Applications to date have included flight critical aerospace apparatus, medical operating equipment and advanced machine tool operations, in some cases complete hydraulic systems have been replaced with intelligent motor control and roller screw linear movement. A satellite roller screw employs matched rollers to rotate (or satellite as the product name suggests) around the screw thread during actuation instead of ball bearings. By design, there is an immediate increase in the physical amount of contact points on the screw that can support a load compared with that of the same diameter ball screw. The satellite roller screw is therefore primarily chosen as part of a transition within a new or existing design to achieve greater load capacity and greater linear positional accuracy, in the smallest envelope space. A roller screw design will always transmit more load than a ball screw nut assembly size for size.
Phil Jones, of ABSSAC says“ lead screws and ball screws have a legitimate use in the market place, but should the application require extreme positional accuracy or perhaps high acceleration forces and rotational speeds, then the satellite roller screw products might be a better solution. Offering a standard, as well a bespoke range of products, ABSSAC has worked on numerous applications through the years where standard lead and ball screw designs just can not compete.
Traditionally, hydraulic cylinders initiate the pressure control required within injection moulding machines to ensure mold integrity. Pneumatic systems can not produce the necessary forces and traditional ball screw designs would have to be oversized to achieve similar forces reliably. During injection moulding, plastic material is heated until molten. A motorized auger screw forces the molten material to the end of the injection cylinder. Once enough material has accumulated in front of the screw, the injection process begins with injection pressure provided by hydraulic actuation. However, using hydraulics inevitably requires the use of hydraulic pumps, pipes, seals and control units within the machine, all of which can be bulky in design and expensive to maintain. The satellite roller screw product, available from Abssac, produce the same linear forces necessary for injection, but also has the advantage of being coupled to less expensive and infinitely more adjustable closed loop electric motor drive designs.
Satellite roller screws are particularly suitable for applications where high axial loads, high speed, and high feed speeds are requested. The design of the product transforms rotary movement into a linear movement via threaded rollers which ensure maximum contacts points between the nut and screw enabling heavier axial loads and greater longevity to any linear application. Roller screws also reduce the space that is necessary for hydraulic actuation and can offer a fully traceable performance.