Common Causes of Poor Bends

For a visual representation of common bending defects and how to avoid them, please view our document: Common Bending Defects and Resolutions.

During the process of bending, a whole range of defects and problems can occur. In most cases, the defects are caused by one of the following factors:

Operator Error is the primary cause of defects

One common operator error is using too much pressure on the pressure clamp, which has the result of pushing out the wiper die and causing more wrinkles. If they continue to increase the pressure, it can lead to cracking of the mandrel and the beads. Increased pressure is not always the solution. In fact, an unnecessary increase of pressure can lead to faster wear on the tools, and increased stress on the machine.

Using a Toolset with Damaged Tools

A toolset for bending tubes is only as strong as its weakest tool. A toolset containing broken or damaged parts will not produce quality bends with an optimal lifespan. Bending with damaged tools will result in increased waste and a sharp drop in longevity for the other tools in the set. For example, if the operator is using a worn-out mandrel or wiper die, this will lead to increase wear on the clamp die, pressure die and pressure clamp. 
The operator must ensure that all parts of the tools are maintained.

Using the Wrong Tools for the Job

Certain tools will execute certain jobs better. For example, using a mandrel too small for a tube, or a heavily worn mandrel, will cause waves and wrinkles in the bend. These waves are likely to damage the wiper die.

Poor choice of material for the tools 

The material of the tools in regards to the tubes they are bending also plays a critical role to a successful bend. This is especially important when selecting the material for your mandrels and wiper dies. (see: Material and Quality of the Tubes)

Incorrect Tool Setup

Even if you have selected the correct size and material for your tools, and they are undamaged, you can still see defects if you do not set them up properly. The tools must be setup on the machine correctly in order to prevent any defects. (see: Basic Tool Setup for additional assistance)

Additional Causes and Information

Of course, there are many other factors that could contribute to a substandard bend, but the aforementioned list contains some of the most common causes.