Benchtop Bioreactors

A unique design, removable components, and tight design specifications deliver for this medical equipment manufacturer.

When Broadley-James set out to create a line of glass benchtop bioreactors that were compact and unique from others on the market, they had some specific motion control needs. The bioreactors were to be used with the company's latest BioNet Bioreactor Control System for research and development, as well as process development work in the Life Sciences Industries.

Small bioreactors are used by biopharmaceutical companies to create novel proteins with important therapeutic properties. Agitation is a mission critical parameter for the devices. In order for the bioreactor to yield reporducible results, agitation must be closely controlled and monitored. BJC needed to find a small brushless motor that could be used to provide motion in the agitator for the glass benchtop bioreactors most often used for cellculture and microbial fermentation.

The Challenge

The company preferred brushless motors for their low maintenance requirements and long life. The motors needed to be small enough to fit into a custom motor housing at the top of the bioreactor. Whenever the device underwent an autoclave procedure the motor needed to be removed. Therefore, in use, the entire motor and housing assembly had to be able to detach from the bioreactor.

Other key motor qualities and specifications were needed to complete the design cycle. The finished system needed to include a precision encoder for reproducible management of the bioreactor's agitation rate. Designers believed that a brushless motor design would allow for low maintenance throughout the life of the system. The compact size of the bioreactor itself required that the motor and motor housing would have to couple to the agitation shaft on top of the glass bioreactor. And, even though the motor had to be compact in size, it still had to deliver high torque over a wide RPM range.

Motor selection

The Maxon 40 mm brushless motor fit all the criteria that the design team came up with. Maxon brushless motors, mith their precision encoders allowed Broadley-James to precisely measure the agitator shaft RPM and control the agitation over a wide range of motor speeds. According to Scott Broadley, "The motors are made to tight tolerances and we had no problem quickly designing a housing that the motors fit into interchangeably."

Maxon's brushless motors are electronically commutated, thus enabling extremely long motor life, since there are simply no mechanical brushes to wear out. Using electronic commutation also minimizes electrical noise. By incorporating high-energy neodymium magnets the result is a very responsive motor while minimizing overall size. The encoder provides both a 3-channel signal as well as commutation signals in order to provide feedback to the control electronics.

Continuous output power is about 200 watts, while the maximum speed is 12,000 RPM. Maximum continuous torque is up to 265 mNm (37 oz-in) depending on the winding. Ambient temperature range is -20 degrees to 100 degrees C (-4 to 212 degrees F), and is built to IP54 standards. Due to their high torque capability in a compact package, the motors are particularly suitable for a variety of additional applications including robotics and factory automation, as well as machining and positioning applications.

Maxon designs, manufactures, and markets fractional horsepower moving coil DC motors and brushless motors ranging in size from 6 to 90 mm (0.2 to 3.5 in) and from 0.03 to 500 watts. The company also has an extensive selection of gearheads, encoders, and control electronics to complement the motors.

Maxon is known for its customer service, as well, and according to Scott, the US group is very skilled at getting back to BJC with information in a timely manner. "The US company is spot-on in returning calls and supplying the information that they have available," he says. Another factor that helped Broadley-James select the Maxon product line was the individual field service engineer. "The Maxon engineer personally worked very hard for us. That service was the deciding factor," Scott said. "Further, their documentation is clean and generally very friendly to use. The motors are made to tight toleraces and we had no problem quickly designing a housing that the motors fit into interchangeably."

Broadley-James designs and manufacturers sensors, bioreactors, and advanced control systems for bioprocess applications in the Life Sciences Industries. The Maxon motor that was incorporated into the company's agitation system provides the precision and reproducibility necessary to successfully operate a benchtop bioreactor in the demanding Life Science fields of recombinant cell-culrture and microbial fermentation.

Maxon Precision Motor, Inc.
Burlingame, CA
maxonmotorusa.com