Sliding Guides Pt 2: Friction & Wear

Linear motion components, linear shafts and linear bushings have different features available to avoid friction.  Friction forces are generated when solid objects in contact make relative motion. It is one force linear motion must overcome for smooth movement in accurate applications.  Friction coefficient is the unit of measure for friction force.  This is what increases the amount of force required to move an object.  These friction forces must be managed properly with lubrication and etc, or may result in troubles shown below.

  1. Friction of solid objects resulting in seizures.
  2. Wear occurs and at an accelerated rate.
  3. Increased power loss.

About Friction

There are two types of friction.
A) Sliding Friction
B) Rolling Friction

The sliding friction is the type seen with Gib Slides, skies and sleds. The [Fig.] shown below is an ancient Egyptian mural. It depicts a scene of transporting a large stone statue. A man can be seen at the center pouring friction reducing lubrication.

egypt

Shown below are friction coefficients of various material combinations. In Figure 1 there is a free body diagram of an object being dragged.

friction

Figure 1

 

-Frictional force can be expressed as Ff = µN

-μ = static (μs) or kinetic (μk) frictional coefficient

-N = normal force (N, lb) = mg (mass, gravity)

Material Combinations Friction Coefficient μ
Mild Steel vs. Mild Steel 0.4
Hard Steel vs. molybdenum disulfide 0.15
Skies vs. Snow 0.05

The rolling friction can be represented by linear motion guides, miniature ball guides, and etc. where friction occurs with balls and rollers. If the sliding friction is to be defied as the “Sled Era”, the rolling friction can be dabbed as the “Rolling Cart Era”.

linear guide

Figure 2 Linear Motion Guides

Rolling friction coefficient examples are shown below. (Sliding friction coefficient and rolling friction coefficient cannot be compared equally.)

Material Combinations Rolling Friction Coefficient f(cm)
Hardened Steel vs. Roller/Balls 0.0005〜0.001
Mild Steel vs. Mild Steel 0.02〜0.05
Pneumatic Tire vs. Road 0.05〜0.15

About Wear

When solid objects are in contact without any lubrication between them, minute surface features are in directly coupled states. Friction occurs when these coupled features are decoupled by sliding motion, and this is the friction resistance (force). When the decoupling occurs, minuscule sections of material are ripped away where they contact. This is the wear. When the friction increases, the wear simply increases also. Proper lubrication is needed to prevent this wearing. Selecting appropriate lubrication is important, especially for mechanisms with high motion speeds and clean room applications.  If adding lubrication is not possible, there are self-lubricating linear bushings available.

The possibilities are endless! Choosing the correct style of linear motion components for your application is crucial for friction and wear prevention.  Considering these factors will bring you longer life to your design.

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

How the Right Rollers Ensure a Better End Product

Welcome Meridian Laboratory to the MISUMI Mech Lab! ...

Get articles like this sent to your inbox every week:

Like us on Facebook

Follow us on Twitter @usa_misumi

Subscribe to our Channel

Follow @misumiusa on Instagram

  • 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
  • Excited for the new graphics #Timelapse #ConfiguredToSaveTime #80Sextillion
  • We are celebrating 10,000 YouTube subscribers! Want to join in? Subscribe and enjoy a great library of videos including Mech Minutes, the Engineer to Engineer technical series and more. Link in bio #80sextillion
  • The 2nd Annual MISUMI vs. MISUMI softball game was a success! Congrats to the Gold team for defending their title 🏆 #ConfiguredToHaveFun #80sextillion