Many industries employ roller screws into their machines to enable higher load densities, faster transportation times, and longer lifespans. Planetary roller screws have become a common tool in many industrial applications with several major options to choose from, all of which are explained further in this article.
What Are Planetary Roller Screws?
Though design varies by type, most roller screws consist of a complex nut with multiple threaded rods surrounding the hollow interior. When placed on a large threaded rod, each of the smaller threaded shafts will “orbit” around the diameter of the rod, and move linearly across the length of the rod as a result. In essence, roller screws work like a high-capacity bearing that relies on the rotational movement of several threaded rods to generate linear motion. From the outside, they look similar to a cylindrical nut that can be moved across the length of a threaded shaft. By placing the load on layered threading, roller screws have many contact points within them, making for very strong load-bearing capacity. As such, they are commonly used for heavy duty manufacturing and industrial processes that involve moving heavy products and machinery.
Types of Planetary Screws
In general, there are four main types of planetary screws available on the market:
Standard Roller Screw: In a standard roller screw, the screw and nut have multiple start threads, meaning that they have two or more intertwined threads running parallel to each other. The standard roller eliminates any movement between the mini rollers and the larger nut around them so there is seamless rotation of the nut around the rod.
Inverted Roller Screw: As the name suggests, the inverted roller screw is the inverse of the standard roller screw, meaning that the rollers are located on the exterior of the nut rather than the interior. As such, they move along the hollow inside of an internally threaded pipe, as opposed to the outside of a rod.
Recirculating Roller Screw: In a traditional planetary design, the threaded rollers simply advance along the screw shaft and do not move axially within the nut. However, in the recirculating design, the rollers only have grooves—not threads—so they do move axially within the nut and therefore need to be recirculated. This design is useful because it offers high load capacity and rigidity, but with very fine leads for applications that require positioning with high resolution.
Bearing Ring Roller Screw: This roller screw type consists of a similar design to the standard roller screw, but with a ring of bearings between the mini rollers and outer shell of the nut. This allows for there to be less rollers to accomplish the same movement, so that bearing ring roller screws are more compact and allow for greater efficiency at a high speed. Nevertheless, they also function well at low to moderate paces.
High Force Transmission: Planetary roller screws are capable of handling extreme weight because each of their threads work as contact points which evenly distribute the load. These contact points also form a lot of friction between the parts which aids their grip and prevents slippage.
Very Rigid: A roller screw is stable and can take a lot of force, so that it can carry and transport sizable loads without issue. The various contact points in the device not only add to its strength but also its sturdy composition.
Fine Threads: Planetary roller screws contain many fine threads which allow the machine to work more fluidly and precisely. When a machine is efficient, it requires less input from the user, making roller screws low maintenance.
Planetary roller screws are effective devices for transporting heavy loads linearly along a threaded rod. They come in several different varieties, but all carry the capability of handling very forceful applications. For access to over 2 billion new, used, obsolete, and hard-to-find components, including roller screws and other industrial devices, you can rely on ASAP Components. As an AS9120B, ISO 9001:2015, and FAA AC 00-56B accredited enterprise, we guarantee the quality and authenticity of all our items. As such, many parts are subjected to rigorous quality assurance measures, tests, verifications, and assessments, to keep to the high standard our customers expect. To receive a quote on any item of interest, simply submit an RFQ form on our website, and you can expect to receive a competitive quote for your comparisons in just 15 minutes or less!
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