How to Cut Closed Cell Foam: Techniques for Cutting Five Types of Foam
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How to Cut Closed Cell Foam: Techniques for Cutting Five Types of Foam

Closed cell foam is a unique material that, in its various formulations, is durable, strong, and can be found in blocks and sheets, or in thicknesses so thin they behave like fabric. Because of this versatility, people often find uses for it in their everyday lives. However, having foam cut to size every time you need it is not realistic. Fortunately, closed cell foam is an incredibly easy material to work with. Whether you’re making pipe wraps, gaskets, weather stripping, or anything else, you’ll need to know how to cut closed cell foam with precision. By considering the following steps, you should be able to easily cut multiple closed cell foam materials.

NOTE: These instructions exclude expanded polystyrene (EPS), which is best cut with hot wire.

Starting

Before addressing the different foam cutting methods, it’s important to address the materials you’ll need. Unlike open cell foam, closed cell materials should be cut with a straight, non-serrated blade such as a razor or craft knife. These knives work well because their blades are disposable and easy to replace as they dull. Scissors can also be used for smaller, informal projects, though they are only effective on particular types and thicknesses of foam. It’s also smart to have a ruler for cutting. Lastly, always cut the foam on a stable surface that will not be damaged.

Cut: Neoprene, Reticulated Polyethylene, Gym Rubber and Roll Polyethylene

Neoprene is a rubbery material, Cross-Linked Polyethylene (XLPE) is slightly “plastic”, Roll Poly is a thin sheet-like material similar to XLPE, and Gym Rubber is spongy, but can be the softest material or firmer among these four types depending on the formulation. Despite these differences, the physical structures of these materials are similar enough that they can be approached the same way when cutting.

using scissors

When it comes to neoprene, gym rubber, XLPE or polyethylene rolls, the first thing to consider is the thickness of the material. If you are working with sheets 1/8″ thick or less, you have the option of cutting with sharp scissors. Scissors are only recommended for recreational projects because they can leave jagged edges. If you are making shapes for bath toys, or trimming the backing for card making, scissors are fast and effective.Because of its flexibility, PE roll is the easiest of these four materials to cut with scissors.

Single pass cutting method

For precise projects involving material thicker than 1/8″, you’ll want to cut with a straight blade. The thickness must again be considered, as it will dictate the method you use to cut with the knife.

If you are cutting sheet 1/2″ or less, you should use the single pass method, where you make a single stroke of the blade that cuts through the entire thickness of the material. Simply follow your pattern down the foam until you have the cut you want The single-pass method ensures the cleanest edges, although it is not recommended for foam thicker than 1/2″ as it becomes difficult to move the blade through the material smoothly. Using the sharpest blade possible is vital for the one-pass method, as dull blades can snag once you get to the heart of the material.

To make your cut, make sure the foam is anchored at the start of the cut to prevent the material from wrinkling under pressure. Start cutting from an outside edge whenever possible and don’t stop cutting once you’ve started.

Multi-pass cutting method

For closed cell foam over 1/2″ thick, it becomes difficult to get a blade through the material in a single pass. Attempting to do so can leave snags or sloppy cuts. Fortunately, the multi-pass cutting method will get the most out of it. Job done well on thick sheets of closed cell foam. Using a straight edge that runs the full length of the cut is the most important aspect of this strategy, as you will need a guide line to follow as you make multiple cuts through the foam.

Once you’ve established your cut line and your straight edge is in place, begin cutting exactly as you did in the one-pass method. But instead of sinking the blade all the way through the foam, just cut about 1/8″ to 1/4″ of the way; enough to keep the blade moving without force. It is also very It is important that each shallow cut extends the full length of the foam. Continue making these long, shallow strokes along your straight edge, cutting deeper each stroke. Do this until you have completely cut through the sheet.

Cut: Polyethylene:

One of the most widely used closed cell foams, polyethylene has a wide range of densities that affect the cell size, firmness and flexibility of the material. At its lowest densities, it has an inconsistent bubbling cell structure, which can affect edge cleanliness. For this reason, we suggest not using scissors when cutting polyethylene. Follow the steps for single pass cutting on sheets over 1/2″ thick and for thicker pieces of polyfoam, use the multiple cut method.

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