If you’re involved in ball screw sizing or selection, you’ve probably noticed that there are several different standards that govern various aspects of ball screw design, from lead accuracy and load capacity to ball nut tolerances and rigidity. Fortunately, in many cases, these standards are in harmony and provide the same (or virtually equivalent) specifications. […]
Applications
Profiled rail accuracy: When accuracy class doesn’t tell the whole story
You’ve chosen a profiled rail and bearing for a high-precision application — machining, cutting, or metrology, for example. The bearing (aka carriage, or runner block) has good load capacity and rigidity, so it should provide long life and low deflection. But when you integrate the assembly into your application, you notice that the system doesn’t […]
Choosing the right stage actuation for dynamic-metrology applications
When measurements are made to discrete product on the fly, it’s key that the motion system minimize error and correct for the rest. Brian Handerhan | Business development manager • Life sciences Patrick Lehr | Product manager • Precision mechanics Electromechanical & Drives Division • Parker Hannifin Corp. Dynamic metrology is the collection of data […]
7 tools every mechanical engineer should have
As computer programs and mobile apps take over our lives, one of the great things about being a mechanical engineer is that there are still aspects of the job that allow — and sometimes require — us to do things by hand, the “old fashioned” way. Granted, drafting boards and T-squares have been replaced by CAD […]
Selecting shafts for linear bearings: two things you need to know
In a round shaft linear bearing system, the shaft acts as the inner raceway of the bearing and plays a significant role in the wear and life of the system. Both recirculating and plain linear bearings as well as track-roller wheel-based linear bearings can use a wide variety of shaft materials, depending on the application […]
Tribology basics for linear bearings
Tribology is the study and application of the principles of friction, lubrication, and wear between two surfaces in relative motion. In linear bearing systems, those two surfaces are the bearing element and the guide raceway. Friction and wear The term “wear” generally refers to deterioration, but when discussing tribology principles in relation to bearings, it refers […]
How to specify linear motion components for vacuum applications
Vacuum applications are common in the manufacturing of semiconductors, liquid crystal and plasma displays, fiber optics, and aerospace components, where linear motion systems are used for the positioning, handling, and alignment of critical equipment. Although vacuum applications are often likened to cleanroom applications, in the category of “special environments,” there is a critical difference between […]
How raceway geometry affects profiled rail guide performance
In the context of profiled rail guides with recirculating balls, the raceway geometry defines how the load-carrying balls are positioned relative to the raceways of the rail and the bearing (aka “carriage” or “slide”). The two most common raceway geometries are referred to as circular arc and Gothic arch, but some manufacturers have adopted a […]
Beam deflection equations for linear systems
When a linear guide, such as a round shaft or profiled rail, deflects or sags, the bearings that travel along the guide experience edge loading (a higher load concentrated at the ends of the bearing), which can cause rough, irregular movement, increased wear, and reduced bearing life. And when a linear guide is incorporated into […]
What are the benefits of a rotating ball nut (aka driven nut)?
When you think of a ball screw assembly, you probably envision a screw shaft with a motor connected to one end. The motor turns the screw, and the ball nut travels along the length of the screw shaft. An alternative setup is to hold the screw shaft stationary and rotate, or drive, the ball nut […]