Foam Fabricating

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Foam fabricating is a broad term used to describe types of foam, applications and uses of those types and the products that can be formed from foam materials. Foam is simply a substance formed that consists of a number of air bubbles trapped in a liquid or a solid. Foam fabricators classify their product by two categories: open-cell foam and closed-cell foam. Closed-cell foam contains foam cells which are sealed, or "closed" and separate from one another. This foam is very dense and has high compressive strength. Because the cells are not broken in this foam and gas and liquid molecules do not freely travel from cell to cell, the cells expand when exposed to heated gas. The expansion fills the material, making closed cell foam an excellent heat insulator, like spray foam. Open-cell foams are lightweight, spongy, soft foams in which the cell walls or surfaces of the bubbles are broken and air fills all of the spaces in the material. This makes the foam soft and weak; as a result, open-cell foams are commonly used for foam padding and foam cushions. In addition, open cell foams are effective as sound barriers, having about twice the sound resistance as closed cell foam. The medical, construction, automotive, electronics and furniture industries all use foam products.

Foam fabricating services, such as foam cutting, work with many types of foam for numerous applications. The most common foam used is polyurethane foam, which is resilient closed-cell foam that biodegrades in direct and indirect sunlight. Typical applications for urethane foam include surgical scrubbers, x-ray positioning pads, EKG pads, insulation foam, protective foam padding, flexible foam seating and custom insulated containers. Polyethylene foam is a closed-cell, expanded, extruded, flexible plastic foam with predictable shock absorbing qualities. Used mainly as a protective packaging material, polyethylene foam is used to wrap products such as computer components, frozen foods, furniture, signs, sporting goods and clothing. Ethafoam is polyethylene foam that offers excellent shock absorption qualities and is often used for blocking, cushioning and bracing protection in material handling and shipping. Polyether foam is low-cost polyurethane foam that provides good cushioning and has acoustic and packaging properties. PVC foam is closed-cell vinyl foam that is pliable and soft and used in gaskets to prevent water transmission. Expanded polystyrene (EPS) is being used in some surprising applications: as padding foam in bedroom slippers, filter foam in air conditioning units, insulation foam, oil rigs, weather balloons and satellites.

Foam can be made from a variety of materials including plastic, low density elastomers and rubber. Typically formed from polymers, foam is made by mixing a number of chemicals and adding a gassing agent. The addition of the gassing agent causes the material to expand and form a foam strip. The foam is comprised of numerous gas bubbles trapped in the material. After foam is formed, a variety of foam fabricating services can be performed, including several types of foam cutting processes. Die cutting is a common foam fabricating process, in which different shapes are cut out of foam strips, blocks or sheets. Water jet cutting uses a fine stream of water under ultra high pressure to perform the same function as die cutting, but offers extremely close tolerances that die cutting cannot achieve. Hot wire cutting utilizes a heated wire in order to form smooth, straight cuts in the foam. There are also several types of foam forming processes. A popular foam forming process is thermal-forming, in which bulk foam materials are heated in order to produce machining shapes like foam sheets. Another forming process, foam felting, produces denser foam materials by means of compressing and curing thick, soft foam materials.

Foam fabricating services produce a large amount of scrap. The first major source of scrap is produced during foam production as well as foam die cutting processes. Foam scrap is produced as a result of the startup and shutdown of the production line when manufacturing runs are changes over and when foam blocks are cut and shaped into the desired end product. The second major source of foam scrap is foam products that have reached the end of their useful life. Scrap foam is often shredded and rebonded and then used for such products as carpet padding and filler for pillows and furniture. Foam scrap can also be burnt in order to reduce waste bulk; however this was more popular in past decades. Although the burning of foam is considered to be non-toxic by U.S. government agencies, as a result of growing environmental concerns and more stringent carbon dioxide emission regulations, many foam manufacturers have turned to recycling as a waste handling method. Recycling offers manufacturers the ability to recoup return on investment, which would be lost by burning the scrap. Although the use of recyclable foam materials is growing, the process of collecting the foam, separating out the contaminants and then shipping the foam economically can be time consuming and costly to those foam manufacturers wanting to recycle.

Images provided by New Dimension Industries

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Foam Fabricating Types

• Acoustic foam is flexible polyurethane foam and serves one of two purposes, depending on whether it is attenuated or non-attenuated. The attenuated foam absorbs sound and is good for soundproofing purposes; the non-attenuated type allows sound to travel through it.
  
• Adhesive-backed foam padding is padding that stays completely intact and provides even pressure distribution. Adhesive-backed foam padding is often used in the medical industry.
  
• Bonded foam is a functional product created by gluing flexible polyurethane particles or shredded flexible polyurethane foam together. The foam block that results is typically peeled into a desired thickness and is most commonly used as carpet cushioning.
  
• Closed-cell foam is a plastic that contains foam cells which are sealed, or "closed" and packed together. Closed cell foam is commonly used for nautical flotation devices, foam mattresses and furniture padding.
  
• Cushion foam is any foam used for cushioning. Uses for cushion foam not only include furniture applications but athletic padding as well.
  
• Ethafoam padding is a closed-cell, expanded, regular (uncrosslinked) polyethylene foam product that is a trademark of The Dow Chemical Company.
  
• Flexible foam is polyurethane foam that is used in furniture such as beds, couches and chairs, because it molds itself to the shape of the body, providing comfort and support.
  
• Foam is a light, spongy materials used for thermal insulation and packaging.
• Foam cushions is any foam used for cushioning purposes.
• Foam cutting refers to the process that is used to cut foam into various shapes and forms.
• Foam padding can be used for virtually any industry or product that requires extra lining for protection, comfort, sound insulation and product protection.
• Molded foam is a cellular foam product that holds the shape of the mold cavity in which is was produced.
  
• Open-cell foam is a lightweight, spongy, soft foam in which the cell walls or surfaces of the bubbles are broken and air fills all of the spaces in the material. Open cell foam applications include water absorption, particulate filtering and thermal management.
  
• Packaging foam is a general term applied to foam that provides the highest protection to a product during shipment.
  
• Plastic foams are made up of a mass of tiny gas bubbles dispersed in a solid gas phase (matrix). Plastic foams are lightweight and have high strength-to-weight ratios.
  
• Polyethylene foam is a very rigid foam made primarily through an extrusion process.
  
• Polyurethane foam and flexible polyurethane foam is different from polyethylene in that it cannot be reheated; it must be shaped into the final product in the foaming process.
  
• PVC foam is a closed-cell foam with very low moisture absorption. It is self-extinguishing, will not rot and has excellent fatigue life and good bond strength with common adhesives and resins.
  
• Rigid foam contains hundreds of millions of closely packed air cells. Rigid foam has excellent thermal performance and is extremely moisture resistant.

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Foam Fabricating Terms

Additive - A material utilized to alter the properties, processing or final use of a base polymer. The quantity of additive is usually articulated in terms of parts per hundred of the total resin in the polymer formulation
 
Air Flow - The quantity of air that can flow through a two foot by two foot by one foot foam sample with a five inch water pressure differential. Air flow is expressed in cubic feet per minute.

Air Traps - Voids in molded foam parts that are the result of the entrapment of air pockets occurring during mold fill out.  Air traps are characterized by shiny, smooth surfaces.
 
Amine - Category of compounds that catalyze in polyurethane foam reactions.
 
Anti-Static Flexible Polyurethane Foam - Foam containing electrically conductive material in order to prohibit static electricity buildup or to promote static discharge. Anti-static flexible polyurethane foam is used mainly for packaging electronic components.
 
Auxiliary Blowing Agent (ABA) - An additive that supplements the main blowing agent water in the production of foam and could create softer or lighter foam.
 
Ball Rebound - A test technique that measures the surface resilience of flexible polyurethane foam by dropping a steel ball of a specified mass from a certain height onto the foam sample. The ball rebound value is the ball rebound height as a percentage of the height of the fall.
 
Basal Cells - Large, irregular cells found beneath the surface of the skin of a molded foam part.
 
Blowing - The method of foaming flexible polyurethane in production. Blowing happens when toluene diisocyanate and water react to create CO 2.
 
Bonding - The blending of two or more components into a composite. Foam is typically attached to other foam grades or polyester fiber.
 
Buffed - The contouring or shaping of flexible polyurethane foam pieces by the removal of foam with abrasives.
 
Bun - A section of foam cut from a constantly produced slab stock kind of foam.
 
Cells - The hollow space left behind in the structure of polyurethane foam encased by polymer membranes or the polymer skeleton after blowing is finished.
 
CFC-Free Foams - Flexible polyurethane foams produced without using chlorofluorocarbons as auxiliary blowing agents.
 
Cold Molding - A process in which high-resiliency foam is produced. Pouring is carried out without heat and foam is cured at or near room temperature.
 
Combustion Modifying Additive - An additive that will decrease the ability of flexible polyurethane foam to ignite or make it burn more slowly.  
 
Compression Force Deflection (CFD) - Also known as compression load deflection (CLD), it is a calculation of the load-bearing capability of a foam.
 
Convoluting - A process involving special cutting equipment to create a foam sheet with dimples.  
 
Clickability - The capability of a flexible polyurethane foam to return to its natural state from the pinched results of die cutting.
 
Closed Pour - A process in which the mold lid is closed and locked in molded foam production and the foaming mixture is injected through ports in the lid of the mold
 
Contour Cutting - The cutting of foam with a specialized saw into patterns from a foam block, creating a custom foam part.
 
Core - The inner area of foam, away from the outer skin.
 
Crushing - A procedure, typically mechanical- or vacuum-assisted, in which the closed cells of a high resilience slab stock or molded foam are opened.
 
Dead Foam - Foam with low resiliency that does not quickly regain its original shape after deformation.
 
Deformation - A method in which the shape of the foam is altered from its original state through compression or heat.  
 
Die Cutting - The cutting out of parts from foam using a process that is similar to stamping out the part.  It is good for long duration runs of cut parts that necessitate uniformity in size.   
 
Drilling - The boring of holes into a foam to enhance air flow, provide for greater ease of button application in tufted design and to make the foam feel softer.
 
Elastomers - Polymers that, when undergoing deformation, resist and recover in a way similar to that of natural rubber.
 
Flame Lamination - Also called "flame bonding" it is the process of bonding flexible foam to a fabric, film or other material by melting the surface of the foam with a flame source and quickly pressing it to the material before the foam resolidifies.
 
High Resilience (HR) Foam - A kind of polyurethane foam created with a combination of polymer or graft polyols. This foam is not as uniform in its cell structure in comparison to conventional products, which enhances the comfort, support, resilience and bounce of the foam.  
 
Hot Wire Cutting - The cutting of foam using high-temperature wires instead of a saw blade. Hot wire cutting is generally used for cutting intricate parts.
 
Isocyanate - A quick way to refer to the group of diisocyanates that are one of the two primary ingredients in the chemical process from which polyurethane foam is produced.  
 
Laminating - A method of bonding layers of foam together in a simple composite. Laminating could be attained with adhesives or with heat processes, such as flame lamination.
 
Peeling - Method of cutting thin sheets from a foam cylinder.
 
Skin - The higher-density exterior surface of foam, typically resulting from the foam surface cooling at a higher rate than the core.
 
Slab Stock - Flexible polyurethane foam produced by the constant pouring of mixed liquids onto a conveyor, which creates a continuous loaf of foam.
 
Slitting - Method a foam cutter uses for cutting sheets from a rectangular foam block.
 
Voids - Significant hollow spaces that inadvertently form in foam structures. Voids are typically the result of inaccurate mold filling or inadequate moldability.

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