The thread design of a power transmission screw—whether a lead screw or a ball screw—plays a critical role in the screw’s function. Aside from the basic thread form (acme, trapezoidal, etc.), the three main aspects of the thread geometry—helix angle, lead angle, and thread angle—help to distinguish different types of screws from each other and play […]
How to calculate motor drive torque for ball screws
When sizing a motor, one of the most important factors is the required torque. In general, motor torque-speed curves outline two primary areas of permissible torque: continuous and intermittent. Intermittent motor torque is allowed only for a short time (specified by the manufacturer) and in most cases is the torque required during acceleration. A motor’s […]
Tubular linear motors for gantry applications
Linear motors are often thought of as either flat or U-channel designs. But tubular, or shaft-type, linear motors have a construction principle that provides higher efficiency and makes them especially well-suited for gantry applications. Benefits of cylindrical design Tubular linear motors consist of a thrust rod (or tube) with permanent magnets and a stator (sometimes referred […]
Moment of inertia: area or mass?
Moment of inertia is an important parameter when sizing and selecting a linear system. But it’s critical to know which type of inertia—planar moment of inertia or mass moment of inertia—is given and how it affects the performance of the system. Planar moment of inertia Planar moment of inertia (also referred to as second moment of […]
Repeatability and Accuracy: What’s the Difference?
There are numerous ways to classify the performance of linear positioning devices such as ball screws, belts, and rack and pinion systems, but the terminology can be confusing. The two most common terms, accuracy and repeatability, and are often used interchangeably. When someone says that a ball screw is very accurate, they may really mean that […]
Earth Day 2016: Energy efficiency in automation
On Friday, April 22, people around the world will celebrate the 46th annual Earth Day, with the theme, “Let’s get really big stuff done for our planet.” And while there are multiple ways for individuals to celebrate and participate, the biggest impacts to our environment come not from individuals, but from industry. Fortunately, some of the […]
Tolomatic hygienic electric cylinder delivers more force, longer service life
Tolomatic ERD all-stainless hygienic electric actuators with new roller screw choice are designed for 100 percent duty cycle and can be deployed in the most demanding of applications, including food and beverage processing. The Tolomatic ERD hygienic all-stainless-steel electric cylinder features a new roller screw option that increases the maximum thrust to 7868 lbf (35.6 kN) for expanded cylinder […]
What are ball splines and rotary ball splines?
Ball splines are often lumped into the category of recirculating linear bearing guides (aka linear bushings), but they offer functionality beyond that of traditional linear bushings. Standard ball splines provide both linear motion and torque transmission, while rotary ball splines combine linear and rotary motion in one device. Ball splines for torque transfer A ball […]
8 Great Engineering Comics
Who doesn’t love engineering comics? Let’s face it—no matter how much you love your job and how great your co-workers and managers are, we all experience frustrations and adversity at work. And nobody epitomizes the plight of engineers quite like Dilbert, Alice and Wally. Over the years, I’ve compiled a list of my favorite Dilbert […]
Ground vs. Rolled Ball Screws: Does manufacturing method matter?
There’s much debate among manufacturers, and sometimes among users, regarding the superiority (or lack thereof) of ball screws with ground threads over those with threads that are formed by rolling. Ground ball screws have traditionally been the choice for high-precision applications, whereas rolled screws offered an economical solution for general industrial and automation applications. But […]