Varian Medical Systems has been using SKF recirculating roller screws for over 14 years in the oncology treatment couches that it manufactures. The roller screws provide the necessary combination of precision, rigidity, repeatability and long-term reliability.
Over 14 years ago Varian Medical Systems, a leader in integrated radiation therapy systems, specified a recirculating roller screw manufactured by SKF to provide the accuracy, precision, rigidity, reliability and high load capacity required for the positioning and lifting of its Clinac, Ximatron and Exact cancer treatment couches.
Over 4000 couches later, without a single failure, the partnership is still going strong, ensuring the manufacture of some of the most superior medical couches available.
Oncology (the treatment of cancer) requires equipment that can provide ultra-precise positioning with incredible levels of reliability. The location and treatment of a cancer tumour requires patients to be positioned under a high energy treatment beam to receive a series of carefully controlled and accurately targeted doses of radiation, spread over a number of weeks. Accordingly, the height of the treatment couch is crucial in order to ensure precise and repeatable targeting of each individual patient within the radiation treatment beam.
Throughout its operating life, a medical couch will be expected to position 25 patients a day with an average of six movements per patient, equivalent to around 375,000 separate cycles. Each movement must be extremely smooth, trouble-free and accurate to within +/-1mm, as any greater positioning error could have a direct impact on the effectiveness of the cancer treatment.
1mm lead from 8-50mm diameter screws
It is for these reasons that the SKF recirculating roller screws were selected. Most importantly, they offer a combination of high precision, rigidity, repeatability and long-term reliability. Additionally, the units allow finite positioning due to the fine lead of 1mm for screws with a diameter between 8mm and 50mm. Furthermore, the mechanical advantage of the rollers screws means that only a low input torque is required from the drive.
Derek Flanagan, UK Manufacturing Manager at Varian Medical Systems, says: "The high-quality manufacturing and construction of SKF's products and proven operating efficiency it offers enables us to design and manufacture some of the world's leading cancer treatment beds, while the outstanding product availability and reliable delivery service allows us to optimise our production performance.
"We aim to continue to work closely with SKF and look forward to further develop of this and future applications, ultimately, so that we can keep providing cancer patients with the best possible treatment options in the battle against this terrible disease."