Safety factors in linear guides

Posted by Emelie Neckman, 2024-08-13

There are plenty of good reasons for using safety factors. They help prevent unnecessary failures that can cost you productivity—or worse, cause injuries or even fatalities.

In linear technology, which includes linear guides we talk about safety factors in relation to both static and dynamic load ratings. The industry follows standards like DIN 637, which specifies how to calculate load ratings and recommends safety factors for different applications.

Let’s start with static load safety factors (i.e., when the balls get permanently deformed by the load). In an ideal world—where every force is known and there's zero risk of injury—you could work with a factor between 1 and 2.

But reality rarely plays that nice.

You typically need a higher factor depending on things like vibration levels, dynamic forces, or manufacturing tolerances in your setup. Unknown forces are always a risk. As a general rule, a safety factor of 3 to 6 is reasonable if there are no unknowns.

If there’s any risk of personal injury—especially in vertical setups—you should go as high as 15, and combine it with a proper risk analysis and safety measures.

For dynamic load safety factors, we’re talking more about the theoretical service life of the guide. The higher the factor, the lower the load on the guide block, and the longer it’ll last. It also contributes to better suspension and stability in your machine.

As a general rule:

• Handling equipment should aim for a safety factor of 5 and up
• Machining equipment might need 10 or more, depending on type

At the end of the day, it’s your decision as the customer what level of safety you want in your application.

Here’s a video on the topic featuring Carry Lindholm from Bosch Rexroth.