Tuesday, October 9, 2012

Explore the Guided Motion Possibilities of Linear Bearings with Applications Engineer Dan Fletcher, Coffee Chat Part III of III

ROLLING RIGHT ALONG Today, we're wrapping up our ongoing conversation about DualVee Motion Technology with one of our Applications Engineers, Dan Fletcher. Click here to read Part I about precision and speed, or Part II about tolerances and lubrication.

Have questions for Dan about this coffee chat series? Send him an email at danf@bwc.com!

SIZING TIPS DualVee guide wheels come in a range of diameters to support different load specs. For example, a single 75 mm 4XXL double-vee wheel can hold radial loads of 3,215 lbf. A single 150 mm vee bearing wheel has a radial load capacity of as much as 11,240 lbf while a four-wheel carriage can handle double that.

What do you need to consider when calculating load evaluations?
Dan: Evaluating guide wheel loads is relatively easy, but it is important to clearly understand the conditions under which they will be used. Start with determining whether the loads are radial or axial (see image).

What factors affect the service life of guide wheel systems?
Dan: Several factors influence the service life of guide wheel systems such as size of the bearing elements, relative spacing, and the orientation, location and magnitude of the load. There's a simple method you can use that will estimate the load/life relationship by defining the loading conditions. The equations (below) are based on clean and well-lubricated track conditions. The ratings and calculations are theoretical values based on ideal conditions. Most  applications will involve less than fully optimum conditions, and in a situation where a particular size bearing may appear marginal in capacity, selection of the next larger bearing size is recommended.

How do you calculate load/life relationships?
Dan: To start, you have to understand three things: The principles of statics, the ability to use free-body diagrams, and the know-how to resolve externally applied forces on a carriage assembly into the axial and radial reaction forces at each linear guide wheel. The most heavily loaded bearing in the design will determine the life of the guide wheel system.

What steps go into sizing and choosing a guide wheel assembly?
Dan: That can be done in three steps. This includes figuring out the radial and axial loads, how much weight is applied to the most heavily loaded bearing, and applying those variables to make up for speed, environment, shock, and vibration.

[ FREE DOWNLOAD ] White Paper: Guide Wheel System Properties, Selection & Sizing

Is all of this difficult to do?
Dan: Only a simple understanding of engineering principles and force analysis is needed to properly evaluate and size these types of systems.