The Ultimate Guide to Wire Mesh for Molded Pulp Applications

Chapter 1

The State of the Packaging Industry

The COVID-19 pandemic put an undeniable strain on the supply chains of almost every industry worldwide. But not only is it affecting the availability of goods, but the way they are delivered to the end-user has also changed.

When the world shut down, restaurants began implementing more comprehensive delivery and take-out options, as dining-in was heavily regulated. There was also an uptick in people becoming health conscious, as not to develop bad eating habits during quarantine.

This caused a dramatic spike in demand for disposable grab-and-go and portion-control packaging. While single-use plastics were once the standard, we are seeing a distinct shift to molded pulp packaging.

Why Replace Single-Use Plastics?

Single-use plastics started gaining traction in the 1970s and boomed in the early 2000s. They are best defined as plastic products designed to be used once and discarded.

So, why replace them? Well, there are several negative stigmas surrounding the product.

First and foremost, single-use plastics place a huge strain on the environment. They are one of the biggest sources of pollution, especially in oceans, and can take several decades to decompose.

This can be particularly troublesome to the habitats of endangered species.

The production of single-use plastics also relies on resources, such as oil, that have become increasingly scarce, increasingly expensive, or both. This, alongside supply chain issues, has made it harder for consumers to get their hands on these products.

Additionally, as medical science and technology continue to grow rapidly, it has been discovered that single-use plastics are associated with substantial health risks. More specifically, it has been discovered that these products have traces of harmful chemicals linked to various ailments.

Why Are Companies Switching To Molded Pulp?

Recent studies have found that consumers prefer brands that use molded pulp. It affords them the feeling of being eco-friendly and doing their part to preserve the world for future generations.

As stated above, single-use plastics have become a concerning burden on the environment. Molded pulp, on the other hand, is widely known as a biodegradable material that will break down naturally with minimal impact on the environment.

To that end, molded pulp is made from renewable resources, commonly recycled paper, that are easy to come by. This makes the production of molded pulp vastly more sustainable than single-use plastics, even in the wake of supply chain issues.

Molded pulp can also be used to package consumer goods with reliable protection. While we have seen single-use plastics used for similar applications, the material has yet to be as reliable as molded pulp.

But above all else, when companies switch to molded pulp products, they commit to eco-friendly operations that are favorable to the end consumer.

Chapter 2

Understanding Molded Pulp

What Is Molded Pulp?

Molded pulp, also referred to as molded fiber, refers to products constructed from a slurry of recycled or virgin fibers. These fibers are typically created by breaking down various materials such as sugarcane, bamboo, straw, wood, and recycled paper.

The fibers are combined with warm water to create a slurry, which is then formed into molded pulp products, such as cutlery, straws, etc.

How Are Molded Pulp Products Made?

Making molded pulp products starts by taking your recycled or virgin material and placing it into an industrial pulper. This pulper works to break down the material into small fibers.

If you are using recycled materials, they must be cleaned and, if being used for food-grade applications, deinked before being introduced to the pulper. If virgin material is being used, this cleaning process can be skipped.

Once broken down, the fibers are combined with warm water, and a pulp-like slurry is made.

At this point, molds in the shape of the product are dipped into the slurry. A vacuum is applied to the molds to collect slurry on the surface of the molds.

As the molds surface, the vacuum also works to dewater the slurry, leaving just the pulp molding. At the same time, the pulp is heated, ensuring a smooth surface.

The molded pulp is released from the molds and subjected to a more vigorous drying process. Once dry, the molded pulp products will undergo a quality control inspection and, if within acceptable tolerances, are prepped for shipment.

Chapter 3

Enhancing Molded Pulp With Minerals

There are several instances in which molded pulp manufacturers turn to mineral fillers to improve the products they provide. Concerns such as improving water drainage, improving molded pulp integrity, preventing the pulp from sticking to the molds, and more can all be resolved with the right mixture of minerals.

What Minerals Are Used When Manufacturing Molded Pulp Products?

Generally, four minerals are used when forming molded pulp to enhance the process. These minerals are talc, kaolin, bentonite, and calcium carbonate.

Talc

Talc is considered the softest mineral on earth and is typically reserved for applications where friction is a concern during the forming process. Additionally, it is used to make slurries with high pitch levels easier to manage.

These factors work together to create a smooth surface that can be easily printed on. Nevertheless, talc is predominantly used when working with a slurry created from wood or recycled paper.

Kaolin

Kaolin, often called china clay, is a mineral that creates a smooth, white finish. Much like talc, this makes for a finish perfect for printing color, labels, and graphics.

Having been used for over 100 years, kaolin is particularly known for allowing for more effective laser marking capabilities.

Bentonite

Naturally found in volcanic ash, bentonite makes slurries with high pitch and sticky levels easier to manage.

Calcium Carbonate

Calcium carbonate is one of the most widely used filler minerals and is a term that can be used to categorize marble, limestone, or chalk. On top of creating a bright, white finish, calcium carbonate can be used as a filler to reduce the amount of fiber in each mold.

What Minerals Are Used When Manufacturing Molded Pulp Products?

Moisture is a prominent concern when forming molded pulp products. Fillers allow manufacturers to have more control over the dewatering process, reducing the amount of energy spent on drying wet molds.

Putting this into perspective, working with a pulp slurry that is 3% calcium carbonate will reduce the moisture present in the formed pulp. This, in turn, yields improved drainage times without substantially impacting the burst strength.

But mineral fillers are not limited to just improved drainage. Fillers, such as talc and kaolin, can also be used when struggling to properly detach molded pulp from the wire mesh molds.

Additionally, fillers can be used to maintain the performance of your wire mesh molds. Mineral fillers, such as talc and bentonite, can reduce the amount of stickies and pitch within the pulp slurry. In other words, your pulp slurry will not easily stick and accumulate on your wire mesh molds.

As a result, you will spend less time cleaning your mesh molds while maintaining uniformity in the quality and dewatering of your molded pulp products. That being said, regardless of what fillers you use, it will change the density of the final molded pulp product.

Using Particle Size Analysis To Fine-Tune Your Pulp Slurry

A critical step in manufacturing high-quality molded pulp products is formulating an easy-to-manage pulp slurry that can accommodate the mold’s profile and level of quality needed. As stated above, mineral fillers can make this process much easier.

But the individual mineral particles must be uniform for the fillers to work effectively and efficiently. This is where particle size analysis comes into play.

Particle size analysis is the process of determining the uniformity of material by analyzing the size distribution of a sample that represents the material’s presence in the production line. It is often employed in the molded pulp industry to analyze the particle size range of the mineral fillers, verifying that a specific amount of mineral filler will deliver the same effect with each use.

This will enable you to standardize your pulp slurries, ensuring customer expectations are met no matter who is operating the production line.

Chapter 4

Woven Wire Mesh in the Molded Pulp Industry

What Is Woven Wire Mesh?

Woven wire mesh, or simply wire mesh, is a screening media that is fabricated using hundreds of individual metal wires. These wires are woven together using a heavily monitored weaving technique, forming pore openings that are precise and rigid.

Its unique characteristics allow it to deliver the flexibility needed to be formed into molds of variating shapes and sizes. To that end, value-added processes, such as heat treatment and calendaring, can be applied to ensure your mesh molds produce quality products.

Why Use Woven Wire Mesh to Manufacturer Molded Pulp Products?

You can use a handful of screening media to form molded pulp products. This includes woven wire mesh, perforated plate, sintered multi-layered mesh, and expanded wire.

Knowing this, the balance between cost-effectiveness, throughput, durability, and flexibility makes woven wire mesh stand out.

As it is woven using thin wires, the amount of surface area the wires close off is minimized. This helps wire mesh be categorized as an open product.

In turn, it can allow for maximum water throughput during the drainage phases.

While not nearly as durable as materials like perforated plate, the durability of wire mesh is still competitive. Typically woven from 304 or 316 stainless steel wires, woven wire mesh is designed to withstand the variating temperatures and pressure loads associated with the mold pulp process.

You will find that the average wire mesh mold can last upwards of eight weeks. Naturally, the lifespan of your wire mesh molds will depend on your process and how you handle them.

As the demand for molded pulp products increases dramatically, designs are becoming more complex. Woven wire mesh is particularly known for its formability, allowing it to accommodate these complex designs.

Materials such as expanded wire and perforated plate struggle to convey these designs as they are too thick and rigid to accurately capture finer details.

But, again, wire mesh has the rigidity to maintain the desired shape throughout its lifespan because of its metallic makeup. Having your wire mesh heat-treated can help improve its ability to be formed and hold its form.

Picking the Right Mesh

One of the more notable benefits of using woven wire mesh to fabricate your molds is the fact that virtually every aspect of the material can be customized to accommodate your needs. In the molded pulp industry, the mesh specifications you will need to fine-tune to perfect your process are mesh count and alloy.

Mesh Count

20 mesh and 40 mesh were once seen as the industry standard and are thus recommended by numerous pulper manufacturers. With this in mind, W.S. Tyler has discovered 24 mesh and 50 mesh to produce desirable results.

Our 24 mesh is a standard square weave; however, it undergoes a specialized annealing process. While a 20 mesh and 24 mesh screen can be used interchangeably, we have discovered that 24 mesh can produce a more favorable finish and retain more fibers without affecting throughput.

Our 50 mesh is a specialized square weave that is outfitted with oblong pore openings. Scientifically calculated, these pore openings work to deliver optimal mechanical stability, balanced flexibility, and desirable water drainage.

Alloy

During the molded pulp process, the pulp slurry is typically heated to temperatures up to 464°F (240°C) and subjected to 50 psi of pressure when being formed. An even distribution of pressure and heat distribution is vital to a consistent product.

But as each molded pulp process features proprietary parameters, you must select an alloy that can accommodate the elements of your process. With that, the four main alloys used for molded pulp applications are stainless steel, brass, copper, and aluminum.

Stainless Steel

Stainless steel is possibly the most popular woven wire mesh material to date. With a manufacturing process based on centuries of research, the alloy has become known for delivering the perfect balance of durability, corrosion resistance, heat resistance, and formability.

It should also be noted that it won’t react with your pulp slurries. This is particularly beneficial when producing food-grade molded pulp packaging.

Brass

Brass is a wire mesh alloy often employed for its ability to retain and effectively distribute heat when forming molded pulp products. At W.S. Tyler, the brass wires used have a chemical composition of copper (85%) and zinc (15%).

This particular chemical blend works to ensure your wire mesh molds combat rusting.

Copper

Copper is a wire mesh alloy known for its ability to conduct heat and electricity. It also has poor resistance to cyanides, halogenides, and ammonia.

That said, copper can resist some of the common corrosive elements associated with molded pulp and features the tensile strength to withstand most forming processes.

Aluminum

Aluminum is a wire mesh alloy often used for its lightweight and corrosion-resistant characteristics. It should be noted that it is the weakest of the alloys listed and may need to be replaced more frequently.

Despite its weak traits, aluminum can accommodate the pressure and heat distribution requirements of most molded pulp processes

Chapter 5

The Fabrication of Wire Mesh Molds

How Are Wire Mesh Molds Made?

In order to ensure an even distribution of vacuum pressure and heat when manufacturing molded pulp products, the molds must be lined with formed wire mesh. As every detail of the molds will be transferred to the molded pulp, your wire mesh must be properly formed.

To do so, a specialized press must be employed. This press drives the mesh into a dye with uniform pressure, perfectly forming the mesh into the profile of your molds.

Understanding the Deep Drawing Process

To probably form your wire mesh molds into the profile of the molded pulp product, they must be deep drawn. Deep drawing is best defined as the process in which a flat piece of mesh is altered to take on the three-dimensional profile of the product.

To properly deep-draw your mesh, you must first cut and pre-form the mesh piece in accordance with the parameters of the final mold. The mesh can then be loaded into the press machine.

This press machine is furnished with a die that accurately depicts the profile of the molded pulp product the mesh mold will be producing. The mesh will then be pressed into the cavity of the die, embedding each detail of the die into the mesh.

After being formed, any unnecessary material is trimmed.

This deep drawing process works to maximize the amount of screening capacity of your process; however, it also ensures your wire mesh molds fit into your equipment perfectly. But as with any value-added process applied to woven wire mesh, the deep drawing of wire mesh must be fine-tuned based on the alloy of the mesh and the profile of the final mold.

NOTE: Once placed into the pressing machine, we have found that turning non-circular wire mesh pieces at a 45-degree angle enables the corners of the mesh piece to be deep drawn effectively.

The Common Issue of Deep Drawing Wire Mesh

The production of molded pulp products that deliver heavily relies on properly drawn mesh molds. For maximum efficiency, you must understand the issues you can encounter when deep drawing wire mesh and how to prevent them.

Cracked mesh, wrinkled mesh, deformation, and spring back are the most noteworthy issues that can hinder your molded pulp production line.

Cracked Wire Mesh

Cracked wire mesh describes the development of broken wires in concentrated areas of a wire mesh mold.

Cause: Drawing wire mesh beyond its limits or if the mesh is woven using wires of low quality.

Wrinkled Wire Mesh

Wrinkled wire mesh describes the development of folds, waves, or ripples in a wire mesh mold as it is being deep drawn.

Cause: Wire mesh often wrinkles when the die is not lubricated thoroughly, too much pressure is applied, or if the mesh is not cut and pre-formed to accommodate the profile of the final mold.

Deformation

Deformation is used to define a wire mesh mold that does not correctly form to the die.

Cause: Not providing enough support to the wire mesh piece as it is being drawn.

Spring Back

Spring back is a term used to describe a wire mesh mold that fails to hold the form of the die, springing back to a flatter orientation.

Cause: Implementing wire mesh that has not been properly annealed.

The Importance of Annealing Your Wire Mesh

It is widely known that wire mesh is relatively flexible as is; however, having your mesh annealed is required for best results. Annealing is the heat-treatment process in which wire mesh is subjected to tremendous heat and pressure in an effort to reduce the internal stress of the wires.

The resulting effect is a wire mesh weave that is softer and easier to form.

Not only does this ensure every detail of the mold is captured without altering the integrity of the pore openings, but it helps the mesh hold its form after being deep-drawn.

Using wire mesh that is not properly annealed or annealed at all increases the risk of mold spring back. Spring back is a term that describes the occurrence in which the wire mesh molds have minimal structural integrity, causing them to spring back to a flatter profile.

As annealing also makes the pore openings more rigid and permanent, wire mesh that is not annealed is typically more sleazy and flimsy. This heavily affects the fiber retention that occurs when forming the pulp, which results in inconsistencies in your final molded pulp products.

Ultimately, using wire mesh that is not annealed makes for a less efficient molded pulp process.

Looking for more information on annealing wire mesh for molded pulp applications? Refer to the following post:

The Benefits of Annealing Wire Mesh for Molded Pulp Applications

The Benefits of Fabricating Your Wire Mesh Molds In-House

There are several benefits associated with fabricating your wire mesh molds in-house. First and foremost, you can produce your particular specifications as needed.

As a result, costly downtime is reduced, and you can maintain desirable lead times.

Manufacturing your own wire mesh molds in-house will also make implementing elements of your brand much easier. Despite third-party companies having the capacity to create dies custom to your brand, the amount of proprietary labor would dramatically impact the cost and lead times of your molds.

The Benefits of Having a Third-Party Company Fabricate Your Wire Mesh Molds

While making your molds can be convenient, it can be a relatively daunting investment. It requires you to invest in all the tooling and any maintenance needed to keep your operation up and running.

With that, the machinery needed to properly press wire mesh into molds can have a large footprint. This can be troublesome when you begin to add in the other equipment needed to develop a comprehensive molded pulp production line.

Another factor of note is that pressing wire mesh molds can prove to be labor-intensive. In other words, a portion of your staff would not only have to be trained to use the equipment, but they would be spending less time contributing to more critical aspects of the molded pulp process.

So, to put it simply, if you must be mindful of your budget (especially unexpected expenses), are limited on space, or often face issues with staff volume, having a third-party company fabricate your wire mesh molds may be a suitable solution for you.

Chapter 6

Comparing Screen Media

Woven Wire Mesh

Woven wire mesh is a screening media known for being an open product. As wires with precise wire diameters are used during the weaving process, the amount of surface area closed off by the wires is reduced and controllable.

To that end, virtually every parameter of woven wire mesh can be customized. In regard to mesh count, more specifically, specifications as small as 400 mesh can be achieved.

This makes it extremely easy to achieve the finish and fiber retention needed to produce quality molded pulp products.

Perforated Plate

Perforated plate is a screening media constructed from a piece of sheet metal with hundreds of uniform pore openings created from laser, water jet, and plasma cutting. Its sheet metal characteristics make it one of the more durable screening media you can choose.

Additionally, it is known for its heat conductivity. This is critical as heat distribution is key to bonding the individual fibers of the slurry and initiating the drying process.

Expanded Wire

Expanded wire is a screen fabricated by taking a piece of sheet metal, cutting a specific number of slits at specific dimensions, and stretching the metal, creating diamond-shaped pore openings. Having comparable durability to perforated plate, it is widely used when extreme and continuous vacuum loads are placed on the screen.

What makes it stand out in comparison to perforated plate is that it can be fabricated to feature finer pore openings, though not as fine as woven wire mesh. It also has better flexibility than perforated plate, allowing it to be used in more complex mold designs.

Multilayer Wire Mesh Laminate

Wire mesh laminate is a screening media fabricated from several layers of woven wire mesh that have been sinter bonded together. The multilayer configuration allows the material to deliver optimal durability while maintaining the accuracy woven wire mesh is known for.

This leaves you with a mold that minimizes the need to be replaced, ultimately increasing production capacity.

Chapter 7

Maintaining Your Mesh Molds

When Should I Repair/Replace My Wire Mesh Molds?

With an average lifespan of 6 to 8 weeks, your wire mesh molds will inevitably develop faults. To prolong the life of your molds, you should handle your mesh with care when cleaning, avoiding abrasive scrubbers and brushes, and remember that more abrasive fibers will cause your molds to wear quicker.

That said, periodic visual inspections are the easiest way to identify any faults in your molds. But you can also pick up on faults in your mesh if you notice inconsistencies in your molded pulp products.

These inconsistencies can be things like clumps or holes throughout your molded pulp.

Repairing Your Wire Mesh Molds

Fortunately, when faults are detected, you can cut around the fault and weld a wire mesh patch in its place. In some cases, you can also weld broken wires back together.

With that said, welding your mesh instead of replacing the mold commonly results in costly downtime. Repairing your mesh is also associated with negatively impacting the mesh performance and aesthetics of the final molded pulp product.

Chapter 8

Ordering Wire Mesh

How Much Does Wire Mesh Cost?

W.S. Tyler has 50 mesh and 24 mesh weaves that are optimized for molded pulp performance. Each specification carries a price tag of $7 per square foot.

With this in mind, we understand that these specifications may not suit you. Your wire mesh supplier can work with you to determine a specification that will output the best results, but the price you can expect to pay will be dictated by the specifications you choose.

Regardless, the quantity of the order will also play a critical role in the cost.

How Can I Manage the Cost of My Wire Mesh?

Placing a purchase order for a set quantity of mesh to be released at specific intervals is the best way to manage costs when ordering wire mesh. This will allow you and your wire mesh supplier to lock you into a price that best suits your operation while also helping you manage inventory.

Ordering mesh in bulk will also work to manage costs. To explain this further, let’s say you require 50 mesh rolls.

Buying 50 rolls would reduce costs to about $6.75 per square foot, whereas a 100-roll order would reduce costs to about $6.50.

Understanding the Buying Process

Purchasing wire mesh will typically start with you requesting a quote from a reliable wire mesh supplier. To help make this process as quick and effective as possible, you should be prepared to tell the supplier about your operation as well as the following regarding your wire mesh needs:

Dimensions

Quantity

Sample requirements

Shop drawings (if having the wire mesh supplier deep draw your wire mesh)

Once it is determined that the wire mesh supplier can accommodate your needs, you will receive a quote reflecting the costs associated with the order. At this point, you will need to either accept the quote or submit any revisions.

After the quote is approved and returned, you must send in a purchase order. The supplier will confirm that the purchase order has been received, start production, and provide lead times as well as tracking information.

To gain a comprehensive understanding of what you can expect when inquiring about wire mesh for molded pulp applications, refer to the linked article:

Molded Pulp: What To Expect When Buying Woven Wire Mesh

Requesting Wire Mesh Samples

To ensure you invest in the wire mesh specifications needed to excel, W.S. Tyler offers samples of all our molded pulp wire mesh. Samples can be obtained in 12″ X 12″ pieces.

While samples come at no cost to you, there is a limit of two samples per specification. To request a sample, simply reach out to our team of experts with your particular needs.