Category Archives: Automotive

Integral Safety Threads

Ball nuts can fail for a variety of reasons. Primarily, it’s fatigue of the bearing balls or the threaded surface, which is why proper lubrication (link to lube blog post) is so important. However, ball nuts can fail prematurely due to misalignment, impact loading, contamination, or external damage to the return circuits. Premature failure may result in the loss of some or all of the balls between the nut and screw. When all the balls are lost the nut is no longer engaged with the screw and therefore may not move when the screw is rotated or, in vertical applications, will free fall along the screw.

In applications where this loss of ball type failure could result in injury or death, this failure needs to be considered in the design. Possible preventative measures include the use of two or more screws supporting the load, use of nuts with multiple independent ball recirculation circuits, use of Ball Deflectors which prevent the balls from exiting the ball nut out the ends.

There is one more preventative measure that has proven itself in testing and in practical use; Integral Safety Threads. These unique solutions that provide the ball nut with a secondary safety thread – a reverse thread in the nut body itself. This special thread extends from the ID (Internal Diameter) of the nut to below the OD (Outside Diameter) of the screw without making contact. In the unlikely event that all the balls in the nut are lost, this “safety” thread will engage the screw and prevent free-fall. Although this thread can be used to lower the load to a safe position, it is not to be used otherwise. This can also be accomplished with the use of a special flange if the ball nut body cannot accommodate the Safety Thread feature.

integral 1 integral 2

CC Actuators 101

CC Actuators are a combination of an electric motor and an acme screw or a high efficiency ball screw. They are designed to be ready to install directly into any industrial or commercial application. They are ideally suited for any OEM application where linear motion is needed. These high-quality actuators feature:

  • Durable construction
  • Dependable performance
  • Long-life operation
  • High repeatability
  • Operation in either compression or tension loading applications
  • Adjustable limit switches
  • Lifetime lubrication
  • Mechanical overload protection
  • Corrosion resistant exterior surfaces

The most common applications are;

  • Telecommunications
  • Architectural Automation
  • Medical and Hospital Equipment
  • Semiconductor
  • Food Processing
  • Farm Equipment
  • Satellite Dish and Antenna Positioning

These rugged solutions come in standard travels of 4”, 12”, 18”, 24” or 36” with duty cycles typically around 30% max “on-time” of 5 minutes at rated load. Further versatility is provided by temperature ratings ranging from -30 to +160 F. Here’s a brief list of typical components, and what to look for when specifying;

Clutch – Should be heavy duty, in order to properly protect gears and components in the event of overload or overtravel.

Load Sensitive Brake – Should safely maintain the actuator’s position when at rest, without consuming power.

Boot – An optional accessory, but important in applications where you will want to protect the actuator tube from contaminants.

Limit Switch – Screw type limit switches offer precise positioning for travel up to 36”. Their design should allow for easily setting limits at both ends of travel. Optionally, Precision Limit Switches are typically available for shorter travel (under 24”) and will provide higher resolution adjustment.

Ball Screw – Look for precision ball screws made of high grade materials for greater efficiency & longer life

Sensors – There are a wide variety of sensor options for stroke control. Application needs should be the primary consideration when selecting, so look for a provider who offers a range.

Keyed – CC Linear Actuators may be ordered with a feature that allows the actuator tube to extend (retract) without being connected to the load. This key also reduces torque in clevises.

cc actuators

Industry Insights at Arm’s Reach

With so many markets, products and changes happening  within the industry, it can be a challenge for designers to know where to find reliable and helpful information . Luckily, we’ve provided two companies who work hard in delivering topnotch, insightful content to help broaden your knowledge of the industry.

You might know Rockwell Automation as the world’s largest company for industrial automation and information, but did you know the company delivers a wide array of white papers, tools and other industrial automation methods, trends and technologies? The Journal from Rockwell  and Our PartnerNetwork™ recently published “The Basics of Ball Screws,” which teaches the key terms, preloading methods and calculations for understanding ball screws.

Rockwell also provides beneficial tools, such as its “Motion Analyzer,” which offers an inertia calculator and compatibility browser for a variety of different products, including linear motion products & systems.

Design World provides daily news in the industry, videos, tech tutorials, webinars and trending topics.According to its website, “Design World is written for engineers by engineers with an emphasis on applying the engineering fundamentals to real world machine design applications across industries including medical, packaging, semiconductor, material handling, and off-highway.” From pneumatics to robotics, the magazine and its digital brand stand as invaluable resources for designers and engineers who wish to be ahead of the curve in the latest industry happenings.

 

Getting the Most out of Your Linear Bearings (Part 2)

In order to get the best performance and life out of your linear bearings, proper lubrication is key.

A lubricant formulated for rolling friction should be used with linear bearings. In applications where operating speeds are low and loads are light,  linear bearings can be used without lubrication at a greatly reduced life. However, it is never recommended to operate linear bearings without lubrication. To protect the highly polished bearing surfaces from corrosion and wear, a lubricant is required.

Where linear speeds are high, a light oil should be used and provision for re-lubrication should be made to avoid operating the bearings dry. For typical applications, a medium-to- heavy oil has good surface adhesion and affords greater bearing protection. Linear bearings 2 inches in diameter and above may use high pressure lithium grease such as Shell Alvania #2 for moderate speed applications. Lubricants containing additives such as molydisulfide or graphite should not be used.

lubrication

Getting the Best out of Your Linear Round Rail Bearings (Part 1)

In order to get the most life and best applications out of your bearings, it’s important to understand the size of the load, how the load will be applied and the length of the stroke. Applying too much weight to a load can significantly reduce the life and efficiency of your bearings. Also, incorrectly distributing the weight on the load can be harmful. In addition to some helpful design considerations, let’s take a look at the load considerations below.

Load ratings are the required design life, shaft hardness and bearing dynamic that affect the load and can be applied to a linear bearing. Two dynamic load ratings are given for each bearing size based on the rotational orientation of the bearing.

The normal load rating is used in applications where the orientation of the ball tracks relative to the load cannot be controlled. The normal load rating is based on a load imposed directly over a single ball track. The normal load rating shown in the specification tables is slightly greater than would be mathematically calculated based on one track loading, because it assumes that the load is shared to some degree by one or more of the adjacent ball tracks.

The maximum load rating assumes that the load is applied midway between two ball tracks as illustrated below. In this orientation the load is distributed over the maximum number of bearing balls.

The normal and maximum load ratings are based on a Rc 60 shaft hardness and a travel life of two million inches. For linear bearing system operating at less than full rated load, the Load-Life Curve may be used to determine the travel life expectancy.

An equivalent load value can be calculated when sizing linear bearings for applications at conditions other than maximum rating.

linear bearings