Mastering Ball Screws Pt. 2: Ball Screw Preloads

Preloading is used to increase the feed accuracy and rigidity of ball screws. Why is this necessary? In many applications utilizing ball screw actuation, position accuracy is of utmost importance. With many ball screw driven actuators, position accuracy can be achieved within a few microns. Any deviation could compromise the design intent. Thus preloading is applied to reduce axial clearance between a ball nut and the screw shaft and to also achieve precise positioning. It is also important to apply the proper amount of preloading to prevent excessive heat generation through the ball screw’s expected life.

■ Ball Screw Preload means: (Definition: JIS B 1192)
The force applied internally to ball screws by assembling in a group of steel balls or using a pair of nuts that are axially mutually displaced, in order to reduce backlash and increase the rigidity of the ball screw.

On the “Axial Clearance” column of the ball screw selection chart shown on page 74 of MISUMI’s Motion System catalog [Direct Download PDF Catalog Here] there are listings such as:

  • 0 (Preload)
  • 005 or Less
  • 030 or Less
  • 10 or Less

ball-screws-2-image-1

ball-screws-2-image-2

Terminology Preload Explanation
Positional Preload Preloading method considers the positional clearance of the screw shaft and steel balls.
Oversized Balls Method

[Fig. 1]
This preloading method ensures 4 points of contact between the ball screw grooves and nut. This is accomplished by inserting slightly oversized steel balls.
Lead Shifted Method This preload is applied by machining the nut with a groove offset at the center in the amount of desired preload.
Spacer Method

[Fig. 2]
A preloading method using a spacer between a set of nuts to achieve the desired amount preload. Ideal for heavy preload.
Pin Method

(For Heavy Preload)

Similar to the spacer method, the nut ends are machined to achieve the desired offset, then pinned together to prevent rotation among each other.
Predetermined Pressure Preload

[Fig. 3]

The preload is applied with a spring.

ball-screws-2-image-3

If backlash or slip is not a major concern in your application, it is advised to choose a ball screw with larger clearance (directly related to accuracy grade). This will keep cost down and prevent overdesigning.

Stay tuned for the next article where we will dive into ball screw performance!

Share this Story
Load More Related Articles
Load More By Carlicia Layosa
Load More In Featured Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

*

Check Also

MISUMI Extrusion Protective Guard

Times are changing in many industries due to ...

Follow @misumiusa on Instagram

  • Even with 80 sextillion configurations, we know how important one part can be. Thank you to everyone doing their part in the fight against COVID-19. Link in bio #worldhealthday #80sextillion
  • MISUMI is on the move! We are excited to announce the relocation of our North American HQ to Glenstar’s Schaumburg Corporate Center. MISUMI is set to undergo a renovation of nearly 48,000 square feet spread over 2 floors of occupancy space. The relocation will allow a more expressive treatment of the MISUMI brand throughout the space. Read more, link in bio. #80Sextillion #ConfiguredToSaveTime
  • Wellness Fair at the office today. Thanks @chiroone @orangetheory  @weareonedigital #ConfiguredToBeHealthy #80sextillion
  • We crushed it at ATX West! Thanks to everyone who stopped by the MISUMI booth and crushed a can in the Bev-Bot 🔥. Let’s continue the conversation, find out how you can configure to save time. Link in bio. #atxwest #80sextillion #configuredtosavetime
  • MISUMI is excited to be at #slas2020 in San Diego. Are you attending? Stop by for a quick Rapid Design demo, and learn how you can save 30% design time! @slas_org #80sextillion
  • Head instructor John explains the different methods of proper installation for accuracy in linear guides during Master Class in Chicago. #80Sextillion #configuredtohavefun
  • Excited to be at #Engineer3D! in MKE. We started the day by kicking off the keynote presentation (swipe for the boomerang). We’re enjoying talking to and getting to know all the Engineers! Are you in attendance? Stop by the MISUMI booth to learn more about Rapid Design and get some swag #EnginerdOnBoard #gsc3d #80Sextillion #solidworks
  • We got spirit! Excited for football this Sunday 🏈 #configuredtohavefun #80Sextillion