Monday, August 1, 2016

Everything You Need to Know to Get Started with Ballscrews

New to CNC machining? You might wonder, like many others, what ballscrews are all about.

What is a ballscrew, and why would you use one anyway?

First, take a look at ballscrew theory. Think of this as your introductory college course to ballscrews. Very simply, ball screws transfer rotational motion into linear motion with next to no friction. They do this at about 90% efficiency. This is far more efficient than any other method that does the same. This greater efficiency also means ballscrews also have a much longer life than other components that perform the same function.

Why would you use a ballscrew?

They’re usually used in situations where you have a lot of lead or need a lot of life. They compare to lead screws, which get used for the same purpose, but they’re used in smaller, lighter duty applications. Lead screws also have more customizability, as you can change the leads, sizes, and their nut configurations quickly and with ease.

How do Ballscrews Work?

They’re pretty simple in nature. The threads on a ballscrew allow a hardened steel ball to transfer rotational motion from a ball nut into linear motion along the shaft. Inside of the ball nut, there’s grooves, and these grooves fit with those on the shaft, allowing the multiple balls to travel along.

Ballscrews also have a high degree of accuracy. They can easily be accurate to 1/10000th of an inch.

Comparing 2 Types of Ballscrews

When you look to buy ballscrews, you’ll run into these common types:

Ground ballscrews
Rolled ballscrews

Ground ballscrews are made when abrasive wheels cut the channels the ball moves through. While they carry a higher price, they do have high tolerances and exceptional accuracy. They also tend to operate much more quietly than rolled ballscrews.

Speaking of rolled ballscrews, their main benefit over ground ballscrews is their cheaper cost. In fact, they can easily cost 15-20x less than their ground counterparts. However, you will sacrifice accuracy. Rolled ballscrews can be found with accuracies similar to that of ground ones. But, they also then carry the same price.

In nearly every case, ground ballscrews work out better than rolled. So when deciding which to use for your CNC machine, the question usually comes down to the accuracy you need and the price you’re willing to pay for it.

Hope that helps

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