In one of our previous articles, we discussed the process of manufacturing wire. Now it is time to talk about the belting side of things. Haul-off and puller belts are the most important belts when it comes to manufacturing wire. These belts are critical in the extrusion process. Haul-off/Puller belts all have a pretty similar make up; a poly-v structure on the pulley side, a cord tension member made of fabric or aramid (Kevlar), and then a cover made of a variety of materials. Haul-off/puller belts come in a variety of sizes with thickness ranging from 3-40mm, widths ranging from 4-40mm, and lengths ranging from 250-3700mm. Even though this article is discussing the wire industry, haul off/puller belts are also used in the plastic, window, pipe, and hose markets.

Pulley Side

The pulley side of things is very straightforward. You have several pitches that the belt could be:

PJ pitch- has a 2.34mm distance between ribs and a depth of 4mm between ribs
PK pitch- has 3.56mm distance between ribs, a 2.4mm depth of the ribs, and a 40 degree angle of the rib
PL pitch- has a 4.76mm distance between ribs and a depth of 10mm between the ribs
PM pitch- has a 9.52mm distance between ribs and a depth of 17mm between ribs

On top of the poly-v backs, we are starting to see more haul-off/puller belts with timing belt backings. For more on timing belts, click here.

Tension Member

These tension members are usually made of one of two materials. Polyester is the weaker of the two materials and generally has a strength that can vary between 190-250 kg per cm belt width. Aramid is the stronger of the two tension members and can have strengths of up to 500 kg per cm of belt width. When it comes to the tension members, a good belt will have the following characteristics:

Needs to be manufactured to be endless/connectionless.

There needs to be no break points.
The belt needs to have consistent running performance.
The belt needs to have high flexibility while having low elongation.

Covers

Covers can be made from a variety of materials; natural rubber, neoprene, silicone, PVC, nitrile, silicone. Materials can come in a variety of colors such as red, blue, green, tan, grey, and white. Hardnesses can vary from 30-90 Shore A.

Natural Rubber - has the ability to stretch and return back to its original size. It is also flexible, sound/vibration dampening, and has a high abrasion resistance.
Neoprene- more durable, versatile and oil resistant than silicone but less than nitrile. It is more ozone, weather, and flame resistant than nitrile.
Nitrile- It is the most chemical, oil, and fuel resistant out of the synthetic rubber. It is also more durable than silicone.
Silicone- More resistant to UV radiation and extreme temperatures. Not as durable as the other two. Also has a “non-stick” effect.
PVC- High abrasion, oil, grease, and acid resistance. PVC has good grip properties and is great for small rollers.

The covers generally have some sort of patter on them. There are longitudinal and transverse grooves, V- grooves that range from 90-150 degrees, and half round profiles to name a few. Most companies will do custom profiles if requested.

So What Is The Best Puller/Haul-off Belt?

Despite a variety of companies, such as Nitta and Commscope offering them, the best belt is the one that fits your purpose. That means that you have to look at your application and choose the best cover for your process. You also need to choose a durometer that is appropriate for your machine.

With all of that being said, there are several examples of a good belt vs a bad one. A good belt is non-directional. That way, when the pattern wears out in one direction, it can be flipped and reinstalled. A good belt also needs the ability to run on small pulleys. A splice will always be the fail point on a belt, so it is better to choose one that is endless. These belts can be spliced and a poor splice will cause RL spikes. Splices can make a belt directional since it gives the belt a lip to get hung on the machine. Lastly, a good belts are ones that are installed at the same time. If you have uneven wear on the belts, you are only opening yourself up to a host of problems.