Plastic Spiral Binding

by: Anna C. Massey

Plastic spiral binding is the fastest growing segment of the mechanical binding industry. The durability of plastic spiral, the vast array of available colors to choose from, and advancements in the automation of the plastic spiral binding process have caught the attention of most binding consumers. Couple that with shortages in the steel industry and rising steel prices and one is forced to sit up and take notice. Plastic spiral has become a viable mechanical binding alternative to the traditional comb or single and double loop wire types of binding.

The plastic spiral binding of today is light years ahead of that being produced 15 to 20 years ago. However, there still can be some important differences between plastic spiral binding manufacturers that can dramatically affect your bindery’s productivity and cost effectiveness.

Base Compound Makes a Difference

Most plastic spiral manufacturers produce the product with a PVC (Polyvinyl chloride) compound. The applicable colorant is added during the extrusion process at which time the PVC and colorant pellets are melted and mixed. The extruded filament is wound as a single strand profile onto spools. Different profiles are produced for specific coordinating coil diameters. The spooled filament is then put through the forming process for manufacture into the specified diameter, pitch, and length of coil that is required.

Although most plastic spiral binding utilizes a PVC base compound, what goes into that compound can differ between manufacturers. Every compound will have different levels of additives that can and do affect the finished product. Additives like impact modifiers help insure the coil is durable and will maintain its shape.

Interesting comparisons have been done between plastic spiral made from high quality compound and that produced with a lower grade of material. A formed coil made with low-grade material literally shattered when slapped against a table. The plastic spiral made from the higher quality compound did nothing more than bounce back. This type of information can be important depending on the project (for example, if the plastic spiral binding will be used in a children’s project).

A 10 mm Coil is a 10 mm Coil – Right?

The profile or gauge of filament used to manufacture a particular diameter of coil is another point of comparison. Some plastic spiral manufacturers use fairly thick, rigid profiles of filament to produce particular ranges of coil diameters. A 10 mm coil may be produced with a filament of 2.0 mm / .080″. Others use thinner filament (1.8 mm / .072″ or 1.5 mm / .060″).

If you are price shopping for potential coil suppliers and are strictly looking at the cost of 10 mm coil, you may not be comparing “apples to apples”. If a manufacturer is using a very thin filament to produce its product, its numbers will look more appealing because the manufacturer is using less material to produce it. It is important to know what profiles of plastic your coil supplier uses to make its various coil diameters.

Plastic spiral binding that is very thin can cause problems during the insertion process. Plastic spiral that is too thick can also cause difficulty when inserting, which can bring down production numbers. Recommendations can and should be made based on the size and shape of the punch hole that a customer needs, as well as the type of coil inserting equipment being used.

A sharp lead edge on the coil is another important factor when the coil is running through the punch holes. How the coil is packed and its condition upon arrival at your location also may affect your bindery’s productivity.

Pitch – The Most Misunderstood Term

Pitch is basically another word for distance or spacing. It describes the distance or spacing between the loops of coil. However, over generalization and the misuse of the correct terminology can complicate an otherwise simple concept.

When it comes to plastic spiral binding, there are a surprising number of options available for pitch. The key is to match the pitch of the coil to your punch pattern. If you punch with a 4:1 pattern, then you should be using 4:1 coil. If you have a 6 mm punch pattern, it is recommended that you use a 6 mm pitch coil. There is enough incompatibility between pitches to slow you down and affect your productivity if the incorrect pitch is used.

Round vs. Elliptical Filament

If you are a bindery or in-plant that has in-house coil manufacturing, this is terminology that applies to you. Purchasing plastic filament on spools for manufacture into plastic spiral binding presents you with the opportunity to compare the different filaments being produced. As not all coil is created equal, not all filaments are created equal either.

Some manufacturers produce a round profile of filament and others produce an elliptical (or oval) shape. An elliptical profile of filament can yield as much as thirty percent more coil per pound than a round profile. Less material also will equate to a reduction in shipping costs. Again, if you are shopping suppliers, a cost per pound comparison is not enough. It is the yield per pound that you need to be comparing.

Talk to your supplier – understand what you’re buying – know what your options are. Plastic spiral binding – there’s a lot more to it than meets the eye.