The automation industry depends on ball screws and lead screws to deliver proper linear motion control systems. Lead screws and ball screws are similar and can be easily confused, with many claiming lead screws are just an inexpensive alternative to ball screws. The ideal linear motion solution for your application depends on several factors.
What Are Ball Screws and Lead Screws?
Ball screws and lead screws are two different types of mechanical linear actuators that create linear motion from rotational motion. A ball screw consists of a screw shaft and a ball nut with matching helical threads. These units are utilized to transmit forces to a dynamic or stationary load with high precision, accuracy, and repeatability. The ball nut utilizes recirculating bearings for a smooth, highly efficient transfer of power from rotational motion to linear motion along the axis of the ball screw with little friction.
Lead screws use a sliding screw shaft and nut threads with no ball bearings between them. The nut and screw shaft move directly against each other on a large contact area, producing higher energy losses due to friction. Lead screws are often used when the application needs a unit that won't "back-drive". However, lead screw designs have evolved to reduce friction. They are ideal for light to medium-duty applications and provide silent, smooth operation.
What Are the Key Differences Between Ball Screws and Lead Screws?
One primary difference between a ball screw vs lead screw is that ball screws rely on ball bearings to reduce friction between the nut and screw, whereas lead screws do not. On a ball screw, the nut and screw have matching helical grooves that permit ball bearings to re-circulate in the races, and they often have a semi-circular shape to accommodate the spherical ball bearing.
Lead screws rely on deeper helical threads and a mating nut that is typically constructed of bronze or a polymer composite. Unlike lead screws, ball screws exhibit a rolling nature that eliminates sliding friction.
It is critical to consider the advantages and disadvantages of each actuator before determining the ideal solution for an application. Consider your specific requirements and compare the characteristics to find the best fit.
In addition, these two products differ significantly in their efficiency – in fact, this is one of the key elements to consider here. Ball screws run with consistent efficiency, which is usually at 90% or better; on the flip side, ACME lead screws will average about 44% efficiency, and may drop as low as 20% due to less consistency. This is because ACME lead screw efficiency depends in large part on its helix angle, which can vary significantly.
Benefits of Ball Screws vs. Lead Screws
When determining if a ball screw or lead screw is the best choice for your application, consider the advantages of each.
- Ball screws: While ball screws produce more noise, they can carry heavier loads than lead screws. They also aren't as rigid; don't self-lock; and offer much higher precision, accuracy, and efficiency. Common applications of ball screws include semiconductors, robots, power steering, and aircraft.
- Lead screws: Lead screws are often less expensive, plus are self-lubricating, corrosion-resistant, smooth, and quiet. Because lead screws offer vibration-free and silent operation, they are often used for medical equipment and personal computing devices. The low efficiency rating is an indication that the lead screw will resist "back-drive".
When Should You Use Ball Screws Over Lead Screws?
A ball screw offers a significant advantage in performance over lead screws in various applications. Ball screws excel in applications where efficiency, precision and high-speed, smooth motion are preferred. Lead screws can be a suitable solution for simple applications where smooth or quiet motion is of more value than rigidity, precision, accuracy, and speed.
Rockford Ball Screw is a leader in linear actuators, serving various industries with ball screws and ACME screws since 1973. We deliver high-quality products with short lead times and competitive pricing. Browse our entire catalog of ball screws or contact us today to learn more about our products.