How confirm the size and dimension of Linear Bearing motion system?

How confirm the size and dimension of Linear Bearing motion system?

First, check the load to be carried and the speed at which it travels. These factors determine the size, style and type of the linear motion system that required. We need to figure out how much weight is required to transfer from point A to point B in the application. It is important to aware of the position of the load relative to the position of the linear bearing system: horizontal, lateral or vertical. The further distance the load is from the bearing makes the greater the required load capacity. Psi is the common parameter to measure the static load capacity of linear bearings.

The moving masses determine the PV value (surface pressure multiplied by speed), that is the operating speed of the linear guide system. Plastic sliding elements can easily achieve speeds above 10 m/sec that are usually required in today's high cycle time manufacturing equipment. Linear guide system easily reach these speeds by taking place of rolling elements and using low-friction shafting materials, such as hard anodized aluminum. The decreased surface load, the higher speeds that can be obtained. That is lighter-weight applications allow for greater running speeds.

We found the average speed per cycle time is more significant than the maximum speed. Because the temperature affects on the bearing system a lot. The friction between a bearing and its rail generates heat during operation. The friction is the product of the coefficient of friction and the normal force pushing the two objects together — in most cases, the weight being carried. The average surface speed is important to calculate the suitability of the linear bearing system.The highest average surface speed is taken over a time period of 10 to 30 minutes in applications with intermittent cycles.

Compared to rolling elements which don’t really have a coefficient of friction(usually listed at 0.001 to 0.002), the linear guide systems with plastic plain bearings take more power to operate. The higher coefficient of friction of a plastic sliding element(around 0.13) needs higher driving force. The friction and wear properties of plastic linear guide systems can be improved possibly by enlarging the bearing clearances and minimizing the permanent load.

Friction values of plastic linear components are at their highest point upon start-up phase and change over time. The coefficient of friction falls to a constant level after a break-in period then remains for the lifetime of the bearings. The self-lubricating feature of plastic bearings creates a lubricating film at the surface of the shaft or rail by transferring the bearing material to the peaks and valleys on the shaft or rail.