Category Archives: Products

Bevel Gear Jacks, Industries, Linear Motion Design Considerations

Advantages to Using Bevel Gear Jack Systems

August 19, 2015 admin Leave a comment

Considering factors such as load, speed, torque and space, there’s no debate that bevel gear jack systems offer unique benefits to worm gear jack systems. The system’s long-duty cycle capabilities and multiple configurations make it a diverse product that suits a variety of applications.

Although worm gear jacks are sufficient for large loads that are infrequently moved, bevel gear jacks offer more flexibility and programmable options for a wider range of applications.

Bevel gear jack systems don’t come with standardized travel lengths, so each one can be built to specification. Bevel screw jacks come available in machine and ball screw models. Machine screw jacks use a trapezoidal acme screw that offers a low backlash between the nut and screw. Ball screw jacks use hardened bearing balls that allow for smooth and efficient movement of the load. Bevel gear jacks have the capability to run continuously at 100-percent efficiency without overheating. Because of the greater efficiency and rolling action, the ball screw can operate at higher speeds or increased duty cycle when compared with the machine screw jack.

Available in three jack configurations, bevel gear screws can move along the lift shaft in a variety of ways to meet customer expectations:

Translating- The translating configuration has a lifting shaft that moves through the gear box. A nut is integrated with the bevel gear such that the bevel gear and nut rotate together. When the lift shaft is held to prevent rotation, the lift shaft will move linearly through the gear box to move the load.

Rotating- A rotating jack has a lift shaft that moves a nut as it turns. The lift shaft is fixed to the bevel gear. This causes the load, which is
attached to the travel nut, to move along the lift shaft.

Keyed- The lift shaft of a translating style jack must be attached to something which prevents the lift shaft from rotating. If it is not, the lift shaft (and the load) will turn and not translate. A feature can be added to a machine screw jack to prevent lift shaft rotation. This type of jack is referred to as a “keyed jack” and is available in translating models. Anti-rotation is accomplished by a square guide attached to the screw translating inside a square stem cover attached to the jack. The square stem tube is supplied with lube fittings.

Want to learn more about bevel gear screw jacks? Here’s a great video

Aerospace, Automotive, Chemical, Communications, Electronics, Factory Automation, Food & Beverage, Industries, Linear Bearings and Pillow Blocks, Linear Motion Design Considerations, Linear Slide Systems, Medical, Military & Defense, MRO, Packaging, Paper, Steel, Transportation

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

August 11, 2015 admin Leave a comment

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.

Aerospace, Automotive, Chemical, Communications, Electronics, Factory Automation, Food & Beverage, Linear Bearings and Pillow Blocks, Linear Motion Design Considerations, Linear Shafting and Shaft Supports, Linear Slide Systems, Medical, Military & Defense, MRO, Packaging, Paper, Steel, Transportation

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

August 6, 2015 admin Leave a comment

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.

Ball Screw Products

Design Considerations for Ball Screw Safety

August 4, 2015 admin Leave a comment

There are several factors conducive to a ball nut failing prematurely, such as misalignment, impact loading, a lack of lubrication, contamination or external damage to the return circuits. However, the primary failure mode for ball nuts is fatigue of the bearing balls or thread surface. 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 or use of industry-leading integral safety thread ball nuts.

The integral safety thread is a unique solution that provides the ball nut with a secondary safety thread– a reverse thread in the nut body itself. This special thread extends from the ID of the nut to below the OD 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.

Acme and Lead Screw Products, Ball Screw Jacks, Ball Screw Products, Linear Motion Design Considerations, Planetary Roller Screw Products, Screw Accessories, Screw Jacks, Worm Gear Ball Screw Jacks, Worm Gear Machine Screw Jacks

Three Popular Screw Types Defined

July 29, 2015 admin Leave a comment

When considering the vast majority of applications in which machine screws are used, it’s important to review the functions of some of the major types of screws. Below, we’ll take a look at the designs, functions and more while we define acme, ball and planetary screws.

Acme Screws:

The acme screw thread, sometimes referred to as the trapezoidal thread, is used for lead screws. They are often needed for large loads, or when the environment is less than desirable.

The acme thread form has been around for over a century, replacing square thread screws which had straight-sided flanks and were difficult to manufacture.

There are two main classes of acme thread forms: general purpose (G) and centralizing (C). The general purpose and centralizing thread forms have a nominal depth of thread of 0.50 x pitch and have a 29 degree included thread angle, which has allowed companies to develop unique screw diameters and leads. European metric Trapezoidal thread forms have a 30 degree Included thread angle.

When compared to general-purpose thread forms, centralizing threads are manufactured with tighter tolerances and reduced clearance on the major diameter. For instance; If an acme nut is side loaded with a radial load, a “G” class will wedge when the nut thread flanks come in contact with the screw thread flanks. To prevent this wedging, a “C” class thread form can be used, since it utilizes less clearance and tighter tolerances are allowed between the major diameter of the nut and the major diameter of the screw.

Industry leaders have developed several unique thread forms, such as stub acme forms and 40 degree included angle, which allow them to provide a variety of diameter and lead combinations.

Ball Screws:

For loads requiring a greater amount of efficiency, companies often turn to ball screws. A ball screw assembly is a device comprised of a nut, screw, and reciprocating ball bearings. The bearings provide the thread engagement between the nut and screw.

Ball screws offer an efficient means for converting rotary motion to linear motion. A ball screw is an improvement over an acme screw just as an anti-friction ball bearing is an improvement over a plain bushing.

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.

Planetary Roller Screws:

Planetary roller screws are remarkable devices designed to convert rotary motion into axial force or vice versa.

The planetary roller screw design offers multiple advantages and reliability for the most demanding applications when compared with other lead screw types due to its rolling motion. These screws offer high efficiency even in relatively shallow lead designs.

The multitude of contact points can carry large loads and provide very high resolution (small axial movement) when using very shallow leads. Planetary roller screws produce high rotational speeds with faster acceleration without adverse effects.

Making Motion Work