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The Science of Manipulating Metal Part 2 – How a Tube is Bent without Breaking

In a recent post, we talked about the science of metal welding. Today, we’d like to talk about the other side of our fabrication services: tube bending. 

Before we get into how metal tubes are bent, we’d like to discuss why tubes are used in the first place. 

Why a Tube and Not a Rod? 

Sometimes, metal tubing is used because something needs to pass through it. Whether it’s air-flow, cords and cables, liquids, or something else, the hollow tube serves a practical function. But tubing is also frequently used in situations where nothing passes through it. 

It may seem strange. Wouldn’t a solid rod be stronger than a hollow tube? The answer is no. 

A tube can support more weight than a rod of the same weight. Because of its round shape, it’s capable of distributing the weight more evenly across the object. This makes it more resistant to bending and breaking. 

So if hollow tubes are so strong, how exactly do we bend them? 

How We Bend Tubes 

Tube bending is an artform that requires care and attention to detail. The trick is to bend the tube without flattening the diameter, creating kinks or ripples, or weakening the outer wall. There are a few ways to accomplish this, and depending on the method, different tools are used, but ultimately, it comes down to precise pressure. 

Too much pressure or misplaced pressure can cause flattening, breaking, or buckling.  

Depending on what the tube is being used for, some flattening is okay. For these jobs, we perform what’s called empty bending. An empty bend means nothing is placed inside the tube at the point of bending. This allows us to bend tubes at a higher rate, while keep costs low. 

For times when shape, diameter, and strength are of high importance, we use a mandrel. A mandrel is an object, typically a ball or rod, that’s placed inside the tube to hold shape. In cases where a tube’s walls are particularly thin or the bend is especially tight, we’ll use a wiper die as well. 

This is a tool that’s placed on the outside of the tube to hold its contour and prevent buckling. 

We also employ CNC (computer numerically controlled) bending for certain projects where speed and low cost are the highest priorities. 

If you’re in need of tube fabrication, contact Ever-Roll today! 

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