Foam Cutting Techniques
This article was born out of some recent “techno-babble” generated about foam-cutting techniques used in the creation of foam inserts. Heading toward two decades in the specific niche industry of creating customized protective case solutions, for a myriad of industrial, military and consumer industries, we have never seen anything like the recent surge in misguided interest in how the foam was cut. In reality, several methods may be incorporated into a single foam insert, depending upon the depth of the foam, the type of foam and complexity of a design. Often times a campaign touting the absolute benefits of one method over another might be something so simple as a business needing to promote what resources are available to them.
We create case foam inserts using a range of techniques, including laser, oscillating knife, wire cutting, water jet, die cut and router; and all have their place with respect to particular jobs. Even government work and large Fortune 500 companies, very rarely specify or care which cutting method is used, because in the end, they will rely upon our expertise and expediency, and the bottom line: Cost, Accuracy, Protection, and Aesthetics. The test is whether it is a clean design, the product fits, all items are well protected, and the cost is in line with the product or the production level. Typically, once the items weight and design are established, we recommend several options for the foam, and once a particular foam is designated, we will determine which of the six different methods of cutting, in combination with one another or as a singular technique, is the most cost effective means of producing a pristine result. A big difference between the various cutting techniques are that a router and laser will allow a surface design, whereas the knife, wire cut, die cut and water jet are usually used to cut clean through each layer of foam.
The laser is a very flexible tool and is typically used for prototyping or for a series of small production runs or customization. Working directly from a design program, it is often used for rapid prototyping. Compared to water jetting, the laser is significantly faster and more efficient. Foam cutting with a laser will produce a clean and fused edge. Foams made of polyester (PES), polyethylene (PE) or polyurethane (PUR) are the best choices for laser cutting or marking (engraving). The downside is the amount of electricity to run and the issue of a diffused beam that can result in a melted burn mark instead of a finely sealed edge.
ROUTER BASED CNC MACHINE:
The router is an extremely cost effective and versatile foam fabrication choice, and when combined with certain foams produces an extraordinary and quality aesthetic. Like the laser, a router can be used for surface designs or complete cuts through a layer of foam. The router is incorporated into foam fabrication where a marking or shallow depth design is desired on a single sheet of foam. Polystyriene and urethane foams work best. The limitations are the foams that work are all very expensive, and the process itself is can be extremely messy.
KNIFE BASED CNC MACHINE:
A knife based system comes equipped with several different styles of knife heads. The most popular for foam, the oscillating head, is designed to provide highly accurate cutting of a wide range closed celled foam or plastic-covered foam. Excessive overcutting issues are overcome with accurate cut capabilities of both the oscillation and tangential head control. The knife system is particularly effective for creating quick turnaround samples and prototypes, the need to cut thicker foam sheets and handling small productions. Incorporating a routing bit to “drill” cavities, the effect is the use of a single sheet of foam to avoid gluing several layers in place for multiple levels, and the computerized knife cutter can produce multiple jobs from a single sheet of foam. The downside is that it is not the best choice for higher production levels and larger cases.
Good old fashion wire cutting is incorporated when working on a project using deep cases and those which require manipulation of large custom fabrications. More and more, companies are turning to the advancements in the area and incorporating the computer-controlled abrasive wire cutting machines that can accurately handle foam up to 50 inches thick. The downside is that with any computer driven system, there is usually a programming fee incorporated in the cost, and it is obviously used for straight cuts, due to the lack versatility found in other cutting and shaping techniques.
Think giant cookie cutter. The precision custom cut of dies formed in die cutting presses, from curves to holes to unique layouts, the cut is always uniform and if designed properly, a perfect fit. In our opinion, the die cutting is best for cutting exact shapes out of foam for case inserts because it is usually more cost effective and can product large runs. Plates are made by setting thin serrated blades into wood to create an exact cutting pattern. The die is only going to be as good as the plate maker. Once the exact specifications are set, foam sheets are placed over the plate and compressed by as much as 80 tons of pressure. This forces the foam over the blades and when the pressure is released, a form which matches the design of the plate has been replicated in the foam. Because of the ability to create multiple sheets of foam in a single movement, it is effectively economical for large production runs. In the same amount of time that a water jet can may a few hundred one item, with the correct set up, the die cutter can makes thousands in the same window of time. The process of die cutting is generally less expensive than other methods since only one machine is needed to cut multiple materials. Die cutting also eliminates wasted products, which means lower cost of production. The downside of die cutting is the amount of time it takes to correct an error. Due to the expense and time required in making a precise plate, this is preferably done during the prototype phase so the time and expense of a new plate is not required.
Water jetting is the process of forcing water though a small opening, often referred to as the orifice or jewel, to concentrate an extreme amount of energy in a small area. The biggest advantage is the ability to cut a myriad of materials from stone and glass (excluding diamonds and tempered glass) and even some metals. But in the foam industry, that just isn’t a pertinent. The real upside is that all the nuances of a design are picked up by the water jet nozzle and it will result in a perfectly replicated design, and if the design has a fatal flaw, it is an easier and much less expensive fix than a die cut. Water jet cutting compares favorably with other cutting methods, offering good accuracy and a very efficient set up time, while cutting a wide range of materials with no change in material properties. There are limitations with respect to the use of a water jet cutting machine, in that some foams are more porous than others. The more porous the product, the more it will cause the jet stream to defuse, and it is therefore chosen on a much narrower range of foam than some of the other fabrication techniques. Open cell flexible polyurethane foam (FPF) is used in hundreds of industrial, medical, packaging and technical applications and a drawback is that foam products will absorb water, so there is a drying time allowance. If corners are cut on this step, it can result in moisture being trapped inside of a waterproof case, which can keep water or moisture in, as effectively as it can keep it out.
Manufacturers in the business of high tech fabrication machinery continuing to develop methods of achieving better and better results when producing shapes from foam with greater and greater capacity for tighter tolerances. . All these great processing advancements have added more design capability and efficiencies to production.
This article is not intended to be all-inclusive on any subject matter, as it is derived from our cumulative business experience in the industry. It is intended to serve as only a reference and the opinion of the author with respect to the general properties, benefits and attributes of various foam cutting technology. The information is offered in good faith and developed from experience and sources believed (again, in our opinion) to be reliable and accurate. It is also offered without warranty express or implied, as to the merchantability, fitness for a particular purpose, or any other matter. We disclaim any and all responsibility for loss or damage arising from any reliance upon such information by any party. We make no endorsements, assurances, warranties, or guarantees concerning the quality, uses or application of foam in conjunction with any specific products produced with any technology reviewed. We make no representation regarding the combustibility of foam under different applications or in different formulations. It is the responsibility of the reader or user of foams used in custom inserts to familiarize themselves with any combustibility or other hazardous characteristics both as to the usage, storage, and any other issues concerning applications and/or combustibility of certain types of foam. Caution should prevail when working with foam to direct any questions regarding fabrication and combustibility of particular foam qualities to individual foam manufacturers.