Manufacturers must consider all parts when designing an item. For example, companies may find they need to choose between a ball screw and a lead screw. Both screws convert rotary motion into linear motion, but there are several differences users must be aware of. The following guide provides an overview of ball screws from Schneeberger and what a person needs to know when choosing between a ball screw and a lead screw.
What is a Ball Screw?
A ball screw includes a ball nut and a threaded shaft. The ball nut sits on the screw and has ball bearings to support it. These bearings provide a rolling surface, which helps distinguish the ball screw from the lead screw. The lead screw features a sliding surface. The ball bearings move between the threaded shaft and the ball nut. The elimination of the sliding motion allows ball screws to operate more efficiently than their lead counterparts.
Rudolph G. Boehm invented the ball screw in the late 1920s. He originally referred to it as an antifriction nut. Today, these mechanical devices are found in a range of everyday products, including 3D printers, cars, and airplanes. Why are they so popular? Are there situations where a ball screw may not be the best option? What should a person know when they are in need of ball screw manufacturing, repair & rebuild services?
The Benefits of Using a Ball Screw
As previously mentioned, ball screws are highly efficient. Compared to lead screws, they are three to four times more efficient, as lead screws have a mechanical efficiency of between 20 to 25 percent. In addition, the ball screw produces minimal friction, thanks to the circulating ball bearings. The smooth gliding surface allows the screw to move with minimal friction. As a result, there is less wear and tear, and the ball screw will last longer than the lead screw under similar conditions.
A ball screw offers equal or better load capacity, so manufacturers use these items in place of lead screws when the load requirements exceed what lead screws are capable of handling. Furthermore, positioning accuracy improves when ball screws are used. Ball screws are ideal for high throughput, high-speed applications and those with long or continuous cycle times.
Ball screws consume less power than lead screws and require smaller motors as a result. These screws are not as rigid as lead screws. In addition, they will not self-lock.
The Drawbacks of Using Ball Screws
Ball screws require significant levels of lubrication, and manufacturers must take this into consideration when determining if they are the right choice for a project. The lubrication minimizes friction while halting corrosion. Without this lubrication, the manufacturer won’t see the anticipated level of efficiency, and the lifespan of the screw decreases. The additional maintenance requirements may lead some manufacturers to choose lead screws instead.
Ball screws are also susceptible to being back-drive at certain lead angles. This is one drawback to the lack of friction seen with these screws. However, a braking system can prevent this from happening. Ball screws cannot be customized to the extent lead screws can, either.
A manufacturer might find the ball screw has issues with vertical applications. These screws are also noisy, which some people find is more than an annoyance, and they come with a higher price tag than lead screws, which can deter companies with limited budgets. Nevertheless, ball screws need to be replaced less often than lead screws, so the manufacturer may save money over time.
Understanding Ball Screw Terminology
Ball screws come with their own terminology, and manufacturers must understand this technology to ensure they make the right choice. Lead is the linear distance the screw travels through each complete turn. Pitch, on the other hand, refers to the space between the threads of the screw. If using a single-start screw, the pitch and lead will be the same. With multiple-start screws, however, these numbers differ.
Recirculating balls in a closed path are referred to as a circuit. When someone speaks of ball screws and turns, they are talking about the number of trips the balls make before they recirculate. The recirculation method plays a role in the relationship between the circuits and turns. When a thread-to-thread or deflector method is used to recirculate the balls in the ball return, the number of turns and circuits will be equal. Each turn of balls is recirculated individually.
However, when an external tube or internal channel returns the balls, they may cross several threads. This allows multiple ball turns within a single circuit. Most multi-start assemblies make use of an internal channel, as this allows multiple circuits.
Where Are Ball Screws Commonly Used?
The average person may not know the difference between lead screws and ball screws, but manufacturers must be aware of common uses for ball screws today. Where might these screws be found?
Photolithography machines often make use of ball screws in microscopic integrated circuits. Gas-powered vehicles have hydraulic systems, while electric vehicles make use of ball screws to eliminate these systems. Vehicles with power steering systems contain one or more ball screws within this system, as well. The same screws might be found in robots, semiconductors, and many other locations today.
Gates within a hydroelectric station are controlled by ball screws, and manufacturers of wind turbines use these screws for directional position and blade pitch. Anyone who has solar panels at their home is benefiting from ball screws, as these screws are used to provide axis movements. In addition, motorized inspection tables make use of ball screws to allow the user to achieve the desired position of the table.
Manufacturers have many options today when it comes to components for devices. Knowing the similarities and differences between lead and ball screws is crucial to ensure the right choice is made. The more information a manufacturer has, the easier it is to decide between the options. With the information presented here, this choice becomes a little easier.
If more help is needed in choosing between lead and ball screws, speak to the screw manufacturer. They will ask a series of questions to determine which screw should be used for a particular application. With expert help, a user can ensure the right choice is made.
