Co-extrusion is the process that feeds two different materials through a common die. Each component retains its original properties, but is fused with the other, to make a single extruded profile. Here are some of the most common benefits of co-extruded profiles.
Cost reduction. A co-extruded die costs more than a single-plate die, but sometimes the lower unit cost of the part justifies a quick payback. You can make most of the part using an inexpensive resin and use the more expensive resin only where needed. Expensive resins might include an NSF, FDA, or oil-resistant grade. Or, it might be a UV-resistant colorable grade, such as these two examples:
Retention devices. A seal, such as the window seal (below, left), is normally made from a soft material, both to accommodate tolerance stacking as well as to allow for thermal expansion and contraction. A soft material, however, may not be the best choice to keep the part from falling out during installation. In the two examples shown below, we co-extruded the retention device using a semi-rigid material. The sealing portion is both flexible and resilient:
Branding/aesthetics. In a world where rubber is usually black, color is an effective way to establish your brand.
Slipcoating. Some applications require a seal that is simultaneously soft and slippery. Unfortunately, softer grades of rubber tend not to be as slick as is needed. Or, in the case of glass-guide channels, a very low drag and highly wear-resistant surface is needed. A common approach in both instances is to co-extrude a very thin (typically 0.005” or less) layer of a specially-formulated slipcoat. Here are some examples:
Part identification. Although we can laser-engrave part numbers onto the surface of your extrusion, sometimes a color-coded surface will help ensure that you or your customer uses the correct part.
Other. Other examples include flexible rubber hinges, soft tubing with chemically-resistant inner core, adding a high-friction layer, adding rigidity for push-in stems, or to add a semi-rigid core to prevent the otherwise elastic extrusion from stretching during installation.
Tri-extrusions. At Reed Rubber, we can also tri-extrude profiles, giving you even more flexibility.
All of the above capabilities begin with a functional need. Think about how you need a certain component to function. What are the obstacles to a fully functioning part? While co-extrusion isn't always the right answer, it is a powerful tool that opens up a world of possibility.