A brushless DC motor for demanding operating room applications

A sterilizable EC-4pole 30 from maxon motor

A sterilizable EC-4pole 30 from maxon motor

A sterilizable EC-4pole 30 from maxon motor

maxon’s new brushless electric motor, the EC-4pole 30, delivers high torque (106 mNm) and is sterilizable – a perfect drive for hand-held surgical tools.

Swiss drive specialist maxon motor has developed a robust brushless DC motor for hand-held surgical tools: the EC-4pole 30. Featuring two pole pairs, this DC motor provides a nominal torque of 106 mNm and an output of 150 W. It has a hermetically sealed rotor, meaning that it can withstand over 1000 autoclave cycles.

Need to operate at overload? No problem!

The EC-4pole 30 is equipped with the special ironless maxon winding, which makes it highly efficient. Another key feature is that the torque and current behave linearly and the drive can be overloaded. It is available with an optional Hall sensor, as well as with a hollow shaft with a diameter of up to 4.1 millimeters.

With the EC-4pole 30, engineers get a first-class drive for surgical hand tools that work flawlessly under the tough conditions of operating rooms.

maxon offers a complete line of dc brushed and brushless motors, gearheads and controllers. Contact us to help find the right solution for your application. info@maxonmotor.com


Select, combine and order – from anywhere in the world.

maxon's e-Shop

e-Shop: Select, Combine and Order from anywhere in the world!

You can search on maxon’s e-shop quickly and easily for a DC or EC motor, combine it either with a gearhead and control electronics, then order the drive system you require, conveniently with just one mouse click, wherever you are.

All catalog products (up to 49pcs per item) can be ordered from maxon motor directly through the online purchase channel. 24 hours a day, 365 days a year- from anywhere in the world. Brush and brushless DC motors and controllers can be purchased individually or as a system solution. Gearheads, sensors and brakes are also available in combination with motors.

All products ordered through the e-shop that are in stock (green light) are dispatched from the factory in Sachseln (Switzerland) within 24 hours on working days.

Users worldwide benefit from the following functions of the maxon motor e-shop:
– display of the full maxon motor modular system (DC and EC motors, gearheads, encoders, brakes, control electronics)
– download of technical data of all drive components in PDF format
– download of DXF and STEP files of all motors and gearheads
– current availability check
– price details for up to 49 items
– direct orders with a part number
– detailed overview of all items on order

To place your order visit: http://www.maxonmotor.com/maxon/view/catalog/

Machine Optimization Through DC Motor Selection

Selecting the right DC motor is an important aspect of optimizing medical machine performance.

There are so many motors on the market today, from heavy-duty AC motors to tiny DC brushless and stepper motors. To use any of the motors users must have a full understanding of the application parameters, including power, speed, torque, physical size, efficiency, lifetime expectations, and other requirements. There have literally been books published about each of these aspects, and to define them all accurately in a short article would be difficult to say the least.

What this article will do is spell out the primary differences between DC brushed and brushless motors, what they can do, where they fit best, and how to decide which to use in your application. DC motors are being used in more and more industrial applications because of their flexibility and long life. Therefore, DC motor selection is often one of the most important steps in providing motion control of a medical machine, whether for prosthetics, medical tools, robotics, or medical training aids

Defining the Application

The medical market is unique in that most devices and machines are operated in a clean environment and around people as opposed to an industrial application. This means that long life and low noise (see Sidebar 1 on Maxon’s new low noise gearhead called the Koax Drive) are key characteristics the drives need to have in order to fit the requirements of many medical machines. DC motors are noted for their life-spans, particularly DC brushless motors which can last tens of thousands of hours in continuous operation, and much longer when operated intermittently.

Key criteria for selecting a DC motor for a medical machine application includes finding out what voltage is readily available for the application and what physical size the motor needs to be. Speed and torque can be determined once these two parameters are determined.

Voltage availability is a critical element in motor selection. Prosthetics, for example, are battery operated, while many rack-mounted devices and surgical tools operate from a 24 V power supply. DC motors are available for use at voltages as low as 1.5V and as high as 48V dependent on required power.

Physical size is often one of the limiting factors in motor selection for medical machines. Often a compromise needs to be made between which motor to use and the available space it needs to fit into. The prosthetics talked about earlier would need a small frame motor, while rack-mounted devices can be designed to accommodate larger devices.

Efficiency becomes a primary concern when you need to worry about power consumption to maximize battery life in a prosthetic hand or in a portable surgical tool like a drill or saw. Such concerns are not so evident in robotic machines used to perform many surgeries today.

As mentioned before, torque and speed also have an affect on motor frame size. High torque motors are often larger in size than their low-torque counterparts, which means that larger mounting hardware and larger housings may be a requirement of the machine. For example, it takes a larger motor to rotate the magnets in an MRI than it does to run the infusion pump for drug delivery. (See Sidebar 2 for more torque and speed information.)

Motor duty cycle could be one of the most telling aspects of a medical machine. Intermittent operation not only reduces the wear and tear on the motor and increases the life of the motor, but it also means that a smaller motor size can be used without depleting the positive characteristics of the machine itself.

Brush or Brushless

Key specifications quickly show that brushless motors last much longer than brushed motors, which rely on a mechanical connection for operation. And brushless motors run much faster as well. If you’re using a brushless motor for reliability, you won’t want to add a gearhead to the mix, though. The mechanical nature of a gearhead automatically means that it’ll have a shorter life cycle. Using a gearhead with a brushless motor will only negate the longevity of the combined system, and therefore reduce the longevity of the medical machine it was designed into. On the other hand, there are times when using a gearhead on a brushless motor is advised. For example, if the environment is such that noise is a concern or that a higher torque is needed, a gearhead will do the job very well.

Brushed motors would need a mechanical gearhead to increase speeds close to those of brushless motors. Using a gearhead with a brushed motor won’t change the life cycle to any great extent. Both are mechanical components that are subject to wear and tear. For medical machines, though, you don’t have to be concerned with dirt or grime mucking up the system. The cleanliness of the hospital allows you to get the most out of your mechanical components.

A real issue in selecting between a brushed and brushless motor is the expertise of the machine builder. Brushless motors either come with built in electronics or with external electronics to operate the motor. It takes some experience to provide the custom electronics many machine builders choose to provide. But for high sales volumes, the costs are easily regained.

Brushed motors, on the other hand, don’t need electronics to run the motor, offering a plug-and-play option to the designer. This means that if the machines are expected to sell in low quantities, a brushed motor will save on the overall cost of the system. A final concern is the power needed for the motors. Maxon motors are available in power ratings up to 250 Watts for brushed motors and 400 watts for brushless motors.

Overall, many medical machine builders are selecting to use brushless motors whenever possible. Long life and high speeds make these motors applicable to a broader array of applications. But as development costs increase and quantities decrease, brushed motors come to the rescue.

maxon's KD 32 Low Noise Gear

maxon's KD 32 Low Noise Gear

 Quiet Drives

The Koax-Drive, KD 32, manufactured by Maxon Precision Motor is a high-torque, but extremely quiet drive designed and manufactured specifically for medical technology (including surgical tools). The drive was designed to make handing instruments a more pleasant experience for users and patients alike.

The drive’s unique torque conversion system is a breakthrough for noise-sensitive environments, even under high loads. The KD 32 has a diameter of 32mm and a coaxial arrangement on the drive and output shaft that makes it ideal for use in applications where space is at a premium. 

maxon's DC Motor Torque / Speed Curve

maxon's DC Motor Torque / Speed Curve

Speed vs. Torque

Although speed and torque are independent requirements in many applications, typically speaking when the torque increases the speed will decrease – if the voltage stays the same. This connection is based on the slope of the speed/torque curve (called the speed/torque gradient), calculated using the formula below and shown in the sample curve shown here.

 Torque = {power [kw] • 30,000} / p • rotational speed [rpm]

For information:
maxon precision motors, Inc.
101 Waldron Road
Fall River, MA 02720
P: 508-677-0520
F: 508-677-0530
S: http://www.maxonmotorusa.com

maxon’s Sterilizable Motors EC Size 5 and EC 13

maxon's Sterilizable EC Size 5 motors. Small, precision and incredibly fast.

maxon's Sterilizable EC Size 5 motors. Small, precision and incredibly fast.

Small, precise and incredibly fast.

maxon motor launches two sterilizable drives for use with or without planetary gearheads in high speed medical applications of up to 90,000 rpm. The drives are characterized by their high nominal speed, extremely low-noise and low-vibration operation, marginal thermal emission and small size.

The drives are identical and possess equal performance data and characteristics.

The motor and gearhead of Size 5 version possess dimensions in U.S. Customary Units resulting in an outside diameter of ؽ inch and a shaft of Ø0.125 inch. The motor has a “Servo Mount”, a well-established type of motor fixation. The EC13/GP13 version is expressed in metrics, which results in an outer diameter of Ø13 mm, a Ø3 mm shaft and a flange with 3 face side threads.

Despite their “personalized outer wrapping”, the two drives are characterized by their similarities. Both are ideal for medical design applications; compact design with very high nominal speed, quiet running, minimized thermal emission and sterilizability of typically 500 autoclave cycles. Both are available either equipped with Hall sensors or sensorless as well as with three different windings. The gearheads come with versions of one, two or three stages as well as with or without output end shaft sealing. Check out our website for additional product information www.maxonmotorusa.com

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