Linear Motion Control - 2021-07-05
When precise linear drive technology supports cancer treatment
A leading manufacturer of radiotherapy machines is using a Monocarrier linear drive unit from NSK to perform the precise movements and adjustments of the emitter, which projects the finely dosed X-rays or proton beams that kill cancer cells. The Monocarrier thus contributes to achieving lasting therapeutic success with minimal detriment to healthy tissue.
Successful cancer treatment is due in part to the performance and accuracy of the latest radiotherapy machines, which enable the highly targeted irradiation of tumours with minimal impact on the surrounding healthy tissue. In high-end radiotherapy machines, the accuracy of the radiation is checked every 10 milliseconds. Tracking of the tumour’s position takes place in real time, and the system can even adjust the guidance of the radiation source in line with the patient's breathing motion. Another factor is beam shaping, where a series of apertures and lamellas impart control.
Clearly, the drive technology in the head of radiotherapy machines has to meet demanding performance requirements. For this reason, a leading global manufacturer of radiotherapy machines (X-ray and proton therapy) has selected a Monocarrier MCM series linear system from NSK to precisely position the irradiation unit.
This linear motion system integrates a high-quality NSK ball screw, a servo or stepper motor, a U-profile linear guide, bearing units and motor adapters in a single compact unit, thus reducing the effort needed for design, assembly and commissioning. The linear guide is equipped as standard with a K1 lubrication unit to ensure long-term, maintenance-free operation.
Key features of the NSK Monocarrier include high rigidity and load carrying capacity, smooth motion, precise positioning, corrosion resistance, and long service life. MCM series Monocarriers are available in five standard sizes with various stroke lengths and pitches.
With the support of NSK's medical technology experts, the developers of the radiotherapy machine configured a drive unit with a Monocarrier MCM03 as its core component. The stroke of the MCM03 is 30 mm with a pitch of 1 mm. In an extremely compact unit, an X-ray proof motor with resolver and the MCM03 sit in parallel on a common mounting, while a toothed timing belt and pulleys provide the power transmission and transmission ratio. As a point of note, most applications do not require a timing belt, but instead take advantage of a coupling that facilitates a direct-drive configuration between the motor and MCM unit. Two mechanical limit switches detect the end positions of the spindle unit.
The use of a high-precision, robust base plate connects the drive system to the surrounding structure. This design means the operator can move and adjust the beam emitter with very high accuracy, ensuring that the radiation targets the foreign tissue precisely and creates the least possible stress for the patient. The NSK Monocarrier makes an important contribution to this outcome.
Picture 1): The drive technology in the head of radiotherapy machines has to meet demanding performance requirements. Photo: Thomas Hecker/Shutterstock
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