How Are Monofilament Fishing Lines Manufactured?

Anglers have been using monofilament fishing lines for the past sixty years, and it’s still going strong. More fishing lines are available today than ever, yet monofilament lines remain as popular now as ever before.   

Monofilament fishing lines are typically made from nylon or a mixture of different plastics. These plastics are melted down and extruded through a die containing holes forming a single strand. Then this line is cooled and stretched out to rearrange molecules for greater strength. 

Do you sometimes wonder how your favourite monofilament line is made? Read on to learn how it’s done.

How Are Monofilament Fishing Lines Manufactured?

An automated machine uses an extrusion process to manufacture monofilament fishing lines of various test strengths and diameters. The manufacturing process can be broken down into 9 different steps.

Here is a youtube video showing the monofilament manufacturing machine operating.

Step 1: Extruder

In the first stage, plastic pellets (all one type of plastic or a mixture of plastics) are dumped into a hopper attached to the extruding unit. 

The hopper is then heated up to melt the plastic pellets and is mixed to ensure a uniform mixture.

While the liquid plastic is being mixed, colour and chemical additives are added to the liquid plastic. Plastic pellets are usually colourless, and adding colour dye will give the fishing line its colour. The chemical additives are used to alternative its characteristics like:

• Strength
• Flexibility
• Stretch
• Abrasion Resistance
• etc.  

Step 2: Die

The liquid plastic moves through an auger screw pushing the material through a die in this step. A die can contain upwards of 200 – 30 holes in which the molten plastic is extruded.   

Each hole creates a continuous fibre that looks like fishing lines that travel through a cooling bath after exiting the die.

Step 3: Cooling Bath

The cooling bath rapidly cools the temperature of the line helping it to solidify so that it can retain its shape for the remainder of the manufacturing process.

Cooling the line down will give it strength and structural integrity.

Step 4: Godet Rolls 1

Most monofilament manufacturing machines are fitted with three sets of rollers that perform an essential part in the drawing and thermosetting processes. Up to six or more rollers per godet prevent the line from slipping as the tension increases on the line.

The first set of godets, or rollers, keeps the lines from tangling and slowly guides the line out of the water bath and into the next production line step, the stretching oven. 

Step 5: Heating Oven

After the line passes through the first set of godets, it will enter a heating oven. The heating oven is used to relieve some of the internal stresses in the line from being rapidly cooled and being stretched by the second set of godets (rollers) after the heating oven. Stretching the line is required to help rearrange the molecules to point in the same direction. 

This process is typically called “drawing,” designed to align the lines’ molecules and gives greater strength. The amount of heat and stretch applied affects the end product’s characteristics, including how much remaining stretch the line has.

Step 6: Godet Rolls 2

The second rollers draw the line from the stretching oven and continue stretching the line to reduce its diameter further. This amount of stretch applied to the line by the rollers is carefully controlled as it directly affects the final product’s diameter. 

Step 7: Annealing Oven

During this step, the line passes through an annealing oven that again heats the line to a specific temperature to relax the lines’ molecules. This process locks in the lines’ desired characteristics. Annealing also prevents the line from shrinking, which can happen over time. 

Step 8: Godet Rolls 3

The final set of godets or rollers keeps the lines that run between godets two and three tensioned and simultaneously feed the completed line to the winding station.

Step 9: Winder

The winder is the last stage in the manufacturing process. As the name implies, this step entails winding the finished lines onto bulk spools. The winding machine can consist of up to 200 – 30 bulk spools. 

After the winder, the line goes off to packaging and shipped to stores.

Monofilament Fishing Lines Materials

The term monofilament fishing line has become synonymous with fishing lines made from nylon.  

Today, we have many different monofilament line materials from which to choose, making things a little confusing. The confusion arises because the term monofilament can no longer be assumed to refer only to nylon lines. Monofilament is only relevant today to describe how the line is made. 

Monofilament lines are made through the extrusion process, producing a single round line with a smooth surface. Using different materials to make monofilament will give the line different performance characteristics. 

The elements determined by the raw material ratios are abrasion resistance, strength, buoyancy, stretch, UV resistance, water resistance, and lifespan. The materials used also impact both the cost and environmental friendliness.  

Below is a list of pretty common materials that have become popular in Monofilament fishing lines. 

• Nylon
  
  Traditionally used to make monofilament fishing lines and is still used today. Modern-based nylon fishing lines are usually mixed with other polymers or chemicals to adjust their characteristics.
  
  If a single polymer is used to make the line, the line is called a polymer. When two polymers are mixed, it’s called a co-polymer; when more than two polymers are combined, the lines are referred to as a multi-polymer.

• High-Density Polyethylene (HDPE)
  
  High-Density Polyethylene is manufactured from ethylene/petroleum through a catalytic process.

• Polypropylene (PP)
  
  Polypropylene is a thermoplastic made from various propylene monomers. In real terms, this means it’s well suited for the use of making monofilament lines or for the making of braided lines. 

The below table outlines the different polymer-based fishing line characteristics.

	Nylon	HDPE	PP
Strength	Good	Good	Good
Abrasion Resistance	Good	Average	Average
Water-Resistant	No	Yes	Yes
Stretch	Yes	No	No
Durability / Lifespan	Average	Good	Good
Environmentally Friendly	No	No	No
Buoyant	Yes	No	Yes
Memory Forming	Yes	No	No
UV Resistance	No	Yes	Yes
Cost	Low	Average	Average

Quality Assurance Testing

Manufacturing companies making monofilament fishing lines perform extensive testing on their products to ensure quality and gather data for future developments. Below are some of the criteria taken into account when line testing is conducted.

• Strength Testing
• Stretch
• Knot Strength
• Suppleness
• Submersion effect
• Temperature influence
• Elasticity
• Line Color 
• Memory Effect 

All major line manufacturers have very sophisticated test labs in which product development and testing are done.  

Independent tests conducted found that many monofilament lines have a larger diameter than advertised and have a higher breaking strain than the advertised test rating.   

Development Of New Monofilament Lines

Fishing line manufacturing companies are constantly improving the quality of fishing lines and introducing new product lines. Significant funds are spent annually on research and development in the quest to enhance fishing lines continually. 

What’s the next big thing? Who knows for sure, but biodegradable fishing lines are not that far off.

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Happy Fishing & Tight Lines