinding application. This application required an actuator with high Force/Acceleration capabilities and high speed position control to meet the desired cutting tool performance.
The customer had been using a BLDC Motor and lead screw mechanical arrangement to produce the linear motion, but was unsatisfied with the results. BEI Kimco engineers were confronted with providing a voice coil actuator capable of producing 1370 N of peak force with a maximum acceleration of 1500 m/s^2 and a diameter no larger than 110 mm. Another important requirement was reliable operational performance at ambient temperature of 40 degrees C.
To meet these requirements, BEI Kimco developed the Voice Coil Actuator Model LA43-67-000A. This un-housed actuator features an exceptional actuator constant (KA) of 28.02 N/watt^0.5, achieved by the patented 3
optimal design configuration and the use of strong, high energy product rare earth magnets. Compact in size, the device measures only 108 mm in diameter and 170 mm in length (at mid-stroke).
Utilization of the LA43-67-000A Voice Coil Actuator also allowed automatic calibration with accurate and fast alignment of the turning system without operator assistance, eliminating the need for manual adjustment and providing a significant time-savings advantage. By using VCAs, instead of the motor and lead screw technology, the customer was able to design a smaller and lighter system with fewer components and therefore less failure modes. The new system was also quieter and offered higher acceleration and more precise movement.
High acceleration and high system precision are the two main advantages made possible by using voice coil actuators. The high Force/low moving Mass Actuator allowed the customer to design a fast tool capable of delivering one of the highest productivity freeform lens turning process in the industry.
Supplying a motor that would meet the requirements for a revolutionary new cast removal system for a leading medical device manufacturer was another technology challenge that led to exciting innovation.
The new cast removal system was developed as part of the manufacturer's continuing goal to develop products that reduce trauma for pediatric patients. The new tool has provided an alternative to the autopsy saw method that has been used for 40-years, which expose the patient to extremely high temperature and noise levels. The new approach uses a proprietary feed wheel which fractures or breaks apart, rather than cuts the cast material.
The motor was designed to deliver consistently high torques to drive through several layers of cast material. It was also critical for the motor to be compact, lightweight and capable of extended battery operation. To meet these requirements, BEI Kimco developed the High Performance Size 23 BLDC Motor with customized housing and shaft. The High Torque Density design delivers continuous power levels approaching 1 HP at speeds up to 20K RPM. Its compact size of just 2.3" O.D x 3.0" L with operating efficiencies in excess of 85%, resulted in a highly satisfactory motor solution - a motor powerful enough to drive the feed wheel yet small enough to support the ergonomics of the final product for a cool running, comfortable patient solution. The motor's competitive price point easily allowed volume production of the new cast removal device.
"It was extremely satisfying to be involved in a project that ultimately reduced trauma for children needing cast removal," says Walter Smith, BEI Kimco's Senior Applications Engineer/Project Manager for Motors. "With our ability to adapt standard motors to meet specific customer needs, we are able to work with medical device manufacturers and other industry designers to consistently meet unique requirements."
When a customer has a specific need, the engineer is faced with the challenge of improving technology to meet that demand. For BEI Kimco, these challenges are on-going and create a continually evolving product line.
Jim McNamara has 33 years of experience with custom electric motors. His experience includes positions as Lab Technician, Design Engineer, Application Engineer and Regional Sales Manager.
About BEI Kimco Magnetics:
BEI Kimco Magnetics is an operation of Custom Sensors & Technologies (CST). BEI Kimco Magnetics was founded in 1974 and is a leading manufacturer of high speed, fractional horsepower brushless BLDC motors, voice coil actuators, smart voice coil actuators and BLDC motor controllers for the Transportation, Industrial, and Aerospace & Defense markets. These products are used across a wide range of applications including medical and scientific, factory and office automation, optics, semiconductor/electronics, military, aviation, space systems, and security. Kimco merges leading-edge capabilities and cost-effective manufacturing know-how with highly customized applications expertise. www.beikimco.com
Custom Sensors & Technologies (CST) is a specialist in sensing, control and motion products.
Through its brands, BEI Kimco, BEI Sensors, BEI PSSC, Crouzet, Crydom, Kavlico, Newall and Systron Donner, CST offers customizable, reliable and efficient components for mission-critical systems in Industrial, Aerospace & Defense, and Transportation markets.
Focused on premium value offers and committed to excellence, CST, with more than 4,000 employees worldwide and sales of $530M US in 2009, is the dependable and adaptable partner for the most demanding customers. www.cstsensors.com