What is the Load Moment of an Electric Linear Slide?

Oh, Vex, what's wrong with your dull face?

A customer asked me, "When selecting an electric linear slide, what do we need to check the load moment for?" but I wasn’t able to explain properly…

That's a question I receive sometimes. In case of electric linear slides, people often think that it is enough if the load mass and transportation speed meet the specification, but actually the load moment is also important. Vex, you know the structure of an electric linear slides, don't you?

Of course! A linear guide converts the rotation of a motor into linear motion with a ball screw, and makes that motion smooth, right?

You're studying well! In order to understand the load moment, the linear guide is the key point. In addition to the load, the linear guide is subjected to forces in the following three directions...
In case of Vex, would it be easier to visualize with your body than to think with your mind?

I see! This feeling of twisting my body was the moment. It's been tough due to lack of exercise lately, but the linear guide was also tough because of the force applied from various directions...

That’s right. You looked painful, but it seems you felt it in your body!
So, if you combine the three directions of force you just learned with an actual electric linear slide, it will look like the figure below.

How do you actually apply the load moment?

The magnitude of the load moment can be found by multiplying the "length" by the "force."

• Length: Length from the linear guide to the center of gravity of the load
• Power: Force applied to load

I found this figure, so take a look.

In this example, when the electric linear slider moves to the right side, the acceleration applies a force to the load in the opposite direction to the direction it is moving, so a load moment in the pitching direction is applied to the linear guide. In addition, if the electric linear slide is installed vertically, the gravitational acceleration will also add a load moment to the slide, so you need to be careful to the installation conditions that is required.

When checking the load moment, it is quite profound to pay attention to the installation conditions in addition to the operation conditions.

That's right. If you want to take the permissible moment into account when selecting, our motor sizing service is recommended. If you provide us with the installation conditions, operating conditions, and load mass, we will be able to introduce the most suitable electric linear slide.

Understood! I'll explain the load moment along with introducing the motor sizing service!