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Merryweather Foam Blog

Since 1948, we have been industry leaders in fabricating unique, foam components for customers in the medical, sound absorption, automotive, and unique packaging industries. At Merryweather Foam, we pride ourselves on our ability to combine experience, innovation, and excellent customer service. We have the knowledge, manpower & equipment to help you get the job done. Visit our website to see our fabrication portfolio as well as our capabilities.

All About Foam Convolution

Foam Convoluting is a process through which the surface of a piece of foam is customized to fit the requirements of a particular application. If a piece of foam in a hospital bed, for example, a unique pattern can be designed to allow for both levels of full body support and long-lasting comfort when compared to other options.

The Benefits of Foam Convolution
Foam Convoluting is a maximum yield process. Customizations to the foam are made specifically to provide the highest possible value given what a piece of foam will eventually be used for. If you use foam convolution to design a new piece of bedding, for example, the foam is customized in a way that will allow for things like:

  • Enhanced levels of air circulation.
  • Maximum support.
  • Increased comfort while still maintaining the desired level of support, and more.

It is for these reasons that flexible foam fabrication is often used across a wide range of industries, including in both bedding and healthcare, to create things like:

  • Acoustic applications, like use as sound treatment for a recording studio, thanks to their sound absorption properties.
  • Privacy panels that are more durable, more attractive and more versatile than concrete alternatives.
  • Office applications like ergonomic furniture, which creates a more comfortable environment for employees to maintain productive without sacrificing their health or stamina.
  • Insulation designed to eliminate drafts in a building, thus keeping cool air in during the summer and warm air in during the winter, increasing the energy efficiency of the whole building and decreasing utility bills at the same time.

Foam convolution is also often used in applications like sound management, acoustic treatment and similar products in an audio recording or other entertainment environment. Depending on the pattern being used, foam convolution can absorb mid and low range sound frequencies much better than alternative options.

The Materials Used in Foam Convolution
During this process, foam can be custom fabricated in one of four ways depending on the intended goal:

  • By pattern
  • By the total size of the pattern being worked with
  • By the depth of each intended cut that will be made
  • The spacing between multiple patterns that all come together to form a single piece.

In addition to the foam itself, a number of important materials are used during the foam convolution process. A specially designed divider is often used to slice a larger piece of foam down the middle, while at the same time also creating the specific pattern that will be present on the final product. A series of rollers move a piece of foam across the divider, allowing for the process to be largely automated after all of the initial design work has taken place.

By and large, foam convolution is one of the single best ways to achieve the results that you're after for a particular application. The products of foam convolution play an important role in the lives of millions of people on a daily basis - from acoustical engineers to patients in hospitals to people just trying to get a good night's sleep - and the process in general is something definitely worth celebrating. Questions about Foam Convoluting or other machine processes? Give us a call--we're happy to help!

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Rotary Die Cutting - Foam Fabrication Capability

Rotary die cutting can be used to create shapes, creases, folds and guides in foam and plastic materials.

What Fabrication Processes Are Available to Business Owners?

Anytime a business needs to produce large numbers of identical and highly accurate shapes through cutting, forming and shaping sheet or rolled metal, or some other material, such as paper or plastic, business owners frequently use a versatile fabrication process called die cutting.

Different manufacturers use varying die cutting processes, which include:

  • Flatbed
  • Press
  • Laser
  • Rotary

What Is the Rotary Die Cutting Fabrication Process and Why Is It Chosen So Often?

Since the rotary die cutting procedure takes place on a heavy-duty cylindrical anvil, or rotary press, it provides a stable and efficient method that works well for clients' high-volume projects. This type of fabrication process produces little waste, mostly due to the sheer simplicity of the machine's design and specific capabilities.

Similar to the idea of a mold in other processes, a die serves as the customized tool that makes the cuts and shapes in the materials chosen. the The most common dies used in the process include engraved dies that offer stability and a solid base due to its mass, adjustable dies for varied blade options and magnetic plate tooling that also offers a stabilizing force due to the power of the magnets.

The rotary die cutting process begins when an operator feeds a long web or sheet of material into the die cutting machine's "station," which is the spot that contains the rotary cutting tool that creates the designed shapes by various methods, including cutting programmed shapes, creating perforations and creases or whittling the sheet or web down to smaller pieces. A set of well-calibrated gears ensure that a rotary die cutting machine will work at the same speed as the rest of the process for high accuracy and quality. As for the flexible foam material, it goes through the machine, the small amount of waste material filters into a catcher for easy clean-up and disposal.

Since the rotary die cutting cylinders feature a limited size, they are only suitable for smaller projects — a few feet wide or less — but that still leaves plenty of options for manufacturers, which include:

  • Polyester foam packaging
  • Gasket foam seals
  • Polyester foam rollers
  • Waterjet cut foam gasketing
  • Waterjet cut polyester foam spiral
  • Polyester foam case insert
  • Reticulated polyurethane foam filter
  • Flexible gasketing material
  • Fabricated foam gasket

Ultimately, this process offers many benefits to a company that regularly needs precision cutting on various materials, quick turnaround times and the potential for taking on multiple projects at once since users can combine die cutting with coating, embossing and lathing processes.

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Thick Material? No Problem! We can cut with Pressurized Water

Our water jet cutting machines leaves clean, straight edges in thick foam. Try it on your next custom foam fabrication job.

Cutting soft materials like foam is hard. Try pushing in the blade of a knife and the material compresses. The thicker and softer the foam is, the more it deflects. The only way is to use the point of the knife: once the surface is pierced the blade can go through.

That's why we have a waterjet cutting machine. Like an incredibly sharp knife, it lets us cut complex profiles from soft materials up to 6" thick. If you need pieces for a flexible foam fabrication, talk to Merryweather about waterjet cutting.

Process basics

In waterjet cutting a needle-thin jet of water moving at near supersonic speed slices through soft material. By moving the jet over a sheet of material it's possible to cut out intricate two-dimensional shapes. Recessed pockets can't be cut with a waterjet though, because it goes all the way through. Instead, the way to make those is from two separate pieces of foam. Combining waterjet-cut pieces that way allows creation of almost any custom foam fabrication.

Why cut with water?

It's a fast way of cutting out large, complicated shapes. It's a clean process with no chemicals or hazardous wastes, and has many other useful characteristics too.

  • Pierce straight through so there's no need to cut in from the outside. Essential for creating contiguous shapes with hollow centers (as you'd need for a pocket.)
  • Cuts very square, even on materials like thick reticulated polyurethane foam, and leaves smooth edges needing little to no finishing.
  • Very narrow cut width or "kerf" thanks to the thin beam. This allows cutting of very intricate shapes and lets us nest shapes to use a sheet efficiently.
  • No sideways forces, so there's no material distortion. This also lets us cut very thin wall sections.
  • No heat, unlike laser cutting, so there's no unsightly edge melting or heat affected zone.
  • There's no tooling or fixturing. All that's needed is a program for the waterjet's computer, and that comes from the CAD of the shape needed.

When is waterjet cutting appropriate?
With no need for tooling, waterjet cutting is ideal for one-offs such as for prototypes or for custom applications needing only a few identical shapes. As a single point-of-cut process, it's not the fastest method but does yield excellent results on thick, soft materials like reticulated polyurethane foam. Waterjet machines are also capable of cutting out very large shapes: ours handles sheets of material up to 60" by 132".

Small quantities that look good
Materials that are thick and soft, like those you might use in a custom foam fabrication, are difficult to cut cleanly. When appearance matters, tooling-free waterjet cutting is a cost-effective method of producing the shapes you need. If you're interested in learning more, contact us today.

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Adhesive Lamination Helps Make Your Product a Success

Multiple materials can be combined through lamination, creating a composite material with unique performance attributes to suit nearly any application. Whether you need tensile strength, cushioning, adhesion, fire resistance, shock absorption or insulation from heat or cold, there is a laminated composite material that can provide an optimum solution for your product. Merryweather Foam specializes in helping our customers achieve the results they want quickly and cost effectively.

The Adhesive Lamination Process

Our specialized adhesive lamination equipment works using pressure and heat to create permanent bonds between dissimilar products. The process works by feeding rolls of two or more different materials through large rollers under precise pressure and temperature conditions. In some cases, one material may have a carefully selected adhesive pre-applied so it comes in contact with the other material during the rolling process. In other cases, an adhesive may be evenly sprayed or rolled on the materials as they unspool so they are thoroughly coated before they enter the rolling area. The new composite material is spooled at the end of the lamination process so that it can be slit to your specified lengths and widths or shipped as for use in your manufacturing facility. Regardless of the number of materials bonded and the adhesive application methodology, the material that results is permanently bonded and will have a combination of the characteristics of each material used.

Adhesive laminated materials are used in many products across multiple industries, including:

  • Medical
  • Industrial
  • Automotive
  • Appliances
  • Electronics
  • Packaging


Any number of materials may be used to create composites with adhesive lamination. The most frequently used materials include polyurethanes, polyurethane foams, polyethylene foams, silicones, low permeability foams for use in wet or harsh environments, closed cell PVC or rubber sponge or foam, Poron™ urethane foams, and Cellasto™ microcellular polyurethane elastomer foams. Each of these materials offers different characteristics, including

  • Density
  • Insulating properties
  • Flexibility
  • Sound absorption
  • Durability
  • Compressibility
  • Abrasion resistance
  • Permeability
  • Solvent and chemical resistance
  • Appearance and aesthetics
  • Buoyancy and weight
  • Flammability and fire retardant specs
  • Regulatory approvals such as FDA, UL, ULC
  • Breathability
Why You Need a Partner with Adhesive Laminating and Composite Expertise

Your application is unique, so you need a unique composite material to give you the exact performance characteristics needed to solve your customers' problems. It requires experience and expertise to combine materials to create a composite with the right characteristics for a unique application.

At Merryweather Foam, we have more than 65 years of experience in helping customers specify exactly the right process and materials to create a composite to help your product succeed in your market. If you are interested in learning more about how our industry-leading adhesive lamination capabilities can benefit your product, contact us today.

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Glossary of Foam Related Terms

Our Engineering & Sales team has developed a helpful Glossary of Foam Related Terms to assist you in the selection and development process of your next project.  

DOWNLOAD: Glossary of Foam Related Terms (PDF)



The reduction of the intensity of a sound signal.


Anything that may be added to a foam mixture, not required to in order to produce the foam. Items such as plasticizers, colorants, colorants, antioxidants, and fillers.


One of the main divisions of organic compounds (those containing carbon) and particularly indicates those compounds having an open chain molecular structure.


The normal temperature of a room or environment in which the foam producing equipment or process is installed. It is often assumed to be 70 degrees "F".

A. S.T.M.:

The initials for the American Society of Testing and Materials.


Board Foot:

A standard of measurement in the foam industry which refers to a square foot of material (1) inch in thickness.


Synonym for gluing, adhering, laminating, or rebonding.


Cut-off segment of the continuously produced loaf of flexible or rigid foam being made by the slab technique. In some cases this block would have a top, bottom, and side skins intact and have cut surfaces only on the ends. In other cases, the top, bottom, and side skins may be removed by in-line trimmers leaving a smooth rectangular block.



The process of tying carbon and hydrogen molecules together to form polyethylene. Usually a chemical or radiation process.


A chemical that has the property of being able to change the speed of a chemical reaction without apparently taking part in the reaction


Known as a bubble or pore. It refers to the cavities left in the foam structure after the bubble walls have completely polymerized and solidified or curled back and fused into the boundary joints to form a skeletal structure.

Cell Count:

The number of cells per lineal inch or centimeter.

Cell Membrane:

The thin intact film that forms the bubble walls in closed cells, also know as windows.

Cell Size:

The average diameter of the pores (bubbles) in the final foam product. Although often still referred to as fine, medium, or coarse, or by the diameter in microns, most people refer to the number of cells per lineal inch.

Clickable Foam:

Foam that recovers 100% form the pinching effects of die cutting or pinching. It is foam that is less likely to have a sealed edge after being cut.

Closed Cell:

The property of foam where each individual pore is sealed off completely

from its neighbor so that no exchange of gas can take place except by diffusion through the walls. With rigid foams, it is usual to try for 100% closed cells to achieve maximum thermal insulation ability and minimal water pick-up. With flexible foams, it is normal to try for 100% open cells for

Compression Load Deflection:

(C.L.D.) The determination of the resistance to compression of a foam sample when the entire area of the sample is compressed.

Compression Set:

The recovery of foam from static or fixed compression. Less than 10% compression set (which is greater than 90% recovery) is usually accepted as good. Also known as "Percent Set".

Compressive Strength:

The resistance of rigid foam to compression.



The weight of a specific volume of foam. Expressed as pounds per cubic foot.

Dielectric Constant:

That property of a dielectric which determines the electrostatic energy stored per unit volume for unit potential.


The measurement of hardness of a foam product. Expressed in terms of the scale in which it is measured, usually the Shore "o", 660-0" or "A" scales.


The gradual yellowing of urethane foam due to a photochemical reaction

occurring from the effect of certain wavelengths of light. It is faster in sunlight than artificial light.

Double Cells:

A synonym for the presence of a scattering of cells (2) to (4) times larger than the uniform background cell diameter.



The percent of its original length to which a specially shaped material will stretch before breaking.

Elastic Medium:

A substance with the ability to return to its original dimensions after the removal of stresses.


To make brittle.


Fine Cells:

A foam with a cell count of 80 or more per lineal inch.

Flame Retardant:

A flame retardant material imports a certain degree of flame retardancy to a foam, i.e. the foam will burn less rapidly.


The relative burnability of the material in a specified situation. Meanings vary according to test method.


A product (flexible or rigid) that has been produced by the internal generation or liberation of a gas in a fluid medium that is simultaneously polymerizing while expanding in a volume.



An affinity to water. Hydrophilic are more absorptive and generally make better sponges.


Water repellant properties or characteristics.


Indentation Force Deflection:

(I.F.D.) Formerly (I.L.D.). The amount of compressive force (stress) needed to cause an indentation deflection (strain) of given magnitude. A measure of the firmness of a foam.


The foaming and swelling of a plastic when exposed to high surface temperatures or flames.


An instrument used to measure the tensile properties of foam.


The chemical process of reticulation.


"K" factor:

A measure of the insulation ability or thermal conductivity of the foam or

material. In English the unit of measure is in BTUs/hour/square foot of area/degree F./inch of thickness. Since the measurement indicates positive heat flow, the relationship to insulating ability is inverse in that the higher the "K" Factor, the poorer is the insulation ability of the product and vice versa.



An ambiguous term applied to certain formulations of foam fulfilling conditions in test method ASTM D 1692. Some of the foams with this label may burn quite rapidly.


Open Cells:

A term applied to foam cell structures characterized by interconnecting cells or bubbles. A foam cell whose membranes have been removed through a post reticulation process.


A vacuum phenomenon wherein a substance spontaneously releases volatile constituents in the form of vapors or gases. In rubber compounds, these

constituents may include water vapor, plasticizers, air, inhibitors, etc.


Having a strong affinity for oil rather that water.

Ozone Resistance:

Ability to withstand the deteriorating effect of ozone (which generally causes cracking).



The rate at which a liquid or gas can penetrate into or through a material in this case foam.


One of many high polymeric substances, including both natural and synthetic products, but excluding the rubbers.


One of the families of compounds that can be prepared with reactive hydroxyl groups and thus can be used as a polyol in the preparation of urethane foam. These polyol are generally more expensive than polyether polyols.


One of the families of compounds that can be prepared with reactive hydroxyl groups and thus can be used a s a polyol in the preparation of urethane foam. These polyol are generally less expensive than polyether polyols.


A high molecular-weight organic compound, natural or synthetic, whose structure can be represented by a repeated small unit, the mer; Synthetic polymers are formed by addition or condensation polymerization of monomers. If two or more monomers are involved, a copolymer is formed. Some polymers are elastomers and some are plastics.


Is a chemical compound with more than one reactive hydroxyl group attached the molecule.


These are families of chemical compounds that can be prepared by reaction

of isocyanate containing material with a hydroxyl containing material.


Resilient Foam:

A foam that has a very rapid recovery from extreme compression and a

fairly linear increase in resistance to compression per inch.


A term describing the unsaturated polymers or monomers used in the paint industry. In particular, those that apply to the polyester family. It is sometimes applied to the polyols in the urethane foam industry.


The normal or natural mode of vibration of a volume of air, panel of material

rod, etc.


The process of removing residual membranes or cell windows from the foam structure so that only a skeletal web like network remains.

Reticulated Urethane Foams:

Very low density urethane foams characterized by three-dimensional

skeletal structure of strands with few or no membranes between the strands, containing up to 97% or more void space..


The amount of rebound when a steel ball is dropped on the foam. It is a measure of how bouncy a foam is. It is expressed as a percentage of the dropped height.



Self Extinguishing:

The ability of a foam to stop burning after it has been started burning in a controlled manner. One test used to determine this is ASTM D1692.

Support Factor:

Also called the comfort factor. It is a function of IFD ratios and is an indication of how much "body" a foam has.


A disturbance in an elastic medium creating a "hearing" sensation to a receiver.

Sound Absorption Coefficient:

The ration of the sound energy absorbed by a surface to the sound energy incident on that surface. Also expressed in percent of absorption.

Sound Pressure Level:

A value 20 times the log10 of the ratio of the pressure of a sound to a reference pressure.

Sound Transmission Loss:

The ration of sound energy incident upon a panel to the sound energy radiated from the opposite side; expressed in dB.


The higher density outer surface of a foam article. It is the result of surface cooling.

Slab Foam:

Foam made by the continuous pouring of mixed liquids on a conveyor generating a continuous loaf of foam as long as the machine is operating.


Classified as free rise foam. A blown elastomer, particularly those with high load bearing and higher densities (8 pounds per cubic foot and higher). It is sometimes used to describe an open cell product and sometimes to refer to a closed cell product.


Tear Resistance:

The ability of a piece of flexible foam to resist deepening a cut already made in the foam sample. Expressed in pounds/inch.

Tensile Strength:

Normally expressed as the pounds per square inch of force required to stretch a foam sample to the breaking point.

Thermal Conductivity:

The ability of a material to conduct heat; the physical constant for quantity of heat that passes through unit cube of a substance in unit of time when the difference in temperature of two faces is 1 degree.


Materials that may not be reheated and softened again. Once the structural framework is set, these plastics cannot be reformed.


Materials that become soft when heated and solid when cooled to room temperature. This softening and setting may be repeated many times.


"U" value:

The overall coefficient of heat transfer. This value incorporates all the factors involved in the transfer of heat from one area to another, including boundary layer transfer of any or all "K" factors. "U" values are generally used in calculating heat transfer of a structure in a particular environment; whereas "K" factors are generally used for single components of a structure.


Zone of invisible radiations beyond the violet end of the spectrum of invisible radiations. Since ultraviolet wavelengths are shorter than the visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.


A term used for years as the common name for a chemical more property called "Ethyl Carbonate". The term is now used to refer to the product of a reaction between a chemical containing reactive hydroxyl groups on its molecule. These compounds are, for the most part, biologically inert. The compounds are called polyurethanes. Since the name refers to the molecular joint between the monomers, many different chemicals can be used as building blocks or monomers with the final product still being known as a urethane compound or polymer.

UV Stabilizer:

Any compound which, when mixed with a resin, selectively absorbs ultraviolet rays.


Water Absorption:

With rigid foam, percent by weight of water pickup on submergence of a specified sample under a specified depth of water.


Cell membranes of walls in flexible foam that are broken or ruptured (but intact) which interfere with free air movement through the foam. Generally a high proportion of windows, as indicated by the shiny reflection of light through a cut surface, indicates a foam tending towards closed cells, which results in poorer physical properties.

Wave Length:


The wavelength of sound is the distance between analogues points on two successive waves.

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