Air bearings provide several advantages over rolling element bearings, including higher travel accuracy and reduced friction and heat generation. But because air is compressible, air bearings can be less stiff and exhibit more deflection under load than similar rolling element bearings (although the stiffness characteristics of air bearings are very linear). However, the compressible nature of air […]
What is cage creep and why does it matter?
Several types of non-recirculating linear bearings use a cage to contain the rolling elements, maintain consistent spacing between them, and ensure even load distribution. But in each of these non-recirculating designs, the cage “floats” between the two moving components, meaning that it’s not constrained and can gradually move away from its intended, centered position. This […]
A guide to stainless steels for linear motion components
For applications that involve corrosive environments, designers of linear motion systems can take precautions such as using covers to protect vulnerable components, ordering parts with special coatings or platings, and strategically placing sensitive components within the machine or system to minimize their exposure to hazardous liquids or fumes. But some applications — due to the nature […]
What are some linear motion options for moving multiple loads independently?
From a mechanical standpoint, one of the more challenging applications in linear motion has traditionally been to move two or more loads independently, as is required in some handling, transport, and inspection applications. While using multiple linear systems, or preassembled actuators, is a simple solution mechanically, this option typically requires a significant amount of space […]
Recirculating roller screws: How do they work and what are their benefits?
Screw assemblies that use rollers as the load-carrying element come in several varieties, with the most common being the traditional planetary roller screw, which provides high load capacities and very high rigidity, capable of outperforming ball screw and hydraulic actuators in some heavy-duty applications. But another type of roller screw — the recirculating roller screw — […]
How to account for ball and lead screw inertia during system design
When sizing a motion system with a ball or lead screw drive, the first step is to determine the screw diameter and lead that can meet the application requirements for thrust force, speed, and compressive (buckling) loads. Once the screw diameter and lead are determined, the next step is to choose a motor that can […]
Ball and lead screw drunkenness: What is it and when does it matter?
Unlike ball screws, which follow industry standards such as DIN ISO 3408, JIS B1192-1997, or ANSI-B5.48 for accuracy classifications, there are no accuracy standards for lead screws. Instead, many lead screw manufacturers have loosely adopted two of the most common ball screw lead accuracy specifications: lead deviation per 300 mm and lead deviation per revolution. Lead deviation […]
What’s the difference between module and diametral pitch for rack and pinion drives?
Gear sizes are typically specified by one of two designations: module or diametral pitch. While both specifications define the size of the gear teeth, module and diametral pitch are calculated differently, with module (sometimes referred to as metric pitch) being the metric sizing standard and diametrical pitch being the Imperial (inch) sizing method. Standard modules for […]
Ball spline preload: How, why, and when it’s applied
Like other linear motion components where rolling elements ride in raceways, ball splines can be supplied with preload. In the case of a ball spline, the main purpose of preload is to reduce angular backlash — clearance in the rotational direction — when torque is applied. Without preload, ball splines have a small amount of […]
What’s the difference between moment and torque in linear motion applications?
In linear motion, we often deal with applications that involve forces applied at a distance from a linear guide — referred to as cantilevered, or moment, loads. In these cases, we’re concerned with guide’s moment load capacity, or its ability to resist rotating. But we also deal with components that should rotate when a force […]
