Molded Foam vs Cut Foam

There are several methods in the upholstery industry that are used to create the seating surface of seats and chairs of all types. The way a seat cushion gets produced depends on a few factors including how much the final product will cost, what type of application the seat itself will be used in, and what visual aesthetic will be. The material chosen by more upholsterers and manufacturers for the inner support system is polyurethane foam but the variations that exist in the production process are what differentiates one manufacturer from another.

The physical makeup of the polyurethane foam that gets formed into multiple foam products starts as a liquid and is made up of two parts, one is a resin-based liquid and one is the activator (also a liquid) that then gets blended. At that point, the mixed two-part foam (still in liquid form) is ready to be poured into a custom-made mold to get a specific shape or into big blocks to be turned into a product that can be cut into any shape that is required. The actual mixture of the resin and the hardener can be altered to produce a final product that has specific qualities based on need. Foam density can be altered depending on the usage to be either more on the firm side to aid in longevity or on the softer side for comfort. The density of the foam (hardness or softness) is known as a compression rate and measured with an Indentation Force-Deflection (IFD) test that physically compresses the foam by 25%. That determines how soft or hard a foam product is going to be and ads a designation in terms of pounds per square feet.

In the world of automobile interior, the seats are comprised of polyurethane foam as well, but the ways that the seat bottoms and backs are constructed can make a huge difference in how comfortable and durable the final product actually is. The two methods of producing foam for interior seating consist of either using pre-cast foam blocks and then cutting them to the desired shape or using a specifically shaped mold to produce a custom shape that can take any form. Both molded foam and cut foam have their advantages and disadvantages.

Cut foam starts as most other products start and that is as a raw material that is available from a supplier. The physical shape is usually a square or a rectangle and can be chosen in different thicknesses and densities based on the needs of the final product. The seat manufacturer then gets to work on the actual cutting process and shapes the foam with a series of knives and saws to achieve the perfect shape. Shaping the foam is a long and specialized process that depends on very skilled labor and can occupy an unknown amount of labor hours depending on the work being performed. When the cut foam method is used to produce automotive seating, the foam blocks are cut and glued vertically, with the final product resembling a loaf of bread with vertical slices next to each other. One of the principal drawbacks is that the glued foam layers can separate over time, the areas that are cut can be slightly more susceptible to wear, and the cutting process is rarely 100-percent repeatable due to the process being mostly hand-made. One advantage that cut foam shaping has going for it is that it is a less expensive process that can be done by one individual, and custom shapes require less setup time.

Making molded foam is a completely different process entirely. The separate foam products get delivered in their liquid form and it is then up to the manufacturer to decide how to mix them to achieve their preferred results. Since the process is manufacturer-controlled, it allows the molded foam to have qualities that cut foam just cannot have. Every aspect of the production process is customizable when starting with liquid foam. When the desired density and physical properties are achieved by the manufacturer, the liquid foam then flows through computer-controlled nozzles and into a mold that is used to customize the shape of the final foam products into anything that is needed. After a short curing time, a fully formed foam product emerges from the mold and is then trimmed of excess stray foam, cured for a predetermined amount of time, and is considered ready to use.

TMI Products uses the molded foam method for producing all the foam products that get used in vehicle interior seating. The process itself starts much as it did above with the two-part liquid foam being mixed to the desired consistency, poured into a mold, and allowed to cure. Once the curing process is over, the fully formed foam product is removed, cleaned of any stray foam, and set aside to cure before usage. TMI takes it upon themselves to make the best interior components in the industry and controls the manufacturing of their foam products from every step of the way. The way that TMI manufactures its foam products varies from the placement of the product itself. Seat bottoms for instance are made from a blend of liquid foam that is a little denser, as a seat bottom will see more impact over its life than a seat back. All of the foam products get a sheet of material that protects the surface from wear in the springs that get permanently attached in the pouring process. The molds that TMI uses are shaped and produced in-house to the specs that are needed to pour foam for the various vehicle that TMI produces products for so a product for a Ford Mustang would be different than a product for a Chevy Chevelle. Once the liquid has time to expand in the heated mold, the seat back or bottom takes shape and in a few short minutes, it is removed and is ready to cure.

The advantages of using molded foam are immeasurable. The amount of customization that can be done is a game-changer for a manufacturer that offers multiple products for vehicles of different year ranges. If a certain mixture of foam is not curing right or does not offer the right density ratings, then it can be adjusted. If the need is to have a protective backing layer or maybe add some strips of Velcro to make the upholstery covers stick better, then those items can be included. Molded foam is also 100-percent repeatable due to all of the controls that are set in place. Mixing the two-part liquid foam is usually computer-controlled, a predetermined amount is then pumped into the molds, allowed to cure in a temperature-controlled environment, and then removed. If a manufacturer has multiple pouring machines and multiple molds to be poured into, the production scale can be increased.

Quality control is the biggest key to the production of any product. When that product needs to be produced on a large scale, streamlining the process as much as possible is the key to producing a product that will be consistent. Producing consistent products is what makes a manufacturer trustworthy to consumers.