Category Archives: Industries

Helpful Formulas for Calculating Ball Screw Life Expectancy

July 21, 2015 admin Leave a comment

Due to their steel-on-steel design, the bearing industry has developed ways to calculate the life expectancy of ball screws. However, other factors, such as contamination, lubrication and improper mounting and installation techniques, can also lessen the life of a ball screw. For manufacturers hoping to extend the life of their screws, it can be beneficial to order a larger size screw to handle a larger load, prolonging the life of the screw.

For applications where the loads and/or rotational speed vary significantly, an equivalent load can be calculated using the following formula:

The life required in revolutions is determined by multiplying the total stroke in millimeters by the total number of strokes required for the designed life of the equipment and then dividing by the lead of the ball nut. Ball nut life is greatly influenced by the operating condition, including speed and vibration the assembly may see. A fatigue factor must be considered when calculating life. To calculate the life for a ball nut use the following formula:

Indirect vibration is any vibration associated near the screw mounting which influences the stability of the assembly. Direct vibration pertains to any vibration directly linked to the screw assembly which influences the stability of the assembly. High cyclical impact is any repetitive impact or high deceleration of the ball screw assembly.

If operation reliability higher than 90 percent is required, then the theoretical life must be corrected by using a reliability factor according to the table.

If total time is needed, the following equation can be used to find the life measured in hours:

Instead of hand calculations, here are some charts to help calculate life expectancy:

Metric:

http://www.nookindustries.com/LinearLibraryItem/Ballscrew_Life_Exp

Inch:

http://www.nookindustries.com/LinearLibraryItem/Life_Expectancy__SRT_Rolled_Inch_Screws

Ball Screw Products, Industries

Extend Ball Screw Life

July 15, 2015 admin Leave a comment

Since ball screws often work in environments full of dirt and debris, manufacturers can take multiple precautions to keep out contamination and preserve the life of the screw.

Sometimes screws are coated with a thin dense chrome, black oxide or nickel-plated finish to help preserve ball screw life. Some manufacturers prefer to equip bellows boots that expand and contract like an accordion as the nut moves along to keep it covered from contamination. Bellows boots can be supplied in numerous materials so that they may be applied in even the most extreme applications.

Another form of protection manufacturers uses are wipers. Nut wipers can be felted or plastic wipers that brush the nut free of any dirt or other contaminants and keep contaminants from entering the ball nut.

There’s so much variance between different ball screw applications that there is no definitive answer for the amount of lubrication needed for each ball screw. However, considering factors such as frequency of use, temperature and viscosity are essential considerations for lubrication options. While a light oil or grease is suitable for most applications, the use of any lubricant containing molydisulfide or graphite should be avoided. A good rule of thumb is to always apply enough lubrication to maintain a thin film of lubricant between the nut and the screw.

Ball Screw Products, Industries

Three Advantages for Using Ball Screws

July 1, 2015 admin Leave a comment

Of all the screws in industry used for motion, ball screws provide unique benefits when compared to other standards, such as roller screws or acme screws. Here are just three of the benefits to using ball screws in your future applications.

High Efficiency – Ball screws typically operate at a minimum of 90 percent efficiency, which makes them an optimal choice in converting rotary motion into precision linear motion.

Load Capabilities – A part of what makes ball screws versatile in so many industries is their ability to carry remarkably heavy loads at fast, efficient speeds.

Cost-Efficient – In the long run, ball screw systems can prove to be a cost-effective alternative to pneumatic or hydraulic systems, which require constant electrical and air power.

What are some of the other ways ball screws have enhanced your business? Let us know below.

Medical, Modular Actuator Accessories, Uncategorized

The New Modular Actuator Calculator Provides Solutions for Bearing Life & Load Considerations

June 30, 2015 admin Leave a comment

When trying to figure out the load size for an actuator, many engineers find themselves making guesses for the bearing considerations. This is because the bearings are buried within the actuator, which makes it impossible to determine their exact location.

Well, thanks to a new modular actuator calculator, engineers can stop guessing and receive precise load figures. The German-developed calculator works by simply choosing the desired product, entering its load definitions and allowing the tool to calculate the bearing stress and load to determine the bearing life of the product. The results can be viewed in an easy-to-read, printable format.

Now, if you want a particular product to last five years, all you have to do is plug in a few definitions and the calculator will determine the load necessary to achieve that life expectancy.

The free-to-use calculator is compatible with Safari and Internet Explorer. To access this resource, visit here.

Industries, Linear Motion Design Considerations, Uncategorized, Worm Gear Machine Screw Jacks

Advantages of a U-Shaped Worm Gear Jack Screw Arrangement

June 25, 2015 admin Leave a comment

In worm gear screw jacks, the “U” arrangement’s configuration is often preferred for manufacturers in the food industry.

U Arrangement For example, a leading cookie manufacturer could be adding a new product that requires a greater distance to the top heating element of the conveyor oven. The oven originally only had a static-top heating element and with this new order, it needs to be adjustable up to 14 inches. The top heating element weighs 5,000 pounds. The manufacturer anticipates only making adjustments to the height once or twice a month.

Our specifications for the U arrangement include a single 5-Horsepower 1750 AC Motor that allows full travel in 36 seconds, food-grade grease, compression load and a double safety factor. The actuators and power train must be located outside of the oven frame. Travel rate is negligible as long as the total travel can be reached in less than 60 seconds. The application’s infrequent cycles makes the use of a machine screw jack the best fit.

Upright rotating jacks allow the jacks to be easily retrofitted to the existing oven with minimal modifications. The jacks will be fully loaded in both the retracted and extended position, but because of the retrofit condition, having a support bearing on the lift shaft will not be possible. A 10-ton jack was selected for the mounting condition to fulfill safety requirement.

For calculating column strength, check out Nook’s calculator, as well as other useful engineering calculators here.

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