What Effect Does Bonded Thread Have On Tensions in a Sewing Application?

When industrial sewing operations require high thread or yarn tensions, properly designed sewing threads and yarns are critical to continuous production flow. Bonded sewing thread and yarn tends to perform well for critical and challenging sewing conditions often faced by manufacturing companies. We’d like to provide some insight into how bonded thread affects tension in industrial sewing and manufacturing.

What is Bonded Thread?

Bonded threads and yarns are encased in a polymer coating during the manufacturing process, typically from application of an agent or resin that creates a sleek, even finish across the surface of the thread. During the bonding process individual filaments or ends are fused together to create a uniform and cohesive single thread or yarn “line”.

Bonded thread processes smoothly with less friction and fraying than uncoated threads. Properly designed, bonded yarns can handle the forces involved in high-speed sewing used by industrial manufacturers with less breakage than unbonded or soft threads.

For more information about the specific characteristics of bonded thread, we suggest that you read our other blog post, What is the Difference Between Bonded and Non-bonded Thread?

Why is Bonded Thread Good for High-Tension Sewing?

When you use bonded thread in high-tension industrial sewing, you’ll notice far less fraying than typically occurs with non-bonded thread. Bonded threads and yarns are also less likely to come apart under the tension of sewing or processing and cause a break in the line.

Bonded thread can take the forces that arise when working with thick materials like synthetic web slings, geotextiles, leather and upholstery. If you’re doing high-speed work that is also multidirectional, common in large-scale industrial manufacturing applications, bonded threads and yarns can withstand the friction and forces much better than soft or uncoated yarns that may be damaged under challenging manufacturing conditions.

For a facility that uses high-speed, high-tension, and/or multidirectional sewing, choosing a bonded top thread will have a positive impact on production by minimizing slowdowns from slippage and breakage, resulting in less downtime and more productivity.

Choosing the Right Thread for the Right Tension

Now let’s look at how to select the proper thread for the tension your operation uses in sewing. Here are some tips for making the right choice.

Use Soft Thread for Bobbins

In a machine that uses bobbins for the lower thread, using soft (unbonded) thread for the bobbin thread is preferable because it flattens out when being pulled out of the bobbin case. This means the tension is more consistent and can be adjusted more precisely, so the thread stays in the tension spring guide.

Bonded thread isn’t always a good choice for bobbins because it doesn’t lay as flat as soft thread. Since bonded thread is typically used with lubricant, it can also create a buildup of lubrication that creates inconsistent tension after long periods of sewing.

Consider Tension Differences

Differences in tension should lead to different choices about thread depending on the level of tension in your devices and processes. Soft (unbonded) thread and bonded thread behave differently under tension. 

Soft thread generally has more tension while being pulled through a tension device and bonded thread will have less tension because it doesn't flatten out. In addition, bonded thread is generally lubricated which also reduces tension to some extent.

Thread Type Matters

The type of thread material is also a consideration. Polyester and nylon bonded threads usually have very similar tension characteristics as long as they are the same size. This means they are close enough in specs to generally not need tension adjustments when changing between them.

However, Dyneema® , Teflon®  Spectra® , and ultra-high-molecular-weight polyethylene (UHMWPE) all tend to maintain less tension than nylon or polyester, even when they are non-bonded and non-lubed. The plastics these threads are made from have an extremely low coefficient of friction, which means that your tensions may need to be increased.

Kevlar® , Nomex® and other aramid threads will produce a higher tension than nylon or polyester. The short-chain fiber structure of aramids gives the thread an abrasive property that causes it to grip the tension device better than other threads, so your tensions may need to be decreased.

Cotton and cotton-like threads cannot be bonded like nylon or polyester, therefore they will flatten when passing through a tension device. Cotton also produces an abrasive effect on tension devices so even when it is lubricated, it will produce more tension than nylon or polyester.

Size Makes an Impact

Keep in mind that the size of your thread is also a consideration because the larger the thread, the more tension will be required to pull it through the machine. If you will be changing from a large thread to a much smaller thread during your process, your tensions may need to be increased or decreased.

For More Information

There are numerous factors to consider when evaluating the use of bonded thread in industrial sewing and manufacturing operations. If you need additional information, we invite you to read the following blog posts on similar topics:

• What is the Difference Between Bonded and Non-bonded Thread?

• Why Do I Need Bonded Thread For My Process?

To ensure you make the right thread selection for your application, contact the experts at Service Thread and we’d be happy to help.