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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.

Why Consider Cross-Linked Polyethylene Foam? A Primer on the Subject

Ever order a steak and find yourself overwhelmed by the choices? How do you want it done? Fries or baked potato? Butter and sour cream with the potato? It goes on and on. Well buying foam gets like that too, and unless you have a background in polymer chemistry some of the questions can be quite baffling.

One of the options foam fabricators throw at buyers is cross-linking. It's actually an important question as cross-linking has quite an effect on the properties of the foam. There are applications that might benefit from it while others won't. And should cross-linking be right for your application you may even be hit with another question: chemically cross-linked or irradiated?

To help you understand the questions, and decide if it's even something to consider, here's a primer on cross-linked polyethylene foam. It explains what the words mean and why you might want your next foam fabrication made from it. Individual sections address:

  • Understanding polyethylene
  • What is cross-linking?
  • Characteristics of XLPE foam
  • Benefits and applications

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Lower your shipping costs with custom-cut XLPE foam for dunnage

Cross-linked Polyethylene Case Insert

Almost every manufactured product gets shipped, and shipping costs money. Minimizing shipping costs is a priority for most businesses. That means using all the space in the truck for product, loading it to it's maximum weight, and ensuring nothing gets damaged in transit. XLPE foam dunnage is proven to help with all three.

Rough roads mean parts are in constant motion. Even when product is generously spaced, shocks and vibration can compress separating materials, letting surfaces touch and leaving marks. Adding more separation might prevent touching, but reduces volume utilization in the truck, pushing up shipping costs. Even if contact is avoided, vibration means movement against the dunnage material. That's a problem with many types of parts, but especially when appearance is critical, as with Class A automotive components.

Polyethylene foam is widely used in dunnage. It compresses and recovers readily, so does a good job of absorbing shocks and vibration. Unfortunately though, it's open-cell structure tends to rub, creating marks on paint and in metal and plastic.

For holding fragile parts and those where surface appearance is critical, cross-linked polyethylene (XLPE) foam performs much better. A closed-cell structure means no edges to abrade part surfaces, so coatings and finishes remain pristine, yet it's still resilient enough to protect against shock and vibration.

Another benefit of XLPE is the ease with which it's cut and shaped, as Merryweather demonstrated when producing inserts for specialized dunnage racking. That helps reduce spacing between parts while still ensuring they won't touch or rub. Tighter intra-part spacing translates to improved weight or load utilization and the low density of XPLE foam also means the excess weight being shipped is minimized.

XLPE foam is available in a range of colors, which can be beneficial for easy product identification, and as a closed-cell foam, is waterproof if left uncovered while outdoors. Unlike wood, it doesn't splinter, and has no sharp edges, so there's little risk of people being injured while loading or unloading parts.

Minimizing shipping costs involves maximizing volume and weight utilization in the truck, but that's not enough if product gets damaged in transit. By choosing the right material for dunnage it's possible to pack individual pieces tightly yet still be confident in them arriving undamaged after even a long cross country journey. Precision cut XLPE foam is the material to use.

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Understanding What the Vertical Contour Cutting Machine Can Do

Contour Cutting is an Excellent Capability for Custom Foam Fabrication

It's difficult to cut curved profiles in foam and get smooth edges. Reciprocating tools tend to tear and leave unsightly steps while methods like water jet and die cutting have limitations with thick materials. In these situations it makes sense to use a vertical contour cutting machine.

Operating principle

Like the band saw used in many industries, vertical contour cutting machines use a continuous steel blade held vertically under tension. The work material, (usually foam,) is placed on a flat table that moves it into the blade to make the cut. Looped over pulleys, the blade moves continuously in one direction, ensuring that it's always cutting, (unlike with a reciprocating saw where half the motion is wasted.) Computer control over both the blade and the table motion allows production of complex shapes.

The cutting blade

As with any sawing process, the teeth shape and pitch must suit the material being cut. For foam 12 to 14 teeth per inch usually gives the optimal combination of cutting speed and edge finish. Some materials cut better with a wave form rather than teeth while others need only a flat knife blade.

The blade itself is made from high quality steel and measures 3.6 mm (0.144") deep and just 0.6 mm (0.024") in thickness. This geometry has two benefits. First, being very thin, there's minimal cut waste, which also minimizes the amount of dust produced. Second, it makes the blade maneuverable.

Blade maneuverability is one area where the vertical contour cutting machine differs from a regular band saw. The contour machine can rotate the blade through 360 degrees. Combined with the shallow blade depth, this lets it turn to cut complex shapes without compressing the foam.

Motion control

The vertical contour cutting machine has three motion axes under computer control. The table moves in one direction, pushing the foam through the blade. Carried on a bridge over the table, the blade can move left and right. If the blade and table moved at the same speed a foam block on the table would be cut at a 45 degree direction.

Axis three is blade rotation. It's this which lets the machine cut circles, corners with tight radii and complex contoured shapes. Internal holes in foam shapes are possible with just a single entrance/exit slot, (which is usually needed for fitting around bars, pipes, extrusions, cable conduit and so on.)

Machine capabilities

Merryweather's vertical contour cutting machine handles blocks of material up to 55" by 94" by 25". Cutting speed is as high as 230' per minute, depending on material density and whether bonded or laminated. Materials appropriate for vertical contour cutting include:

  • Polyurethane
  • Convoluted foam
  • Polyethylene
  • Cross-Linked polyethylene (XLPE)
  • Expanded polyethylene (EPE)

Material with densities up to 9 pounds can be cut, as can bonded layers of foam and foam laminated with either foil or textile material.

Process characteristics

  • Straight, smooth sides produced on thick foam blocks.
  • Cuts complex 2D shapes.
  • Programmed directly from CAD files.
  • "Nesting" function in software maximizes material utilization.
  • No tooling, so no tooling costs or delays for tool manufacture.
  • Ideal for small quantity orders
  • Small "kerf" (cut width) means minimal waste and dust.

Quality results

A vertical contour cutting machine is the best way of producing smooth, straight-sided shapes in soft materials like foam. Merryweather's machine handles large blocks of material quickly and efficiently with minimal waste. As no tooling is needed this process is ideal for both small and large quantity orders.​ Not sure if vertical contour cutting is the right capability for your project? Get in touch with us and we will be happy to answer any questions you have about custom foam fabrication cutting capabilities. 

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