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Maxon Motor UK has supplied 120 motor drives, with associated gearheads and encoders, to Varian Medical Systems for its HD 120 MLC computerised radiation machine.

This comes as medical scientists involved in the development of radiation therapy face a constant challenge: to maximise the treatment’s impact on tumours while minimising damage to healthy tissue.

The machine – also known as a ‘high-definition multi-leaf collimator’ – features 120 individually adjustable tungsten leaves that can be positioned to form an aperture shaped to direct the radiation in a pattern that exactly matches the shape of the tumour.

Varian Medical Systems chose 120 Maxon brushless DC (electronically commutated) motors with diameters of 8mm, 10mm or 13 mm to move the tungsten leaves.

Furthermore, the radiation can be delivered from different angles to match the contours of the tumour.

With this level of control, the radiation intensity can be adjusted to deliver a higher dose to more aggressive areas of the tumour and a lower dose around sensitive healthy tissue.

Each drive is equipped with a compatible Maxon planetary gearhead and encoder, taking the length of the individual drive systems to between 17.0mm and 24.6mm.

This allows all of the motors to fit into an area measuring just 40cm x 40cm.

The motors feature neodymium magnets, which increase their strength, despite their compact design.

The shape of the aperture, formed by the positioning of the leaves, needs to be adjusted quickly and precisely in response to pre-programmed data.

Maxon claims that, as its motors have no magnetic detent, their movements can be controlled with great accuracy.

High torque is needed to overcome friction within the system of synchronously adjusting leaves.

The performance of the Maxon drive systems ranges between 0.5W and 1.5W and the nominal torque goes up to 1.61mNm.

Matching the company’s gearheads with reduction ratios from 4:1 to 1024:1 are said to increase their torque to 200mNm.

maxon motor is the world’s leading supplier of high-precision drive systems.

maxon has earned a reputation for constant innovation and unflinching reliability – seeing the company’s products used by the world’s top engineers in fields as demanding as space exploration, formula 1 racing and sub-sea applications.

The maxon product range is developed on a modular basis, giving literally hundreds of thousands of perfectly compatible motor, gear and controller combinations to suit a huge array of applications. With full customisation possible for almost every product, maxon’s experienced sales engineers are on-hand to assist design engineers select precisely the right solution for their needs.

DC motors with ironless winding and flat motors (up to 500W output power, mechanical and electronic commutation).
Planetary, spur and special gears.
Sensors (encoders, DC tachos, resolvers).
Servo amplifiers, position controllers.
High-tech CIM and MIM components.
Customer specific drive solutions.

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