Product category:
Ballscrews, Linear Guides, Jacks, Dampers
News Release from: SKF UK | Subject: Recirculating roller screws
Edited by the Engineeringtalk Editorial
Team on 01 August 2001
Ultimate accuracy maintained in medical
couches
Varian selected SKF EPL's recirculating roller screws, to ensure control over the positioning of the scissor lift mechanism on its Clinac and Ximatron treatment couches
Oncology, or the treatment of cancer, requires equipment with accurate positioning and incredible reliability With this in mind, Varian, the international market leader for oncology machines, has selected SKF Engineering Products Limited (EPL) as a systems partner to supply its positioning and lifting needs
This article was originally published on Engineeringtalk on 25 Jan 2007 at 8.00am (UK)
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It was for this reason that Varian selected SKF EPL's recirculating roller screws, to ensure control over the positioning of the scissor lift mechanism on its Clinac and Ximatron treatment couches.
Throughout the operating life of a couch, it will be expected to position 25 patients a day with an average of six movements per patient, equivalent to roughly 375,000 separate cycles.
Each movement must be smooth, trouble-free and accurate to within just 1mm, as any further positioning error would reduce the effectiveness of the treatment.
The roller screws perform with absolute precision and meet the other vital requirements of rigidity, repeatability and long-term reliability.
Other positioning options such as vertical screws would not be accurate enough, and would also restrict patient access, and hydraulic equipment in a clinical environment is unacceptable due to the inherent risk of leakage.
SKF EPL chose the recirculating roller screw solution over a ballscrew because the load is transmitted from the nut to the shaft through the barreled surface of all the engaged rollers.
This significantly increases the number of points of contact and therefore the contact surface area.
A ballscrew will only transmit the load through the engaged balls in the respective groove.
Also, in a single start screw, the ball diameter is limited to 70% of the lead of the screw.
The recirculating roller screws allow finite positioning due to the fine lead of 1mm for screws between 8mm and 50mm diameter.
An added mechanical advantage of the roller screw is that it only requires low input torque from the drive and increases its resolution.
So reliable were the SKF EPL products, and so dependable was the company, that Varian subsequently agreed to SKF EPL taking on the role of system provider, whereby it now supplies the complete scissor lift actuator assembly for the couches.
Indeed, SKF EPL has been elevated by Varian to "Core and Approved Supplier" status. Request a free brochure from SKF UK ...
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