New Line of Premium Ball Screws for Linear Actuators

Steinmeyer ground ball screws have served the demanding requirements of machine tool applications for years, delivering precision positioning under high loads and high duty cycles. For the first time, we are excited to introduce an extension of this product line that has been engineered for the low duty cycle application of linear actuators.

This line of premium ball screws not only reaches high thrust requirements, but also offers long service life, low maintenance, and unmatched reliability. Designers of linear actuators now have the option of specifying a premium ball screw from Steinmeyer.

The ball screws for actuators line includes a wide range of diameters, leads, and nut configurations. Like all Steinmeyer products, these screws have been meticulously designed and manufactured to deliver world-class performance – specifically engineered for linear actuator applications. We offer the widest size selection in the industry, with diameters up to 160 mm and pitches down to 0.5 mm. The screws features dynamic load capacity of up to 1,400 kN and may be specified up to 100% of DLC. Rolled versions are also available upon request for more economical solutions.

Contact a Steinmeyer engineer to learn more about Steinmeyer premium ball screws.

Customer Spotlight: Mundt & Associates – Revolutionary Laser Systems Technology

Founder of Mundt & Associates, Ron Mundt, recently took the time to speak with us about his company’s state-of-the-art laser systems and the key role that our ball screws play.

If you do not know Mundt & Associates, it is a worldwide leader in high-precision laser micro-machining. The company delivers customized systems for aerospace, military, medical, and other highly demanding applications.

Mundt is world renowned for crafting the highest performing laser machine tool systems, so it is paramount that it employs superior quality components. A precision ball screw is critical in delivering the laser positioning accuracy required for intricate cutting and scribing applications.

We are proud to say that Steinmeyer is Mundt’s leading supplier of ball screws. Every screw that we supply to Mundt is precisely engineered to achieve extreme positioning accuracy. We also stock their screws in our U.S. warehouse to support just-in-time manufacturing and short lead-times for delivering machines to Mundt global customers.

We know the amount of pride Mundt takes in delivering innovative laser systems and understand how important it is that they receive the highest quality ball screws.

“We continue to use Steinmeyer ball screws in our systems year after year because we know they are providing us with the highest quality ball screw available. We wouldn’t put anything less into our machines.”

‒ Ron Mundt, President – Mundt & Associates, Inc.

Contact a Steinmeyer engineer to learn more about Steinmeyer precision ball screws.

Be Wary of “Lubed for Life” Marketing Claims

“Your ball screw is lubed for life, so it’s maintenance free!”

Have you ever heard such a claim from your vendor?  If so, you should be wary.  Like most things that sound too good to be true…

Every ball screw is pre-lubricated at the factory.  The on-going maintenance cycle depends greatly on the application.  For most machine tools, Steinmeyer recommends the first ball screw lube check at 500 hours.  Depending on the results, customers may set future intervals shorter or longer.

Some vendors advertise ball screws with that are “lubed for life” at high loads.  This sounds fantastic: maintenance free operation and high performance!  But if you stop to think about it, high loading naturally decreases the life.  So this combination is possible not because the maintenance interval is so long, but because the life is so short!

This logic reminds me of when Bugatti announced a 1001 horsepower sports car some years ago, with a top speed of 200 MPH.  If you go flat out, you’ll run out of gas in 15 minutes.  But don’t worry, because the tires will melt in 12 minutes!

Other vendors advertise lubrication units mounted inside the nut.  These are usually plastic rings impregnated with oil.  Such an approach may very well extend the early maintenance intervals, but they eventually run out.  At that point, you are forced to send the screw back to replace the lubrication unit, or revert to typical lubrication methods.  Furthermore, you have no choice over the lubricant; you are stuck with whatever is in the plastic.  Given these caveats, you have to ask whether this approach really gives you any net benefits.

Lubricating Rotating Nuts

Lubricating Rotating Nuts blog imageRotating nuts have long presented challenges for lubrication.  Not anymore! Steinmeyer is excited to announce the release of our new patented system for lubricating rotating nuts.

It is a tremendously efficient system that uses centrifugal force to splash lubricant back onto the shaft.  The key is a series of small plastic gears that rotate around a larger plastic gear.

The lubrication port and the large gear are held in place by the lubrication line.
This assembly is stationary while the smaller gears rotate with the nut.  Whatever oil is introduced inside the nut is guided naturally towards the shaft.

This approach has the added benefit of reducing the annoying “whistling” sounds produced by high acceleration of ball screws.  The result is a much quieter work environment.

Contact Steinmeyer engineers to learn more about our solution for this long standing problem.

Throwback Thursday: Ball-Screw Rigidity is a Matter of Definition

Not all ball-screw makers spec products the same way.

This stiffness test rig uses a force sensor to measure axial thrust. A bracket clamped onto the drive journal prevents backdriving of the screw. The nut block has exchangeable inserts and hydraulically clamps to the cast-iron base. Three LVDT sensors measure relative motion between a shaft and nut. They attach to the unloaded portion of the screw and their tips touch the nut flange from behind. The arrangement averages all deformations of the nut body but does not include changes in shaft length. Forces in the rig can reach several thousand Newtons, though the shaft elastic displacement is only a few microns.

Read the full article here.

Defining Different Double Nuts

Ball screws classified as “double nut” appear to be aptly named. However, what seems to be a simple distinction varies from one vendor to another. Let’s clarify the true definition of a double nut and the unique features of Steinmeyer designs.

Taken literally, a double nut is composed of two separate nuts that are more or less identical. The purpose of this design is to preload the two nuts against each other and achieve two-point contact on the balls. Preload eliminates play and helps build additional stiffness, keeping the nut centered on the shaft. While there are many ways to achieve preload, Steinmeyer defines double nuts as those that have two-point contact. This makes sense as it describes the double nut from a performance point-of-view, regardless of the design details.

The main design challenge involving double nuts is how to join them. Various solutions have been developed around the industry to solve this issue, but most require complex joining with spacers, shims, fitting keys, pins, and setscrews. We believe in a simpler approach.

Steinmeyer’s patented UNILOCK coupling system avoids complicated hardware by using a special epoxy.  It is proven to deliver a robust connection of the two nut halves, making our double nut nearly as compact and stiff as a single-piece design. It also prevents radial slippage of the two halves, so that the UNILOCK double nut cannot be misaligned. The coupling is rugged and absolutely tight to prevent the loss of lubricant.

Contact our motion control engineers to learn the benefits of UNILOCK for your application.

Life Expectancy for Single vs. Double Nuts

Life expectancy equations provided by some manufacturers only cover nuts having two-point contact. But what about four-point nuts? And what about the effects of preload?

The fundamental determining factor of life expectancy is duty cycle, which includes load, thrust, speed, and duration of the travel. Calculating these forces is commonly understood. But preload is a very important factor in ball screwgraph life calculations and must always be considered.  In cases where the applied external load is low, preload can determine as much as 90% of the life.

Steinmeyer engineers have developed a preload graph that consists of two curves: each representing the force-deflection curve of one ball nut in a double nut configuration. It shows how deflections increase with greater force (and vice versa). It also displays how the forces in the opposite nut decrease as soon as deflection results in an axial displacement. For example, with double nuts, the higher the thrust carried by one nut, the more likely it will be the first to fail if not properly preloaded.

Since single nuts have four-point contact there are twice as many load/unload cycles for each given spot on the ball surface. The preload penalty of the four-point contact configuration is anywhere between a 50% life reduction (if the only force the nut sees is due to preload), and no reduction at all if there is zero preload. Real-world applications fall somewhere in between.

Lastly, if thrust is high enough to cause sufficient deflection, one set of balls in a double nut may run unloaded, which is generally unacceptable and potentially catastrophic. The preload must be high enough to ensure unloading will never occur.  This isn’t the case for single nuts since there is no ball set to be unloaded, and exceeding the limits in the preload graph above is not a problem. Therefore, the life penalty depends on preload – life increases as preload is reduced

Contact Steinmeyer engineers to the see if which nut design is right for your application.

Does a Single Nut Have the Same Life Expectancy as a Double Nut?
Learn the facts. Download now: http://goo.gl/g8fl92Single or Double Nut thumbnail

Key Takeaways:

  • Differences between single and double nuts
  • Determining the life of a ball screw
  • Calculating impact of usage/application
  • Understanding the effects of preload